Performance and Results Annual Report 2007 · which utilize selected technology net-works. Customers are offered laser-specific solutions that encompass design engineering, material

ILT

Performance and ResultsAnnual Report 2007

Annual ReportFraunhofer Institute for Laser Technology ILT2007

Industry and the consumer society arebecoming ever more demanding. Onthe one hand, products are expectedto offer excellent value for money,which they can generally only doif they are mass-produced. On the other, more and more customers arerequesting high-quality solutions speci-ally tailored to their individual needs.Product managers are increasingly confronted with such key concepts as‘mass customization’ and ‘one-pieceflow’. A number of industrial sectorsare producing a growing variety ofproducts, while at the same time maintaining a good price-performanceratio and all the positive features of asuccessful brand, such as an attractivedesign, high functionality, excellentreliability and pronounced user-friend-liness.

Laser technology has proven to be anexcellent problem-solver in reconcilingall these different requirements. It canbe perfectly integrated into modernproduction systems to ensure flexibility,quality and automated operation. The Cluster of Excellence »IntegrativeProduction Technology for High-WageCountries« at RWTH Aachen Univer-sity, of which the Fraunhofer ILT is amember, has long been working tosolve the dilemma that opposes eco-nomies of scale and scope. The firstachievements, such as the series pro-duction of customized dental prosthe-ses by selective laser melting, havealready been introduced on the marketin close collaboration with an innovativeindustrial partner. Another noteworthyaccomplishment is the combination ofdifferent laser manufacturing processesin integrated laser systems.

A first step in this direction was thecombination of laser welding and cutt-ing without retooling, using specialoptics. This success is likely to encou-rage further synergies between suchprocesses as structuring and polishingin tool making. Laser-based solutionscould also help to miniaturize productswhile at the same time allowing for awide variety of product versions. Overthe last few years, the Fraunhofer ILThas developed various processing stra-tegies such as the TWIST and SHADOWtechniques for high-speed precision joining with flexible path control. Theseare of particular benefit to the clock-making, medical and precisionengineering sectors.

The market trends of numerous in-dustries are consistently pushing thedevelopment of laser technology. TheFraunhofer ILT is responding to thechallenging questions and require-ments of its industrial R&D partnerswith creative solutions. Our annualreport will give you an idea of ourmany and varied project results. Wewould also be delighted to take on anychallenging tasks your own companymay have for us. With this prospect inmind, I wish you an inspiring read andlook forward to your feedback.

Yours sincerely,

Professor Reinhart Poprawe M.A.

Fraunhofer ILT Annual Report 2007 3

Foreword

Profile of the Institute 6

Declaration of Principles 7

Business Areas 8

Board and Committees 10

Contacts 11

Core Areas 12

Services 14

Facts and Figures 16

References 19

Fraunhofer USA Center for Laser Technology CLT 20

Coopération Laser Franco-Allemande CLFA 22

Fraunhofer Alliance Surface Engineering and Photonics VOP 24

The Fraunhofer-Gesellschaft at a Glance 26

Laser Technology at RWTH Aachen 28

Cluster of Excellence »Integrative Production Technology for High-Wage Countries« 30

European Laser Institute ELI 32

PhotonAix e. V. - Competence Network for Optical Technologies 33

Some Special Research Results from the Business Areas of Fraunhofer ILT

Laser and Plasma Sources 35 - 60

Laser Material Processing 61 - 106

Laser Plant and System Technology 107 - 118

Laser Measurement and Testing Technology 119 - 139

Patents 140

Dissertations 141

Diploma Theses 141

Scientific Publications 142

Lectures 144

Conventions and Conferences 148

Trade Fairs 150

Publications 151

CD-Rom »Laser Technology« 154

Technical Book »Laser Technology for Manufacturing« 155

Information Service 156

Imprint 157


Contents

6 Fraunhofer ILT Annual Report 2007

DQS certified by DIN EN ISO 9001Reg.-No.: DE-69572-01

Short Profile

ILT - for more than twenty years, this ab-breviation has stood for extensive know-how in laser technology. Innovative solutions for manufacturing and pro-duction problems, development ofnew technical components, competentadvice and training, highly-qualifiedpersonnel, the latest technologies andan international reputation: these arethe guarantors for long-term businessrelations. The numerous customers ofthe Fraunhofer Institute for Laser Tech-nology ILT belong to various sectorslike automobile industry, mechanicalengineering, chemical and electricalengineering, steel construction, preci-sion mechanics and optics.

With more than 250 employees and10.000 m2 of usable floor space theFraunhofer Institute for Laser Technolo-gy is world-wide one of the most important development and contractresearch institutes of its specific field.The four business areas cover a widerange of actual and vertical integratedtopics. In the business area »laser andplasma sources« development activitiesare concentrated on innovative diodeand solid state lasers for industrial useas well as compact EUV-sources for lithographic use in semiconductorproduction. The business area »lasermaterial processing« offers solutions in cutting, ablation, drilling, welding,soldering, surface treatment and microprocessing. The activities cover a widerange of applications from macro processing via nano structuring to biophotonics.

In the business area »laser plant andsystem technology« prototypes are developed, built up and installed on site.Process monitoring and control as wellas system components and controlsoftware are part of the activities. Inthe business area »laser measurementand testing technology« processes andsystems for inspection of surfaces, forchemical analysis, for testing the accu-racy of dimensions and geometry ofworkpieces as well as for analysis ofstatic and dynamic deformations aredeveloped.

The comprehensive offer of services of the Fraunhofer Institute for Laser Technology ranges from research anddevelopment as well as system construc-tion and quality assurance to adviceand training. Industrial laser systemsfrom various manufacturers as well asan extensive infrastructure are availablefor the work on research and development projects.

In the Laser User Center of the Fraun-hofer Institute for Laser Technologyguest companies work in their own separated laboratories and offices. Thebasis of this special form of technologytransfer is a long-term cooperation agreement with the institute in thefield of research and development. The surplus value lies in the use of thetechnical infrastructure and in theinformation exchange with ILT´sexperts. Already 10 companies profitfrom the advantages of the Laser UserCenter. Besides laser manufacturersand laser users, entrepreneurs from the areas of special machine production,laser processing and laser measurementfind a suitable frame to realize their ideason an industrial scale.

Profile of the Institute

Mission

We occupy an international top positionin transferring laser technology toindustrial application.

We continually expand the knowledgebase and know-how in our sector andmake significant contributions to theongoing development of science andtechnology.

Working with our partners in industry,science and government, we createinnovations on the basis of new beamsources and new applications.

Customers

The customers needs are the focus ofour work.

Discretion, fairness and a spirit of part-nership are top priorities in our customerrelationships. Our customers can relyon us.

We tailor solutions and their cost-effective implementation to thedemands and expectations of ourcustomers, with the objective of creating a competitive advantage.

We support industry’s needs for newspecialists and managerial staffthrough project-based partnershipswith our customers.

We want our customers to be satisfied- because we want them to return.

Chances

We strategically expand our knowledgebase across the network.

Fascination Laser

The unique characteristics of laser lightand the resulting diversity of applica-tions, are a constant source of inspirationand fascination.

Staff

Teamwork between the individual and the group is the foundation of oursuccess.

Strengths

Our broad spectrum of resources enables us to offer one-stop solutions.

Management style

Cooperative, demanding and suppor-tive. Knowing the value of our staff asindividuals and the value of theirknow-how and their commitmentforms the basis of our managementphilosophy. We involve our staff in theformulation of goals and the decision-making process. We place a high valueon effective communication, goal-oriented and efficient work and cleardecisions.

Position

We work within vertical structures,from research to application.

Our expertise extends from beam source,machining and measuring techniques,to application, through to integrationof systems into the customer’s produc-tion line.


Declaration of Principles

Laser and Plasma Sources

This business area encompasses thedevelopment of diode laser modulesand systems as well as diode-pumpedsolid-state lasers with different reso-nator structures (stab,slab,fiber), the design of new diode laser structures,the microassembly of diode lasers and optical components, and the develop-ment of plasma systems.

For more than 10 years spinn-offs ofthe Fraunhofer ILT are set up in the framework of some projects. In coope-ration with the Fraunhofer IAF newstructures are being designed whichpermit the manufacture of diode lasersdemonstrating higher beam quality. The business area continues to enjoy a unique reputation in the assembly of high-power diode lasers and in particular the installation of automatedassembly and test facilities. Work inthe plasma technology sphere focuseson the development of EUV beamsources for semiconductor lithography.The main target markets for the busi-ness area as a whole are laser machining,medical engineering and metrology,along with the component market forinformation and communications tech-nology.

Laser Material Processing

Production processes addressed by this business area include cutting andjoining techniques applying micro- andmacro-technology, as well as surfaceengineering. The services providedextend from process development forthe manufacture of sector-specific products and the integration of theseprocesses in production lines, throughsimulation services for laser applications,to the production of samples in sup-port of series production start-up. Thestrength of the business area is rootedin its extensive process know-how,which is tailored to specific customerrequirements in each case. In additionto process development, the businessarea offers complete system solutionswhich utilize selected technology net-works. Customers are offered laser-specific solutions that encompass designengineering, material specification,product design, production equipmentand quality assurance. In addition tothe target market of material process-ing, the business area also addressescustomers in the medical engineering,biotechnology and chemical sectors.


Business Areas

Laser Plant and System Technology

This business area focuses on the deve-lopment of prototype equipment forlaser and plasma-technology applica-tions, as well as on laser systemsengineering, particularly in the fields of automation and quality assurance.Areas of application embrace welding,cutting, hardening, repair coating, drilling and micro-joining. The systemtechnology offered provides completesolutions for process monitoring, com-ponents and control systems for preci-sion machining, laser-specific CAD/CAMtechnology modules, as well as soft-ware for measurement, open- and closed-loop control and testing. For its work in process monitoring in parti-cular the business area can draw onextensive and, where required, patent-protected know-how. In this sectornumerous systems have already beenlicensed for companies. Target marketsinclude laser equipment and compo-nent manufacture as well as all sectorsof production industry which deploylasers in their manufacturing activity or intend to do so.

Laser Measurement and Testing Technology

The services provided by this businessarea include the development of mea-surement and testing processes and related equipment for material analysisand for geometric testing and surfaceinspection. The requisite measurementand testing software is tailored to customer-specific problem areas. Materialanalysis is based on the deployment oflaser-spectroscopic processes, focusingon the analysis of metallic and oxidicmaterials, identification testing of high-alloy steels, rapid recognition of mate-rials for recycling tasks and analysis ofgases and dust. Special electronic com-ponents are developed for the parallelprocessing of detector signals of highbandwidth.

In biophotonics joint projects are car-ried out in the field of highly sensitivefluorecence detection for protein chipsand laser scattered light measurementsin sub-µl test volumes for protein crystallization. As part of the area’s work on geometric testing and surface inspection components, devices andequipment are being developed for obtaining 1 to 3D information aboutthe geometry or surface properties ofworkpieces. These include processesand special systems for testing the stability of bar and strip products anddevices for the 1D to 3D scanning ofunit goods. Target markets include theproduction and the recycling industrywhich conduct measurement andtesting fast and close to the process.


Business Areas

Board

The Board of Trustees advises theFraunhofer-Gesellschaft as well as theInstitute’s management and supportsthe links between interest groups andthe research activities at the institute.The Board of Trustees during the yearunder review consisted of:

C. Baasel (chairman)Carl Baasel Lasertechnik GmbH

Dr. Ulrich HefterRofin-Sinar Laser GmbH

Dipl.-Ing. H. Hornig BMW AG

Dr. U. Jaroni ThyssenKrupp Stahl AG

Prof. Dr. G. Marowsky Laserlaboratorium Göttingen e. V.

MinRat Dipl.-Phys. T. Monsau Ministerium für Arbeit und Soziales,Qualifikation und Technologie des Landes NRW

Dr. Rüdiger MüllerOsram Opto Semiconductors GmbH & Co. OHG

Dr. Joseph PankertPhilips Lighting B.V.

Prof. R. Salathé Ecole Polytechnique Fédéral de Lausanne

MinR Dr. Frank Schlie-RoosenBundesministerium für Bildungund Forschung BMBF

Dr. Dieter SteegmüllerDaimlerChrysler AG

Dr. Ulrich StegerMinisterium für Innovation, Wissenschaft, Forschungund Technologie des Landes NRW

Dr. Klaus WallmerothTRUMPF Laser GmbH & Co. KG

The 23rd Board of Trustees meetingwas held on September 19, 2007 at the Fraunhofer ILT in Aachen.

Directors’ Committee

The Directors’ Committee advises theInstitute’s managers and is involved in deciding on research and businesspolicy. The members of this committeeare: Dipl.-Betrw. (FH) Vasvija AlagicMBA, Dipl.-Phys. A. Bauer, Dr. K.Boucke, Dr. A. Gillner, Dr. J. Gottmann,Dipl.-Ing. H.-D. Hoffmann, Dr. S. Kaierle,Dr. I. Kelbassa, Dr. E.-W. Kreutz, Prof.Dr. P. Loosen, Dr. W. Neff, Dr. R. Noll,Dr. D. Petring, Prof. Dr. R. Poprawe,Prof. Dr. W. Schulz, B. Theisen,Dr. B. Weikl, Dr. K. Wissenbach.

Health & Safety Committee

The Health & Safety Committee is responsible for all aspects of safety and laser safety at the Fraunhofer ILT.Members of this committee are: Dipl.-Betrw. (FH) Vasvija Alagic MBA,K. Bongard, M. Brankers, A. Hilgers, Dr. E.-W. Kreutz, A. Lennertz, Dr. W. Neff,E. Neuroth, Dipl.-Ing. M. Poggel, Prof. Dr. R. Poprawe, B. Theisen, F. Voigt, Dipl.-Ing. N. Wolf, Dr. R. Keul(Berufsgenossenschaftlicher Arbeits-medizinischer Dienst BAD).

Science & Technology Council

The Fraunhofer-Gesellschaft’s Science & Technology Council supports and advises the various bodies of theFraunhofer-Gesellschaft on scientificand technical issues. The members are the institutes’directors and onerepresentative elected from the science/technology staff per institute.

Members of the Council from the ILTare: Prof. Dr. R. Poprawe, B. Theisen,Dr. C. Janzen.

Staff Association

In March 2003 the staff associationwas elected by the employees of theFraunhofer ILT and the Department of Laser Technology. Members are:Dipl.-Ing. P. Abels, Dipl.-Ing. G. Backes,M. Brankers, Dipl.-Phys. J. Geiger, M. Janßen, Dipl.-Phys. G. Otto, B. Theisen (chair), Dr. A. Weisheit, Dipl.-Ing. N. Wolf.


Board and Committees

Prof. Dr. Reinhart Poprawe M.A. (-110)Director

Dipl.-Phys. Axel Bauer (-194)Marketing and Communication

Dipl.-Betrw. Vasvija Alagic MBA (-181) Administration

Dr. Bruno Weikl (-134)IT-Management

Dr. Alexander Drenker (-223)Quality Management

Prof. Dr. Peter Loosen (-162)Vice Director

Dr. Konstantin Boucke (-132)Laser Components

Dipl.-Ing. Dieter Hoffmann (-206)Solid State and Diode Lasers

Dr. Reinhard Noll (-138)Laser Measurement and Testing Technology

Dr. Willi Neff (-142)Plasma Technology

Dr. Dirk Petring (-210)Cutting and Joining

Dr. Konrad Wissenbach (-147)Surface Treatment

Dr. Arnold Gillner (-148)Micro Technology

Dr. Stefan Kaierle (-212)System Technology

Prof. Dr. W. Schulz (-204)Modelling and Simulation


Contacts


Core Areas

Laser ComponentsDr. Konstantin Boucke

• Active und passive cooling of diode lasers

• Expansion-matched coolers and mounting technologies for laser diode bars

• Mounting of laser diode bars with indium- and AuSn solder

• Characterization and testing of diode lasers in the wavelength regime between 630 nm and 2.1 µm

• Design and assembly of micro-optical systems

• Fiber coupling for singlemode and multimode fibers

• Automation of high-precision assembly processes for lasers and optical systems

Solid State and Diode LasersDipl.-Ing. Dieter Hoffmann

• Development of solid state and diode lasers

• Development of fiber lasers • Methods and components

for frequency doubling • Optical design for lasers, beam guid-

ing and forming of laser radiation • Development of diode laser modules

and systems • Design and characterization

of optical components • Development of components

for solid state and diode lasers

Laser Measurement and TestingTechnologyDr. Reinhard Noll

• Laser measurement processes for online inspection tasks

• Development, construction, integration and testing of laser measurement and testing equipment

• Chemical analysis of solid, liquid and gaseous substances with laser spectroscopy

• Spectroscopic monitoring of welding processes

• Fluorescence analysis • Quantification of protein

interactions using label-free laser scattering methods

• In vivo diagnostics for online mo-nitoring of minimal invasive surgery

• Measurement of distances, profiles and shapes with laser triangulation

• Real time operation and automation

Plasma TechnologyDr. Willi Neff

• Development of plasma based EUV/XUV-sources

• Development, construction and integration of components for EUV/XUV-measuring systems (microscopy, surface characterization,measurement of reflectivity …)

• Power generators for pulsed plasma formation

• Process control and monitoring systems for spatially arranged systems based on micro seconds

• Atmospheric pressure plasma for surface modification (sterilization of packaging material, functiona-lization …)

Cutting and JoiningDr. Dirk Petring

• Cutting, perforating, drilling, deep-engraving

• Welding, brazing, soldering• High-speed processing• Thick section processing• Cutting and joining of special

materials• Welding with filler material• Laser-arc hybrid technologies• Product-oriented process

optimization• Multi-functional manufacturing

processes• Design and implementation

of processing heads• Sensor-based process control• Computer-supported simulation

and optimization• Multimedia training and information

systems

Surface Treatment Dr. Konrad Wissenbach

• Fabrication of load orientated layers by means of heat treatment, trans-formation hardening, remelting, alloying, dispersing and laser cladding

• Development of maintenance and repair processes for tools and components

• Development of powder feeding nozzles and inside processing heads

• Rapid prototyping and rapid manu-facturing for production of metallic and ceramic parts and tools

• Polishing, structuring, smoothing and roughening by remelting metals,glass and plastics

• Functionalising of thin layers • Generation of structured layers

by remelting• Cleaning of surfaces


Core Areas

Micro TechnologyDr. Arnold Gillner

• Laser micro welding of metals and combinations of dissimilar classes of material

• Laser welding of thermoplastics and thermoplastic elastomers with diode and fiber lasers

• Laser micro soldering of metals and glasses

• Micro bonding of glass, semicon-ductors and ceramics

• Laser-assisted punching, bending and embossing processes

• Precision cutting and drilling of metals, ceramics, semiconductors and diamonds

• Micro structuring with Excimer and Nd:YAG lasers

• Micro drilling with solid-state lasers• Ablation and structuring processes

using picosecond and femtosecond lasers

• Nano structuring by interference-based processes and multi-photon excitation

• Micro tool engineering in hardmetals, ceramics and diamonds

• Surface structuring for functional component design

• Marking and labeling• Cutting and perforating of paper,

plastics and composites• Laser medicine for tissue therapy• Laser applications for biotechnology• Cell manipulation and biophotonic

analysis techniques• Photochemical processes• Consulting, feasibility studies,

and development of processes for laser-based manufacturing

• Process qualification under close-to-real production conditions

Modelling and SimulationProf. Dr. Wolfgang Schulz

• Generation of EUV-radiation • Design of optical resonators

for high power diode lasers • Beam guiding, beam shaping • Flow and heat transport in gases

and melt • Movement of phase boundaries • Dynamical models of removing,

cutting, welding and drilling • Evaluation and visualization of data

from measurement and simulation • Computational steering of

simulations• Numerical methods and codes,

finite elements and finite volumes in domains with free boundaries, adaptive cross linking

• Diagnostics of laser radiation and laser manufacturing processes

System TechnologyDr. Stefan Kaierle

• Process monitoring and control for quality assurance

• Process analysis and process development tools

• Development of online sensors and control systems (e. g. seam tracking,velocity measurement, positioning, distance measurement and control, multi-sensor technology and net-works)

• Automated testing of processing results (e. g. systems for seam evaluation)

• Process trials and testing • Feasibility studies • Pilot-run series• Integration of laser technology into

existing production facilities • Remote and scanner applications • Integrated processing heads • CAD/CAM-supported laser

processing • Offline path planning and simulation• Conception and design of plants • Pilot plants • Control techniques for laser plants • Consulting, education and training


Services

The services of the Fraunhofer Institutefor Laser Technology ILT are continuallybeing adapted to the practical require-ments of industry and include the solution of manufacturing problems as well as the realization of test series. In detail this means: • development of laser beam sources • manufacturing and assembling

technology • pulsed power supplies and control

technology • beam guiding and forming • development, set-up and testing

of pilot plants • process development • process monitoring and control • model and test series• integration of laser technology into

already existing production plants • X-ray and plasma systems

Cooperations with R&D-Partners

The Fraunhofer Institute for Laser Technology ILT is cooperating withR&D-partners in different ways: • realization of bilateral, company

specific R&D-projects with and without public support (contract for work and services)

• participation of companies in public-funded cooperative projects (cofinancing contract)

• production of test, pilot and prototype series by Fraunhofer ILT to determine the reliability of the process and minimize the starting risk (contract for work and services)

• companies with guest status at Fraunhofer ILT (special cooperation contracts)

By means of cooperation with otherresearch organizations and specializedcompanies the Fraunhofer Institute forLaser Technology offers solutions evenin the case of interdisciplinary tasks. A special advantage hereby consists inthe direct access to the large resourcesof the Fraunhofer Society.

During the implementation phase of new laser processes and products, companies can acquire ‘guest status’at the Fraunhofer Institute for LaserTechnology and use the equipment,infrastructure and know-how of the institute as well as install their own systems.

Services

Facilities

The usable floor space at the Fraun-hofer Institute for Laser Technology ILTamounts to more than 10,000 m2.

Technical InfrastructureThe technical infrastructure of the institute includes a mechanical and electronic workshop, a metallurgic laboratory, a photographic laboratory,a laboratory for optical metrology aswell as a department for design andconstruction. The Fraunhofer ILT alsohas a video conference room and acomputer network.

Scientific Infrastructure The scientific infrastructure includes a library with international literature,patent and literature data bases as well as programmes for calculation of scientific problems and data bases for process documentation.

Equipment The equipment of the Fraunhofer Institute for Laser Technology ILT is permanently being adapted to the state-of-the-art. At present, essentialcomponents are: • CO2-lasers up to 20 kW• lamps and diode pumped solid

state lasers up to 8 kw• disc lasers up to 8 kW• fiber lasers up to 4 kW• diode laser systems up to 3 kW • SLAB laser• excimer lasers• ultra short pulse laser• broadband tunable laser• five-axis gantry systems• three-axis processing stations • beam guiding systems• robot systems

• sensors for process control in laser material processing

• direct-writing and laser-PVD stations• clean rooms for assembly of diode

lasers, diode laser systems and diode pumped solid state lasers

• live sience laboratory with S1 and S2 classification

• devices for process diagnostics and high speed video analysis

• laser spectroscopic systems for the chemical analysis of solid, liquid andgaseous materials

• laser triangulation sensors for distance and contour measurement

• laser coordinate measuring machine • confocal laser scanning microscopy

Fraunhofer ILT abroad

Since its foundation, Fraunhofer ILT has been involved in many internationalcooperations. The objective of thesecooperations is to recognize newtrends and current developments andto acquire further know-how. The customers of Fraunhofer ILT can directlybenefit from this. Fraunhofer ILT carriesout bilateral projects as well as interna-tional cooperative projects with foreigncompanies and subsidiaries of Germancompanies abroad. These companiescan also contact Fraunhofer ILTthrough: • international subsidiaries of

Fraunhofer ILT • foreign cooperation partners of

Fraunhofer ILT• liaison offices of the Fraunhofer

Society abroad


© AVIA-Luftbild, AachenDipl.-Ing. Martin Jochum

Services

Employees 2007

Employees

• 6 Mitarbeiter haben ihre Promotionabgeschlossen

• 26 Studenten haben ihre Diplomarbeit am Fraunhofer ILTdurchgeführt

44 % Undergraduate assistants

8 % Administrative staff

13 % Technical staff

4 % External employees, trainees

31 % Scientists/engineers

Facts and Figures


Employees at the Fraunhofer ILT 2007 number

Personnel 137- Scientists and engineers 81- Technical staff 35- Administrative staff 21Other employees 123- Undergraduate assistants 113- External employees 7- Trainees 3Total number of employees at the Fraunhofer ILT 260

• 3 members of staff completedtheir doctorates

• 29 undergraduates carried out their final year projects at the Fraunhofer ILT

Revenues and Expenses

Expenses 2007 (100 %) Revenues 2007 (100 %)


Facts and Figures

44 % Material costs

17 % Investments

39 % Staff costs

35 % Additional financing from Federal Government, States and EU

21 % Basic financing from the Fraunhofer-Gesellschaft

44 % Industrial revenues (without investments)

Expenses 2007 Mill. EUR

- Staff costs 8,5- Material costs 9,6Expenses operating budget 18,1

Investments 3,8

Revenues 2007 Mill. EUR

- Industrial revenues 8,0- Additional financing from Federal Government,

States and the EU 6,3- Basic financing from the Fraunhofer-Gesellschaft 3,8Revenues operating budget 18,1- Revenues from projects abroad (already included in total) 2,1

Investment revenues from industry 0,5

Fraunhofer industry ρInd 47,2 %

Budget Growth

The following graph illustrates thebudget trend over the last 8 years.

Facts and Figures


14,8

17,5 17,116,4

17,4

18,618,0 18,1

Project revenues - public funding

Project revenues - industrial funding

Basic financing by Fraunhofer


References

March 2008Printed with the kind permission of our partners.

The companies listed here represent a selection of the Fraunhofer ILT’smany clients.

Short Profile

The Fraunhofer Center for Laser Tech-nology CLT, located in Plymouth,Michigan, has a 1250 m2 developmentcenter housing $9 million worth of themost varied, leading edge laser equip-ment in North America. This area hasestablished itself as the center for laserproduction, system integration andindustrial users in the USA.

The on-going goals are: • Integration in scientific and

industrial development in the USA• Accumulation of know-how at the

German parent institute through student exchange programs and early recognition of trends led by the USA

• Know-how growth at CLT through close cooperation with the Universityof Michigan and the Wayne State University as well as other leading US universities

• Local provision of services to international companies on both continents

• Strengthening position in the R&D market

The central philosophy of FraunhoferUSA is the creation of a German-American joint venture where give and take occur in harmony. The win-winsituation is an essential prerequisite for both sides. The Fraunhofer Gesellschaft is always interested inconsidering and trying to develop relationships on the American side that strengthen mutually.

The American partner universities’ interest concentrates on: • Using the competence of the

Fraunhofer Institutes • Using the experience in the

introduction of new technologies into the market

• Providing the connection between industry and university

• Providing practical training for students and graduate students

The CLT develops powerful, high-brilliance fiber lasers in collaborationwith the University of Michigan. Thebasic research is carried out at the university, while Fraunhofer undertakesthe development of high-brilliancepump sources, system integration, prototype construction and applicationtests. In this context, the CLT hasimplemented new technologies andmanufacturing methods that makediode lasers comparable to solid-statelasers in terms of their performance.The two establishments are currentlyworking together on a number of research projects in this area.

The CLT is also collaborating with Wayne State University to developcost-efficient manufacturing processesfor alternative energy production andstorage. The focus is on solar cells and lithium-ion batteries, which arecurrently going through a huge de-velopment spurt due to the trendtowards hybrid vehicles. Laser-inducedseparation and joining of similar, butalso dissimilar, classes of material suchas metal and plastic form the techno-logical basis for these processes.


Fraunhofer USA Center for Laser Technology CLT

In 2001, the Visotek company wasspun off from the Fraunhofer CLT inorder to market the center’s results inthe field of fiber-coupled high-powerlasers and specialized lens systems.2007 saw the launch of Arbor Photo-nics with the support of the Universityof Michigan to market developmentsin the area of flexible fiber lasers withdiffraction-limited beam quality andhigh pulse outputs.

Services

The CLT offers services in the field of laser processing, the developmentof optical components and speciallaser systems. This covers the entirespectrum from feasibility studies, process development to pre-seriesdevelopment as well as prototype production of laser beam sources andlaser systems which are ready to use.As an independent institution smalland mid-sized companies are given theopportunity to develop and test theirprocesses on Fraunhofer machineswith the help of Fraunhofer personnel.It is also possible to develop and testcomplete systems at the CLT. Ourcustomers come from the automobileindustry, construction industry, shipbuilding and medical engineering.

Employees

Both Germans and Americans areemployed at the CLT. The goal is torotate German employees so that thecollected experience can be broughtover to the parent institutes and tooffer German employees the opportu-nity to become further qualified duringtheir stay in the USA. Furthermore, students from the Technical Universityin Aachen write their diploma thesis in the USA.

Equipment

Current equipment in the CLT lab con-sists of: CO2 lasers with up to 8 kWpower, Nd:YAG laser from 250 W to4.4 kW, diode lasers from 30 W to 3 kW, frequency trebled Nd:YAG laserand excimer laser, a number of specialand hybrid optics, a series of 3, 5 and6 axes systems, as well as severalrobots.

References

• US Air Force Research Laboratories• Office of Naval Research• Michigan Lifescience Corridor• Alcan• Borg Warner Automotive• Dana Corporation• DaimlerChrysler• Ford Motor Company• General Motors• Hemlock Semiconductors• Nuvonyx• LASAG• PRC• Rofin Sinar• Spectra Physics• Siemens VDO• Trumpf• Visteon

Operating Budget 2007*

*Post-calculation has not occurred yet

Contact

Dr. Stefan HeinemannDirector

46025 Port StreetPlymouthMichigan 48170USA

Phone +1 734 354-6300Extension -210Fax +1 734 354-3335

[email protected]

Mio. US$

Operating budget 2.4 - Staff costs 1.1- Material costs 1.3


Fraunhofer USA Center for Laser Technology CLT

Short Profile

At the CLFA in Paris, the FraunhoferInstitute for Laser Technology ILT hasbeen cooperating since 1997 with leading French research organizations,including ARMINES, the École Natio-nale Supérieure des Mines de ParisENSMP, the École Nationale Supérieurede Mécanique et des MicrotechniquesENSMM in Besancon, the engineer uni-versity Louis de Broglie in Rennes andother major laser application centers in France. Multidisciplinary teams ofspecialists from Germany and Francework together on the transfer of laserassisted manufacturing processes toEuropean industry. The CoopérationLaser Franco-Allemande is a memberof the Club Laser et Procédés, theFrench association of laser manufac-turers and users.

The on-going goals of the CLFA are: • Integration into scientific and

industrial development in France• Growth in know-how by faster

recognition of trends in the fields of European laser and production technology

• Strengthening the position in the R&D market

• Assembly of a European competencecenter for laser technology

• Increase of mobility and qualificationlevel of employees

The CLFA is actively participating in therealization of European research and isa result of increasing link of applicationoriented research and development inthe field of laser technology in Europe.

The cooperation of the Fraunhofer ILTwith the French partners contributes to the improvement of the presence ofthe Fraunhofer Gesellschaft in Europewith the advantages for the Frenchand German sides equally taken intoconsideration. On an international scalethis cooperation further strengthens theleading position of European industryin the laser supported manufacturingprocess.

The French partners’ interests concen-trate on:• Using the competence of the

Fraunhofer ILT for French companies• Using the experience of the Fraun-

hofer ILT in the introduction of new technologies

• Providing the connection between industry and university with practicaltraining for students and graduate students

Together with their French cooperationpartners, ILT staff at the CLFA recentlyspun off a new company called Poly-Shape, which provides French custo-mers with services in the field of ge-nerative manufacturing processes. Its technology was presented to inte-rested industrial partners at a jointstand during the Paris Air Show at Le Bourget in June 2007.


Coopération Laser Franco-Allemande CLFA

¸

Services

The CLFA offers services in the field oflaser material processing. This coversthe entire spectrum from applicationoriented fundamental research andtraining, feasibility studies and processdevelopment to pre-series developmentand system integration. Small and mid-sized companies have the opportunityhere to get to know and test lasertechnology in an independent system.The open development platform allowsthe French customers to test and qua-lify new laser supported manufacturingprocesses.

Employees

At the CLFA employees from Franceand Germany work together. A mutualexchange of personnel occurs betweenAachen and Paris for joint projects. The employees therefore have theopportunity to improve their compe-tence especially with regard to mobilityand international project management.

Equipment

In addition to the technical resourcesavailable at the Fraunhofer ILT in Germany, the CLFA possesses its own infrastructure at the Centre desMatériaux Pierre-Marie Fourt, an out-station of the Ecole des Mines de Parisbased in Evry, south of Paris. Facilitiesinclude access to the center’s materialanalysis laboratories. The technicalinfrastructure of other French partnerscan also be shared on a project- orcustomer-specific basis.

Locations

Paris - at the École Nationale Supérieuredes Mines de Paris ENSMP, in centralParis.

Evry - on the premises of the Centredes Matériaux Pierre-Marie Fourt,roughly 40 km south of Paris.

Contact

Dr. Wolfgang KnappDirector

CLFA c/o Armines60 Boulevard Saint Michel75272 PARIS Cedex 6France

Phone +33 1 4051-9476 Fax +33 1 4634-2305

[email protected]/clfa.html


Coopération Laser Franco-Allemande CLFA

Competence by Networking

Six Fraunhofer Institutes cooperate inthe Network Surface Engineering andPhotonics VOP. Complementary com-petencies allow to adapt the researchactivities to the rapid technologicalprogress in all industrial applicationfields in a permanent, apace and flexibleway. Co-ordinated strategies, in linewith the current needs of the market,create synergy effects and provide a larger service for the benefit of thecustomers.

Fraunhofer Institute for ElectronBeam and Plasma Technology FEP

The ambition of FEP is the researchand development of innovative processes for the utilisation of highperformance electron beams and vacuum sealed plasmas for surfacetechnology. Priority is given to problemslike process monitoring, quality control,reproducibility, scaling, and profitability.

Fraunhofer Institute for PhysicalMeasurement Techniques IPM

The Fraunhofer IPM develops opticalsystems for applications in spectros-copy and light exposure technology. A major focus is the realisation of highlydynamical systems. Besides a rapidactivation, they require special compe-tencies in signal processing as realisedthrough robust and low maintenancemeasurement systems for the infra-structure monitoring of high speedroads.

Fraunhofer Institute forLaser Technology ILT

In the area of laser technology, theinteractive relationship between laserdevelopment and laser applications isof prime importance. New lasers allownew applications, and new applicationsset the stage for new laser systems.This is why the Fraunhofer ILT is conti-nually expanding its core competenciesthrough close cooperation with leadinglaser manufacturers and innovativelaser consumers.

Above: Fraunhofer FEPMiddle: Fraunhofer IPMBelow: Fraunhofer ILT


Fraunhofer Alliance Surface Engineering and Photonics VOP

Fraunhofer Institute for SurfaceEngineering and Thin Films IST

As an industry oriented R&D servicecentre, the Fraunhofer Institute forSurface Engineering and Thin Films ISTis pooling competencies in the areasfilm deposition, coating applicationand film characterization. Presently, theinstitute is operating in the followingbusiness fields: mechanical and auto-motive engineering; tools; energy;glass and facade; optics; informationand communication; life science andecology.

Fraunhofer Institute for AppliedOptics and Precision Engineering IOF

The core of the research activity ofFraunhofer IOF is optical systemsengineering aimed at a steady improve-ment of light control. The institute'sfocus is on multifunctional optical coatings, optical measurement systems,micro-optical systems, systems for thecharacterisation of optics and compo-nents for precision mechanics assem-blies and systems.

Fraunhofer Institute for Materialand Beam Technology IWS

The Fraunhofer IWS is conductingresearch in the areas of laser techno-logy (e.g. laser beam welding, cutting,hardening), surface technology (e.g.build-up welding), micro machining aswell as thin film and nano technology.The integration of material testing andcharacterisation into research anddevelopment constitutes and upgradesthe IWS spectrum.

Contact und Coordination

Speaker of the NetworkProf. Dr. Eckhard Beyer

CoordinationUdo KlotzbachTelephone: ++49 (0)351 / [email protected]

The Instituteswww.fep.fraunhofer.dewww.ipm.fraunhofer.dewww.ilt.fraunhofer.dewww.ist.fraunhofer.dewww.iof.fraunhofer.dewww.iws.fraunhofer.de

Above: Fraunhofer ISTMiddle: Fraunhofer IOFBelow: Fraunhofer IWS


IST

ILT

IPM

IOF

IWS

FEP

Fraunhofer Network Surface Engineering and Photonics VOP

The Fraunhofer-Gesellschaft

Research of practical utility lies at theheart of all activities pursued by theFraunhofer-Gesellschaft. Founded in1949, the research organization under-takes applied research that drives eco-nomic development and serves thewider benefit of society. Its services aresolicited by customers and contractualpartners in industry, the service sectorand public administration. The orga-nization also accepts commissions fromGerman federal and Länder ministriesand government departments to par-ticipate in future-oriented research pro-jects with the aim of finding innovativesolutions to issues concerning the indus-trial economy and society in general.

Applied research has a knock-on effectthat extends beyond the direct benefitsperceived by the customer: Throughtheir research and development work,the Fraunhofer Institutes help to rein-force the competitive strength of theeconomy in their local region, andthroughout Germany and Europe. Theydo so by promoting innovation, accele-rating technological progress, improv-ing the acceptance of new technologies,and not least by disseminating theirknowledge and helping to train theurgently needed future generation ofscientists and engineers.

As an employer, the Fraunhofer-Gesell-schaft offers its staff the opportunity todevelop the professional and personalskills that will allow them to take uppositions of responsibility within theirinstitute, in other scientific domains, inindustry and in society. Students work-ing at the Fraunhofer Institutes haveexcellent prospects of starting anddeveloping a career in industry by virtueof the practical training and experiencethey have acquired.

At present, the Fraunhofer-Gesellschaftmaintains more than 80 research units,including 56 Fraunhofer Institutes, at40 different locations in Germany. Themajority of the 13,000 staff are qualifiedscientists and engineers, who workwith an annual research budget of 1.3billion euros. Of this sum, more than 1 billion euros is generated throughcontract research. Two thirds of theFraunhofer-Gesellschaft’s contract re-search revenue is derived from contractswith industry and from publicly financedresearch projects. Only one third is contributed by the German federal and Länder governments in the form of institutional funding, enabling theinstitutes to work ahead on solutionsto problems that will not become acutely relevant to industry and societyuntil five or ten years from now.

Affiliated research centers and represen-tative offices in Europe, the USA andAsia provide contact with the regionsof greatest importance to present andfuture scientific progress and economicdevelopment.

The Fraunhofer-Gesellschaft is a recog-nized non-profit organization whichtakes its name from Joseph von Fraun-hofer (1787-1826), the illustriousMunich researcher, inventor and entre-preneur.

Fields of Research

The Fraunhofer-Gesellschaft concentrateson research in the following fields:• Materials technology, component

behavior• Production and manufacturing

technology• Information and communication

technology• Microelectronics, microsystems

engineering• Sensor systems, testing technology

• Process engineering• Energy and construction

engineering, environmental and health research

• Technical/economic studies, information transfer

Target Groups

The Fraunhofer-Gesellschaft is commit-ted to working for the economy as awhole, for individual businesses andfor society. The targets and benefi-ciaries of our research activities are:• The Economy: Small, medium-sized

and large companies from industry and service sectors can all benefit from contract research. The Fraun-hofer-Gesellschaft develops con-crete, practical and innovative solutions and furthers the applicationof new technologies.The Fraun-hofer-Gesellschaft is an important ‘supplier’ of innovative know-how to small and medium-sized com-panies (SMEs) not equipped with their own R&D department.

• Country and society: Strategic research projects are carried out at federal and state level, promoting key technologies or innovations in fields of particular public interest, e.g. environmental protection, energy technologies and preven-tative health care. The Fraunhofer-Gesellschaft also participates in technology programs initiated by the European Union.


The Fraunhofer-Gesellschaft at a Glance

Range of Services

The Fraunhofer-Gesellschaft developsproducts and services to full maturity.We work closely with our clients tocreate individual solutions, combiningthe efforts of several Fraunhofer insti-tutes if necessary, in order to developmore complex system solutions. Theservices provided by the Fraunhofer-Gesellschaft are:• Product optimization and

development through to prototype manufacture

• Optimization and development of technologies and production processes

• Support for the introduction of new technologies via:- Testing in demonstration centers

using highly advanced equipment- In-house training for the staff

involved- On-going support, also sub-

sequent to the introduction of new processes and products

• Assistance in assessing new technologies via:- Feasibility studies- Market analyses- Trend analyses- Life cycle analyses- Evaluation of cost-effectiveness

• Supplementary services, e.g.:- Advice on funding, especially

for SMEs- Testing services and quality

validation

The Advantages of Contract Research

Cooperation between all the Fraunho-fer institutes means that our clientshave access to a large number ofexperts covering a wide range of com-petencies. Thanks to common qualitystandards and professional projectmanagement, the Fraunhofer institutesensure that research projects achieveresults that can be relied on. Our insti-tutes are equipped with up-to-datelaboratory technology, making themattractive to companies of all sizes andfrom all industrial sectors. As a strongcommunity, we can provide our part-ners with reliability and economicbenefits: the Fraunhofer-Gesellschaftcan bring the knowledge already gained from cost-intensive preliminaryresearch into joint projects.

Research Facilities in Germany

The Fraunhofer-Gesellschaft at a Glance


Jointly shaping the future

The RWTH Aachen University Chairsfor Laser Technology LLT and the Tech-nology of Optical Systems TOS, alongwith the study and research depart-ment for the non-linear dynamics oflaser production methods NLD, repre-sent an outstanding cluster of exper-tise in the field of optical technologies.This permits supercritical treatment ofbasic and application-related researchtopics. The close cooperation with theFraunhofer Institute for Laser Technolo-gy ILT not only permits industrial con-tract research on the basis of soundfundamental knowledge, but also pro-vides new stimuli for the advanceddevelopment of optical methods, com-ponents and systems. The synergy ofinfrastructure and know-how is put toactive use under a single roof.

This structure particularly benefits up-and-coming young scientists and engi-neers. Knowledge of current industrialand scientific requirements in the opti-cal technologies flows directly into theplanning of the curriculum. Furthermore,undergraduates and postgraduate students can put their theoretical know-ledge into practice through projectwork at the three chairs and at theFraunhofer ILT. University courses aredrawn up jointly as well. The interdis-ciplinary collaboration between phy-sicians and engineers, for instance, has resulted in a university seminar foradvanced dental training being set up.Teaching, research and innovation -those are the bricks with which thethree university departments and theFraunhofer ILT are building the future.

Chair for Laser Technology LLT

The department of laser technology atRWTH Aachen University has been en-gaged in application-oriented researchand development in the fields of inte-grated optics, integrative production,ablation - modification - diagnosis(AMD), drilling and generative processessince 1985. Its activities in integratedoptics focus on investigating the inte-gration of high-power diode laserswith waveguide lasers and beam-shap-ing optical components, as well as thedevelopment of novel integrated powerlasers. The Cluster of Excellence »In-tegrative Production Technology forHigh-Wage Countries«, in which theLLT is involved, is working largely onthe integration of optical technologiesinto production processes and on theproduction of optical systems.

Ultra-short pulsed lasers are beingtested in basic experiments and usedto process nano and micro componentsof practical relevance by ablation, mo-dification or melting. Single-pulse, per-cussion and spiral drilling techniquesas well as trepanning are being used toprocess metals and multi-layer systemsmostly made up of metals and ceramics.This technology is useful for drillingholes in turbine blades for the aerospaceindustry, for example. Work in the fieldof generative processes focuses mainlyon new materials, smaller structures,higher build-up rates, micro coating,process monitoring and control, andthe development and enhancement ofthe university’s own plants and systems.

ContactProf. Dr. Reinhart Poprawe M. A.Director of the departmentPhone +49 241 8906-109Fax +49 241 8906-121 [email protected]

Academic director Dr. Ingomar Kelbassa(deputy director) Phone +49 241 [email protected]


Laser Technology at RWTH Aachen

Chair for the Technology of Optical Systems TOS

By establishing the Chair for the Tech-nology of Optical Systems in 2004,RWTH Aachen accorded recognition tothe increasingly central role of highlydeveloped optical systems in manufac-turing, the IT industries and the lifesciences. Research activities focus onthe development and integration ofoptical components and systems forlaser beam sources and laser devices.

Highly corrected focusing systems for a high laser output, beam homogeni-zation facilities and innovative beamshaping systems are all key compo-nents of laser systems used in produc-tion engineering. The performance of fiber lasers and diode-pumped solid-state lasers, for instance, is determinedby optical coupling and pump lighthomogenizers. Waveguide structuresfor frequency conversion are yet an-other topic of research. In the area ofhigh-power diode lasers, micro- andmacro-optical components are deve-loped and combined to form completesystems. In addition, assembly tech-niques are optimized.

ContactProf. Dr. Peter LoosenDirector of the department Phone + 49 241 8906-162Fax +49 241 [email protected]

Study and research departmentfor the non linear dynamics of laserproduction methods NLD

Founded in 2005, the study and re-search department for the non lineardynamics of laser production methodsNLD explores the basic principles ofoptical technology, with emphasis onmodeling and simulation.

Mathematical, physical and experimen-tal methods are being applied andenhanced to investigate technicalsystems. The application of mathema-tical models is helping to achieve abetter understanding of dynamic inter-relationships and to create new pro-cess engineering concepts. The resultsof these analyses are made available to industrial partners in the form ofpractical applications in collaborationwith the Fraunhofer Institute for LaserTechnology ILT.

The main educational objective is toteach a scientific, methodologicalapproach to modeling on the basis ofpractical examples. Models are derivedfrom the experimental diagnosis oflaser manufacturing processes and the numerical calculation of selectedmodel tasks. The diagnostic findingsand the numerical calculations arethen used to mathematically reducethe model equations. The solution characteristics of the reduced equationsare fully contained in the solutions tothe starting equations, and are notunnecessarily complex.

ContactProf. Dr. Wolfgang SchulzDirector of the study and researchdepartmentPhone +49 241 8906-204Fax +49 241 [email protected]


Laser Technology at RWTH Aachen

Cluster of Excellence

In the Cluster of Excellence »IntegrativeProduction Technology for High-WageCountries« process engineers andmaterials scientists based in Aachenare developing new concepts andtechnologies offering a sustainableapproach to industrial manufacturing.

A total of 18 chairs and institutes of RWTH Aachen, together with theFraunhofer Institutes for Laser Techno-logy ILT and for Production TechnologyIPT, are working on this project, whichin the first instance will run until theend of 2011.

Funding of approx. 40 million euroshas been granted to this Cluster ofExcellence, an initiative that unites thelargest number of research groups inEurope devoted to the objective ofpreserving manufacturing activities inhigh-wage countries.

Production in high-wage countries

The competition between manufac-turers in high-wage and low-wagecountries typically manifests itself as a two-dimensional problem, opposingproduction efficiency and planningefficiency.

In each case there are divergent ap-proaches. With respect to productionefficiency, low-wage countries tend to focus exclusively on economies ofscale, whereas high-wage countriesare obliged to seek a balanced equili-brium between scale and scope, inother words being able to satisfy cus-tomer requirements in respect of a particular product while at the sametime attaining a minimum productionvolume.

A similar divergence is evident with res-pect to the second factor, that of plann-ing efficiency. Manufacturers in high-wage countries aim to continuouslyoptimize their processes, using corres-pondingly sophisticated, capital-intensiveplanning methods and instruments, and technologically superior productionsystems. In low-wage countries, by contrast, production needs are betterserved by simple, robust, supply-chain-oriented processes.

In order to maintain a sustainable com-petitive advantage for production sitesin high-wage countries, it is no longersufficient to aim for a better positionthat maximizes economies of scale and scope or reconciles the opposingextremes of a planning-oriented and avalue-oriented approach. Instead, thegoal of research must be to cancel outthese opposite poles as far as possible.Ways must be found to allow a greatervariability of products while at thesame time being able to manufacturethem at cost levels equivalent to massproduction. This calls for value-optimizedsupply chains suited to each product,without excessive planning overheadsthat would compromise their cost-effectiveness.

Tomorrow’s production technologytherefore requires a thoroughly newunderstanding of these elementary,interrelated factors.

Integrative production

The Cluster of Excellence »IntegrativeProduction Technology for High-WageCountries« is aiming for the long-termgoal of increasing the competitivenessof German production technology. Theoverarching hypothetical solution liesin achieving the next higher level ofproduction integration.


Cluster of Excellence »Integrative Production Technology for High-Wage Countries«

The production dilemma: Scale/scopevs. planning-oriented/value-oriented,source: WZL Aachen.

Individualized production

Individualized production involves allowing for a high degree of productvariability and dynamics at costs equi-valent to those of mass production.Concepts are being developed that willenable the optimum combination andconfiguration of the different elementsin a production system to be identified.At the same time, advanced manufac-turing technologies such as selectivelaser melting (SLM) are being furtherrefined, and will eventually enableone-piece-flow concepts to be imple-mented at the same costs as mass production.

Virtual production

The introduction of greater flexibility inproduction processes necessarily resultsin an increased volume of preparatoryand planning activities. In the clusterdomain Virtual Production Systems,the aim is therefore to improve plann-ing quality while simultaneously re-ducing the quantity of work involved.This is being done by developing dis-crete models representing, for instance,laser welding processes and materials,linking them together and integratingthem in a virtual supply chain.

Hybrid production

By integrating a number of discreteprocesses in a single hybrid process, it is possible to reduce the length ofsupply chains and hence organizethem more efficiently. In the clusterdomain Hybrid Production, methodsare being investigated that will enablesupply chains to be systematicallyhybridized, and hybrid technologiessuch as laser-assisted incremental sheetforming are being developed.

Self-optimizing production

Self-optimization is a way of optimiz-ing production processes withoutincreasing the volume of upstreamplanning activities. In the clusterdomain Self-optimizing Production,methods and technologies are beingdeveloped to increase the cognitivecapabilities of production systems suchas a laser cutting plant or an assemblysystem for optical components.

Contacts

Fraunhofer ILTDipl.-Phys. Christian Hinke Phone: +49 241 [email protected]

Cluster of Exellence Office Dr. Lutz SchappPhone: +49 241 [email protected]


Cluster of Excellence »Integrative Production Technology for High-Wage Countries«

The official opening of theCluster of Excellence in October2006, source: WZL Aachen.

Source: WZL Aachen.


European Laser Institute ELI

Short Profile

The European Laser Institute was foun-ded in 2003 through an EU-funded ini-tiative. The ELI mission is to strengthenand further enhance Europe’s positionin the field of laser technology. In addi-tion, ELI aims to raise public awarenessof the significance and prospects of theEuropean laser technology industry. ELIis a network composed of more than20 leading research facilities includingthe Fraunhofer ILT as well as small andmedium-sized companies. This meansthat in addition to its participation inregional and national competence net-works, as an ELI member the FraunhoferILT is also part of an influential, Euro-pean-level laser technology network.

Furthermore, the international co-operation of industry and research,especially in the field of EU researchsupport, is forced by ELI. Amongst others, ELI creates adequate platformsby organizing conferences, workshops,summerschools etc. In the future, thisis supported by the cooperation withthe respective representations (e. g.EPIC, AILU, WLT). A strong cooperationwith the Laser Institute of America(LIA) already exists in the organizationof international conferences (ICALEO,PICALO, ALAW) as well as the Journalof Laser Applications (JLA).

Executive Commitee

The members of the committee representing the ELI are: • Dr. Stefan Kaierle (chairman),

Fraunhofer ILT, Germany• Abdelkrim Chehaibou,

Institut de Soudure, France• Dr. François De Schutter,

Lasercentrum Vlaanderen, Belgium• Dr. Paul Hilton,

TWI, Great Britain• Dr. Wolfgang Knapp,

CLFA, France• Prof. Dr. Veli Kujanpää,

Lappeenranta University of Technology, Finland

• Prof. Dr. José Luis Ocaña,Centro Láser U.P.M., Spain

Contact

Dr. Stefan KaierlePhone +49 241 8906-212Fax +49 241 [email protected]

Short Profile

PhotonAix, the Competence Networkfor Optical Technologies and Systems,was founded in 2002 by the FraunhoferInstitute for Laser Technology ILT, theFraunhofer Institute for ProductionTechnologies IPT and the Laboratory of Machine Tools and ProductionEngineering WZL of the RWTH Aachen.Aachen-based Photon Aix and eightother regional competence networksin the field of optical technologiesmade up of more than 400 membersfrom research and industry are concen-trating their skills with the mutual goalof promoting optical technologies intheir respective regions.

These networks represent the full range of »Made in Germany« opticaltechnologies, from laser-based mate-rials processing and biophotonics totransportation and aerospace applica-tions. The competence networks areprimarily engaged in providing servicessuch as technology management,start-up consulting, regional techno-logy and industry marketing, qualitytraining and education initiatives, andfostering communications within thenetwork. The regional concentration of expertise leads to practical, real-timeproblem resolution and an acceleratedtransfer of research results into market-ready products.

Highlights 2007

Besides participating in Photonics West2007 in San Jose, USA, and LASER2007 in Munich as a joint exhibitorwith the other German competencenetworks for optical technologies, themajor events of 2007 were the Euro-pean technology platform Photonics21and the formation of the North Rhine-Westphalian initiative NRW-Photonics.

The objective of the technology plat-form Photonics21 is to further streng-then Europe’s leading role in the fieldof optical technologies and to coordi-nate joint research and developmentactivities.

A study carried out with the EuropeanCommission and published in December2007 forecasts continued success foroptical technologies in the future.Annual revenues generated by opticaltechnologies in Europe, currently at 49 billion euros, are predicted to growat an average of 7.6 % per year until2015. About 250,000 people in Europeare already working in the field of op-tical technology today.

Contact

PhotonAix e. V.Dipl.-Phys. Christian HinkeManaging directorSteinbachstraße 1552074 Aachen

Phone +49 241 8906-352Fax +49 241 [email protected]


PhotonAix e. V.Competence Network for Optical Technologies

Some Special Research Results from the Business Areas of Fraunhofer ILT

Laser and Plasma Sources 35 - 60

Laser Material Processing 61 - 106

Laser Plant and System Technology 107 - 118

Laser Measurement and Testing Technology 119 - 139

Note from Institute DirectorWe would like to point out that thepublication of the following industryprojects has been coordinated with our customers. In principle, industryprojects are subject to the strictestobligation to maintain secrecy. Wewould like to take this time to thankour industrial partners for their willing-ness to have their reports listed pub-lished.


Research Results 2007

Laser and Plasma Sources

This business area encompasses thedevelopment of diode laser modulesand systems as well as diode-pumpedsolid-state lasers with different reso-nator structures (stab,slab,fiber), the design of new diode laser structures,the microassembly of diode lasers and optical components, and the develop-ment of plasma systems.

For more than 10 years spinn-offs ofthe Fraunhofer ILT are set up in the framework of some projects. In coope-ration with the Fraunhofer IAF newstructures are being designed whichpermit the manufacture of diode lasersdemonstrating higher beam quality. The business area continues to enjoy a unique reputation in the assembly of high-power diode lasers and in particular the installation of automatedassembly and test facilities. Work inthe plasma technology sphere focuseson the development of EUV beamsources for semiconductor lithography.The main target markets for the busi-ness area as a whole are laser machining,medical engineering and metrology,along with the component market forinformation and communications tech-nology.


Business AreaLaser and Plasma Sources

Automated assembly technologyfor miniaturized lasers for materialsprocessing. Microslab demonstrator on a ceramic substrate.

Vaporizing heat sink for diode lasers 38

Single-mode fiber-coupling of frequency-stabilized tapered lasers 39

Modeling of frequency doubling in periodically poled non-linear crystals 40

Superpulsed diode lasers for laser materials processing 41

Fiber-coupled diode lasers for pumping fiber lasers 42

Transformation optics for de-coatingmetal parts by high-power laser 43

Automated assembly technology for miniaturized lasers for materials processing 44

InnoSlab-based amplifier for sub-ns laser pulses with an energy of 100 mJ 45

Femtosecond InnoSlab amplifiers of high average output 46

Highly efficient laser pulse source for a space-based LIDAR system 47

Diode-seeded fiber amplifier for LIDAR applications 48

Integrated frequency-stabilizing electronics for LIDAR-based pulsed lasers in aerospace 49

Energy scaling of pulsed Nd:YGG-based laser beam sources at 935 nm 50

Broadband tunable Ti:sapphire laser with nanosecond pulses 51

Compact frequency converter for tunable laser radiation 52

Q-switched Nd:YAG laser with an average output in the kW range for surface processing 53

Linearly polarized fiber lasers with high average output 54

White light interferometer for characterizing optical coatings for ultra-short pulse lasers 55

Generating sub-ns laser pulses of variable pulse duration with pulse energy in the mJ range 56

Probe for the analysis of a laser-induced plasma 57

Ray tracing in inhomogeneous media 58

Surface analysis with extreme ultraviolet radiation for the characterization of thin films 59

Data transmission with low latency 60


Contents

Task

Heat management for actively cooledindustrial diode laser systems calls for ahigh flow of heat and a low tempera-ture difference between the cooled sur-face and the cooling medium. It is ad-vantageous to have as small a coolingmedium flow rate as possible in orderto avoid erosion and corrosion in theheat sink, as these shorten the service life of the heat sink and thus also of thediode laser. These requirements can bemet by utilizing the vaporization processas a cooling principle, given that theevaporation of a liquid extracts largequantities of heat from its environmentin the right conditions.

Method

In accordance with the requirements, a selection of different cooling mediais assembled and then further narroweddown in preliminary tests. The heatsink prototypes, whose dimensions aresimilar to those of commercially avai-lable microchannel heat sinks, are

designed on the basis of flow tests.The heat sink prototypes are to be accurately examined using a speciallydeveloped test rig that predeterminesthe heat flow, registers the tempera-ture at several positions on the heatsink, and measures the flow rate andthe temperature of the cooling medium.

Results and Applications

Investigations of various prototypes of a vaporizing heat sink and various cool-ing media are being carried out usingthe purpose-built test rig in order toverify their influence on the vaporiza-tion process. In these tests, the consis-tency of the cooled surface and thegeometry of the vaporization chamberare varied. The heat sinks are beingfurther optimized based on the resultsof this investigation, and can nowachieve a heat flow of 40 W on a sur-face measuring 2 x 10 mm2 with atemperature difference of 20 K bet-ween the cooling medium and thecooled surface. It is hoped to achieve a cooling capacity of 80 W in a sub-sequent stage of development.

Contacts

Dipl. Phys. M. Werner, Tel.:[email protected]. K. Boucke, Tel.: [email protected]


Vaporizing heat sink for diode lasers

Test rig for examining different prototypes of a vaporizing heat sink.

Task

Numerous applications require fre-quency-stabilized diode laser modulesthat enable the laser beam to be coupled into a single-mode fiber(SMF). Some examples of such applica-tions are pump sources for solid-statelasers, fiber lasers, Raman amplifiersand frequency-doubling (second har-monic generation) crystals.

Until now, the type of laser most com-monly used in such modules has beenthe ridge laser, which can achieve anoutput of up to 400 mW in an SMF.Recent improvements in design havenow resulted in new tapered lasersthat feature a higher optical outputpower than that of ridge lasers withonly a slight deterioration of the beamquality. The aim is therefore to developa frequency-stabilized tapered lasermodule that can achieve a higher out-put than the available ridge laser mo-dules in an SMF.

Method

The laser’s frequency is stabilized usingan external resonator. The resonator is set up either in front of the taperedlaser’s front facet with the help of avolume Bragg grating integrated in a micro-lens (VHG-FAC) or on the backof the tapered amplifier with a fiberBragg grating (FBG). Stabilization witha VHG-FAC requires no additionaladjustment, whereas rear FBG stabili-zation requires the same amount ofadjustment as SMF coupling.

The module measures 32 x 32 x 62 mm2.The laser heat sink is cooled and itstemperature regulated by a Peltierelement. The materials used in themodule are selected such that theirinevitable thermal expansion has as

little influence as possible on the effi-ciency of the SMF coupling process.The optical fiber-coupling and frequen-cy-stabilizing elements are mountedusing silica glass and Macor compo-nents, and fixed with a UV-hardenedadhesive once they have been adjusted.

SMF coupling of a tapered laser requi-res the use of separate lenses that col-limate the fast and slow axes, as thistype of laser is highly astigmatic. Theoptical system used for SMF couplingtherefore consists of three lenses. TheSMF is mounted in an FC/APC con-nector, in which the fiber facet is tiltedby 8° to the optical axis to preventback-reflections into the laser.


As regards frequency stabilization, it hasbeen demonstrated that an FBG-stabi-lized tapered amplifier with a line widthof 0.11 nm has a narrower bandwidththan a VHG-FAC-stabilized tapered laserwith a line width of 0.13 - 0.4 nm. Withan output of 5 W, however, the taperedlaser is more powerful than the taperedamplifier, which only has anoutput of 1.6 W. With respect to SMFcoupling, the initial interim result hasbeen a coupling efficiency of > 50 percent and a fiber-coupled power of ≈ 500 mW. These values, and thus theperformance of available modules onthe market, are to be exceeded by far in the near future by further optimizingthe lens system for tapered lasers.

Contacts

Dip.-Ing. G. Kochem, Tel.: [email protected]. K. Boucke, Tel.: [email protected]


Single-mode fiber-coupling of frequency-stabilized tapered lasers

10 mm

Above: Module with a frequen-cy-stabilized tapered amplifier.Below: Frequency stabilizationby FBG and VHG-FAC.

Task

Using semiconductor laser diodes it isnow possible to produce laser radia-tion of good beam quality in a widerange of frequencies and with outputsof up to several watts (over 100 Wwith inferior beam quality). In thegreen frequency range, however, nosuitable semiconductor materials areavailable. One possibility for producinggreen radiation is provided by frequen-cy doubling of infrared radiation. Inthe project described here, the aim isto convert 1060 nm cw radiation withan output of 5 W into 530 nm radia-tion. As this power is relatively small for efficient non-linear processes, peri-odically poled crystals will be used forphase matching, because this enableslarge effective coupling coefficients to be utilized. The process will then beoptimized with the assistance of simu-lation calculations.

Method

Three-wave coupling, of which fre-quency doubling is a special case, iswell understood theoretically. Approxi-mation solutions exist for estimatingthe conversion efficiency. Such appro-ximation solutions can also be used forperiodically poled crystals. However,when it comes to examining the influ-ence of the beam profile, temperatureeffects as a result of absorption etc.,numerical models have to be applied.For this purpose, a split-step methodwas implemented in which the wavepropagation and the non-linear coupl-ing are calculated alternately in two

separate steps: The absorption of theradiation as it passes through the crys-tal is calculated, from this the tempe-rature in the crystal is determined bymeans of a finite-element method, andin a further pass the refraction indices,which determine phase matching, arecalculated with the aid of this location-dependent temperature. The proce-dure is repeated until a stationary con-dition is reached.


LiNbO3, which exhibits a very highcoupling coefficient, is used in the pro-cess. The figure shows the rise in thefrequency-converted output along thedirection of propagation given opti-mized values for radius and position of the beam waist. For the blue curvethe periodic structure was explicitly re-flected in the numerical algorithm; forthe green curve a homogeneous crys-tal with 100 per cent phase matchingand a correspondingly adapted valuefor the coupling coefficient was as-sumed. At 1060 nm the irradiated output amounts to 5 W. The modelcalculations indicate conversion effi-ciencies of almost 40 percent.

Ansprechpartner

Dr. R. Wester, Tel.: [email protected]. K. Boucke, Tel.: [email protected]


Modeling of frequency doubling in periodically poled non-linear crystals

Rise in the output of the frequency-converted wave (530 nm) along thedirection of propagation at an irra-diated output of 5 W(1060 nm).

Task

Compared with other laser types diodelasers offer higher efficiency, greatercompactness and lower system costs.Diode lasers have therefore becomeestablished as radiation sources in many areas of medical applications and materials processing. In applicationswhere high peak pulse outputs are required, however, it has not been possible to use diode lasers owing totheir restricted pulsability. These in-clude marking and the removal of coatings. For such applications the aim is to develop a diode laser systemwhich is operated with short pulses (< 500 ns) at about ten times largerelectrical current compared to the no-minal operation resulting in distinctlyhigher intensities on the workpiecethan conventional diode lasers.

Method

The implemented demonstrator usesshort bars with an aperture of 800 µmx 1 µm. The diode lasers are operatedwith a pulse power source which,using adequately short pulses, enablesthe operation at ten times larger elec-trical current compared to the nominaloperation in CW or long pulse mode.To increase the output further, twobars are superpositioned by means ofpolarization multiplexing, and to achieveas high a power density as possible on the workpiece, the aperture of theshort bar is anamorphotically imagedonto the workpiece.


The short bars employed are operatedwith a pulse current of up to 250 A,which enables a maximum pulse outputof 300 W per bar to be attained at apulse length of 100 ns. By imaging theexit aperture of the short bar, a spotmeasuring 400 µm x 5 µm is attained,which corresponds to a power densityof 30 MW/cm2. With the new system, it has been possible to successfully demonstrate various applications, including the removal of paint layersand the marking of plastics.

The project was funded by the GermanMinistry of Economics and Technology(BMWi) under project number 14508 N/1.

Contacts

Dipl.-Ing. M. Traub, Tel.: [email protected]. H.-D. Hoffmann, Tel.: [email protected]


Superpulsed diode lasers for laser materials processing

Demonstrator of a superpulseddiode laser system.

Task

To pump fiber lasers, brilliant, fiber-coupled diode lasers based on con-duction-cooled heat sinks are required.At a pump wavelength of 976 nm forYtterbium fiber lasers, the aim is toprovide 50 W per module from a fiberwith a core diameter of 105 µm. Thiscore diameter is compatible with com-mercial fiber combiners which are usedfor power scaling of the pump source.

Method

Two concepts for fiber coupling ofconduction-cooled diode lasers arebeing examined. The first concept is based on five 90 µm wide singleemitter diodes, each with a laser out-put of 7 W, which are optically stackedand coupled into the fiber with spheri-cal optics. The distributed arrangementof the beam sources ensures efficientheat removal of the power loss andthus the high absolute radiant powerof 7 W per individual diode. Opticalbeam forming facilitates the efficientcoupling of each individual emitter diode by means of one adjustmentstep. Compared with the state of theart, which is to use one individual emitter,10 individual emitters are coupled intoone fiber by optical stacking and po-larization coupling. The second con-cept is based on 800 µm broad stripeemitters with 28 W of laser power ineach case (diode laser array with 4 - 5emitters and a high fill factor). Two po-larization-coupled broad stripe emitterswhose beam profile has been symme-trized with a microstep mirror are cou-pled into the fiber with anamorphoticimaging optics. The concentrated ar-rangement of the diode lasers permitseasy beam forming using individuallenses without microlens arrays at acomparatively high power density.


The fiber-coupled diode laser pumpmodules achieve a laser output of 43 W from a fiber with a diameter of 105 µm based on two broad stripeemitters, and 60 W based on 10 in-dividual emitters. The diode lasers presented are used as pump sourcesfor fiber lasers. The pump wavelengthscan be adapted for optical pumping ofsolid-state lasers. Further uses includedirect applications like plastics process-ing and laser medical engineering.

Contacts

Dipl.-Ing. C. Wessling, Tel.: [email protected]. H.-D. Hoffmann, Tel.: [email protected]


Fiber-coupled diode lasers for pumping fiber lasers

Fiber-coupled diode laser pump modules (fiber diameter 105 µm, numerical aperture 0.22):Above: 60 W module based on individual emitter diodes.Below: 43 W module based on broad stripe emitter diodes.

Task

De-coating by pulsed laser has a signi-ficant advantage over conventionalcleaning processes in that it enables in-dividual layers to be ablated selectively.Contamination of the surrounding areacan be reliably prevented by siphoningoff the solid and gaseous ablation pro-ducts and by abstaining from the use of chemicals. Using a 1-D scanner, thelaser beam is deflected perpendicularlyto the feed direction inside special pro-cessing optics for the removal of surfacecoatings. However, the achievable ab-lation rate is limited by the scanner’smaximum deflection frequency, parti-cularly at laser outputs of more thanone kilowatt average laser power.

Method

The deflection frequency of the scan-ner is limited due to the mass momentof inertia of the applied mirror. A solu-tion is to use transformation optics to achieve a beam aspect ratio of 1:4before the laser beam hits the scannermirror with a symmetrical power densitydistribution. In this way, it is possible to use a mirror with the same surfacearea but only half the width, which re-duces its moment of inertia by a factorof four. This, in turn, enables a signifi-cantly higher scanning frequency.


Based on the transformation concept,an optical processing system for de-coating was developed and tested suc-cessfully. The ablation rate was increa-sed by 30 percent compared to con-ventional scanner optics, achieving amaximum scanning frequency of 200Hz. The maximum scanning speed rea-ched was 24 m/s, using focusing opticswith a focal width of 160 mm, whichproduces a deflection width of up to60 mm. Such deflection widths areachieved due to the larger focal widthof the focusing optics and the reducedinertia of the mirror compared to con-ventional optical systems. The result isa significantly increased process speed.

The optical system can achieve an efficiency of 90 percent, and is suitablefor use in combination with fiber-coupledNd:YAG lasers with an output of up to2 kW.

Contacts

Dipl.-Ing. M. Traub, Tel.: [email protected] Dipl.-Phys. C. Johnigk, Tel.: [email protected] Dipl.-Ing. H.-D. Hoffmann, Tel.: [email protected]


Transformation optics for de-coating metal parts by high-power laser

Transformation optical system.

Task

Laser systems for labeling, marking andengraving metal, plastics and ceramicsare used in a wide variety of applicationsand already occupy a fast increasing share of the global market for labelingsystems.

Automating the assembly of such lasersopens up the possibility of producingand supplying them in large batches atcompetitive prices. In the cluster of excel-lence ‘Integrative Production Technologyfor High-Wage Countries’, a miniaturizedslab laser is currently being designedwhich meets the requirements of auto-mated assembly. Suitable strategies for robot-based assembly are also being developed.

Method

The InnoSlab laser developed at theFraunhofer ILT enables system compo-nents to be arranged in a compact andplanar way, thus making it easier touse automated assembly technology to build the microslab laser. In addition,the use of a ceramic base plate facili-tates the hybrid integration of opticaland electrical functions via a structured,electrically and thermally conductivelayer. The components are fixed withthe degree of freedom required for later adjustment using joining tech-niques that satisfy the given thermaland electric requirements and ensurelong-term-stable, accurately positionedassembly, without the need for addi-tional adjusting aids. To ensure cost-efficient manufacturing, strategies arebeing developed to enable the assem-bly of functioning lasers, even given

a static tolerance distribution of indivi-dual laser components. The aim is tosignificantly cut costs through automa-ted assembly, adapted constructiontechniques and an optimized systemdesign.


A microslab laser system is being testedin the laboratory with regard to the required assembly accuracy of thecomponents employed. On the basis of homogenizing pump optics, the lasercan be assembled in an extremelycompact arrangement using a microlens array for pump beam forming anda positively confocal hybrid resonatorwith an overall length of 150 mm. Thelaser can achieve an output of 8 W cwwith excellent beam quality. Further-more, proof of principle has beenestablished that a functioning pumpoptical system can be assembled in aplanar configuration using automatedjoining processes. A semi-automatedassembly process using 6-axis parallelkinematics is currently in the develop-ment stage.

Contacts

Dipl.-Ing. J. Dolkemeyer, Tel.: [email protected]. M. Funck, Tel.: [email protected]. H.-D. Hoffmann, Tel.: [email protected]


Automated assembly technology for miniaturized lasers for materials processing

Above: Microslab demonstratoron a ceramic substrate.Below: Conventionally assembledlaboratory setup.

Task

A collaborative project funded by theBMBF aims to develop a laser plasmasource for generating EUV radiation inthe wavelength range between 2.3 nmand 4.4 nm. This spectral range is called the ‘water window’ and can beused to examine biological samples,for instance. Plasma generation requireslaser pulses in the sub-ns regime witha pulse energy of more than 100 mJ ata pulse repetition rate of 1 kHz.

Using an InnoSlab-based amplifier,seed pulses with an energy of 2.5 mJand a duration of between 500 ps and1 ns are to be amplified to 100 mJ at a pulse repetition rate of 1 kHz. Thisapplication requires a good beam quality of M2 < 4.

Method

The target parameters can be achievedby means of a three-stage chain com-prising an InnoSlab pre-amplifier andtwo InnoSlab power amplifiers. Thepre-amplifier is pumped from one endby eight diodes, and the two poweramplifier stages from two ends of theslab crystal by sixteen diodes. The am-plifier resonator is operated exclusivelywith planar optics, which reduces thetime and cost of development.

Particular attention is given to aspectssuch as suppressing parasitic oscillationsof the amplifier, reducing ASE effects,and keeping below the optical system’sdamage thresholds.


The first amplifier stage can achieve a stable peak pulse energy of 65 mJ at a pulse repetition rate of 1 kHz. No degradation of the optics was observed in a series of fatigue tests lasting several hours.

The beam quality and the shape of the seed pulses remain virtually un-changed. In order to reach 100 mJ, thesystem is currently being extended bytwo identical InnoSlab amplifier stages.

Contacts

Dipl.-Phys. D. Esser, Tel.: [email protected]. M. Höfer, Tel.:[email protected]. H.-D. Hoffmann, Tel.: [email protected]


InnoSlab-based amplifier for sub-ns laser pulses with an energy of 100 mJ

InnoSlab-based pre- and power amplifiers.

Task

For many years, the Fraunhofer ILT hasdeveloped InnoSlab amplifiers basedon neodymium-doped crystals. Now,the institute intends to use also Ytter-bium-doped materials (YAG, KGW,KYW) in a slab geometry in order toamplify pulses with durations of lessthan 1 ps. The aim is to reach an ave-rage output of several 100 W, whichcan be achieved using a seed power of ~1 W at repetition rates of > 10 MHzwithout chirped pulse amplification.

Method

Using high-power diode lasers of thelatest generation, a high-brilliancepump source with an average outputof 400 W was developed. This providesthe high pump power densities requiredfor efficient amplification in Ytterbiumdoped crystals. A slab crystal of 10 x10 x 1 mm3 can be pumped bilaterally

with a total average output of 800 Wusing two sources. Efficiency can beimproved by folding the transmittedpump radiation back in a moderatelydoped laser medium to increase thepump intensity.


In a preliminary test prior to full assem-bly, a unilaterally pumped InnoSlabamplifier was implemented. TheYb:YAG crystal, pumped with a powerof 400 W, was seeded with a commer-cial laser oscillator (300 mW, 277 fs,63 MHz). An average power of 77 Whas been achieved with a pulse durationof 786 fs and a beam quality of M2 < 1.3.These data correspond exactly to thesimulation calculations carried out pre-viously. In the case of bilaterally pum-ped amplifiers, the numerical simulationspredict average outputs of > 300 W.This opens up new applications for ultra-short pulsed lasers in the field ofhigh-rate materials processing, plasmageneration, and efficient production ofshort-wave radiation through non-linearprocesses.

Contacts

Dr. P. Rußbüldt, Tel.: [email protected]. T. Mans, Tel.: [email protected]. H.-D. Hoffmann, Tel.: [email protected]


Femtosecond InnoSlab amplifiers of high average output

Bilaterally pumped fs InnoSlab amplifier.

Task

Spatially resolved measurements ofconcentrations of molecules (such aswater vapor or carbon dioxide) or aero-sols in the atmosphere using LIDAR(Light Detection and Ranging) requirehighly stable, narrowband, short laserpulses of high energy. The key criteriawhen selecting a suitable laser sourcefor satellite-based operation are thatthe system is reliable and efficient, andof a compact and light design.

In this project, a laser source is requi-red which generates laser pulses withan energy of at least 70 mJ and a wave-length of 1064 nm at a repetition rate of 100 Hz. These laser pulses arethen tripled in frequency to at least 21 mJ and 355 nm outside the resona-tor with the help of nonlinear crystals.The system should be capable of ope-rating in space continuously for at least3 years.

Method

A Q-switched resonator with a diode-pumped Nd:YAG rod serves as the laser oscillator. Pulse generation is fre-quency-stabilized with the help of aseed laser. This enables laser pulses tobe generated in excellent spatial andtemporal quality.

Downstream of this is a diode-pumpedNd:YAG amplifier operating on the InnoSlab principle, which amplifies theenergy of the laser pulses without sa-crificing quality, thus largely determi-ning the efficiency of the overall sys-tem. The special geometry of the Inno-Slab laser provides the ideal basis for ahighly efficient amplification process,and also renders the system insensitiveto degradation of the pump diodesand temperature fluctuations.


Using a flexible laboratory setup,1064-nm laser pulses with more than80 mJ of energy were generated andthen converted to pulses of more than30 mJ and 355 nm by means of non-linear crystals. The system’s optical-optical efficiency exceeds the require-ments by far. In order to demonstratethe laser’s specific suitability for use ina satellite, the first step was to trans-late the frequency-stabilized oscillatorinto a compact design with a base areaof 400 x 200 mm2. The cascaded slabamplifier stages featured in the designprovide an excellent means of scalingto higher pulse energies such as thoserequired, for example, in LIDAR systemsused for molecule detection.

Contacts

Dipl.-Phys. J. Luttmann, Tel.: [email protected]. H.-D. Hoffmann, Tel.: [email protected]


Highly efficient laser pulse source for a space-based LIDAR system

Above: Preliminary design ofthe satellite-based laser source(exploded diagram).Below: Compact design of the frequency-stabilized laseroscillator.

Task

Pulsed LIDAR systems emit short laserpulses and can determine the distanceto diffusely scattering objects by measur-ing the signals’ time delay. The perfor-mance potential depends directly on thelaser system itself. The repetition rate(approx. 0.5 to 2 MHz) is defined by thenumber of measuring points required in a given time period. The maximumrange of the measuring instrument ispredetermined by the pulse peak output(greater than 1 kW) in connection withthe beam quality (M2 < 1.5). Temporalproperties such as pulse duration and jitter determine the achievable accuracy.

As part of an internal Fraunhofer pro-ject, the ILT is currently collaboratingwith the Fraunhofer IPM to develop a fiber laser system for scanner-based dis-tance measurement.

Method

In order to meet the high demands ontiming, i.e. externally triggerable pulseswith durations in the sub-ns range andlow pulse jitter combined with the ne-cessary pulse peak outputs in the kilo-watt range and average outputs of se-veral watts, the laser must be designedin an oscillator-amplifier configuration.The temporal and spectral propertiesof the laser pulse are determined by apulsed laser diode, whose signal runsthrough a two-stage fiber amplifier arrangement. This concept offers maxi-mum variability with regard to thetemporal parameters, such as free triggerability within a time window of2 µs and variable repetition rates.

Fiber amplifiers with fully fiber-integra-ted structures have several advantagesover conventional laser-rod amplifiers:• They do not require adjustment.• The beam parameters are not

influenced by the power setting.• A high amplification and efficiency

can be achieved.


The prototype presented here is passivelycooled and equipped with controlelectronics that monitor the laser’sfunctions. Internally, they monitor suchfactors as the temperatures of the laserdiodes, while externally they ensurethe laser is not damaged by missingtrigger signal, for example.

Other possible areas of application for this laser system are measurementtechnologies with temporally shapedlaser pulses, micro-materials processing,life sciences or precision laser drilling.

Contacts

Dipl.-Phys. J. Geiger, Tel.: [email protected]. H.-D.Hoffmann, Tel.: [email protected]


Diode-seeded fiber amplifier for LIDAR applications

Above: Prototype of a pulsedfiber amplifier for LIDAR applications.Below: Laboratory setup of the fiber amplifier.

Task

High-resolution measurements of windspeeds or the concentration of gasessuch as water vapor, methane and CO2

in the atmosphere using LIDAR (LightDetection And Ranging) require highlystable narrowband laser pulses withbandwidth-limited pulse durations in the range of 10 - 100 ns. These are usually generated by seeding a Q-switched laser with a highly stablelow-power narrowband laser sourcewhile actively stabilizing the resonatorlength. The systems required for aero-space applications typically have a pulserepetition rate in the 100 Hz range. Insome applications, it is advantageousto generate pulse trains with as small a pulse distance as possible. Frequency-stable operation must also be ensuredunder the influence of strong vibrations.

Method

The methods selected to adjust the re-sonator length are based on measure-ments of the seed signal and enablethe suppression of mechanical oscilla-tions up to the multi-kilohertz range.In addition, the ‘Ramp-Delay-Fire’ pro-cess developed and patented by theFraunhofer ILT enables a dynamicallyoptimized prediction of the pulse emis-sion time accurately to within a fewtens of nanoseconds. The control unittakes the form of electronics integra-ted in SMD technology. The use ofFPGA- and microcontroller-based sub-processes combines a strict programsequence determined down to the nanosecond range with the flexibilityrequired for the dynamic decision-making process. By cascading severalcontrol circuits and using dynamic value tables, it is possible to achievenot only frequency stability, but alsoother operational characteristics such

as pulse energy stability. By varying theparameters, it is possible to set operat-ing points in such a way that all theseoperational characteristics are fulfilledsimultaneously. The types of sensors,actuators and control techniques em-ployed vary according to the specificapplication.


In the experiments carried out at theFraunhofer ILT, a pulse bandwidth ofless than 8 MHz (pulse repetition rate100 Hz, pulse duration 30 ns, pulseenergy 12 mJ, M2 < 1.1) and an excep-tionally high frequency stability wereachieved even under the influence ofmajor disturbances to the resonatorlength. When generating double- andtriple-pulse trains, it was possible to reduce fluctuations of the pulse energyto just a few percent, at a pulse dis-tance of 100 µs. At present, the re-searchers are investigating ways of increasing the pulse repetition rate inorder to create resolution advantagesfor helicopter-borne LIDAR instruments.

Contacts

Dipl.-Ing. V. Morasch, Tel.: [email protected]. H.-D. Hoffmann, Tel.: [email protected]


Integrated frequency-stabilizing electronics for LIDAR-based pulsed lasers in aerospace

Integrated frequency-stabilizingelectronics.

Task

The task is to evaluate the duration-dependent absorption of narrow-bandlaser pulses for satellite-based measure-ment of climate-relevant water vapordistributions with the DIAL process.This requires the availability of specificwavelengths in the range of suitablewater vapor absorption lines around935 nm.

Innovative mixed-garnet crystals offerthe possibility of using direct diode-pumped systems in this wavelengthrange, which in turn makes it possibleto achieve the high efficiency and lowcomplexity necessary for space missionsas compared with established titaniumsapphire lasers or optical parametricoscillators. A cooperative project between Hamburg University and theCrystal Research Institute FEE has pro-duced the first Nd:YGG crystals withthe mechanical and optical quality needed for Q-switching. Pulse energiesof around 4 mJ and 100 Hz have beendemonstrated with an efficiency of 9 percent (absorbed pump light to laser light). The researchers are cur-rently investigating InnoSlab-basedamplifiers for energy scaling in themulti-10-mJ range.

Method

A numerical model for simulating theamplification processes, taking re-absorption effects of the quasi-3-levelsystem as well as ASE and thermal lenseffects into account, was implementedto identify and interpret system-rele-vant parameters. Extensive parameterstudies enabled to identify promisingpump geometries and amplifier con-figurations.


Pulse energies in the 40 mJ range arepredicted with an Innoslab amplifierpumped by both ends. Experimentalimplementation is currently being in-vestigated.

As water vapor significantly determinesthe energy balance of the atmosphere,the use of robust LIDAR systems withemission at a wavelength of 935 nmon mobile platforms such as airplanesand satellites, as well as of ground-based LIDAR systems, can be expected.In principle it has been shown that tailor-made laser crystals and adaptedlaser designs render feasible the directand efficient generation of application-specific wavelengths for metrology andmaterials processing.

Contacts

Dipl.-Phys. J. Loehring, Tel.: [email protected]. H.-D. Hoffmann, Tel.: [email protected]


Energy scaling of pulsed Nd:YGG-based laser beam sources at 935 nm

Above: Slab-based amplifier.Below: Nd:YGG boules byHamburg University (left) andthe FEE (right).

Task

Owing to their great spectral bandwidthand high amplification, Ti:sapphire lasersare the workhorses among tunable solid-state lasers in science and engi-neering. Their fundamental tuning rangecovers wavelengths between about670 nm and 1100 nm. The special feature of the solution presented isthat a wavelength range of more than300 nm and an optical finesse of morethan 10,000 are achieved with a singleset of lenses - without replacing anycomponents. The mechanical design of the demonstrator is distinguished by its ease of assembly and ease ofmaintenance, and supports long termstable alignment-free operation.

Method

An industrial frequency-doubled Q-switched laser is used as pump sourcefor the Ti:sapphire laser. Nanosecondpulses are generated by gain switching,requiring no further optical switch. Inthe demonstrator, the optical resonatoris mechanically separated from the water and electricity connections andhermetically encapsulated. The wave-length is adjusted using high-precisionpiezo-based alignment mechanismsmade by Steinmeyer FMD DresdenGmbH. The laser control supports two operating modes: setting a freelychosen fixed wavelength, or continuoustuning across a selected wavelengthrange.


At a burst frequency of 1 kHz, pulseenergies of more than 3 mJ, pulse durations of around 10 ns and a beamquality of M2 < 1.2 are achieved. Whenthe system is continuously tunedacross a selected wavelength range,the line width is about 300 GHz. Dur-ing operation with a freely chosen fixed wavelength, the user can switchbetween line widths of about 300 GHzor less than 10 GHz.

Because of its high pulse output andexcellent beam quality, the laser is emi-nently suitable for frequency conversion.It can, for example, form the basis of a solid-state laser system that can betuned from 210 nm to 1000 nm.

Areas of application for this system arehigh-throughput investigations in thesemiconductor industry, bioanalysisand materials science. The system hasan automated wavelength adjustmentmechanism which was also used to record the curves

Contacts

Dipl.-Phys. B.Jungbluth, Tel.: [email protected]. H.-D. Hoffmann, Tel.: [email protected]


Broadband tunable Ti:sapphire laser with nanosecond pulses

Above: Demonstrator with robust, easy-to-assemble andeasy-to-maintain mechanicaldesign.Below: Excellent performanceand wide tuning range withoutreplacing optical components

Task

The tuning range of today’s Ti:sapphirelasers covers more than 300 nm in thered and near-infrared spectral range. By means of non-linear frequency con-version, this output spectrum can betransformed into shorter wavelengthsranging into the ultraviolet. To generatea frequency-shifted output spectrumbetween 210 nm and 500 nm, at leastthree different conversion processes areneeded - frequency doubling as well astrebling and quadrupling of the funda-mental laser radiation. The solution presented combines these conversionprocesses in a single compact andalignment-insensitive module.

Method

In the module the two-stage conversionprocesses, in this case frequency tripl-ing and quadrupling, are realized bycombining positively birefringent BIBOcrystals with negatively birefringentBBO crystals. By selecting a suitable typeof interaction, the two crystals can bearranged directly behind each other,without any optics in between. As a re-sult, the beams in the second convertercrystal are always optimally aligned toone another. For tuning to the adjacentinput wavelength, both crystals areturned in the same spatial plane. Thismakes it possible to stack all the con-version stages on the same mechanicalplatform, producing an extremely com-pact configuration.


Given an adequate tuning range of the fundamental laser, the convertercovers a wavelength range between210 nm and 510 nm without anygaps. Using the described arrange-ment, outputs of 1100 mW were de-monstrated with frequency doubling,500 mW with frequency tripling and200 mW with frequency quadrupling.This corresponds to conversion effi-ciencies of 50 percent, 20 percent and10 percent.

The converter presented here serves asa module for a solid-state laser systemwith a tuning range of 210 nm to1000 nm. The system permits automa-tic switching between different wave-length ranges and computer-controlledadjustment of the desired wavelengthwith an accuracy of better than 5 pm.

Applications of the system includehigh-throughput investigations in thesemiconductor industry, bioanalysisand the materials sciences.

Contacts

Dipl.-Phys. B. Jungbluth, Tel.: [email protected]. H.-D. Hoffmann, Tel.: [email protected]


Compact frequency converter for tunable laser radiation

Compact module for generatingfrequency-converted radiationfrom UV to VIS.

Task

To increase the efficiency of polishing,coating-removal and structuring on large surface areas, high-power beamsources are needed. The object of thisproject was to develop a fiber-coupledQ-switched solid-state laser with pulsedurations in the 100 ns range and anaverage output distinctly higher thanthe 850 W currently provided by com-mercially available beam sources.

Method

Based on a pulsed Nd:YAG laser deve-loped at the Fraunhofer ILT with anoutput of 800 W from a fiber with 600 µm core diameter, a compact, mobile laser system for industrial usewas designed by coupling two lasermodules based on a diode-pumpedrod laser.


Using a 400 µm fiber for beam delivery,the Q-switched laser achieves pulse outputs of 500 kW and a pulse durationof about 100 ns at 35-kHz repetitionfrequency. This represents an averagepower of 1700 W at the fiber output.The average power has thus been morethan doubled. Owing to the improvedbeam quality, optionally a four times increased power density on the workpiece or a two times larger working distance is available. The system’s highperformance capability means that large surface areas can now be cost-efficiently processed.

Contacts

Dipl.-Ing. R. Meyer, Tel.: [email protected]. H.-D. Hoffmann, Tel.: [email protected]


Q-switched Nd:YAG laser with an average output in the kW range for surface processing

Laser housing.

Task

The cw output of fiber lasers has risenrapidly during recent years. However, thecurrently available high-output systemsoperate with random polarization. The task was therefore to demonstrate whether linearly polarized laser radiationcan also be generated with fiber laserson a stable basis with an output in kilo-watts.

Method

Comparative tests of generating linear-ly polarized laser radiation with fiberlasers were carried out. Both graded-index and microstructured fibers wereempirically examined in various confi-gurations.

During this work, fiber laser resonatorswith and without a polarizer inside the resonator were compared with oneanother, and the polarization degree of the laser radiation was measured atvarious winding radii.


A polarization degree of over 97 per-cent was achieved with both fiber laserresonators and fiber amplifiers. Theoutput was 850 W, limited by the avai-lable pump output. The polarizationstatus was very stable, making it safeto assume that the polarized outputcan be increased into the range exceed-ing 1 kW.

The experiments coincided very closelywith the results of the digital simulationobtained using a numerical simulationtool developed at the Fraunhofer ILT.

The investigated concept makes it possible to implement fully fiber-inte-grated laser resonators with fiberBragg gratings and a pump based on fused combiners.

In addition to material processing,where precise control of polarizationcan lead to better and more reprodu-cible results, another potential field of application is that of frequency con-version. Furthermore, polarized laserbeams can simply be overlapped witha polarization coupler, for example inorder to scale the output, to combinetime-modulated and unmodulated laser beams, or to generate a custo-mized intensity distribution in the focus.

Contacts

Dipl.-Phys. J. Geiger, Tel.: [email protected]. H.-D.Hoffmann, Tel.: [email protected]


Linearly polarized fiber lasers with high average output

Above: Microstructured fibersfor generating linearly polarizedlaser radiation.Below: Test set-up for an output of 850 W.

Task

When passing through optical systemsor reflected by dielectric mirrors, femto-second laser pulses are influenced by differences in the group delay dis-persion (GDD) between the individualspectral elements. For example, thepulse duration in dielectrics is leng-thened by a positive GDD, which fre-quently has to be offset by optical elements with a defined negative GDD.A particularly elegant solution is to usechirped mirrors, where it is possible to achieve any desired GDD by varyingthe thicknesses of the dielectric coat-ings. In theory, chirped mirrors makeit possible to achieve any desiredspectral GDD. In practice, however, minor fluctuations in thickness, of themagnitude of a single atom, occur inthe coatings. These alter the GDD sosignificantly that it becomes necessaryto measure the GDD for many appli-cations. This measuring process mustbe such that it can be routinely perfor-med by the manufacturer with a highdegree of accuracy as well as being reproducible.

Method

The GDD is determined by measuringthe spectral phase displacement occurr-ing on reflection from a flat mirror,using a Michelson white-light interfero-meter. A white light interference patternoccurs when using the same arm lengthand an identical optical beam path. Tilting one of the mirrors produces apattern of stripes that is equidistant in flat mirrors. A cross-section throughthis interference pattern (gap) is spec-trally split (upper figure). If dispersivemirrors are incorporated in one arm of the interferometer, a wavelength-dependent displacement of the inter-ference stripes can be observed. Thisforms the basis on which the GDD iscalculated.

This measuring principle was improvedvis-à-vis previous configurations insuch a way that the luminosity of theset-up was increased by several ordersof magnitude. A compact easy-to-ope-rate mechanical set-up (lower figure)and a computer-assisted automaticmeasuring process including evaluationwere implemented.


An easy-to-operate device for measuringthe GDD of flat mirrors was developed.Thanks to a quick-change device for thetest objects, exposure times in the msrange and an automated measuringprocess, the dispersion of mirrors can bedetermined rapidly (~1 min) and repro-ducibly.

So far, measuring devices in the wave-length ranges of 900 - 1100 nm, 500 - 950 nm and 250 - 800 nm for use in industrial quality control havebeen delivered.

Contacts

Dr. P. Russbueldt, Tel.: [email protected]. H.-D. Hoffmann, Tel.: [email protected]


White light interferometer for characterizing optical coatings for ultra-short pulse lasers

Above Interference pattern of a dielectric mirror.Below: White light inter-ferometer for 900 - 1100 nm.

Task

As part of a joint project funded by theBMBF, a laser plasma source for gene-rating XUV radiation in the wavelengthrange between 2.3 nm and 4.4 nm is to be developed. This spectral rangeis known as the »water window«, andpermits applications such as the exami-nation of biological samples. To createthe plasma, laser pulses in the sub-nsregime with an energy of more than100 mJ at a pulse repetition rate of 1 kHz are needed.

This report presents the generationand pre-amplification of the laser pulsesto a pulse energy of approximately 2.5 mJ. The pulse duration is to be adjustable between about 500 ps and1 ns.

Method

A laser-diode-based optical pulse generator with a regenerative amplifierappears to be the best solution for theplanned range of parameters. The pulseduration, shape and energy of theseed diode emission can be varied bymeans of gain switching and bias cur-rent and by a modulator incorporatedin the chip using an electric circuit ofthe size of a credit card. The laser pulsesthus generated are amplified to the required pulse energy by means of theregenerative amplifier. Faraday isolatorsprotect the laser diode from back-re-flected radiation. The pulse repetitionrate can be freely selected between 0 and 10 kHz.


Pulse energies up to 2.7 mJ at a pulserepetition rate of 1 kHz and diffraction-limited beam quality are achieved withthe Nd:YAG based regenerative ampli-fier. The pulse duration can be adjustedbetween 300 ps and 1.5 ns. The diode-seeded regenerative amplifier opensup a multitude of further potential applications in the field of microma-chining. The present goal is to extendthe system to 2 kHz at the identicalpulse energy and to move the lower limit of the pulse duration range to below 100 ps.

Contacts

Dipl.-Phys. D. Esser, Tel.: [email protected]. H.-D. Hoffmann, Tel.: [email protected]


Generating sub-ns laser pulses of variable pulse duration with pulse energy in the mJ range

Electrically pulsed laser diode with beam shaping optics.

Task

To understand the physical processes in the targeted applications, it is indis-pensable to investigate the parametersof a laser-induced plasma. When usingvarious materials in combination withlow pulse energies and consequentlylow emitted luminosity values, an ana-lysis using optical methods is time-con-suming and expensive. Direct analysisof the plasma flow can reveal factsabout the propagation rate, the tem-poral development of the density ofthe ablated material, and the plasmatemperature.

Method

A robust probe with a simple operatingprinciple was developed to enable time-resolved examinations of the plasma.Density measurements are performeddirectly in the ion flow, which is mea-sured using a Faraday capacitor with a negative bias against the housing.The probe is positioned directly in theplasma flow, with the plasma enteringthrough a specified opening in thehousing. The electrons are diverted tothe housing, while the ions impinge on the Faraday capacitor where theytrigger a current signal. This signal islocally amplified in a vacuum to mini-mize interference during transmission.It can be measured directly using anoscilloscope. The propagation rate isdirectly determined from the signalsand subsequently incorporated in thecalculation of plasma density.


The new probe was used to investigateablation plasmas. The density develop-ment of plasmas generated by a ps laser with burst lengths ranging from0.5 to 100 µs was investigated for various materials. Fluctuations in thedensity were identified that can be attributed to shielding phenomena.Thanks to the fast and direct measuringmethod, any dependencies of the plas-ma parameters on the laser parameterscan be efficiently investigated. Theprobe concept is flexible in terms of itsphysical size and temporal resolution,enabling it to be adapted to meet the specific requirements. The robuststructure of the probe permits its useunder extreme conditions such as in a vacuum or in corrosive plasmas. Because of its compact design, theprobe can easily be integrated in existing facilities.

Contacts

Dipl.-Phys. M. Strotkamp, Tel.: [email protected]. H.-D. Hoffmann, Tel.: [email protected]


Probe for the analysis of a laser-induced plasma

Above: Probe in the laboratory setup.Below: CAD drawing, cross-section of the probe.

Task

The ray tracer already developed at theFraunhofer ILT is to be expanded to co-ver ray propagation in inhomogeneousmedia with a spatially dispersed indexof refraction.

The beam-forming property of the ma-terial vapor or plasma, or of an ultra-sonic flow of the working gas, are tobe more closely examined.

Method

To calculate the geometrical and opti-cal propagation of laser beams, the ei-konal equation is solved with spatiallyvarying dispersion of the refractive in-dex. The light rays in inhomogeneousmedia are not straight lines, but non-linear curves. Because wavefronts pass-ing through an area with inhomoge-neous dispersion of the refractive indexcannot be clearly displayed or mayoverlap one another, the dispersion ofthe power output in the diffracted la-ser beam is projected onto a Cartesiangrid in the background and recorded.The ray tracing algorithm also coversmethods of interpolating dispersions of the refractive index that have beenentered point by point, as well as anadaptive refinement of the grid (seefigure).


The results of a model assignment forray tracing in inhomogeneous mediaillustrate how the beam is refracted in spatially isotropic dispersion of therefractive index (figure). The results ofray tracing in inhomogeneous mediashow that the light rays and wave-fronts are changed by density altera-tions in the ultrasonic flow of the cutt-ing gas.

This greater understanding of theeffect of refraction in the gas phase on the beam shape at the absorptionfront is applied in the design of beam-shaping optics.

The project presented was sponsoredby the German Research FoundationDFG as part of the Cluster of Excellen-ce »Integrative Production Technologyfor High-Wage Countries«.

Contacts

Dipl.-Phys. U. Eppelt, Tel.: [email protected]. Dr. W. Schulz, Tel.: [email protected]


Ray tracing in inhomogeneous media

Light rays and wavefronts shining throughspherical dispersion of the refractive index.

Task

Grazing-incidence reflectometry withextreme ultraviolet radiation (EUV) inthe wavelength range from 1 to 50 nmmakes it possible to characterize thinfilms on the nanometer scale. Thecomposition, thickness and surfaceroughness of a film system can be de-termined indirectly from its reflectivitycurve, through the combination ofnon-linear regression techniques andthe transfer matrix formalism. The re-flectivity can be determined either as afunction of the incident wavelength ata fixed angle of incidence or vice versa.It is even possible to determine an effective roughness of concealed filmswithin the system. This method repre-sents an alternative to existing tech-niques and is intended in particular toestablish the use of EUV radiation inmetrology. Before now, such measure-ments were only possible on synchro-tron-based radiation sources. The se-miconductor industry in particular willbenefit from the use of the EUV mea-surement technique, which is intendedfor widespread use ranging from de-fect detection on wafers through tocharacterization of optical componentsin the shortwave spectral range.

Method

To evaluate the reflectivity curves, nu-merous computer simulations wereperformed and a MATLAB-based toolwas developed for modeling thin films.This enables the reflectivity curves ofvirtually any thin film system to be cal-

culated in the spectral range from 0.01to 40 nm. Experiment-specific parame-ters, such as detector resolution capa-city and beam divergence, can also beincluded. Typical film systems for EUVapplications consisting of Si, SiO2, Zn,C, Mo, Ag etc. were simulated.


It was shown that noise has a direct in-fluence on the precision of the fittingalgorithm. In a single-layer thin-filmsystem (< 10 nm thickness), for exam-ple, with sub-nm roughness values andan absolute reflectivity measurementaccuracy of +/- 0.5 percent, the filmthickness can be determined very well,with a deviation of 0.2 percent. Theroughness of the revealed film can bedetermined with a precision of < 10percent, and that of the concealed filmaround 20 percent. The material com-position can be determined from thereflectivity curve on the basis of theelement-specific absorption edges. Thesequence of the elements in the filmsystem can be derived from the peakheights. An EUV reflectometer was de-signed and is already being produced.

Contacts

M. Banyay M.E., Tel.: [email protected]. L. Juschkin, Tel.: [email protected]. Dr. P. Loosen, Tel.: [email protected]


Surface analysis with extreme ultraviolet radiation for the characterization of thin films

Above: Wavelength-dependentreflectivity curve of an Al/Ag/Sifilm system.Below: 3-D model of the EUVreflectometer for measuringthin films.

Task

A low-latency data transmission systemfor real-time control of a plasma deviceis to be developed. It must permit thetransmission of measured charges inthe nC range and be capable of drivingspatially distributed power semicon-ductors with a timing accuracy < 10 ns.The data transmission system must beresistant to electromagnetic interfe-rence and bridge potential differences>10 kV at voltage transients >100 kV/µs.It should have a modular structure topermit expansion, and should featureself-diagnosis functions and a redun-dant architecture. Asynchronous eventsshould reach their drain within one µs,as should the data.

Method

Based on low-cost, readily available Gi-gabit-Ethernet components, a doublering of glass fiber is put in place whoselogical function is that of a determinis-tic, centrally controlled bus. The leanprotocol is implemented in programm-able logic. To ensure the exact mea-surement and generation of times, allbus users are equipped with synchro-nized clocks whose pulse is derivedfrom the synchronous data transmis-sion. Depending on the glass fibercomponents selected, distances of upto several kilometers between the par-ticipants are possible provided that theadditional delay of 5 µs/km due to thefinite speed of light is acceptable.


It was shown in a prototype that thephysical transmission layer operatesfaultlessly and enables a signal transittime delay of 100 ns per bus user. In apreliminary stage of the protocol stillto be implemented, analog measuredvalues were transmitted via a point-to-point connection.

Thanks to its modular structure, itshigh electromagnetic immunity andlow latency, this data transmission sys-tem is eminently suitable for imple-menting fast control loops in wide-area systems. This system also lendsitself to the safe driving of switchingelements at high potential - such asstatic inverter stations for high-voltagedirect current transmission lines.

Contacts

Dipl.-Ing. S. Probst, Tel.: [email protected]. W. Neff, Tel.: [email protected]


Data transmission with low latency

Above: The system’s double-ring topology.Below: Data transmission inthe physical layer.

Laser Material Processing

Production processes addressed by this business area include cutting andjoining techniques applying micro- andmacro-technology, as well as surfaceengineering. The services provided extend from process development forthe manufacture of sector-specific products and the integration of theseprocesses in production lines, throughsimulation services for laser applications,to the production of samples in sup-port of series production start-up. Thestrength of the business area is rootedin its extensive process know-how,which is tailored to specific customerrequirements in each case. In additionto process development, the businessarea offers complete system solutionswhich utilize selected technology net-works. Customers are offered laser-specific solutions that encompass designengineering, material specification,product design, production equipmentand quality assurance. In addition tothe target market of material process-ing, the business area also addressescustomers in the medical engineering,biotechnology and chemical sectors.


Business AreaLaser Material Processing

Cutting adhesive seals for microtiter plates.

Computer-aided robust design as exemplified by laser cutting 64

Welding thick steel plates by disc laser 65

Zero-gap lap welding of ZE-Mg sheets 66

Strength testing of CO2 laser MAG hybrid welds 67

Physical model for root formation and gap-bridging ability during laser welding 68

Simulating the welding process 69

Distortion caused by welding: struc-tural stability of reduced models 70

Modeling the absorption of laser radiation on metallic surfaces 71

Direct simulation of Maxwell equations 72

Micro-laser dispersing of X-ray visible markers on stents 73

Process-engineering technique for the laser cladding of brittle intermetallic compounds 74

Laser cladding of mesh structures on High Pressure Turbine parts 75

Additive manufacturing of aluminumcomponents for volume production by selective laser melting 76

Increasing the build-up rate of selective laser melting (SLM) processes 77

Modeling of laser treatment of filmsproduced by nano-dispersion 78

New applications for high-strength steel sheets through local heat treatment 79

Laser polishing of glass molds 80

Dual gloss effect created by laser polishing 81

Laser beam microwelding of 2-D optical waveguide arrays 82

Laser beam-assisted bonding of silicon and glass for wafer level packaging, MEMS packaging and display packaging 83

Laser beam-assisted bonding of silicon-silicon for wafer level chip packaging and MEMS packaging 84

Femtosecond laser welding of glass-glass and glass-silicon 85

Laser beam soldering of glass components using glass solder 86

Lap welding of transparent PE films with CO2 laser radiation 87

TWIST - new process for microwelding plastics 88

Laser-assisted joining of plastics with metal and ceramic components 89

Cutting adhesive seals for microtiter plates 90

Fine cutting 91

Fine cutting of silicon 92

Precision-drilling of shaped holes in steel 93

In-situ determination of drilling depth during percussion drilling 94

High-precision nozzle drill holes in Inconel® 690 nickel-based super alloys 95

Influence of process gas on percussion drilling 96

Plasma diagnosis during laser drilling 97

Drilling with efficient melt expulsion 98

Micro-perforation of balloon catheters 99

Diagnosis of ultra-fast, laser-inducedmelt dynamics of metals 100

Improved solid-state laser microablation processes with tailored pulse trains 101

Synthetic microhairs for sensory applications 102

Creating periodic nanostructures by three-beam interference 103

3-dimensional micro- and nano-structures inside sapphire produced by selective, laser-induced etching 104

Changing the refractive index of glass materials using a double-pulsefemtosecond laser 105

Laser-induced forward transfer of proteins, cells and active agents 106


Überschrift

Contents

Task

The existing high demands on the qua-lity and reliability of products and manu-facturing techniques call for the use ofrobust processes. Processes must bemade suitably robust as early as duringthe design phase, which involves mo-dels and simulations, and in whichproduction tolerances and inevitablescattering have to be taken into account.This is to be demonstrated using lasercutting as one example.

Method

In order to develop efficient modelingand simulation techniques that canmeasure the effects of varying parame-ters, experimental results of the cuttingprocess are needed for validation pur-poses and as a complementary data-base. These results can be obtained bycarrying out a full diagnosis of the pro-cess, its determining factors and theoutcome. In a series of cutting tests,the lateral movements of the cuttinghead, the nozzle distance, the laser ra-diation, the thermal process emissionsand the kerf characteristics are re-corded simultaneously at high tem-poral resolution. By means of statisticalanalysis, it is then possible to establishcorrelations between these variablesand resulting factors such as theroughness of the cutting edges andthe kerf geometry.


The first systematically recordedmeasurement data are now available,and are being used to create meta-models and model reduction methods.They also serve as a basis for thenecessary further development ofmathematical techniques enablingfaster calculation or the characteriza-tion of scatter.

The measurement technology employedto record the dynamic behavior of thelaser and the system delivers importantadditional information over and abovethe set objectives, which can help todevelop laser cutting processes involv-ing high-brilliance beam sources.

This work is being supported by theFraunhofer-Gesellschaft in the contextof its MAVO project ‘CAROD – Com-puter Aided Robust Design’, which isbeing coordinated by the FraunhoferSCAI.

Contacts

Dr. F. Schneider, Tel.: [email protected]. M. Niessen, Tel.: [email protected]. D. Petring, Tel.: [email protected]


Computer-aided robust design as exemplified by laser cutting

System and process diagnosis for laser cutting.

Task

A series of welding tests were carriedout on steel materials with a wall thick-ness of up to 10 mm using a disc laser(TruDisk 8002) with a maximum out-put of 8 kW provided by Trumpf Laser-technik.

Method

The laser beam was fed into the colli-mation and focusing optics via a 20-meter optical fiber with a diameter of200 µm. The optics each had a focallength of f = 200 mm so that, byimaging the fiber on a scale of 1:1, a focus diameter of 200 µm wasproduced. Welds were also performedwith a focal length of f = 300 mm anda resulting focus diameter of 300 µm.Welding curves were produced in 10-mm-thick sheets of structural andstainless steel with a maximum laseroutput of 8 kW at the workpiece. Theinert, protective gas argon was fed tothe welding zone through either anoff-axis or a coaxial nozzle selectively.


Weld depths were measured at diffe-rent welding speeds and with focuspositions ranging from + 2 mm to - 7 mm. Due to the high brilliance ofthe laser, it was possible to producevery narrow weld seams similar tothose created during electron beamwelding. At focus positions of 0 mmand below, smooth and even seamsurfaces were produced, while positivefocus positions > 0 mm resulted ineruptions and irregularities on the seamsurfaces of both materials, particularlywhen using the off-axis nozzle. Whenapplying the coaxial gas nozzle, agreater weld depth was achieved withthe same gas flow rate. The seam qua-lity and the quality reliability of thewelding process also improved.

Contacts

V. Nazery Goneghany, Tel.:[email protected]. N. Wolf, Tel.: [email protected]. D. Petring, Tel.: [email protected]


Welding thick steel plates by disc laser

Welds in stainless steel 10 mm,laser output 8 kW.Above: Full penetration weld,feed rate 3 m/min.Below: Partial penetrationweld, feed rate 10 m/min,depth 5.6 mm.

Task

Electrolytically galvanized sheet steel is a widely used material in the carmanufacturing industry. By adding avapor-deposited magnesium coating,which is thermally alloyed into thezinc, it is possible to reduce the zinccoating while retaining the material’sgood corrosion properties. The newsheets were tested for their weldingsuitability by means of laser beam lapwelding.

Method

The tests were carried out using an 8 kW disc laser (TruDisk 8002) built byTrumpf. The laser beam was guided tothe processing station via a 20-meter-long optical fiber with a diameter of200 µm and focused by means of 1:1imaging. The 0.77-mm-thick sheets,equipped with Zn coatings of 2.3 µm,2.5 µm, 3.1 µm and 3.5 µm, and a0.3-µm-thick Mg coating, were weldedwithout a gap by means of a squareweld on the lap joint, with the »go-side«(Mg coating) on the inside.The sheets,which were welded with outputs rang-ing from 4 kW to 6 kW at a feed rateof up to 10 m/min, were then analyzedto determine their porosity comparedto one another and to a reference ma-terial with a 7.5-µm-thick Zn coating.


In general, it can be said that the thin-ner the Zn coating, the smaller the sizeand number of pores. It was shownthat, as a function of the laser outputwithout changing the feed rate, theincreased melt volume (Zn vapor)generated at 6 kW tends to produce a greater number of pores. Given acoating thickness of 3.5 µm, a laseroutput of 4 kW and a feed rate of 5 m/min, the resulting pores constitutearound 3.8 percent of the overall jointsurface. This increases to 6.4 percentat 6 kW. The pores are located mainlyin the transition area between the twojoin partners. They can be reduced byadapting the laser output and the feedrate. The welds produced on the ZE-Mg sheets have a much better appear-ance and are of a far higher qualitythan those on the reference material,which tended towards strong meltejections and a large number of poresacross almost the entire range of the test due to its thicker Zn coating. The seam surfaces and roots of all full penetration welds created at feedrates of up to 10 m/min on the ZE-Mgsheets have a high-quality appearance.

The test sheets were made availableto the Fraunhofer ILT courtesy of DOCDortmunder Oberflächen Centrum, asurface engineering center belonging toThyssenKrupp Steel, which developedthe new coating for these sheets.

Contacts

Dipl.-Ing. N. Wolf, Tel.: [email protected]. D. Petring, Tel.: [email protected]


Zero-gap lap welding of ZE-Mg sheets

Lap weld in ZE-Mg sheets (Zncoating thickness 2.5 µm), laseroutput: 6 kW, feed rate: 10 m/min. Above: Seam surface (left) and root(right).Below: Cross section of the seam.

0,5 mm

Task

Laser MAG hybrid welding is alreadysuccessfully employed in many areas.However, there is a great need to fur-ther refine the technique so that it canalso be used for metal plates thickerthan 15 mm. In the context of HYBLAS,a European project funded by theRFCS, process methods for laser hybridwelding of steels with yield strengthsof up to 690 MPA were further deve-loped and tested for their suitability by means of comprehensive mecha-nical-technological investigations.

Method

For the purpose of the tests, metal pla-tes with thicknesses of 12 to 25 mmmade of the materials EH 36 and RQT701 and prepared for V- or Y-shapedwelding joints were butt-welded in asingle pass using the laser MAG hybridtechnique. This was done using a 20-kWCO2 laser built by Trumpf, a programm-able welding power source by Froniusand the hybrid welding head developedby the Fraunhofer ILT, the nozzle ofwhich integrates both the laser beamand the MAG process. The welding pat-terns used were produced after success-fully optimizing the process - a necessarystep particularly for thick-walled plates.The dynamic strength tests were carriedout in the form of four-point bendingtests and tensile tests at the IEHK insti-tute at RWTH Aachen University and at the CORUS company in Rotherham,UK - both of which are partners of theHYBLAS project.


For all wall thicknesses up to 25 mm,the tests resulted in excellent fatiguestrength values according to Eurocode3, all of them lying in the region aboveFAT Class 100 and extending as far asFAT Class 250. Due to this high seamquality and other significant advance-ments regarding welding speed andthe ability to bridge gaps in a singlepass, which in turn lead to high pro-ductivity and minimum warping, thelaser MAG hybrid welding technique is now also a viable option for highlystressed welds in thick material. Poss-ible areas of application include heavy-duty vehicle construction (e.g. excavat-ing machines), shipbuilding, pipelineconstruction, off-shore engineeringand special-machine construction.

The work described here was carriedout as part of the EU project »Econo-mical and Safe Laser Hybrid Welding ofStructural Steel« (HYBLAS), which wassponsored by the Research Fund ofCoal and Steel (RFCS).

Contacts



Strength testing of CO2 laser MAG hybrid welds

Fatigue strength diagram forvarious plate thicknesses.

Task

Until now, the maximum ability tobridge gaps during laser welding hasbeen determined in purely empiricaltest runs. In future, a physical model is to enable the sound assessment andoptimization of achievable processlimits in terms of gap-bridging ability.

Method

The energy and mass balance in thewelding joint can be optimized by carefully selecting the laser output, thefocusing parameters and the wire feedrate of the filler material. What limitsthe ability to bridge gaps is the diffi-culty of retaining the required meltvolume in the weld gap. This dependslargely on the pressure balance in theroot area of the seam. This balancedetermines the characteristics of theroot, which can vary between twoextremes - a convexity to the extentthat material drops through, or a con-cavity with the associated notching ef-fect. The main factors contributing tothe pressure balance when weldingthick sheets of steel are the gravita-tional forces acting on the melt, thedynamic pressure of the melt flow, andthe capillary pressure supporting themelt as a result of the surface tensionof the root.


The maximum bridgeable gap widthdepends on the thickness of the ma-terial, the surface tension in the rootarea, and the density and downwardflow rate of the melt, which is a gaugeof the process dynamics.

The developed model explains thequantitative dependency of the gap-bridging ability on the process dyna-mics (flow rate), root oxidation andsheet thickness. The effect of measuressuch as root shielding gas and horizon-tal welding position, too, can now bequantitatively assessed. Comparisonsbetween theoretical and experimentalresults based on the example of laserMAG hybrid welding of high-strengthsteels 15 mm thick confirm the con-clusive nature of the developed forma-lism.

In principle, the model can also incor-porate the arc pressure, even thoughthis factor has proven negligible in theparameter range examined so far. Themodel is also transferable to numerousother welding processes involving rootformation, thus helping to design andoptimize them with greater reliability.

Contacts



Physical model for root formation and gap-bridging ability during laser welding

Pressure balance of the root area.

Task

The properties of the product afterwelding reflect the prehistory of thematerial and the transformationsduring production. The task consists of incorporating the change in thematerial from a microstructure forma-tion model into the simulation of thewelding process. The additional pro-perties of the larger model resultingfrom this combination are to be closelystudied. Multi-scale thermophysicalmodeling enables relevant phenomenawith a bearing on material propertiesto be taken into account at any pointin the process chain.

Method

In order to reach a new quality in thecombined model, a deeper understand-ing of the interaction between tempe-rature and stress during solidificationand microstructure formation is deve-loped. The interaction takes place ondifferent scales of time and space,which are determined by the micro-structure formation on the scale of nu-cleation and by models of welding onthe scale of the thermal penetration.The dynamic model of welding and thethermomechanical model of the stres-ses are first examined to ascertain thesensitive dependence of the resultingvalues on spatially varying materialproperties and stresses from the pre-history. A partial aspect consists inidentifying the areas of qualitativelydifferent solution characteristics (pro-cess domains) of the partial modelswith regard to their combination. Thewelding model is expanded to includemultiple reflection in the capillary andspatially three-dimensional properties.


The existing process model for weldingdescribes the form of the capillariesand the temperature field in the sur-rounding material during surface andfull penetration welding. As a free sur-face or the absorption and reflectionfront for the laser radiation the capillaryis part of the solution and is not given.Multiple reflections of the laser radiationin the capillary are calculated with theexisting ray tracer. The connection ofthe laser and welding parameters withthe occurrence of multiple reflectionsis determined as the result (top figure).The spatially distributed temperature in the solid material is determined byanalytical solutions of the 2-D heatconduction in the area of the steep ca-pillary walls and 3-D heat conductionat the foot of the capillaries.

The work presented was funded by the German Research Foundation DFG in the Excellence Cluster »Integrative Production Technology for High-WageCountries«.

Contacts

Dipl.-Phys. S. Pfeiffer, Tel.: [email protected]. Dr. W. Schulz, Tel.: [email protected]


Simulating the welding process

Above: Reflection in the capillary: small feed.Below: Reflection in the capillary: large feed.

Task

Computer simulation of distortioncaused by welding is not standardindustrial practice because the qualityof the results is inadequate. To reducethe calculation time, for instance,simplified versions of the models areapplied although their actual proper-ties have not been adequately inves-tigated. A systematic examination ofthe structural stability is intended tohighlight the sensitive dependence of the numerical solution on a modelstructure which has been reduced instages.

Method

The examination focuses on three industry-relevant components (gearwheel, microcomponent, car bodycomponent) and three steel materials.The numerical and analytical solutionsfor distortion and internal stresses areinitially compared on components ofreduced geometrical complexity. Thesensitivity of the simulation results tothe boundary conditions and structureof the model is examined. To gain aheat source for the FEM welding dis-tortion simulations, an efficient simula-tion of the reduced process model forsurface and full penetration welding isdeveloped.


The existing simulation of the processmodel for welding is analyzed in orderto be able to describe more preciselythe properties of the heat source forcoupling the process model to thethermomechanical calculation. Thetransition from heat-conduction weld-ing to penetration welding, the tran-sition from penetration welding todeep welding, and the transition fromdeep welding to full penetration weld-ing are identified as process domains.The analysis starts in particular withthe question whether the suitableselection of a heat source for the ther-momechanical calculation depends on the existing process domains or canbe derived solely from the geometricalshape of the weld seam.

The work presented is funded by theResearch Association Steel ApplicationFOSTA.

Contacts

Dipl.-Phys. S. Pfeiffer, Tel.: [email protected]. Dr. W. Schulz, Tel.: [email protected]


Distortion caused by welding:structural stability of reduced models

Capillary form, temperaturefield and molten bath iso-therms from the reduced pro-cess model for surface welding.

Task

The absorption of laser radiation onmetallic surfaces depends not only onthe optical properties of the metal, butalso, and very sensitively, on the angleof the Poynting vector relative to themetal surface. This is important in par-ticular in the context of cutting andwelding using laser radiation, becausehere angles of incidence are reachedwhich correspond to the Brewsterangle. A big difference in absorptionoccurs as a function of the radiationpolarization. The Fresnel formulas arenormally used for calculating the ab-sorption, but strictly speaking these areonly valid for plane waves and flat sur-faces. To determine the validity limitsof the Fresnel formulas and possibledeviations for the case of Gaussianbeams, the wave equation for the pro-pagation of a radiation field is solvedwith the Gaussian profile.

Method

A time-independent two-dimensionalwide-angle beam-propagation method(BPM) is used for solving the Maxwellequations. In this method, wave propa-gation is separated in the main directionof propagation by applying an SVE of ahigher order, so that local resolution ofthe numerical process can be distinctlyreduced. In the main direction of propa-gation z all material properties are con-stant, as are also all the field variables

in y direction. The wave equation forthe Ey component describes the case ofvertical polarization, the wave equationfor the Hy component describes the parallel polarization. The two other fieldcomponents differing from zero in eachcase can then be calculated from theMaxwell equations.


The graphic shows the absorptionalong a metallic surface calculated bymeans of the Fresnel formulas, usingthe Poyting vector to determine theangle of incidence and the absorptionas provided by the BPM method. Themean angle of incidence is 87°. Thereare only slight differences between theFresnel formulas and the BPM solution.

Contacts

Dr. R. Wester, Tel.: [email protected]. Dr. W. Schulz, Tel.: [email protected]


Modeling the absorption of laser radiation on metallic surfaces

Absorption along a metallic sur-face of p-polarized radiation. The mean angle of incidence is87°, the wavelength 1.06 µm.The complex refraction index is20-i20.

10 µm

Task

On the absorption front, such as thedrill-hole wall, the surface of the ca-pillaries in welding or the cutting front,the laser radiation is reflected, ab-sorbed and diffracted. Reflection,absorption and diffraction change thedirection and amount of the Poyntingvector and thus the laser beam tool.

The beam-forming effect of the ab-sorption front on the laser radiation isexamined closely, taking into accountthe wave properties and the boundaryconditions of strongly absorbing media.

Method

For the rigorous solution of Maxwellequations, the finite difference timedomain (FDTD) method is applied. The material equations of Drude andLorentz are used to describe the op-tical properties of the material. For theconditions on the outer edge of thecalculation area, absorbing boundaryconditions of the PML type (perfectlymatching layer) and periodic boundaryconditions are selected.


The reflection, transmission and absorp-tion of a plane wave on a flat boundarylayer can be stated analytically. Theaccuracy of the numerical solution ischecked by reproducing the Fresnelformulas (top figure). For the rigoroussolution of the Maxwell equation, anested grid is inserted for discretization,on which electric (E) and magnetic (H)field components are laid. The discreti-zation of the evolution equation for theelectric and magnetic field is shown inthe lower figure. The field amplitude ofthe electric field is the solution of themodel task under consideration (middlefigure). By comparing solutions fromthe FDTD method with boundary ele-ment methods (BEM) and methodswhich take into account higher ordersof the slow varying envelope (SVE) ap-proximation, the solution characteristicsof the tasks are stated and the effect ofthe absorption front on the beam formare determined. The result is a beamforming process for the incident laserradiation with which the quality charac-teristics of drilling, welding or cuttingare obtained.

The work presented is funded by theGerman Research Foundation DFG inthe Excellence Cluster »IntegrativeProduction Technology for High-WageCountries«.

Contacts

Dipl.-Phys. U. Eppelt, Tel.: [email protected]. Dr. W. Schulz, Tel.: [email protected]


Direct simulation of Maxwell equations

Above: Degree of reflectionover the angle of incidence.Middle: Field amplitude of theelectric field.Below: FDTD pattern of thenumerical calculation.

Task

After implantation of a stent in thehuman body, a check is performed toensure that the blood vessel is not ob-structed and that the implanted stenthas been positioned exactly in thehuman vascular system. However, ifthe stent is made of nitinol (a shapememory alloy), the low density of thematerial makes the stent structure al-most or completely indistinguishablefrom surrounding tissue and bonewhen the final X-ray examination isperformed. This problem can be reme-died by creating X-ray visible markersmade of tantalum, niobium or plati-num on defined parts of the stent.

Method

The first step in producing the X-ray vi-sible markers is to cut areas, measuring1 x 2 mm, out of the nitinol tube, pro-jecting from the ends of the stentstructure (spoons, top picture). X-rayvisible markers made of tantalum arethen created on the spoons by meansof micro-laser dispersing. In this me-thod, the laser radiation creates a meltpool on the surface of the substrate,into which the powdered tantalumfiller material is added.


Using fiber lasers with a high beamquality, controlled melt depths can beachieved on nitinol substrates with athickness of 200 µm. Due to the diffe-rence between the melting tempera-tures of the two materials (nitinol:1310 °C, tantalum 3017 °C), the tan-talum particles are not melted andevenly distributed throughout the mol-ten substrate material. When the meltsolidifies, the tantalum particles form a layer that is impenetrable by X-rays,thus significantly increasing X-ray vi-sibility by contrast with the substratematerial (bottom picture). By preciselycontrolling the applied laser energyand ensuring a precise and even inputof the filler material, highly repro-ducible results can be obtained usingthis process. In a final fabricationstage, the laser dispersed areas arefinished by electropolishing.

Contacts

Dipl.-Ing. T. Jambor, Tel.: [email protected]. K. Wissenbach, Tel.: [email protected]


Micro-laser dispersing of X-ray visible markers on stents

Above: Stent with cut spoons.Below: X-ray image of a stentwith tantalum spoons createdby laser dispersing.

2 mm

Task

Materials based on intermetallic com-pounds such as Ti-Al, Ni-Al or Fe-Al arerenowned for their excellent mecha-nical and chemical properties at hightemperatures. In conjunction with theirlow density, this predestines them foruse in aerospace or engine applicationsas a substitute for conventional high-temperature materials based on nickeland cobalt. They nevertheless presentone drawback: their elevated brittle-ness at room temperature, whichcauses problems when they are pro-cessed or machined. To avoid the ge-neration of cracks, forming processesand certain coating and joining proces-ses have to be carried out within nar-rowly defined process windows. TheFraunhofer ILT is developing a process-engineering technique that will enableintermetallic compounds to be joinedor coated without risk of cracking in areduced oxygen atmosphere.

Method

To avoid the generation of cracks dur-ing laser cladding, a preheating deviceis being designed that will allow temperatures of up to 1000 °C to bereached. A mobile inert-gas hood is also being designed and built to reduceoxidation of the workpiece during pro-cessing. Experimental trials are beingconducted on the titanium aluminidegroup of materials. Identical-type alloyswith and without additions of TiB2 areused as the filler material.


A heating stage (100 x 150 mm2, toppicture) assembled of ceramic heatingelements, to which modular units canbe added to extend the heated surfacearea, is used for preheating. The inert-gas hood covers a surface area of 400 x 600 mm (top picture). The laseroptics and powder feeding nozzle areintegrated in the hood. The undersideis sealed with metallic brush strips.Welding tests at temperatures of up to 950 °C were performed using this experimental setup (middle picture).Crack-free results were obtained whenjoining or coating titanium aluminidesat preheating temperatures in excessof 800 °C. The middle illustrationshows a wear-resistant coating madeof a TiAl alloy enriched with 40 per-cent by volume of TiB2 particles. Gra-dual, controlled cooling after the lasercladding operation reduces the risk of crack formation during the coolingphase. The use of an inert-gas hoodsignificantly reduces oxidation of thesample. Potential applications envi-saged for this process-engineeringtechnique include applying wear-resis-tant coatings to engine valves and therepair of turbine blades (regenerationof worn-down volume or welding-onof blade segments).

Contacts

Dr. A. Weisheit, Tel.: [email protected]. K. Wissenbach, Tel.: [email protected]


Process-engineering technique for the laser claddingof brittle intermetallic compounds

Above: Heating stage with inert-gas hood.Middle: Heated sample (950 °C).Below: Micrograph of a laser-clad coating of TiAl + TiB2.

0,05 mm

Above: CAD model of HPT liner 1 with NC tool paths.Below: Deposited mesh struc-tures on HPT liner 1 part.

10 mm

10 mm

Task

The aim is to apply mesh structuresmade of the nickel base super alloyInconel® 625 on the surfaces of HighPressure Turbine (HPT) parts of aircraftengines made of the single-crystallinesolidified alloy CMSX-4 by means oflaser cladding. The mesh structuresincrease the bonding and shearingstrength of the Thermal Barrier Coa-ting (TBC), which is subsequentlyapplied by Atmospheric Plasma Spray-ing (APS). The defined mesh structuresfeature a cross-sectional width of 340 µm and a maximum height of 500 µm at their intersections.

Method

The laser cladding process is performedusing an ytterbium fiber laser (IPG YLR- 200) with an emitted wavelengthof λ = 1080 µm and a maximum outputpower of PL = 250 W. The decoupledlaser light is guided by optical fibersfrom the laser beam source to thehandling system and through a fo-cusing lens to the processing location. The beam diameter in the focus is df = 60 µm. In order to obtain the required track width, the laser beam is defocused to a diameter of 280 µm.Powder made of the nickel base superalloy Inconel® 625 is used as additivematerial. The NC tool paths stringentlyrequired for laser cladding are createdon the basis of a CAD model of theHPT liner 1 using the CAD/CAM systemDCAM 5. The 3-axis Varilas plant builtby Schuler Held is used as the handlingsystem.


By selecting suitable processing para-meters, mesh structures with a trackwidth of 340 µm and a maximumheight of 500 µm at their intersectionscan be successfully deposited on HPTliner 1 parts. The system can also pro-duce structures of down to 60 µm inwidth if necessary. TBCs are currentlybeing applied to the first mesh-cladparts by Atmospheric Plasma Sprayingat the Jülich research center. The coat-ings are then being tested for increasedbonding and shearing strength by thecustomer.

This work is being carried out in colla-boration with Rolls-Royce and formspart of the publicly funded project »Engine 3E«.

Contacts

Dipl.-Ing. B. Burbaum, Tel.: [email protected]. (FH) P. Albus, Tel.: [email protected]. I. Kelbassa, Tel.: [email protected]


Laser cladding of mesh structures on High Pressure Turbine parts

Task

The additive process of selective lasermelting (SLM) is used in the direct in-dustrial manufacturing of metallicfunctional components. Industry’s ac-ceptance of the process and the extentto which it is employed depends partlyon the range of materials that can beprocessed and the availability of know-ledge on the mechanical properties ofthe components. The Fraunhofer ILT iscurrently qualifying SLM for the alumi-num die-casting alloy AlSi10Mg as partof the BMBF’s »Alugenerativ« project.Additive manufacturing by SLM repre-sents an economical alternative to thevarious types of mold casting, such as die casting, when producing series-identical functional prototypes, one-offparts and short-run batches. The useof additive techniques to manufacturesuch parts on an industrial scale is sub-ject to the fundamental requirementthat their mechanical properties shouldat minimum match those of conven-tionally manufactured components.

Method

The primary objective when qualifyinga material for SLM is to obtain a com-ponent density approaching 100 per-cent without any cracks or fusion de-fects. This involves evaluating the pro-cess parameters, especially scanningvelocity and laser output power, re-quired to produce components with adensity approaching 100 percent. Toassess the effect of scanning velocityand preheating on tensile strength,yield strength, breaking elongation,hardness and fatigue limit, test geo-metries are then manufactured atdifferent scanning velocities with andwithout preheating, and the resultingmechanical properties are compared.


The high reflectivity and thermal con-ductivity of aluminum by comparisonwith steel permits component densitiesapproaching 100 percent to be achievedwith a laser output of 150 W or higherand a scanning velocity of 100 mm/s.At a laser output of 250 W, the scann-ing velocity can be increased to 500 mm/s. At a lower scanning velo-city of 50 mm/s or at a higher preheat-ing temperature of 300 °C, a moreductile microstructure is produced, expressed as lower hardness, lowerstrength and higher breaking elonga-tion. The results of tension and fatiguetests demonstrate that the mechanicalproperties are at least equivalent to the strength parameters of series-pro-duced components made of die-castAlSi10Mg according to EN 1706 speci-fications (see top figure). This finding is of major importance to future indus-trial applications of the technology.In the next stage of the project, we intend to investigate the correlationbetween process parameters and heattreatment, microstructure and mecha-nical properties in more detail, and de-termine the effect of subsequent heattreatment on the mechanical proper-ties. Other aluminum alloys will also be qualified for industrial use. The firstdemonstrator components (see lowerfigure) are being manufactured.

Contacts

Dipl.-Ing. D. Buchbinder, Tel.: [email protected]. K. Wissenbach, Tel.: [email protected]


Additive manufacturing of aluminum components for volume production by selective laser melting

Above: Tensile strength Rm

of SLM samples made fromAlSi10Mg as a function of scann-ing velocity, preheating tem-perature, and the direction inwhich the component is built up.Middle and below: High vol-ume-production AlSi10Mg valvemanufactured using SLM (incooperation with Festo AG &Co. KG).

Above: Selective laser meltingof a powder film.Below: Typical application:Mold insert with contouredcooling channels manufacturedusing SLM.

Task

The Cluster of Excellence »IntegrativeProduction Technology for High-WageCountries«, of which the FraunhoferILT is a member, is pursuing the long-term objective of increasing the com-petitiveness of German productiontechnology. One of the key researchissues concerns solving the dilemmathat opposes economies of scale andscope, through the creation of newadded value structures that permitlow-volume manufacturing at costs of mass production while retaining theability to satisfy the market demandfor individualized products at the sametime. From a technological point ofview, additive manufacturing tech-niques with their almost infinite geo-metrical variability represent one of the areas of greatest potential. A majorcost factor in the SLM process deve-loped by the Fraunhofer ILT for theprocessing of metallic materials is themanufacturing cycle time, which most-ly depends on the volume of materialthat has to be built up to produce thecomponents. For economic reasons,greater cost-efficiency needs to beachieved by increasing the build-up rate.

Method

The experiments conducted to date in-dicate that there is only limited scopeto increase the build-up rate on thebasis of higher laser output power anda corresponding increase in the scann-ing velocity at a constant beam dia-meter. Increasing the laser outputpower while maintaining a constantbeam diameter has the effect of in-creasing the light intensity at the pointof processing. This in turn leads to ahigher incidence of spattering, whichhas a negative effect on the process as

a whole. To avoid this, the beam dia-meter has to be modified. Experimen-tal investigations were performed inwhich the process parameters scann-ing velocity, layer thickness and scan line spacing were adapted to a higherlaser output power and beam diameter.Process windows defined by suitablesets of parameter values can be identi-fied on the basis of the smoothness of the generated layers, which permitan even deposition of powder and the build-up of test structures with adensity approaching 100 percent.


For the first time, experiments usinghigh-alloy steel (1.4404) demonstratedthat it is possible to build up teststructures with a density approaching100 percent by widening the beamdiameter from 0.2 mm to 0.8 mm and1.2 mm respectively and increasing thelaser output from 250 W to 650 W.The highest build-up rate achieved was6.5 mm3/s, which represents a greaterthan fivefold increase with respect tothe present state of the art (approx.1.2 mm3/s). The next stage of the pro-ject involves constructing a prototypeplant with a laser output of 1 kW thatwill be used to adapt the results of thefundamental research to the manu-facture of real-life components, suchas mold and die inserts. This will makethe additive manufacturing techniqueby means of selective laser melting amore economical and hence attractiveoption for many users.

Contacts

Dipl.-Ing. H. Schleifenbaum, Tel.: [email protected]. K. Wissenbach, Tel.: [email protected]


Increasing the build-up rate of selective laser melting (SLM) processes

Task

Films produced by nano-dispersion of-ten require subsequent heat treatmentin order to obtain the desired functio-nality (e.g. electrical conductivity, abra-sion resistance). The heat treatmentprocesses conventionally used for thefunctionalization of nanoparticle filmspresent the drawback of overlong pro-cess cycles in excess of 1 hour (limitingthe possibility for inline monitoring)and an extremely high thermal load. In many cases, these processes necessi-tate temperatures that lie above thedecomposition temperature of certainsubstrate materials such as glass andpolymers.

A laser process is therefore being deve-loped for the thermal post-treatmentof films produced by nano-dispersionon glass and polymer substrates.

Method

There are no references in current lite-rature providing guidance on the ex-tent to which furnace processes can be replaced by high-speed thermalprocesses such as those implicit in lasertreatment. A series of experimentstherefore had to be planned to obtainstatistical data by systematically varyingthe process temperature and the hold-ing time, in order to define a processwindow. These plans were accompa-nied by a process model that was usedto determine the requisite process para-meter settings at each selected testpoint. The process model was basedon calculations of the proportion oflaser light absorbed by the nanoparticlefilm, taking into account the variationin optical properties as a function ofthe wavelength, and the effect of multiple reflection at the interfaces asa function of the film’s thickness for

commonly used laser wavelengths.This heat input was then used in a 3-Dheat transfer equation for compositematerials consisting of a nanofilm dis-persed on a glass or polymer substrateto calculate the resulting temperaturetime cycles and the heat penetrationdepth.


A process window defined in terms ofprocess temperature and holding timewas determined by assigning the ex-perimentally established functionalproperties to the calculated tempera-ture cycles (upper figure). The processparameters were mathematically opti-mized with respect to processing rateper unit area and heat penetrationdepth (lower figure) on the basis ofthis process window, for the purposeof generating functional films by meansof laser treatment.

Contacts

Dr. N. Pirch, Tel.: [email protected]. K. Wissenbach, Tel.: [email protected]


Modeling of laser treatment of films produced by nano-dispersion

Above: 3-D temperature field. Blow: Temperature-depth pro-files as a function of laser out-put power, beam diameter andscanning velocity.

Task

The automotive industry is increasinglyproducing body or chassis parts fromsheets of high-strength steels (e.g.dual-phase or martensitic steel) in or-der to save weight and improve vehiclesafety. These steels are generally cold-formed in the high-strength state inwhich they are delivered. However,their high strength limits the degree to which they can be formed and thusalso the range of components forwhich they can be used. If the localformability of such steels were im-proved by softening them throughheat treatment, their range of applica-tions could be significantly expanded,thus opening up new design possibilities.

Method

Suitable process parameters for locallysoftening high-strength steels havealready been determined in a basicresearch project. They are now beingtested in practice on selected samplecomponents. An FEM simulation of theforming process is carried out to deter-mine which sections of the plate willbe deformed to a critical degree andneed to be treated. These are thenheat-treated using Nd:YAG laser radia-tion with temperature control.


The upper figure shows a car bumpermade of martensitic steel with a tensilestrength of 1400 MPa. Local softeningof the steel made it possible to form the critical area of the bend withoutproducing any cracks. Crash tests haveshown that the bumper’s high per-formance has been maintained, whileits geometrical design possibilities havebeen significantly increased.

The softening of steel can also be usedfor applications outside the automotiveindustry, such as for the steel caps ofsafety shoes. These are conventionallymade of hardenable steels, which areinitially formed in their soft state andsubsequently tempered. The bottompicture shows shoe caps made of adual-phase steel (Rm = 1000 MPa). Thecritical area of the 90° bending anglewas successfully formed by locally sof-tening the plates. The subsequent crashtest showed that they had the same ab-sorbent properties as caps made of con-ventional steels (bottom picture, left).

Contacts

Dipl.-Ing. D. Maischner, Tel.: [email protected]. A. Weisheit, Tel.: [email protected]. K. Wissenbach, Tel.: [email protected]

Above and Middle: Reshapedbumper made of martensiticsteel with a softened zone in thebending radius (sheet thickness1.6 mm); Source: Wagon Auto-motive.Below: Locally softened shoecaps (left: after crash test) madeof dual-phase steel (sheet thick-ness 1.6 mm); Source: ISCO.


New applications for high-strength steel sheetsthrough local heat treatment

Task

Laser polishing is a new, automatedproduction technique for polishingmetal surfaces, in which the material is smoothed by remelting a thin surfacelayer (< 100 µm). The aim was to de-monstrate the basic suitability of thisprocess for tool and mold constructionusing the example of a glass mold. Themachine tool required to do this wasdeveloped in a project called »Polar«. It comprises a milling center built byHermle, which was adapted for laserpolishing by integrating a beam sourceincluding optics with a beam expanderand a 3-D scanner, plus a process chamber.

Method

First of all, the process parameterssuch as scanning speed, laser outputpower and trace offset were adaptedto the material 1.2782, which is fre-quently used for glass molds. Theoverall surface area of the mold wasdivided into subareas for processing. Aspecial »border strategy« was appliedto ensure that the borders betweenthe subareas were not visible, or onlyfaintly. A software system specially developed for path generation helpedto program the routings more quickly.


After setting and programming thesystem, the polishing process wascarried out fully automatically. Byadapting the process parameters, itwas possible to achieve a roughness of Ra = 0.15 - 0.2 µm on coarselyground glass molds by laser polishing.No manual finishing was required afterthe laser process, which meant thateach half of the mold was completelypolished in just 20 minutes. The laser-polished molds were subsequently tes-ted in production, and demonstrated a surface quality suitable for standardwine glasses.

Contacts

Dipl.-Ing. T. Kiedrowski, Tel.: [email protected]. K. Wissenbach, Tel.: [email protected]


Laser polishing of glass molds

Laser-polished glass mold (front right),ground glass mold (front left), cast stemof a wine glass (background).

Task

A structured or grained effect is oftenrequired when manufacturing plasticcomponents such as automobile in-strument panels. The tools used toproduce these components thereforehave to be structured accordingly. Themethod most commonly used is photo-chemical etching. The structures areoften designed to imitate natural ma-terials such as leather or to provide atechnical function. They also have tofulfil demanding requirements in termsof touch and appearance. The aim ofthis project is to create variable opticaleffects using the new manufacturingtechnique of laser polishing by selec-tively finishing defined areas of the toolstructure, e.g. only the indentations.When the component is removed fromthe mold, only the raised sections ofthe structure are brilliantly smooth.The new method enables surfaces tobe produced that were not possiblebefore, or required considerable timeand effort.

Method

Experimental investigations of selective,locally resolved laser polishing wereperformed on tool inserts made of thematerial 1.2343 with rough-grained andfine-grained surfaces. The process in-volved scanning the surface in meander-ing loops, while the laser power and thescanning velocity in the processing pathwere modulated as a function of theexisting structure (only the indentationsare polished).


By modulating the process parameterslaser power and scanning velocity, it was possible to set locally definedvalues for roughness and hence fordegree of gloss. The range of glosscould be varied from the original matroughness to high brilliance by select-ing the appropriate laser power andscanning velocity. Resolution and pro-cessing speed are significantly depen-dent on the time constant of the laserbeam source, i.e. the time required bythe beam source to change the laserpower. The lower the time constant,the greater the processing speed andresolution. Tool inserts with an etchedsurface imitating the grained structureof leather were polished to an edgedefinition of < 20 µm and subsequent-ly used to produce plastic componentsexhibiting a dual gloss effect. The pre-sently obtainable processing speed is 3 min/cm2 at a resolution of 100 dpi.

In the further course of the project, it is planned to transfer these results to three-dimensional components, e.g.automobile instrument panels, and toreduce the processing time.

Contacts

Dipl.-Phys. A. Temmler, Tel.: [email protected]. K. Wissenbach, Tel.: [email protected]

Above: Section of a tool insertwith photochemically etchedleather-grain structure (mat andlaser-polished).Middle: Edge definition bet-ween the etched zone and thelaser-polished zone.Blow: Surface of a plastic com-ponent with a dual gloss effectcreated by laser polishing.

50 µm

50 µm

2 cm

2 cm


Dual gloss effect created by laser polishing

Task

Optical waveguide arrays are neededfor the parallelization of optical trans-mission routes. To assemble these ar-rays, support systems of the highestprecision in the sub-micrometer rangeare required. A new approach involvesjoining together ultra-precisely struc-tured carrier plates for optical fibers to form an array. These carrier platesfeature parallel grooves spaced 250 µmapart which serve as passive adjust-ment structures for alignment of theoptical waveguides. For this purpose,the carrier plates are butt-welded ontoribs (width 75 µm).

Method

The alloy CuNi18Zn20 used for the assembly component comprises 62 %copper, 20 % zinc and 18 % nickel(German silver). Due to its alloy ele-ments and surface properties, Germansilver is comparable with brass whenused for laser beam welding. The highreflectance of both metals makes it difficult to couple the laser radiation.Moreover, metals with a high proportionof zinc represent a particular challengefor welding applications because theevaporation temperature of the zinc ataround 900 °C is below the melt pointof the other alloy elements. During thewelding process the zinc evaporatesand suddenly escapes from the weldvolume, taking liquid melt with it. Thiscauses pores in the seam, uncontroll-able welding splashes and an irregularupper bead.


To optimize quality, a new approachbased on a fiber laser and scanner optics is adopted. The stability of themolten bath is distinctly improved byan oscillation movement (wobbling)imparted to the feed. A non-reprodu-cible transition from keyhole weldingto heat-conduction welding is not ob-servable. The roughness of the surfaceis also reduced. By means of whitelight interferometry, it is possible to demonstrate a reduction in the Ra values from 4 - 5 µm without wobbl-ing to 2 - 2.5 µm with an imparted os-cillation movement. If the parametersare suitably selected, there is no observ-able melting of the 75-µm-wide ribs.

Such arrays can be used as optical waveguide plugs for parallel transmis-sion or as a redundant system for thetransmission of large volumes of data.The regular arrangement of the opticalwaveguides at a distance of 250 µmfrom each other means that they canbe coupled onto VCSEL arrays.

Contacts

Dipl.-Ing. F. Schmitt, Tel.: [email protected]. A. Gillner, Tel.: [email protected]


Laser beam microwelding of 2-D optical waveguide arrays

Above: Welded 2-D optical waveguide array.Below: Detailed image of a weldseam at the rib and base transitionof two carrier plates.

Above: Feed movement withimparted circular oscillationusing scanners.Below: Coaxial illumination ofbonded silicon/glass samplesusing a scanner.

1 mm

Laser beam

Circularoscillation

Task

In hybrid microsystem technology, thesemiconductor industry and micro-electromechanical systems (MEMS), fra-gile microelectronic components suchas uncased silicon chips are encapsu-lated at wafer level (wafer level packag-ing). The encapsulation usually takesplace by means of large-area joiningtechniques such as wafer fusion bond-ing or anodic bonding. These processesexert a high thermal loading on thesensitive components and exhibit lowflexibility with regard to the joint geo-metry. As an alternative and additio-nally to wafer bonding, the laser en-ables the heat influence zone and thedistortion it causes to be minimizedthrough exact control of the energydeposition.

Method

The principle of the laser beam bond-ing technique is based on transmissionjoining, in which one of the partsbeing joined is transparent for the laserradiation applied (e.g. glass) and theother is absorbent (silicon). The mainpart of the energy in the laser beam isimplemented as heat at the interfaceof the parts being joined and the con-tact point is specifically, locally and selectively heated. After appropriatepreparation of the surface, the intro-duction of heat creates a high-strengthoxygen bridge between the two join-ing partners.


To increase flexibility and process relia-bility, a fiber laser with a wavelengthof λ = 1090 nm was deployed in com-bination with a rapid galvanometerscanner, as an alternative to localizedcontour joining with a focused laserbeam.

By imparting an oscillation motion during the feed, scanners enable therequisite flexibility to be achieved withregard to bond seam width and geo-metry. In addition, this »wobble func-tion« has a positive impact on the heatinfluence zone during joining, with theresult that no melting occurs on thejoining front.

The bonding results achieved generallyshow that fiber lasers combined withscanners can be used for bonding sili-con and glass. In addition, it is possibleto produce melt- and crack-free bondedconnections at feed speeds of up to 10 mm/s without the need for thermalprocess control. As a result, the tech-nique is also suitable for the assemblyof micro-optical components on semi-conductor-based lighting elementssuch as LEDs.

Contacts

Dipl.-Ing. F. Sarı, Tel.: [email protected]. A. Gillner, Tel.: [email protected]


Laser beam-assisted bonding of silicon and glass for wafer level packaging, MEMS packaging and display packaging

Task

Microelectromechanical systems(MEMS) such as acceleration sensors,silicon-based pressure sensors and rate-of-rotation sensors combine sensitiveelectrical, mechanical, thermal and alsochemical functions. As these systemsare particularly prevalent in the autoindustry, they must be encapsulated toensure long-term stability. The encap-sulation is usually provided by large-area joining techniques such as siliconwafer bonding. Along with wafer-to-wafer bonding, chip-to-wafer bonding,in which individual chips are positionedand bonded on pre-processed siliconwafers, has recently come to the fore.The joining techniques used up to nowcan exert considerable thermal andmechanical loadings on sensitive circuitsand especially on micromechanical com-ponents such as sensors. As an alterna-tive and a supplement to wafer bond-ing, the laser enables the heat influencezone and the distortion it causes to beminimized through exact control of theenergy deposition.

Method

The principle of laser bonding is basedon transmission joining, in which thelaser radiation penetrates the partsbeing joined and is absorbed at theconnection point by applying suitablemeasures. The energy in the laser beamis transformed into heat at the inter-face of the join partners.

For the material pairing of silicon andsilicon, a new type of fiber laser beamsource with a wavelength of 2 µm isused along with absorbing interme-diate layers, which act as functionalconductive layers on the chip.


In cooperation with the Fraunhofer Institutes IZM and IWM, it was shownthat transmission joining with laser radiation of wavelength λ = 2 µm and a laser spot of 50 µm can be applied toproduce high-strength silicon-on-siliconconnections without melt formation.Examinations of the joint zones show a melt-free connection which shows ahigh strength of the joining area exceed-ing the strength of the base material.

The new selective joining techniqueprovides a process with which thermallyand mechanically sensitive silicon com-ponents can be joined at high speedand with high precision.

Contacts

Dipl.-Ing. F. Sarı, Tel.: [email protected]. A. Gillner, Tel.: [email protected]


Laser beam-assisted bonding of silicon-silicon for wafer level chip packaging and MEMS packaging

Above: IR transmission image of a spiral-shaped bond betweentwo silicon substrates.Below: Fractured silicon surfaceafter micro-chevron testing.

200 µm

100 µm

Above: Micrograph of a glass-glass weld seam (microscope image).Middle: Micrograph of a glass-silicon weld seam (SEM, etched).Below: Surface of a silicon substrate after separation of the glass-silicon bond (SEM).

20 µm

Silicon

Glass

Silicon

Glass

20 µm

Task

Ultra-fast engineering is becoming anestablished discipline in the engineer-ing domain. The present demand forhighly precise, customized productscalls for the development of new ultra-precise manufacturing techniques,such as in microengineering. In thecurrent trend towards miniaturizationof optical components and systems(such as micro and nano optics,OLEDs1, VCSELs2), the joining of glass-glass and glass-silicon with bondingzones in the µm range represents asignificant challenge which until nowhas only been mastered to a limitedextent. The innovative OLED lightsource requires a higher-quality joiningseam, as it needs to be gas-tight(impermeable to oxygen and watervapor).

Method

Welding with ultra-short pulsed laserlight (pulse duration t < 1 ps) is beingtested as a novel method of joiningsimilar and dissimilar classes of ma-terial, such as glass-glass and glass-silicon. Through multi-photon proces-ses, the laser light is absorbed exclu-sively in the focus at sufficiently largeintensities of > 1010 W/cm2, and theglass is melted locally in the focus(approx. 1 - 100 µm3). The short im-pact time of the pulses means thatheat does not penetrate very deeply,causing less thermal stress than longerpulse durations. This makes it possibleto micro-weld inside the volume ofglass materials with a weld seam in the µm range. The overall objective ofthese tests is to establish material- andprocess-based principles for qualifyingthe joining of similar and dissimilar

types of glass, and of glass and silicon,with ultra-short pulsed laser light. Aprocess control system for fs joining isalso being devised by monitoring thelaser process.


Bonds were achieved when joiningtechnical glass materials (D263 andAF45 Schott) to substrates of silicon ordissimilar glass using ultra-short pulsedlaser light. By selecting suitable para-meters, it was possible to producecrack-free weld seams 20 µm wide and 30 µm deep in glass-glass bonding(see upper and middle figures). Thebonding strength is extremely high, as demonstrated by the fact that glassresidues can be detected on the siliconwhen test samples of a glass-siliconbond are separated (lower figure).

One of the purposes of joining glassmaterials and glass semiconductors isto seal housings, such as those ofOLEDs1 in the lighting industry orMEMSs3 and MOEMSs4 in the semi-conductor industry.

1 OLED: Organic Light-Emitting Diode2 VCSEL: Vertical-Cavity Surface-Emitting Laser3 MEMS: Micro-Electro-Mechanical System4 MOEMS: Micro-Opto-Electromechanical System

Contacts

Dr. A. Horn, Tel.: [email protected]. I. Kelbassa, Tel.: [email protected]


Femtosecond laser welding of glass-glass and glass-silicon

Task

Glass solders, which are typically pro-cessed at temperatures above 500 °C,are now widely used for hermeticallysealing glass components and in appli-cations where electrical insulation is required. As the durability and mecha-nical loadability of a glass solder con-nection depend on the stresses arising,most joining processes are subject to atemperature-time profile, which meansa high temperature loading for the entire assembly. For many applications,e.g. the encapsulation of microsensorsand microactuators, these necessaryprocess temperatures are too high, andas a result individual components aredamaged by diffusion processes. Theneed for a low-temperature joiningtechnique or a joining method wherethe introduction of energy is locally limited is therefore apparent.

Method

Laser beam soldering using glass soldermakes it possible to concentrate theenergy needed for making the con-nection so that it is spatially limited tothe joining zone and thus to minimizethe total increase in heat of the com-ponents being joined. The energy ne-cessary for melting, wetting and con-necting the parts being joined is basedon the absorption of the laser radiationapplied in the glass solder. The local in-troduction of energy must be adjustedin terms of time and geometry in such a way that the viscosity neededfor adequate flowing and wetting isachieved in the glass solder and theevaporation of glass solder constituentsis avoided.


By applying a thermally optimized process strategy, overheating of thecomponent can be avoided. An evenlevel of heating, melting and connec-tion-formation of the glass solder inthe joining zone is also achieved. Hightemperature gradients are avoided in this approach, which results in homogeneous, crack- and bubble-freesoldering.

Possible applications of this techniqueinclude sealing microsensors and micro-actuators, encapsulating organiclighting devices and producing liquidcrystal displays.

Contacts

Dipl.-Ing. H. Kind, Tel.: [email protected]. A. Gillner, Tel.: [email protected]


Laser beam soldering of glass components using glass solder

View of a laser-soldered soda-lime glass sample.

150-µm transparent PE films welded using CO2 laser radiation. Seam width 1.5 mm, feed 100 mm/s, laser power 28 W,circle diameter 17 mm.

Task

Polymer films can be lap welded with-out contact by means of Nd:YAG, diode or fiber laser radiation (wave-length in each case around 1000 nm)if the upper film is transparent and thelower film is absorbent. If both joiningpartners are transparent, the lowerfilm can be provided with suitable absorbers, but this often destroys thetransparent appearance of the weld.Alternatively, lasers are available withwavelengths for which both films possess adequately high absorption capability. Within a feasibility study the aim was to examine whether trans-parent 150-µm PE films can be weldedby means of CO2 laser radiation.

Method

Although nearly all plastics exhibit veryhigh absorption in the infrared spectralrange, thin polyethylene (PE) possessesoptical properties which are well adap-ted to lap welding at 10.6 µm, the wavelength of the CO2 laser. LDPE filmwith a thickness of 73 µm, for example,has a reflectance of R = 5 %, a trans-mittance of T = 85 % and an absorp-tance of only A = 10 %. This results in a penetration depth of 656 µm. The upper film is therefore sufficientlytransparent for the lower joining part-ner to melt.


At an average laser power of P = 28 Wand a feed speed of v = 100 mm/s, thelaser beam is moved over the films bygalvanometer scanner in the horizontalx-y plane, and with a defocused beam,a seam of 1.5 mm width is produced.The two films are pressed together bybeing stretched over a crowned sur-face. This is all it takes to form the clo-sure needed for welding. The coolingproblems that exist for the tool andenvironment in the hot wire weldingprocess currently used are avoided bythe laser method. The cost-efficiencyof both processes is currently beingcompared.

Contacts

Dipl.-Phys. G. Otto, Tel.: [email protected]. A. Gillner, Tel.: [email protected]


Lap welding of transparent PE films with CO2 laser radiation

Task

Laser beam welding of plastics hasbeen the subject of applied researchsince the early 1990s and has mean-while crossed the threshold to industrialapplication. The scope of this processextends from the production of weldsfor microengineering components tothe reproducible and process-reliablejoining of large components with highlyloadable welds. As a result of new developments in medical and biotech-nological microsystems, the joiningtechnique is having to meet higher requirements with regard to miniaturi-zation. By combining a fiber laser andan innovative, highly dynamic irradiationstrategy a new technique - TransmissionWelding by an Incremental ScanningTechnique (TWIST) was developed forthis purpose.

Method

The new approach incorporated inTWIST combines the incremental me-thod of contour welding with the highdynamics and associated effects ofquasi-simultaneous welding. Suchcomplex, precise and rapid movementsof the laser beam can only be realizedwith the components of high-speedscanning technology such as galvano-meters, polygon scanners and reso-nance scanners. There are several waysof producing such welds. The variousmovement elements such as circles, sinusoidal movements and Bernoullilemniscates can be combined to createseam geometries of complex shape. Ifthe laser beam is moved at a very highpath speed of up to 4 m/s in such anelement and this element is moved atthe same time along the desired seamcontour at the desired feed speed,high-quality welds with joint geome-tries < 100 µm can be produced.


A reduced heat influence zone withflexible adjustment of the weld seamwidth between 130 µm and 500 µm aswell as the fundamental characteristicthat the components are invisibly welded with little distortion are theoutstanding features of the TWISTtechnique. In particular current deve-lopments in microfluidic componentscall for innovative joining techniques,as channel structures with a width of50 µm have to be sealed. The heat influence zone produced by conven-tional contour welding is too big andthe channels can be blocked by melt,preventing the component from per-forming its function. The TWIST tech-nique can also be used for welding thinplastic films (100-µm polypropylene).With such advantages, the new tech-nique expands the applications of plas-tics welding by laser, while providinggreater process flexi-bility and higherprecision in the micro to macro range.

Contacts

Dipl.-Ing. A. Boglea, Tel.: [email protected]. A. Gillner, Tel.: [email protected]


TWIST - new process for microwelding plastics

Above: Various irradiation strategiesfor the TWIST technique.Below: Seal welding of membraneswith variable seam widths.

Above: Metal screw thread in plastic.Below: Plastic-ceramic composite.

Task

Plastic is becoming increasingly im-portant as a construction material fornumerous products in the technical en-vironment, and in this context plasticcomponents frequently have to beconnected with other components made of metal or ceramics.

Method

With a newly developed laser-basedjoining technique, high-strength con-nections can be very rapidly producedbetween plastics and other materials.

The LIFTEC technique (patent pending)is based on the fact that all thermo-plastic polymers are transparent or atleast translucent in the unpigmentedstate. At the beginning of the processthe non-plastic component or a part of it is heated by laser radiation whichpasses through the plastic joining part-ner. Under mechanical pressure thecomponent is pressed onto the plasticpart. As this happens the plastic is hea-ted by thermal conduction to a tempe-rature above its melting point and thecomponent or part of it penetrates intothe plastic. Given the selection of asuitable component geometry, a solid,positive bond is formed after cooling.

Compared with other heating con-cepts already in use, heating by meansof laser radiation takes place more orless independently of the thermal andelectrical conductivity of the materialbeing pressed into the plastic. This means that, in addition to metals, other materials including ceramics can be bonded with plastics. In theprocess, the properties of both mate-rials can be combined to create hybridcomponents of high mechanicalstrength (hardness), wear resistance

and good temperature stability whichare at the same time light in weightand amenable to variable shaping. Ifplastics with different melting pointsare used, it is possible to join two plas-tics with each other, or to bond plasticwith wood.


Fundamentally, the technique can bedeployed wherever it is useful to com-bine the properties of plastic and metalor ceramics. For example, it can beused on spectacles to form a betterbond between the frame and the plas-tic lenses, producing a stronger jointwhich is less liable to loosen and alsoopening up new scope for design crea-tivity. The same approach can be ap-plied for joining PVC windows or wallpanels to metal frames to form a stable,impermeable unit.

Contacts

Dipl.-Ing. J. Holtkamp, Tel.: [email protected]. A. Gillner, Tel.: [email protected]


Laser-assisted joining of plastics with metal and ceramic components

Task

For a special application in bioprocessengineering, commercially available 96-well microtiter plates are modifiedin such a way that in each case two adjacent cavities are connected with asmall channel in the cover. The cavitiesand channels are sealed by means ofan adhesive film which for this purposehas to be provided with 8 x 12 = 96circular recesses.

Method

The adhesive film with a material thick-ness of 0.25 mm is placed on a plasticcarrier film with a thickness of 0.15 mmand has to be cut in this combination.After cutting, the carrier film is removedand the adhesive film is applied to themicrotiter plate. Plastics absorb radia-tion in the infrared spectral range very

well and so a CO2 laser with a wave-length of 10.6 µm is used for this task.During preliminary tests the parametersfeed speed v, laser power P, nozzlepressure and distance, which are im-portant for cutting, were initially deter-mined so as to cause mini-mal damageto the adhesive layer. In the next step,a contour-adapted film support wasbuilt with which average quantities of approx. 100 units at a time can bereproducibly cut.


With an x-y axis system, a CO2 laserand a cutting head containing a lenswith a focal length of f = 63.5 mm,the combination of adhesive film andcarrier film was cut without any smokeresidue at v = 80 mm/s and P = 25 W.The film support is highly suitable forreproducibly cutting smallish quanti-ties. For an intended reduction of thecycle time it will be necessary to auto-mate the present manual system.

Contacts

Dipl.-Phys. G. Otto, Tel.: [email protected]. A. Gillner, Tel.: [email protected]


Cutting adhesive seals for microtiter plates

Laser-cut combination of adhesive film and carrier film,thickness 0.4 mm, hole diameter6.5 mm, perforated grid for 8 x 12 microtiter plate.

Above: The Mach number of a cylindrical-conical nozzle.Below: The pressure from evaporation and flow of gasand vapor.

Task

The effect of the ultrasonic flow andits interaction with the fast flowingmetal vapor are particularly importantfor the quality of fine cutting. Ourunderstanding of the connection bet-ween cutting parameters and qualityfeatures, the potential for improve-ment and the limits of the processwere analyzed.

Method

The flow of a cutting gas in conical,conical-cylindrical and Laval nozzles iscalculated. A study of the eight nozzleparameters shows their connectionwith three result parameters which are important for cutting: mass flow in the cutting joint, gas pressure andgas speed along the cutting front. The coupling of the gas flow with themovement of the melt front, melt andvapor are then examined.


The results show that the effect of thestagnation point flow on the nozzleflow is an important phenomenon infine cutting. The driving forces (pres-sure gradient, shear stress) along thecutting edge exhibit strong depen-dence on the nozzle parameters (topfigure), from which the process do-mains are identified with qualitativelydiffering solution behavior. The indi-vidual process domains are differen-tiated by means of the dominant ap-pearance of different physical pheno-mena: effect of the gas flow into thegas nozzle, inflow of metal vapor intothe gas nozzle (bottom figure), detach-ment of the gas flow from the topedge of the cut, acceleration of themelt in the opposite direction to thegas flow and detachment of meltdrops on the top edge of the cut.

The determination of a suitable nozzletype and the nozzle parameters is indi-cated and the sensitivity of the para-meters to the solution is shown.

The work presented was funded by the German Research Foundation DFGunder reference number SCHU1506/1-1and is being continued in the ExcellenceCluster »Integrative Production Tech-nology for High-Wage Countries«.

Contacts

U. Jansen, Tel.: [email protected]. Dr. W. Schulz, Tel.: [email protected]


Fine cutting

Task

Crack-free cutting of silicon is anexample of the work involved in cutt-ing very thin but relatively wide com-ponents made of brittle-hard materials.To improve the breaking strength of Si wafers, the edge zone, which is degraded by cracks, is expensivelyremoved in an acid bath.

A better understanding of what hap-pens when brittle-hard materials arecut is intended to indicate unexploitedpotential and the limits of fine cutting.

Method

The flow of the cutting gas and in par-ticular its mechanical effect on the thinwafer are examined as a function ofthe nozzle parameters. In addition tothe gas flow, the material is mechani-cally loaded when the recoil pressureof the evaporating material acquireshigh values at the beginning of thepulse. The heating effect of cuttingproduces radial and azimuthal stressesin the environment of the cutting frontwhich are compared with the breakingstress.

To calculate the ultrasonic flow of thecutting gas, the existing simulation ofthe friction-free Euler equations is ex-panded by including the interactionwith the evaporating silicon.


The mechanical loads caused by thegas flow, evaporation (top figure) andthe thermomechanical effect (bottomfigure) as variables distributed in timeand space are stated as the result.

The thermomechanical load cyclecauses crack formation with a charac-teristic spatial structure (bottomfigure). The dynamic stress condition in the material produces crack pro-pagation vertically to the cutting edgewhich is deflected by the stress field inazimuthal direction. The change in thedirection of propagation takes place at a distance reflecting the magnitude of the thermal penetration depth. Thethermal energy deposited in the ma-terial and the penetration depth of theheat are closely connected with theappearance and length of the crack.

The work presented was funded by theGerman Research Foundation DFG underreference number SCHU1506/1-1.

Contacts

Dr. M. Niessen, Tel.: [email protected]. Dr. W. Schulz, Tel.: [email protected]

Above: Distribution of the pressure caused by an ultrasonic flow of gas. Below: Crack formation,temperature (black), radial stress (blue), azimuthal stress (red).


Fine cutting of silicon

Task

There is high demand in industry forprecision-drilled holes of defined shapein the diameter range of less than 100 µm with a high aspect ratio. Theseinclude, for example, drill holes fornozzles (injection nozzles, spinningnozzles) and air-cushioned bearings, as well as lubrication and ventilationdrill holes. In particular, shaped holeswith a positive taper ratio, i.e. with alarger hole exit than entry, are required.Such holes cannot be produced byconventional laser drilling methodssuch as percussion drilling, and the necessary small diameters cannot beachieved by trepanning. Another pro-blem is that the precision with regardto the roughness of the drill hole wallis not high enough. The stated require-ments are, however, fulfilled by themost recent of the laser beam drillingtechniques - spiral drilling.

Method

In spiral drilling the rotating laser radiation removes the material by meansof numerous short high-energy laserpulses, while the laser radiation movesinto the depth of the material. Thecontinuous rotational movement alongthe wall of the drill hole produces asmooth, homogeneous surface. Thedifferent taper ratios are achieved byvarying the setting angle of the laserradiation on the workpiece. The laserradiation then rotates along the lateralsurface of a cone, whose opening angleis proportional to the taper angle ofthe drill hole. A variant of the spiraldrilling method makes it possible toproduce small holes. In an optical sys-tem developed at the Fraunhofer ILT

for spiral drilling, the laser radiation rotates on itself additionally to the rotational movement in relation to theworkpiece. Through this additional rotation spirally drilled holes can bemade down to a diameter range whichmatches percussion drilling.


By means of spiral drilling in which theradiation rotates on itself, shaped holescan be produced with a taper ratiofrom the entry diameter to the exit diameter of 1:3 for 1 mm componentthickness to 1:4 for 2 mm thickness.The roughness of the hole wall is in the range Ra < 1 µm. By changing thesetting angle of the laser radiation andthe hole diameter during the drillingprocess, countersunk holes or holeswith defined tapering can be produced.

Contacts

Dipl.-Ing. W. Wawers, Tel.: [email protected]. A. Gillner, Tel.: [email protected]


Precision-drilling of shaped holes in steel

Above: Examples of various taper ratios.X5 CrNi 18 - 10, d = 1 mm.Below: SEM image of the wall of a spirally drilled hole in X5 CrNi 18 - 10.

Entrance 65 - 70 µm

65 µm 85 µm 120 µm 160 µm 200 µm

Exit

Task

The hole geometries obtained by laserdrilling, including factors such as thehole depth, are currently analyzed bymeans of destructive testing methodssuch as the longitudinal grinding ofdrill holes followed by a microscopicexamination. In order to replace thesedestructive methods and reduce thetime and cost involved, a new tech-nique is being applied which enablesthe hole depth to be determined in-situ during the percussion drilling.

Method

The hole is drilled at a defined distance(approx. 100 µm) from the polished sidewall of the stainless steel workpiece. As the material heats up during impactof the laser pulses and cools down inthe interval between two consecutivepulses, plastic deformations are inducedin the workpiece’s side wall. These de-formations are photographed from theside with a high-speed camera (MotionXtra HG-100K by Redlake), which issynchronized with the laser beam source(upper figure). The photographs are taken between pulses to avoid po-

tential overexposure due to opticalemissions (melt, plasma etc.) producedby laser radiation. To evaluate the re-sults, the resolution (µm/pixel) of thephotograph is determined, and thelength of the deformation is measuredbased on the number of pixels in thephoto.


Destructive testing methods are beingreplaced by in-situ determination ofthe hole depth during the percussiondrilling. The depth of laser drill holes isbeing measured with a temporal reso-lution of 50 ms. The spatial resolutionis 29 µm/pixel and is dependent on themagnification of the camera lens andthe size and pixel number of the camerasensor.

The determined drill hole depths areused to investigate the maximumdepths that can be achieved usingdifferent parameters (lower figures).

Contacts

Dipl.-Ing. J. Dietrich, Tel.: [email protected]. I. Kelbassa, Tel.: [email protected]


In-situ determination of drilling depth during percussion drilling

Above: Photographs of thesurface deformations producedduring percussion drilling.Below: Measured drill holedepths versus laser pulses asachieved using the processgases oxygen, argon and heliumwithout changing the processparameters.

Above: Cross-section of a drill hole in Inconel® 690.Below: Bar chart showing the evaluation of 93 drill holediameters.

500 µm

Task

In nuclear power plants, precisionnozzle drill holes with a diameter of350 µm and a depth of 2 mm are re-quired. Due to the immense thermo-mechanical stresses encountered inthis environment, components aremade of the nickel-based super alloyInconel® 690. This austenitic alloy hasvery high strain-hardening properties,is very tough, and has low heat con-ductivity. This causes major stress andwear in tools during machining proces-ses, particularly mechanical drilling. By trepanning with laser radiation, drillholes with the required precision of ± 25 µm can be produced with littleeffort compared to alternative proces-ses such as electro-discharge machin-ing (EDM) or electro-chemical machin-ing (ECM).

Method

Trepanning involves two process steps:1. A through-hole is pierced by per-

cussion drilling (several pulses on the same area of the workpiece).

2. The hole is then given its final dia-meter by trepanning (laser cutting).

Suitable process windows are deter-mined for each of the two steps by sys-tematically varying such parameters as:• Focus position during trepanning• Feed rate• Number of passes

The drilling results are analyzed andevaluated in terms of their geometricaland metallurgical features on the basisof longitudinal sections.


• Drill holes with a diameter of 350µm can be produced in 2-mm-thickInconel® 690 with a standard devia-tion of 6 µm.

• The diameter tolerance of ± 25 µmspecified by the customer is achievedfor all drill holes.

• The diameters of the drill holes aredetermined by means of a 100-per-cent final inspection by transmittedlight microscopy, and are measuredand recorded with the help ofimage processing software.

Contacts

Dipl.-Ing. K. Walther, Tel.: [email protected]. I. Kelbassa, Tel.: [email protected]


High-precision nozzle drill holes in Inconel® 690 nickel-based super alloys

Task

Drilling by laser radiation can be doneusing various different techniques,such as single-pulse or percussion drill-ing or trepanning. In order to achieve a specified drill hole geometry, it isnecessary to know exactly which pro-cess parameters to select (intensity distribution of the laser light, focusposition, process gas) and what theproperties of the material are. The typeand pressure of the process gas em-ployed play an important role in termsof productivity (drilling speed) and withregard to the quality of the drill hole(geometry and reproducibility).

Method

In a series of tests, percussion drillholes are produced with an increasingnumber of pulses using different pro-cess gas settings (type and pressure).The holes are metallographically pre-pared and metallurgically analyzed bymeans of longitudinal sections. Thepenetration depths (maximum depthto which material has been melted)and the free hole depths (depth downto the first closure of the drill hole) aredetermined. The two figures show theresulting penetration depths (lowerdotted line) and the free hole depths(upper line) in progression for eachnumber of pulses.

Significant differences are observedbetween the effects of the two processgases argon and oxygen at a totalpressure of 5 bar. In the case of argon,the drilling channels are interspersedwith inclusions, while in the case ofoxygen, the drill holes only have inclu-sions at the base of the drilling chan-nel. When using oxygen, the melt thatstill fills nearly the entire drilling chan-nel after the first pulse is driven out asthe number of pulses increases. Drillholes made using the process gas ar-gon feature an irregular distribution ofinclusions and have no clear tendencyin terms of the hole depth.


The tests show that the process gasparameters have a strong influence onthe drilling result. This means that, inaddition to the laser parameters, it isalso important to set the process gassuitably for each application and eachset of drill hole specifications (e.g. pro-cess duration, diameter tolerance orpermissible thickness of the oxide layer).By dynamically regulating the pressurein line with the hole depth, it is poss-ible to pierce a through-hole morequickly and with smaller fluctuations inthe process duration.

Contacts

Dipl.-Ing. K. Walther, Tel.: [email protected]. I. Kelbassa, Tel.: [email protected]


Influence of process gas on percussion drilling

Above: Argon 5 bar, as a function of the pulse number.Below: Oxygen 5 bar, as afunction of the pulse number.

1 2 3 5 10 20

1 2 3 5 10 20

Above: Temporal expansion of the plasma inside preparedblind drill holes, including thetimes at which the images weretaken relative to the start of thepulse in ns.Below: Test setup.

Task

Diagnosis during laser drilling generallyincludes the lateral observation of gasand plasma dynamics above the drillhole, the coaxial observation of opticalradiation emitted from the drill hole(in-situ) or a metallurgical analysis bymeans of light or electron microscopy.Due to the limited optical accessibilityof the drill hole, only the processestaking place near the surface can beobserved (expansion of plasma in thehalf-space), which provides insufficientinformation about the vapor and plas-ma dynamics. Alternative approaches,such as drilling in transparent materialto enable optical observation of theprocess, provide only a limited indica-tion of what the process would looklike in metal, due to the differing physical properties of the materials.Non-destructive techniques, such asimaging the drill holes with X-rays, arenot suitable for resolving the processdynamics due to the small temporaland spatial resolution achieved.

Method

Blind drill holes are prepared in metalfoils of various thicknesses (30 -100µm) by making cuts in the foils. Thewidth of the cut gaps corresponds tothe diameter of the drill holes. Opti-cally transparent materials are placedon either side of the metal foils as win-dows. The drilling process is continuedat the prepared drill holes, and is ob-served laterally through the windowsby means of high-speed photography(lower figure). The dynamics of theplasma, or the shock front, are thendetermined in temporal and 2-D spatialresolution (upper figure). The measure-ments include the spread and the expansion rate of the plasma and theshock front. Using a comparable test

setup, the intensity and broadening of spectral lines is measured by spec-troscopy, and from that, it is possibleto determine electron densities andtemperatures in the plasma. Thesefactors can be used to calculate thespace- and time-resolved absorptioncoefficient in the plasma, and the plas-ma frequency in the drill hole. Fromthe results, it is then possible to deriveinformation on optical properties ofthe plasma (absorption and refraction),which can be used to adapt the subse-quent pulses in order to optimize thequality (e.g. thickness of the melt film)and productivity (e.g. drilling speed) ofthe drilling process.


• Time- and space-resolved diagnosisof the optical emissions of spatiallyconfined plasma in the drill hole

• Spatial resolution ≥ 1 µm, temporalresolution ≥ 1 ns

• Expansion and expansion rate of plasma and shock front

• Electron and ion temperatures anddensities inside drill holes

Contacts

Dipl.-Phys. M. Brajdic, Tel.: [email protected]. I. Kelbassa, Tel.: [email protected]


Plasma diagnosis during laser drilling

Task

A spatially resolved drilling modelwhich is able to describe the time-de-pendent formation of the drill hole is akey element in understanding the phy-sical mechanisms at work when drillingusing laser radiation. As far as the useris concerned, the main issue is to findways of avoiding the formation of recast on the wall of the drill hole.

Method

The predecessor model describes thedrilling process with a spatially inte-grated representation of the hole bot-tom face. The physical phenomena ofheat conduction, flow of the melt andevaporation are taken into account.The model is expanded with the in-clusion of spatial resolution at the holebottom face. The geometrical shape ofthe evolving drill hole is calculated andis part of the solution. By analyzing thedrilling model for the process variantof percussion drilling, the cooling ofthe outflowing melt is examined dur-ing drilling.


The formation of a drill hole by expul-sion of a molten phase is performed by accelerating the melt arising at thebase of the drill hole and deceleratingthe melt along the wall of the hole.The formation of recast on the wall ofthe hole results from the flow equili-brium, which depends on the heatingof the melt surface, the transport ofheat in the flowing melt and cooling inthe surrounding material. The resultsof an initial model task for the spatiallyresolved drilling model can be seen inthe figure. The hole bottom face, thetemperature in the solid and in themelt, the flow speed of the melt, themelt film thickness and the recastthickness on the wall of the hole areparts of the time-dependent solution.

By taking the local events at the holebottom face into account it is possiblefor the first time to simulate and ana-lyze in detail the model for the forma-tion of the drill hole as well as forstructuring and material removal.

The work presented was funded by the German Research Foundation DFGin the Excellence Cluster »IntegrativeProduction Technology for High-WageCountries«.

Contacts

Dipl.-Phys. U. Eppelt, Tel.: [email protected]. W. Schulz, Tel.: [email protected]


Drilling with efficient melt expulsion

Simulation of the spatially resolvedmodel.

Above: Balloon catheterwith a partially inflated balloonat its tip.Below: Array of 50-µm holes in the balloon casing.

Task

The systemic delivery of drugs to treatlocal vascular diseases has the disad-vantage that large volumes of the activeingredient have to be introduced intothe bloodstream. Under these condi-tions, it is impossible to accurately dosethe concentration of the drug at thetarget site. The dose could be regulatedmore efficiently if the drug seeped out through small pores in a ballooncatheter placed directly adjacent to the vessel wall.

Method

Balloon catheters are used in medicalapplications where vessels need to bewidened or probes need to be tempo-rarily fixed in place. The balloon casingis initially wrapped tightly around aguiding catheter during insertion, andis then expanded at the target site by filling it with a physiological salinesolution. The drug, together with thesaline solution, can then seep outthrough small openings drilled into thecatheter’s balloon casing with an ArFexcimer laser. The appropriate size and number of holes is determinedthrough preliminary tests in a waterbath.


Excimer lasers enable holes to be drilledinto the balloon casing without any visible degradation. The risk of particlesbeing released during insertion is low,as any particles present in the area arecarried away by the rinsing fluid.

At diameters of 20 µm and above, the liquid flows through the holes at asteady rate with an upstream pressureof 5 bar. Holes with a diameter of 30 µm typically result in a flow rate of30 µl/min. In this case, the upstreampressure can be varied between 1.5and 6 bar to control the flow. The drugcan be dosed by adjusting the numberand size of the pores.

This project was carried out in coope-ration with PD Dr. G. A. Krombach of the Department of Diagnostic Ra-diology at RWTH Aachen UniversityHospital.

Contacts

Dr. M. Wehner, Tel.: [email protected]. A. Gillner, Tel.: [email protected]


Micro-perforation of balloon catheters

Task

The physical processes and processlimits involved in materials processingwith ultra-short pulsed laser radiation(pulse duration tp < 1 ps) have not yetbeen sufficiently examined. The knownadvantages of femtosecond lasers,such as melt-free ablation and a lowthermal load on the material, are oftenrestricted to small fluences. The use ofhigh-energy (F > 10 Jcm-2), ultra-shortpulsed laser radiation produces ther-mal and non-thermal melt formationand significantly influences the ma-terials processing results.

The aim of these tests is to visualizethe dynamics of plasma, material va-por, melt formation and melt solidifica-tion in metals and to define processlimits.

Method

A novel optical pump&probe measur-ing technique for temporally and spa-tially resolved visualization and analysisof ultra-fast phenomena is used. Thisinvolves Transient Quantitative Phasemicroscopy (TQPm) for determiningthe quantitative optical phase, changesin the transient indexes of refraction,and melt volumes, at a temporal reso-lution of 100 fs and a spatial resolutionof 1 µm. The melt dynamics of metalsare examined at up to τ = 2 µs afterirradiation with n = 1 to 8 laser pulses.


The dynamics of the laser-induced meltformation and material ablation ob-served in aluminum can be divided intoseveral characteristic time regimes. Asa function of the process parameters,expulsion of the heated evaporatedmaterial (τ < 200 ns), explosive melt-free ablation (200 ns < τ < 700 ns) andthe formation of melt films (τ > 700 ns)are observed. Assuming rotationalsymmetry, the volumes of the ablatedmaterial particles are measured intemporal resolution. The dynamics ofthe ejected material featured qualita-tive and quantitative differences de-pending on the number of pulsesused. At τ > 700 ns, for example, meltformation increases with increasingpulse energy and number, whereas theformation of material vapor diminishes.

The experience gained by this tempo-rally resolved diagnosis can be used to control microstructuring processescarried out with ultra-short pulsedlaser radiation, and to model laser-induced phase transitions.

Contacts

Dipl.-Phys. I. Mingareev, Tel.: [email protected]. I. Kelbassa, Tel.: [email protected]


Diagnosis of ultra-fast, laser-induced melt dynamics of metals

Above: Melt expulsion in Al (τ = 1.67 µs), left: shadow image,right: calculated phase image.Below: Surface modification withmelt deposits after 8 laser pulses.

5 µm

Above: Ablation with pico-second triple pulses. Middle: Comparison betweena spectrum produced by meansof a plasma model and thedetected spectrum of a C75sample.Below: Results of the plasmasimulation.

Task

The aim is to improve the efficiency oflaser beam microablation by increasingthe ablation rate, while at the sametime keeping surface roughness suffi-ciently low by reducing the portion of liquid material during the process.

Method

By using tailored, time-modulated laserpulse trains, the project goal is to ma-ximize material ablation and improvethe diagnosability of the plasma dyna-mics without increasing laser energy.One approach involves dividing theenergy of a discrete laser pulse intopulse bursts with interpulse separa-tions in the nanosecond or micro-second range. Laser-induced break-down spectroscopy is used to investi-gate the induced plasma signal forpossible correlation with the volume ofmaterial removed. By analyzing andmodeling the plasma dynamics, controlrules are to be derived which aim atmaximizing the ablation rate.


During laser microstructuring with pico-second multipulses, the processing re-sult can be widely varied by alteringthe burst parameters. The use of pico-second dual or triple pulses improvesthe ablation rate by up to 90 percentfor each layer. This can be achieved ex-clusively by temporal variation of theintensity without changing the overallenergy input. By carefully selecting the process parameters, an ablationvolume of 1 µm per layer with a sur-face roughness of Ra ≤ 0.6 µm can beachieved using picosecond triple pulses(see upper figure).

The plasmas generated during micro-ablation are detected using space- andtime-resolved measurements. The diag-nosis of characteristic plasma dynamics(temperature and density of electrons,expansion of the plasma) is to help indeveloping an online monitoring sys-tem that measures the current ablationefficiency of the laser pulse.

A model-based analysis of the dyna-mics of the melt during the ablationprocess, the behavior of the plasmaafter the laser pulse hits the sample,and the spectral emission of the plas-ma are carried out as a function of time.The detected spectra can be simulatedusing a model for calculating spectralplasma emissions, which incorporatesmaterial properties as well as spatiallyresolved and spatially integrated plas-ma dynamics (electron temperatureand density, plasma expansion) andtheir temporal characteristics (seemiddle figure). The absorption ofradiation energy and thus also thetransport of radiation to the workpieceis described on the basis of a fluiddynamic simulation of the plasma andvapor (see lower figure).

Contacts

Dipl.-Phys. C. Gehlen, Tel.: [email protected]. (FH) C. Hartmann, Tel.: [email protected]. U. Eppelt, Tel.: [email protected]


Improved solid-state laser microablation processeswith tailored pulse trains

Task

Tiny hairs acting as flow sensors areoften found in the natural environ-ment. Spiders, for example, have smallhairs in their joints that provide infor-mation on their angular position. Fishhave what is known as a ‘sideline sys-tem’, which helps them to map theirfluidic environment. To transfer theseprinciples to manmade systems, it isnecessary to produce synthetic micro-hairs of different geometries with diameters of 20 to 200 µm and lengthsof up to 1 mm.

Method

Microhairs with diameters in the micro-meter range are produced using a ‘lostmold’ (lost wax or investment casting)technique. The advantage of this tech-nique is that it enables force-free de-molding of the filigree structures bysimply melting the surrounding matrix.Microhairs produced in this way can bemade to have virtually any dimensionsand geometries. Combined with pie-zoelectric elements, they can be usedto develop sensors for medical applica-tions. By grading the lengths of the mi-crohairs on such a sensor element andpassing it through a stenosis, forexample, it is possible to draw accurateconclusions as to the geometry of thestenosis. To this end, the signals of thepiezoelectric element must be analyzedwith regard to both their strength andtemporal sequence.


Following initial studies on the ablationbehavior of wax and a comprehensiveparameter study on the drilling of cast-ing molds, the first microhair arrays arenow available and have already beentested in combination with piezoelectricsensor elements. The signal sequencegenerated by pressure on the micro-hairs is clearly recognizable and can be matched to the different microhairlengths. The hairs produce much weaker signals when they are bentthan when they are impressed, the ratio being approx. 1:10. It is thereforepossible to match individual signals to the corresponding microhairs andgiven loading conditions (shearing, folding, bending) on the basis of theirsequence and strength.

In addition, such microhairs can beused to measure flow mechanics evenwithout an added sensor element. Thisinvolves analyzing the deflection of microhairs in the shear field of theflow near the wall. The simulation ofbiological structures, such as the sen-sory hair cells in the inner ear, can help in analyzing the flow-mechanicalevents taking place during the hearingprocess.

Cooperation partners: Prof. C. Brücker,Institute of Mechanics and Fluid Dyna-mics, Freiberg University of Mining andTechnology.

Contacts

Dipl.-Chem. P. Jacobs, Tel.: [email protected]. A. Gillner, Tel.: [email protected]


Synthetic microhairs for sensory applications

Above: Signal sequence under normal loading conditions (Source: IMFD Freiberg).Below: Array of microhairs.

Task

Nanostructures offer great potentialfor imparting new functions to surfaces.As an example, nanostructuring canproduce superhydrophobic propertieson polymers and other materials. Furthermore, nanostructures can beused to generate optical effects andfunctions. By stringing together nano-structures of differing periodicities, for example, it is possible to form anindividual color code that can be usedto distinctly label products. The colorcode is only visible when illuminatedfrom a specific direction.

Method

In order to produce nanostructures in the 100-nm range, a three-beam interference system was set up whichmerges three coherent beamlets tocreate periodic structures. The periodof these structures depends on the wavelength of the laser and the setmerging angle. The intensity profilecreated by superposition of these threebeamlets enables a higher contrast to be achieved than with a classic two-beam interference system. A frequency-tripled Nd:YAG laser with λ = 355 nm and a sufficient coherencelength was used as the beam source.


The developed structuring system wasused to produce nanostructures in thinpolymer films by photochemical ablation.By varying the angle of exposure, it is possible to produce structures of200 nm, for example, with a period of approximately 1 µm (see figure).Smaller structures under 100 nm canalso be created by altering the irradia-tion conditions. The resulting stripepatterns serve to analyze cell growthproperties on synthetic surfaces. Evenvery complex patterns can be createdwith this system by rotating the com-ponent and by dual and multiplestructuring. In this way, the wettabilityof a surface can be selectively alteredin certain places to give it superhydro-phobic properties (lotus effect).

Contacts

Dipl.-Phys. S. Beckemper, Tel.: [email protected]. A. Gillner, Tel.: [email protected]


Creating periodic nanostructures by three-beam interference

Periodic nanostructures in photoresist, period 1 µm, feature width 250 nm.

Method

By focusing femtosecond laser light in-side the volume of transparent dielec-trics (sapphire, glass), it is possible toachieve local changes in microstructureand thus also in etchability. This makesit possible to produce 3-dimensionalmicro- and nanostructures by sub-sequent etching with hydrofluoric acid.


It is possible in sapphire to achievedifferences in etchability of up to10.000:1 between modified and un-modified areas. This enables the manu-facture of µ-channels with diametersbetween 1 and 10 µm at lengths of

more than one millimeter. Periodic nanostructures (nano planes) can beformed in the irradiated area as afunction of the focusing parametersand the average laser power. The nanoplanes are always oriented perpendi-cularly to the polarization of the laser radiation. Their orientation is not influ-enced by changes in the traversing di-rection. By selectively etching the nanoplanes, it is possible to produce nanos-copic cavities measuring approximately100 nm x 10 µm x 1 mm at writingspeeds of 1 mm/s. Potential areas ofuse include microfluidic systems forbiological and chemical applications,and photonic crystals for integratedoptical elements.

Contacts

Dipl.-Phys. D. Wortmann, Tel.: [email protected]. (FH) H. Horn-Solle, Tel.: [email protected]. J. Gottmann, Tel.: [email protected]


3-dimensional micro- and nanostructures inside sapphire produced by selective, laser-induced etching

Above: Transmitted light micros-cope image of a partially etchedµ-channel.Middle: SEM images of cross-sections of the etched areas to a depth of 500 µm; above: nanocavities, below: microchannel.Below: Schematic outline of thelaser-induced volume modification.

modified channel

etched microchannel

Scan direction

1 µm

2 µm

Method

By focusing femtosecond laser radia-tion inside the volume of glass ma-terials, their refractive index can belocally increased. The use of doublepulses with time intervals in the sub-nanosecond range produces a signifi-cantly greater change in the refractiveindex than the use of single pulses.


When pure silica glass is irradiatedusing fs double pulses with time inter-vals of between 400 and 800 ps, it is possible to increase changes in therefractive index by a factor of 1.5 to 2compared to the use of single pulseswith the same total energy. This in-creased difference in the refractive in-dex between modified and untreatedmaterial results in an increase by thesame factor in the numerical apertureof the waveguide fabricated using thisprocess.

The results obtained in this project are among the world’s highest valuesachieved so far for silica glass, andopen up the prospect of producingwaveguides with numerical aperturesof the same magnitude as those ofdiode lasers. The results can be ex-plained by the active influence of thesecond pulse on the relaxation chan-nels of intermediate electronic states,and the microstructural changes result-ing from this. Areas of application in-clude wave-guiding or beam-shapingelements of integrated optics, such as beam splitters, coupling structuresfor diode lasers or waveguide lasers.

Contacts

Dipl.-Phys. D. Wortmann, Tel.: [email protected]. J. Gottmann, Tel.: [email protected]


Changing the refractive index of glass materials using a double-pulse femtosecond laser

Above: Changes in the refractiveindex versus the timing interval of the double pulses, at a fixedpulse-energy ratio of 50 %.Below: Photograph of the far-field distribution of a waveguidefabricated in silica glass using fsdouble pulses.

Task

To improve the acceptance of surgicalimplants by the body, a surface has to be created on them which matchesthe biological surroundings as closelyas possible. This biofunctionalizationrequires a technique with which sam-ples of proteins, cells or active agentscan be selectively deposited on surfaces.In this way, the aim is to produce sys-tems modeled on nature which, forexample, facilitate the ingrowth of artificial implants in the body or makeit possible to conduct chip-based in vitro testing.

Method

For this task, a process and machinetechnology for the selected transfer of biologically active substances is developed which can be integrated inexisting systems, e.g. for protein spott-ing. The aim is to create products withnew properties, in particular in bioana-lysis, medical engineering and regene-rative medicine. The basis for the inno-vative process is provided by a laser-based transfer system known as LIFT(Laser Induced Forward Transfer). Inthis process, a substance located on a film as a transfer medium is transpor-ted by laser ablation onto a substrate.Transfer takes place via a laser-activeabsorber layer carrying the proteins or cells which evaporates under laserirradiation. The resultant pressure wavetransports the proteins and cells overshort distances to the substrate.


Protein arrays can be produced at thehigh speed of approx. 1,000 spots persecond. With the present setup, thespot sizes can be varied from 20 µm to 200 µm. Lines and tracks of proteinscan also be written. In a next step theintention is to produce complex samplesof various proteins in order to study the reaction of cells to them. It has also been shown that cells and cell networks can be transferred. Givensuitable selection of the laser parame-ters, no loss of vitality was observed.The cells adhere to the substrate sur-face and proliferate, which means thatconstructs of different cell types can bedeveloped and cultivated. In a furtherstep nanoparticles can be transferredby LIFT to precisely targeted locationson surfaces which are charged withactive agents, thus making it possibleto create innovative bioactive coatingson different moldings.

This project is being funded under theInnoNet program (16-IN 0490) andconducted in cooperation with thecompanies Arthro Kinetics, Aurentum,BioCat, Boston Scientific TZ, CryLaS,GeSim and the Institute for InterfacialEngineering of Stuttgart University.

Contacts

Dr. E. Bremus-Köbberling, Tel.: [email protected]. A. Gillner, Tel.: [email protected]


Laser-induced forward transfer of proteins, cells and active agents

Target support layer

Substrate

Above: Schematic of the LIFT process.Below: Protein array with spot sizes of 60 µm (fluorescenceimage) produced using LIFT.

Laser Plan and System Technology

This business area focuses on the development of prototype equipment for laser and plasma-technology ap-plications, as well as on laser systems engineering, particularly in the fields of automation and quality assurance.Areas of application embrace welding,cutting, hardening, repair coating, drilling and micro-joining. The systemtechnology offered provides completesolutions for process monitoring, com-ponents and control systems for preci-sion machining, laser-specific CAD/CAMtechnology modules, as well as soft-ware for measurement, open- and closed-loop control and testing. For its work in process monitoring in par-ticular the business area can draw onextensive and, where required, patent-protected know-how. In this sector numerous systems have already beenlicensed for companies. Target marketsinclude laser equipment and compo-nent manufacture as well as all sectorsof production industry which deploylasers in their manufacturing activity or intend to do so.


Business AreaLaser Plant and System Technology

Development of cladding headsfor laser cladding.

Development of a multifunctional production cell with integrated combi-head 110

Development of a boroscopically guided processing optic for Laser Metal Deposition 111

Welding of shock absorber valves: development, qualification andknowledge transfer 112

In-situ measurement of laser systems 113

Robust autonomous joint tracking for quality assurance in laser welding 114

Strategies for process monitoring in plastics welding using laser radiation 115

False friends 116

Analysis and application of methods and algorithms to ensureconstant product quality 117

Computational steering system for parallelized simulation calculations 118


Contents

Task

Combined processing, in which theprocess change between laser cuttingand welding can be made rapidly with-out having to retool, facilitates very flex-ible and highly productive use of lasersystems. The benefits are especiallystrong if the entire system includinghandling and clamping equipment isoptimally matched to the efficient pro-cess chain and the high accuracy ofcombined processing. This applies, inparticular, to high-speed applicationson highly dynamic systems and to 3-Dapplications.

In systematic parameter variations with the combi-head, cutting speedsof 38 m/min, for example, were de-termined on 1 mm thick steel sheetsusing a fiber with a diameter of 150 µm,and 135 m/min with a diameter of 50 µm. At these speeds it is not theprocess but the machine which is thelimiting factor for 2-D and much moremarkedly for 3-D applications.

Method

In cooperation with the companies ReisRobotics as the machine manufacturerand Laserfact as the manufacturer ofthe combi-head, a combi-head with aconnection flange arranged coaxially to the optical machine axis and with acompact additional axis is being deve-loped which can be optimally integratedin the mirror beam guidance of a robotportal system. The beam guidance running internally in the robot arm makes it possible to move in three rotaryaxes without any movement of the fiber.This reduces the strain on the fiber andconsiderably increases the permissibledynamics during rapid reorientations ofthe head and high accelerations. Thedynamic additional axis integrated in

the head serves the purpose of distancecontrol. The ability to rapidly changethe focusing optics and a protectiveglass cover increase operating conve-nience.


Components of the head such as thecapacitive distance control and thenozzle assembly have already beensuccessfully tested. The head will beintegrated in the beam guidance ofthe portal system in January 2008. Thismeans that, in addition to the combi-head with direct fiber coupling, a co-axial variant is also available for testingthe multifunctional production ofsheet metal assemblies comprisingtailored blanks through to three-dimen-sional vehicle components.

The work is being funded by the Ger-man Federal Ministry of Economics andTechnology (BMWi) as well as by thecompanies Reis Robotics, Laserfact andLBBZ under the InnoNet project »FlexibleProduction Cell for Combined LaserProcessing with Adaptive Gripper Tech-nology (koLas)«.

Contacts

Dr. F. Schneider, Tel.: [email protected]. D. Petring, Tel.: [email protected]


Development of a multifunctional production cellwith integrated combi-head

Combi-head with coaxial connectionfor 5-axis systems and robot with integrated beam guidance (graphic: Laserfact).

Task

Within a project with Rolls-RoyceDeutschland, a boroscopically guidedprocessing optic for Laser Metal Depo-sition is being conceived, designed andmanufactured. Its aim is to conducton-wing repairs to aircraft enginecompressor blades which have beendamaged, for instance by Foreign Ob-jects Damage (FOD).

Conventionally, Rolls-Royce Deutsch-land already blends small, usuallysharp-edged defects on damagedblades by means of boroscopicallyguided milling in the engine, so thatthe notch effect under load (in opera-tion) caused by this defect is distinctlyreduced.

A combination of boroscopic blendingwith an additive manufacturing pro-cess such as LMD is intended to facili-tate the repair of more major defects.

Method

In the concept phase, the requirementsin terms of size - limited by accessibilityand processing conditions -, requiredprocess media and design aspects aredetermined. The beam path is calculatedon the basis of the technical specifica-tions issued by laser and optical fibermanufacturers, and the optical compo-nents are designed accordingly.

The processing optic (top figure) is de-signed as a modular system comprisinga coating head, a collimation and fo-cusing module, an optical fiber andprocess media transfer unit, and a guide tube support. Along with thesupply lines for powder and inert gas,two water-cooling circuits are integrated.The laser radiation is collimated andfocused, exiting coaxially from the pro-cessing optic.


Three modules of the processing opticare made of copper and then chrome-plated. The module supporting theguide tube is made of steel (bottomfigure).

A diode laser system with a maximumoutput power of 1 kW is used as thelaser beam source. The laser radiationis coupled into the processing optic bymeans of a specially produced opticalfiber with a maximum outer diameterof 8 mm. The optical fiber is guided by the guide tube, on whose movabletip the processing optic is assembliedby means of Bowden cables.

After assembly of the optical systemand connection to the guide tube andoptical fibers, general functional testsare successfully conducted. Initialcoating tests on flat substrate plateshave been successful. The next stepwill be to implement the process onblade-like samples.

Contacts

Dipl.-Ing. (FH) P. Albus, Tel.: [email protected]. I. Kelbassa, Tel.: [email protected]


Development of a boroscopically guided processing optic for Laser Metal Deposition

Above: Exploded drawing of the processing optic withcoating head, collimation andfocusing module, optical fiberand process media transfer unit,optical fibers, support andguide tube (from left to right).Below: Fully assembled pro-cessing optic.

Task

The task is to develop and qualify laserwelding for shock absorber valves withdefined preload forces. The productand the process are to be scaled up for cost-effective full-scale production.The aim is to develop a capable pro-cess with an index of cp > 1.33. Later itis intended to build a production facilitywith a capacity of > 2 million parts perannum.

Method

The customer is a manufacturer ofshock absorbers and other productswhich it supplies to the auto industryand is seeking to increase the precisionof damper production. To this end a laser welding technique has been developed and laboratory-tested whichmakes it possible to precisely adjustthe speed-power characteristic ofshock absorbers. The strength index is cp > 1.33.


Pre-series testing of the process wascarried out with a preloading device installed on a laser unit at the Fraun-hofer ILT. It achieved cycle times of ap-prox. 30 seconds per part and weldeda significant number of shock absorbervalves. In the preloading device, theparts were tensioned with defined forces.The relative movement between the la-ser beam and the workpiece is achievedby rotating the parts. This induces disruptions which increase the scatterof the damper characteristics and thusadversely affect control of the pro-duction process. The capability index isless than 1 and so the device is beingincrementally improved. In addition to solving the production-engineeringtask, the success of the project deci-sively depends on an effective transferof the knowledge gained. It is there-fore planned to build and operate theproduction facility initially at the Fraun-hofer ILT. During its operation at theFraunhofer ILT, employees of the cus-tomer will be trained and familiarizedwith laser technology. Only then willthe unit be integrated in a productionline on the customer’s premises.

Contacts

Dipl.-Ing. M. Dahmen, Tel.: [email protected]. S. Kaierle, Tel.: [email protected]


Welding of shock absorber valves: development, qualification and knowledge transfer

Detailed view of a shock absorber valve being welded.

Task

Process input parameters on the work-piece can only be checked – if at all –sporadically during maintenance workon production units. What’s more, thecheck is in most cases restricted tomeasuring the focus position andpower of the laser beam. Owing to theprinciples involved and because nosuitable instruments exist, it is not pos-sible to measure the decisive kinematiccharacteristics of machining systems,which means that the positioning ac-curacy, feed speed and accelerationcannot be checked during machining.This is particularly true of the scanneroptics which are frequently used inhigh-brilliance laser systems. In this case, it is only possible to control theaxes of motion by means of positionerson the scanner mirrors. All this meansthat there is only limited scope for con-trolling the path of the beam on theworkpiece.

Method

The coaxial process control (CPC) sys-tem developed at the Fraunhofer ILTobserves the interaction zone throughthe beam path with a digital high-speed camera. The process zone andthe surrounding area are illuminatedby an integrated secondary light sourcewhich almost completely outshines thelight emitted in laser machining. Theimages of the process are interpretedby a computer in real time. The surfacestructure of the workpiece is analyzed,especially in areas outside the interac-tion point. By calculating the two-dimensional correlation, the motionvector of the workpiece is determined

from the sequence of images. This can then be used to calculate the kinematic variables of acceleration and feed speed as well as the tool interaction point.


This process enables the true kinematicvariables of a laser system to be direct-ly determined during operation. As a result it is possible to systematicallyidentify and remedy problems causedby deviations from process parameters.

In future the technique will be particu-larly useful for avoiding process faultsin the deployment of new, highly focus-able laser beam sources in the multi-kilowatt range. Exploiting the techno-logical advantages of these systems, e. g. to maximize process speed andthereby reducing the available processwindow, entails a risk of undesired andunnoticed fluctuations in the processinput parameters. Such fluctuationscan be reliably identified and avoidedby using this technique.

Contacts

Dipl.-Ing. P. Abels, Tel.: [email protected]. S. Kaierle, Tel.: [email protected]


In-situ measurement of laser systems

Above: Measured contour of a laser cutting process withrounded edges and other faultsin the cut contour.Below: Starting sequence ofa large laser welding unit withundesired transient events inthe processing speed.

Task

The integration of a joint tracking sys-tem with coaxial process control forthe butt welding of D36 shipbuildingsteel is to be tested. This applicationuses a hybrid welding process with adouble-focus laser beam followed byMIG welding.

The aim is to examine the improve-ment of a system for joint trackingwith integrated optical speed measure-ment in comparison with a conven-tional forerun sensor. In addition, the scope for process observation with the object of quality assurance simul-taneously with processing is to be investigated.

Method

The camera-based system for coaxialprocess control (CPC) with external illu-mination developed at the FraunhoferILT is used as the sensor system. TheCPC system is integrated in the beampath of the processing laser by meansof a dichroitic mirror.

The wavelength and power of the laserradiation used (CO2 laser up to 8 kWbeam power) makes the set-up particu-larly challenging. The coaxially arrangedcamera permits visualization of themolten bath by recording the reflectedradiation from the processing area.


The autonomous joint tracking systemis different from conventional seamtracking systems in that it performs anadditional measurement of the relativespeed between the sensor and work-piece. This offers the advantage thatthe number of measured signals recor-ded can be kept to a minimum. More-over, this method is not affected bytwisting and lateral movement of thewelding head as positional errors areavoided by direct measurement of the relative shift. By taking positionalerrors into account, it is also no longernecessary to calibrate the sensor aftera tool change or after changing the robot path or feed speed. The processobservation system in welding appli-cations with CO2 laser radiation is cur-rently being further developed, prima-rily with a view to detecting weldingerrors.

Contacts

Dipl.-Ing. W. Fiedler, Tel.: [email protected]. S. Kaierle, Tel.: [email protected]


Robust autonomous joint tracking for quality assurance in laser welding

Above: Measured speed compo-nents in feed direction relative to the observation camera.Below: Camera image of a structuralsteel plate butt-welded at vS = 2.4m/min, s = 6 mm.

Task

Industrial laser welding of plasticsshould be as robust as possible withregard to batch fluctuations of the material, permissible production tole-rances of the individual parts and assembly tolerances, but unavoidablefluctuations in the parameter rangecan nevertheless occur. The resultantprocessing faults have to be reliablydetected, even at high production vo-lumes. The aim is to make it possibleto use optical process monitoring in anindustrial context to detect problemsthat can occur in plastics welding.

Method

The work is carried out jointly with theindustrial partners Amtron GmbH, HufTools GmbH and LIMO-LissotschenkoMikrooptik GmbH under a project funded by the ‘Stiftung Industriefor-schung’ industrial research foundation.A key aspect of the research is toexamine the specific informative capa-bilities of coaxial locally integrated andlocally resolving process observation.Methods for measuring the secondaryradiation and observing with externalillumination are also compared. A pro-cessing head using a modular opticalsystem developed at the Fraunhofer ILTwas designed and built for this purpose,making it possible to perform simulta-neous observation with the variousstrategies.


To conduct the fundamental tests, anexperimental arrangement using suit-able modules and specially adaptedoptical elements was built. In this ar-rangement the processing laser radiationand the radiation emitted or reflectedby the workpiece are transported in acommon beam path. To this end, theoptical and spectral beam paths werecalculated and all the optical compo-nents were provided with correspond-ing coatings. For observations using a CMOS camera, which is sensitive inthe visible wavelength range between400 nm and 900 nm, the suitability of various illumination strategies wasexamined. During the investigations itwas found that the seam width, jointdefects, scratches and decompositioncan be detected on the materials poly-carbonate (PC), polypropylene (PP) andpolyamide (PA) when using locally re-solved observation under bright field illumination.

Contacts

Dipl.-Ing. S. Mann, Tel.: [email protected]. S. Kaierle, Tel.: [email protected]


Strategies for process monitoring in plastics welding using laser radiation

Camera image: welding of PC,2 mm + 2 mm, 19 W, 3 m/min,500 Hz.

Task

False friends are not exactly popular -either in private life or in welding.When metal sheets are lap-welded bymeans of laser radiation, a false friendmay be created if there is too wide agap between the parts to be joined,even though the root of the weld is visible. A dreaded process fault has oc-curred, and the sheets are not weldedtogether. It is the job of coaxial processcontrol (CPC) to detect the defect.

Method

The CPC system developed at theFraunhofer ILT is located directly in the beam path of the laser processingsystem. Observation is conducted withthe beam. The secondary radiationemitted during the process is decoupledfrom the beam path by means of spe-cial optical components and observedwith high-speed cameras. The recor-ded process images are interpreted bya computer in real time. The integrationof external illumination provides inno-vative options. The processing operationis illuminated by a light source whichalmost completely outshines the lightemitted during welding. This makes itpossible to distinguish between moltenand solid material. The tests show thaton a sheet combination of stainlesssteel, the defective joint in the lapweld correlates with the length andwidth of the melt zone at the interac-tion point. The characteristic changes

in the molten bath length and widthduring processing were observed anddocumented using a specially deve-loped image processing algorithm for the CPC system. Given that the dynamics of the molten bath are usedto detect any faults, individual imagesdo not provide an adequate basis formonitoring. This special challenge wassuccessfully overcome by analyzingimage sequences.


The correlation of the molten bathlength with the gap in the lap weldwas shown for the described application.Bridgeable gaps result in a reducedwidth of the melt. Defective jointswhich cannot be detected either fromthe top or bottom of the seam result in a longer molten bath, whereas thewidth does not change. The CPC sys-tem with the analysis algorithm deve-loped determines the length and widthof the molten bath and thus enablesthe false friend to be detected.

The field of application for this moni-toring method covers a broad range ofsectors in which lap welds produced bylaser radiation are required. Particularlyin the auto industry, many interestingpossibilities exist for its application,especially in the welding of car bodyparts.

Contacts

Dipl.-Ing. P. Abels, Tel.: [email protected]. S. Kaierle, Tel.: [email protected]


False friends

Image sequence for analyzing theexternally illuminated process zone.Intermediate stages of image analy-sis through to automatic approxi-mation of the interaction zone bymeans of a rectangle (from top tobottom).

Task

The introduction of new process se-quences and their monitoring and con-trol represents a great challenge bothfor the machine manufacturer and theuser of the production facilities. In par-ticular the difficulty involved in plann-ing for the possible occurrence offaults or disruptions calls for new ap-proaches which enable the functioningand performance of automated pro-duction processes to be assured at anearly stage through monitoring andactive control.

Method

In the Cluster of Excellence »IntegrativeProduction Technology for High-WageCountries«, greater insights into pro-cess models, signal analysis methodsand systems for quality monitoring andmeasurement uncertainty detection are being gained. A key area is the development of process-overarchingapproaches based on the mutual inter-disciplinary exchange of experienceand knowledge among individual specialist areas.

The work at the Fraunhofer ILT focuseson the development of methods andalgorithms for the automated setting-up, monitoring and control of lasercutting processes.


The applicability of generally valid, reduced models to the production process is being examined at theFraunhofer ILT using laser cutting as an example. To this end, the requisitesensor systems are being designed andverified. The work includes developingnew methods for signal generation(see figures) and analysis.

In addition, all the machine, product,process and sensor data are being classified in detail and systematicallyrecorded.

The goal is to achieve a deeper under-standing of the process by determiningand dealing with measurement un-certainties in the sensor system on the one hand and uncertain model parameters on the other.

This forms the basis for the integrationof self-optimizing setup, monitoringand control systems into the productionprocess.

Contacts

Dipl.-Ing. S. Mann, Tel.: [email protected]. S. Kaierle, Tel.: [email protected]


Analysis and application of methods and algorithmsto ensure constant product quality

Camera image of a laser-cuttingprocess without external illu-mination (above), with externalillumination (below).

Task

The use of computer simulation inlaser production technology sets highrequirements for the coupling of models.The analysis of solution characteristicsis considerably improved by a means of controlling the simulation procedureduring computation. The task consistsin preparing an environment (frame-work) for the rapid and flexible deve-lopment of parallelized simulation calculations in a modular system. Theframework contains:• Computational steering system (CSS)• Visualization / analysis• Data structures for coupling• Numerical methods

Method

The computational steering system(CSS) is expanded by adding a nume-rical toolbox and lays down a uniforminterface/program structure for simu-lation codes. The required flexibility isachieved by using the programminglanguage C++, a uniform data struc-ture and algorithms from the StandardTemplate Library (STL). Abstract datastructures and basic template classesare defined for numerical tools, andinitial variants of numerical tools areimplemented in the following areas:• Grid generation• Parallelization• Solution of linear equation systems• FEM, FVM methods• Automatic differentiation

The CS system and numerical tools usea client-server architecture, with com-munication via the message passinginterface (MPI). A command line inter-face permits the initialization of batchoperation for parameter studies.


The basic functionality of the numericaltoolbox has been completed. Initial simu-lation programs have been produced as a modular system and tested in appli-cation projects. Examples of CS systemapplications include welding (upper fi-gure), cutting (lower figure) and super-sonic gas flow.

The work presented is funded by theGerman Research Foundation DFG in the Excellence Cluster »IntegrativeProduction Technology for High-WageCountries«.

Contacts

Ulrich Jansen, Tel.: [email protected]. Dr. W. Schulz, Tel.: [email protected]


Computational steering systemfor parallelized simulation calculations

Above: CSS welding.Below: CSS cutting.

Laser Measurement and Testing Technology

The services provided by this businessarea include the development of mea-surement and testing processes and related equipment for material analysisand for geometric testing and surfaceinspection. The requisite measurementand testing software is tailored to customer-specific problem areas. Materialanalysis is based on the deployment oflaser-spectroscopic processes, focusingon the analysis of metallic and oxidicmaterials, identification testing of high-alloy steels, rapid recognition of mate-rials for recycling tasks and analysis ofgases and dust. Special electronic com-ponents are developed for the parallelprocessing of detector signals of highbandwidth.

In biophotonics joint projects are car-ried out in the field of highly sensitivefluorecence detection for protein chipsand laser scattered light measurementsin sub-µl test volumes for protein crystallization. As part of the area’s work on geometric testing and surface inspection components, devices andequipment are being developed for obtaining 1 to 3D information aboutthe geometry or surface properties ofworkpieces. These include processesand special systems for testing the stability of bar and strip products anddevices for the 1D to 3D scanning ofunit goods. Target markets include theproduction and the recycling industrywhich conduct measurement andtesting fast and close to the process.


Business AreaLaser Measurement and Testing Technology

Laser-induced plasmas ignitedon rock samples during thesingle particle analysis for theseparation of minerals.

Blue lasers for ultra-high precision triangulation - BLU 122

Identification testing of pipeline components using laser spectroscopy - LIAS 123

Element-specific characterization of steel scrap streams 124

Rapid identification of light metal alloys for automated sorting - SILAS 125

Single particle analysis for the separation of minerals during the extraction of primary raw materials - EIGER 126

Imaging laser analysis of element distribution in construction materials 127

Online analysis of minerals at the extraction site 128

Rapid laser-assisted analysis of metallic and non-metallic inclusions in steel - REAL 129

Characterization of ultrafine particulate matter in industrial process emissions 130

Optical stand-off detection of explosives and improvised explosive devices - OFDEX 131

Marker-free Raman screening 132

Quantitative polarized light microscopy 133

Laser coagulation system with integrated real-time monitoring of vascular occlusion 134

Integrated microfluidic diagnostic systems - IMIKRID 135

Endoscope for »cold« laser neurosurgery 136

Optical coherence tomography (OCT) in endoscopy 137

Optical coherence tomography (OCT) for layer thickness measurement of loose goods 138

White-light Mach-Zehnder interference microscopy in transmission 139


Contents

Task

There is a need for new concepts to meet the increased requirements of modern manufacturing lines with automated process and quality control.This includes new concepts of laser triangulation sensors. More compact,lighter, faster, more precise and morestable are just a few of the featuresdemanded by industrial users, such asrolling mills and automotive industry.As part of the BLU collaborative re-search project, which is financed bythe German ministry of economics anda number of small and medium-sizedenterprises, novel technologies arebeing tested together with industrialpartners for use in triangulation sensors.

Method

One aspect of the project involves in-vestigating the use of new shorter-wave-length laser beam sources in triangu-lation sensors. The use of such sourcesand a coupling into single-mode opticalfibers is expected to yield a higher spatial resolution and accuracy than is possible with the sensors that arecommercially available at present.

At the same time, construction materialsare systematically conducted with the aim of producing more stable and lightweight sensors. These, in conjunction with time and space mo-dulation of the laser beam, will formthe basis for a new generation of trian-gulation sensors.


Today’s commercially available laser diodes operating in the blue-violet wave-length range do not meet the high beam-quality specifications requiredfor precision triangulation. A highlystable device for coupling the beam into a single-mode fiber that is suitablefor industrial applications is thereforebeing developed together with one ofthe project partners. The improved beam quality enables measurements tobe performed to an accuracy that canonly be achieved with HeNe-lasers atpresent. In parallel to the developmenton the sensor, trials of optical measur-ing systems employing new stabilizationmethods are being tested on productswith a metallic bright surface at a cold-rolling mill. Furthermore, investigationsare being carried out on new methodsfor measuring the contours of high-precision components with a high sur-face quality.

Contacts

Dipl.-Ing. (FH) A. Lamott, Tel.: -133,[email protected] Dr. R. Noll, Tel.: -138,[email protected]


Blue lasers for ultra-high precision triangulation - BLU

Laboratory setup using blue-violetlaser for triangulation.

Task

Industrial pipeline systems are com-monly found in chemical engineeringplants, at oil and gas extraction sites,and in thermal and nuclear powerplants, as well as being used in thefood processing industry, includingbottling plants, and by manufacturersof liquid gas products. To ensure thesafety and reliability of the piping fitt-ings, the appropriate materials for theapplication must be employed - bothin terms of resistance to corrosion andtheir compatibility with one another.

Manufacturers of pipeline components(fittings, pass-over offsets, and runs)must therefore guarantee that the material composition of their productsconforms to specifications. When inte-grated in an automated manufacturingline, LIAS verifies the identity of eachmanufactured product without slowingdown the production flow. The resultsare output at the same rate as the production process and are fully do-cumented. Non-conforming productscan be rejected automatically.

Method

A scanner equipped with movable mir-rors directs the laser beam onto freelydefinable areas of the workpiece. Aspectral analysis of the resulting plasmaglow is performed to identify the ma-terial on the basis of the concentrationof alloy elements it contains. The sur-face does not need to be prepared beforehand. Foreign matter on the sur-face, e.g. oils, oxides or scale, is eitherlocally ablated or penetrated by the laser. LIAS has integrated referencesamples that it uses for automatic self-testing, thus complying with therequirements of ISO 9001 with respectto the control of measuring and testequipment.


The test pieces in this instance arepipeline components of different geo-metries and dimensions. The system isdesigned for industrial application andis capable of performing fully automatedmaterial identification tests on up to 4 million test pieces per year.

Contacts

Dipl.-Ing. (FH) R. Fleige, Tel.: [email protected]. R. Noll, Tel.: [email protected]


Identification testing of pipeline components using laser spectroscopy - LIAS

Above: Measuring head containing the laser beam source and scanner.Below: Use of flexibly directedlaser beam for identification testing. Several freely definablepoints on the test pieces can be verified. Duration of test < 0.5 sec/test point, tested volume (HxWxD) 100 x 400 x 400 mm3.

Task

As well as responding to environmentalconcerns, the recycling of steel scrap forreuse in steel production has taken ona new, economic, significance due tothe rising cost of raw materials and thegrowing scarcity of natural resources.The better we are able to characterizethe chemical composition of steelscrap, the greater the value of the re-covered fraction. Conventional frac-tionation processes (magnet extraction,density analysis, etc.) only cover a limi-ted number of characteristics, and aregenerally not sufficiently selective withrespect to the elements that can play a critical role in recycling. The definedtask is to develop and verify the suita-bility of a process for the on-site cha-racterization of steel scrap streams onconveyor belts.

Method

Laser-induced breakdown spectroscopy(LIBS) was chosen as the method forelement-selective characterization.Further development of this methodwas required to enable a reliable ave-rage element concentration to be obtained. A demonstration setup willbe installed in a shredder plant and on the premises of an arc furnace forthe purposes of on-site testing.


In the first phase of the project, laseranalysis experiments were performedon samples of steel scrap in order tofind laser parameters that permit thelaser to penetrate coatings or layers of dirt. The design of the demonstratorsetup for on-site testing was completedand construction started.

The work is being supported financiallyby the European Community’s Re-search Fund for Coal and Steel (RFCS)and the Fraunhofer-Gesellschaft.

Contacts

Dipl.-Ing. D. Eilers, Tel.: [email protected]. V. Sturm, Tel.: [email protected]. R. Noll, Tel.: [email protected]


Element-specific characterization of steel scrap streams

Typical example of material entering(above) and leaving (below) a shredderplant.

Task

Preliminary sorting of shredded alumi-num scrap is a necessary stage in thesecondary production of the light me-tal. As well as being separated intotwo main categories, cast and wroughtalloys, the latter category of material is further subdivided into the so-called1000-groups. Conventional separatingand preparation methods are not sui-table for this task. As a result, a signi-ficant proportion of aluminum pro-duction still takes place using energy-intensive primary production methods.The most challenging aspect of thepreliminary sorting of scrap is the factthat a chemical analysis has to be per-formed in a fraction of a second on discrete moving objects on the con-veyor belt. Especially in the case of oldaluminum scrap, surface contaminationor coating material has to be removedwithin the allotted measuring time inorder to generate a representative, ob-ject-specific test result.

Method

Aluminum workpieces are scattered ona conveyor belt (v = 3 m/s) and passeda detection unit. A set of coordinatesfrom the object surface, selected onthe basis of optical and geometricalcharacteristics, is transmitted to a lasermeasuring instrument. A pulsed laserbeam is focused on this selected zoneby means of scanner mirrors. The laser-induced plasma is detected antiparallelto the beam propagation direction andanalyzed by a spectrometer in real time.This multi-element analysis serves asthe basis for ejecting the workpiecesinto different fractions at the end ofthe conveyor belt.


In cooperation with a laser manu-facturer, a laser system was developedthat is capable of emitting time- andspace-modulated laser light from asingle oscillator. The first part of thislaser beam penetrates surface coat-ings or contamination. Subsequentanalysis pulses in the same pulse trainthen interact with the material lyingunderneath the surface. The scannersystem is repositioned during theemission of this laser beam. Experi-mental results show that it is possibleto achieve crater depths of 300 µmand more in aluminum materials usingthis laser beam, depending on the beam orientation. This approach hasmade it possible for the first time tosuccessfully demonstrate the separationof mixed scrap consisting of cast andwrought alloys. In this application, theidentification accuracy was over 90%at a yield of 100%. At present, theimproved analysis method is beingused to validate the performance of ademonstration sorting machine as partof an industrial study on subcategoriesof wrought alloys. Development workon a prototype is projected to start inJanuary 2008.

Contacts

Dipl.-Phys. Ü. Aydin, Tel.: [email protected]. R. Noll, Tel.: [email protected]. J. Makowe, Tel.: -327 [email protected]


Rapid identification of light metal alloys for automated sorting - SILAS

Above: Snapshot of a laser-induced plasma on a movingpiece of aluminum scrap (v = 3 m/s).Below: Image of craters in a ground aluminum surface.On the left: Mark left by theanalysis pulse of a spark-sourcespectrometer (crater depth < 10 µm); on the right: 4 cratersproduced by a time- and space-modulated laser beam (crater depths > 150 µm).These craters were producedwhile the sample was travelingat a velocity of v = 3 m/s relativeto the laser measuring system.The time/space-modulated laserbeam was repositioned accor-dingly.

Task

Before processing extracted primaryraw materials, such as limestone or other minerals and ores, the mineral of economic value has to be separatedfrom inferior inter-grown accessoryrock. Owing to the comparatively lowprice at which these raw materials aresold, the separation must take place inthe immediate vicinity of the extractionsite, transportation of the extractedmaterial being uneconomical in manycases. At present, there is no cost-effi-cient automated process capable ofsorting primary raw materials online onthe basis of single particles. A collabo-rative research project was thereforelaunched to develop a laser-assistedsorting process for the separation of limestone and dolomite. Its scope mayconceivably be widened to include other ores and minerals.

Method

After reducing and separating the rawmaterial, it is fed to the measuring system in the form of single particlesand/or rock fragments. These samplesare individually analyzed by laser spec-troscopy in the moving stream of mate-rial and ejected as separate fractions inaccordance with the measurement re-sult. One of the foremost objectives ofthe project is to implement a demon-strator and prove its ruggedness underreal-life industrial operating conditions.


The first stage of the project involvedconducting fundamental spectroscopicanalyses as a means of assessing thevarious influential factors. In the se-cond stage of the project, an initial se-ries of tests was carried out on movingrock samples (limestone/dolomite) witha known chemical composition. Themain difference between these sam-ples was their relative MgO/CaO con-tent. The threshold values of the Mgdetector channels were therefore sub-jected to closer examination in respectof their suitability as sorting criteria. Ineach examined class of materials, theidentification correctness exceeded90% at a recovery of 100%.

In order to carry out these tests, a newPaschen-Runge spectrometer with de-tector channels adapted to the above-mentioned application was bought,and a special housing designed for it in compliance with the IP standard foruse in an industrial environment. Oncethis spectrometer system has been in-tegrated in the demonstration sortingplant, it is planned to conduct endu-rance tests using a high volume of ma-terials (> 1 t). The flexible design of thesorting system makes further validationtests using different material streamsconceivable. The online separation ofmetals offers interesting prospects as asupplementary application to the sepa-ration of minerals and ores.

Contacts

Dipl.-Phys. Ü. Aydin, Tel.: [email protected]. R. Noll, Tel.: [email protected]


Single particle analysis for the separation of minerals during the extraction of primary raw materials - EIGER

Above: Laser-induced plasmasignited on rock samples.Below: Paschen-Runge spec-trometer system enclosed in avibration-proof double-walledhousing. The spring-suspensionbase of the spectrometer andits housing designed to EMCspecifications allow the systemto be deployed in a real-life in-dustrial environment or an out-door location.

Task

Corrosive changes can be provoked inconcrete structures and buildings, suchas bridges and multistory car parks, byvarious environmental factors (vehicleexhaust fumes, road salt, etc.). Thesoundness of the structure can be per-manently damaged by the infiltrationof elements such as nitrogen, sulfurand most particularly chlorine. To opti-mize the cost of remedial maintenance,the concentration and depth of pene-tration of these elements must be de-termined as accurately as possible. Ananalysis system is being developed thatwill enable engineers to determine thecontent of these elements in buildingmaterials on-site, allowing them to assess damage on the basis of »ele-ment maps« and repair the structure in an appropriate manner as a functionof the degree to which the structurehas been damaged.

Method

Laser-induced breakdown spectroscopyis a non-contact method used to analyzethe chemical composition of solids, liquids and gases. It allows the con-centration of different elements to beestablished simultaneously very rapidly.Drilling cores extracted from thestructure are split, and the fracturedsurface is scanned using a focusedNd:YAG laser beam. At the points where the laser pulses hit the surface,minute quantities of the drilled core arevaporized and ionized, creating a plas-ma. The element-specific line emissionsfrom the plasma enable the elementalcomposition of the material at thispoint to be determined.


As part of the project, a demonstratorwas designed and built that enablesthe creation of automated 2-dimen-sional element maps. The range of wave-lengths used to detect the plasmaemissions was broadened to allow parameters to be set for different am-bient gases and pressures when per-forming measurements in a controlled-environment test chamber. This makesit possible to detect spectral lines atwavelengths ranging from 130 nm to920 nm. A detection limit for elemen-tal concentrations of chlorine of below1 percent is targeted by the use ofspectral lines in the VUV and IR ranges.

The project is being conducted withthe financial support of the Germanministry of economics, various indus-trial partners, and the Fraunhofer-Gesellschaft.

Contacts

Dipl.-Phys. C. Gehlen, Tel.:[email protected]. R. Noll, Tel.:[email protected]


Imaging laser analysis of element distribution in construction materials

Above: View through the observation window into thetest chamber. A laser-inducedplasma is ignited on the surfaceof the sample, and its emissionsare fed to a spectrometer via a direct light channel.Below: ILCOM demonstrator.

Task

In underground mining, the machinesused to extract minerals are still con-trolled manually. The inevitable pre-sence of surrounding rock lowers thequality of the extracted mineral and increases the quantity of material thathas to be transported to the surface.One of the objectives of the project isto develop an analysis module for usein underground workings that enablesthe relative proportion of surroundingrock to be determined in real time.

In surface mining, prospect holes aredrilled to investigate mineral deposits.A real-time analysis module for theseborings is being developed that can takethe place of the presently employed laboratory analysis. On-site analysis will make it possible to adapt the holematrix dynamically to the prevailinggeological conditions and consequentlyproduce a more accurate geologicalmodel using fewer resources.

Method

The rock dust produced during ex-traction is drawn off and a chemicalanalysis is performed by laser-inducedbreakdown spectroscopy directly in theair-stream. The online analysis processis capable of distinguishing betweenthe mineral of economic value and surrounding rock.

In the case of underground mining,the project focuses on differentiatingbetween hard coal and clay slate. Inthe case of surface mining, the analysissystem is initially intended for use in lime-stone quarries. The same technique is nevertheless transferable to other types of exploitable mineral and asso-ciated surrounding rock.

The use of the analysis module in under-ground workings imposes special de-mands with respect to vibration, dustand water resistance.


Initial results suggest that laser-inducedbreakdown spectroscopy is a viablemeans of distinguishing between thematerial to be exploited and associatedsurrounding rock. In the case of hardcoal, for instance, the presence of highlevels of silicon and other elementsand a rapidly decreasing carbon con-tent indicate that the extracted materialcontains a high ratio of surroundingrock.

The project is being conducted withthe financial support of the Germanministry of economics, various smalland medium-sized enterprises and in-dustrial partners, and the Fraunhofer-Gesellschaft.

Contacts

Dipl.-Phys. T. Kuhlen, Tel.: [email protected]. P. Jander, Tel.: [email protected]. R. Noll, Tel.: [email protected]


Online analysis of minerals at the extraction site

Above: Samples of limestoneand hard coal as well as surround-ing rock.Below: Eickhoff shearer loader.

Task

The number, distribution and compo-sition of metallic and non-metallic in-clusions are important quality criteriain steel manufacturing. These inclusions,which typically range in size from 0.1 µm to 100 µm, affect the proper-ties of the material, reducing its fatiguestrength and even leading to fracture.Inclusions frequently consist of a com-bination of different elements, for instance MnS or TiN. A means of de-tecting the presence of so-called lightelements such as C, N, O, P and S istherefore required. As far as possible,the analysis is to be performed withoutthe need for elaborate preparation ofthe sample.

Method

A ground or milled sample is all that is needed to analyze the purity of thesteel. The sample is placed in a measur-ing chamber filled with a shielding gas,where its surface is scanned by the be-am of a focused diode-pumped solid-state laser. A small quantity of thesample material is vaporized at the fo-cal point of the laser beam to form aplasma. The emissions from the plasmaare resolved spectrally, converted intoelectrical signals, and analyzed. Thehigh measuring frequency of 1 kHzemployed in this method enables asample surface area of 10 mm x 10 mmto be analyzed in 10 minutes. Duringthis time, element maps for up to 48 different chemical elements areproduced simultaneously, with a reso-lution of 20 µm.


A number of steel samples wereexamined for their distribution of metallic and non-metallic inclusions. A particular focus of this series of testswas to investigate the behavior ofdouble analysis pulses by comparisonwith the previously employed singlepulses. Different algorithms for pro-cessing the element maps and filteringout the inclusions from the bulk mate-rial were tested and evaluated.

The work is being supported finan-cially by the Research Fund for Coaland Steel (RFCS) and the Fraunhofer-Gesellschaft.

Contacts

Dipl.-Ing. (FH) M. Höhne, Tel.: [email protected]. R. Noll, Tel.: [email protected]


Rapid laser-assisted analysis of metallic and non-metallic inclusions in steel - REAL

Element map showing MnS inclusions, S (red) Mn (blue).

Task

Air pollution with fine and ultrafineparticulate matter has recently becomerecognized as one of the main publichealth risks. Significant sources of anthropogenic particles are vehiculartraffic and industry.

Extremely small nanoscale particulatesrepresent an elevated health risk be-cause their size allows them to pene-trate deep into the human organism.At the same time, these aerosol parti-culates are the most difficult to detectand make a high demand on the mea-suring instrument, hence there is apressing need for further research.This project concerns the developmentof a method for determining the com-position of particulates, with particularemphasis on the concentration ofheavy metals.

Method

Two methods of measurement arebeing developed on the basis of laser-induced breakdown spectroscopy forthe chemical analysis of the particulates.In the first method, the particulates arecollected, classified by size, on filtersand then analyzed in the laboratory. In the second method, single particlesare analyzed directly in the air stream.This latter method additionally permitsrapid online characterization. To obtainreliable measurement results, it is ne-cessary to produce samples and aero-sols that enable instruments to be calibrated for all relevant elementsover a range of concentrations cover-ing several orders of magnitude.


Results of analyse conducted on emis-sions from steel factories indicate, forexample, an elevated content of lead,cadmium and copper in particulates of about 200 nm in diameter, whereashigher concentrations of other metalsare found in larger particulates. Thechemical composition of the particu-lates varies widely as a function oftheir size, and is characteristic of thespecific process giving rise to theiremission. This finding permits process»fingerprints« to be established, whichin turn permit a classification of thesources of emissions. The correlationbetween particulate size and compo-sition also allows a better estimation of the health risk associated with thedifferent types of emission. Measure-ments based on particulate size can also be obtained when analyzing par-ticulates directly in the air stream. Theshort time required for such measure-ments allows them to be used directlyfor process control. The results of theproject will be used to develop emission-reduction strategies for the industrialplants under study. The method can also be employed universally in otherbranches of industry, engine develop-ment and nanotechnology.

The project receives financial supportfrom the European Union’s ResearchFund for Coal and Steel (RFCS) and theFraunhofer-Gesellschaft.

Contacts

Dr. C. Fricke-Begemann, Tel.: [email protected]. N. Strauß, Tel.: -196 [email protected]. R. Noll, Tel.: [email protected]


Characterization of ultrafine particulate matter in industrial process emissions

Above: Laser spectroscopy methods can be used to analyzeboth particulates collected onfilters and airborne particulates.Below: Lead content of finedust particulates ranging in sizefrom 40 nm to 4 µm emitted by two different productionprocesses.

Task

Terrorist attacks have been on the risefor the past several years, particularlyin the form of car and suitcase bombs.So far, there is no system available thatcan detect such »improvised explosivedevices« (IEDs) from a safe distance.

Furthermore, there is a great demandin the civil and environmental protectionsector for systems capable of remotechemical analysis. These could help tomonitor emissions or provide assistancewhen dealing with accidents involvinghazardous chemicals, for example inthe petrochemical industry.

Method

Four Fraunhofer Institutes have joinedforces to develop a system for thestand-off detection of hazardous andexplosive materials, based on severaloptical methods that complement oneanother.

The Fraunhofer ILT, for its part, is inves-tigating the use of both laser-inducedbreakdown spectroscopy and Ramanspectroscopy. Laser-induced break-down spectroscopy is a techniquewhich enables high measurement frequencies and allows the elementalcomposition of a material to be deter-mined precisely even over a distance of several meters. Raman spectroscopyenables substances with similar atomiccompositions to be differentiated onthe basis of frequency measurementsof the molecules’ characteristic naturalvibration. The two techniques thus deliver complementary information onthe sample under test. Combining thetwo techniques increases the probabi-lity of detection and reduces the rate

of false alarms when searching for explosive materials. On the basis of ex-perience gained by the Fraunhofer ILTin laser analysis over distances of up to 12 meters, the researchers are deve-loping methods and data analysis algo-rithms that will allow them to detectthe slightest traces of explosives evenover distances of up to 50 meters.


Tests carried out on ammonium nitrate,one of the main components of ANFOexplosives, show that laser-inducedbreakdown spectroscopy can help to detect small amounts of nitrogen-containing compounds over a distanceof 5 meters, even in the presence ofatmospheric nitrogen. The sensitivity of Raman spectroscopy has meanwhilebeen improved to such an extent thatthe presence of traces of ammoniumnitrate in a fingerprint correspondingto a density of 160 µg/cm2 can be un-mistakably identified.

The project is being implemented withthe financial support of the Fraunhofer-Gesellschaft.

Contacts

Dr. P. Jander, Tel.: [email protected]. R. Noll, Tel.: [email protected]


Optical stand-off detection of explosives and improvised explosive devices - OFDEX

Raman spectral lines of a fingerprint containing traces of ammonium nitrate.

Task

The analysis of biochemical interactions,especially specific interactions betweenproteins and their binding partners, is one of the basic tasks performed inpharmacological laboratories as part of the drug discovery process. In expe-rimental screening, fluorescent dyesare used as marker molecules when searching through extensive libraries of compounds for potential active drugingredients that possess a specific affi-nity to biologically relevant target pro-teins (e.g. enzymes or signal transmit-ters). In a scientific project togetherwith partners from industry and re-search, we have been investigating theuse of Raman spectroscopy as a meansof detecting biochemical interactionswithout employing fluorescent mar-kers, and we are building a demons-trator for experimental screening.

Method

Using Raman difference spectroscopy,it is possible to analyze binding eventsbetween proteins and their ligands. A specific ligand binding event altersthe vibrational spectrum of the inves-tigated protein. By computing the difference between the spectra of thebound and the free proteins, the bandshifts can be obtained in a sensitiveway. To prevent the Raman signalsfrom being submerged under a stronglyfluorescent background, the projectemploys a special background reductiontechnique. A narrow-bandwidth ex-ternal cavity diode laser allows images of two mutually offset Raman spectrato be obtained by slightly shifting theexcitation wavelength. Since only theRaman signals present this offset, whilethe fluorescent background does not,it is then possible to remove the effectof the fluorescent background.


Initial recordings of the Raman spectraof proteins with a good signal-to-noiseratio were obtained using a laboratorysetup consisting of a highly sensitiveCzerny-Turner spectrometer with acooled CCD detector. To separate theexcitation light from the Raman signals,a compact module was designed andbuilt to accommodate a narrow-band-width dichroic mirror, a laser line filterand a band-pass filter. The spectrometerwas connected to this arrangement viaa tunable fiber coupler. The fiber actsas a pinhole aperture, resulting in a set-up that functions similarly to a confocallens system with three-dimensionalspatial resolution. The setup is capableof measuring minimal-volume samplesand is designed to face upwards, allow-ing fluids in glass-bottomed microtiterplates to be analyzed.

The project is being conducted with the financial support of the Germanministry of economics, various smalland medium-sized enterprises, and theFraunhofer-Gesellschaft.

Contacts

Dr. C. Janzen, Tel.: [email protected]. R. Noll, Tel.: [email protected]


Marker-free Raman screening

Compact module for face-up confocal Raman microscopy.

Task

Polarized light microscopy betweencrossed polars is the standard techniquefor viewing birefringent structures(crystals, polymers or glass under com-pressive or tensile stress). However, thequality of the images obtained is highlydependent on the orientation of thesample relative to the direction inwhich the applied light is polarized. A novel type of quantitative polarizedlight microscopy makes it possible togenerate false-color images that areunaffected by the position of the sam-ple and reproduce the transmission,amplitude and orientation of its bire-fringence. Such images can be used,for instance, to determine the qualityof single crystals being grown to inves-tigate protein structure.

Method

The key components of a quantitativepolarized light microscope are a mono-chrome light source, a rotating polari-zer, and a circular analyzer consistingof a λ/4 plate and a polarization analy-zer. These components are integratedin a transmission microscope with alens and a CCD camera for recordingthe images. The quantitative birefrin-gence analysis is performed by taking aseries of images with the polarizer setto different angles each time. By ma-thematical transformation, it is possibleto calculate the transmission, amplitudeand orientation of the birefringence atany point on the sample on the basisof the individual frames.


A polarized light microscope for thedescribed quantitative analysis was integrated in a demonstrator for auto-mated, rationalized protein crystallo-graphy. The polarized light microscopeis capable of analyzing the difficult-to-characterize precipitates that oftenform during crystallization experiments.An important aspect is the ability todistinguish between amorphous, non-birefringent and microcrystalline, bire-fringent precipitates. It is also possibleto clearly differentiate between bacte-rial growth or image distortions causedby interfacial artifacts and the crystallinestructures themselves. And finally, aqualitative characterization of the crys-tals is also possible, since only singlecrystals exhibit a uniformly orientedoptical axis. The demonstrator and itspolarized light microscope are currentlybeing evaluated in the applications la-boratory of a partner institute, wherevarious aspects of polarized light mi-croscopy are being tested.

The project is being conducted withthe financial support of the Germanministry of economics, various smalland medium-sized enterprises, and theFraunhofer-Gesellschaft.

Contacts

Dr. C. Janzen, Tel.: [email protected]. R. Noll, Tel.: [email protected]


Quantitative polarized light microscopy

Above: Demonstrator for pro-tein crystallization with integra-ted quantitative polarized lightmicroscope.Below: Characterization of thequality of protein crystals. Theimages show the transmission(above), amplitude (middle) andorientation (below) of the bire-fringence.

Task

Minimally invasive laser surgery inblood-carrying tissue requires an en-doscopic coagulation technique toocclude transected blood vessels. Bytissue coagulation high-power cw lasersources are suitable for this purpose,because they can be coupled into anendoscopic laser surgery system via theoptical channel. An optical coherencetomography system capable of provid-ing three-dimensional images of bloodvessels has been developed in order toobserve the coagulation process anddefine suitable coagulation parameters.

Method

The endoscope developed for the lasercoagulation application focuses a laserbeam (Nd:YAG, λ = 1064 nm, P = 25 W)through a micro-optical channel ontothe blood vessel requiring occlusion in-side the surgical cavity. Changes occurr-ing in the blood vessel during coagu-lation are observed using optical cohe-rence tomography (OCT). A galvanome-tric scanner mirror moves a measuringbeam transversally to the diameter ofthe blood vessel being coagulated. Dur-ing the transverse scan, the OCT systemrecords image data in the vertical planeperpendicular to the movement of themeasuring beam, to a depth of approxi-mately 1.5 mm below the surface ofthe tissue. A new depth scan (A-scan) isstarted every 50 µm to obtain images ofa 1-mm cross-section of the vessel. TheA-scan is performed at a frequency of200 Hz, and a cross-sectional imageconsists of 20 A-scans with a lateral displacement of 50 µm. These imagecapture settings enable a 1-mm cross-section of the vessel to be imaged at a frame repetition rate of 10 Hz. One

pixel represents a scanning depth of 4 µm. The imaging parameters such asframe repetition rate, frame size, pixelsize, and the A-scan can be adapted tothe process being examined.


An extensive series of coagulation ex-periments were conducted ex vivo onover 700 blood vessels of the cardio-vascular network of pigs’ hearts, usingvarying settings for output power andpower density and varying the size ofthe irradiated area and the duration ofexposure. As a result, a process win-dow could be identified in which lasercoagulation resulted in reliable occlu-sion of vessels with diameters rangingfrom 150 µm to 1000 µm. In a secondstage of the project, coagulation ex-periments were conducted using con-stant irradiation parameters and the time dynamics were observed with theaid of the OCT system. For the first time, we were able to visualize the dy-namic processes that take place duringcoagulation in a blood vessel andcould determine the average durationof exposure required for cauterization.On average, the coagulation processtook about 2 s to cauterize a bloodvessel. The software package developedfor the laser coagulation system permitsthe coagulation process to be vieweddynamically as a series of sections(photo above) and as a diagram plott-ing distance against time (photo below).

Contacts

Dr. A. Lenenbach, Tel.: [email protected]. R. Noll, Tel.: -138 [email protected]


Laser coagulation system with integrated real-time monitoring of vascular occlusion

Above: Series of sectionsthrough a blood vessel (Ø 200µm) during coagulation. The duration of irradiation increasesfrom left to right. There is an interval of 100 ms betweeneach of the consecutive images.The sequence starts when thecoagulation laser is switchedon; the time to coagulation isapprox. 0.6 s.Below: This diagram plots thechange in the distance betweenthe upper and lower walls ofthe blood vessel (Ø 900 µm) during the coagulation processas a function of time, startingfrom the instant at which the laser is switched on. The time to occlusion by coagulation is3.5 s.

1m

m

Task

The aim of the IMIKRID project is todevelop a technology platform forpoint-of-care diagnostics providing a highly sensitive means of detectingmolecular marker proteins in blood serum and sweat.

Method

IMIKRID refers to a diagnostic chip in-tegrated in a microfluidic cell togetherwith four independent single-molecule-sensitive sensor components that convert a biological response into anoptical or electronic signal. The surfacesof the sensors extend into the fluidicchannel and are coated with multi-functional nanoparticles that bind spe-cifically with the analyte molecule ofinterest in the blood serum. In the caseof the electronic sensor (seFET = sen-sitivity enhanced FET), the biologicalinteraction is detected without the useof marker molecules by means of charge transfer in the sensor. The sig-nal transducer function of the opticalsensor is based on the marking of thebound analyte molecule with a fluores-cent label, which provides an opticalsignal of the specific binding of theanalyte when excited with light of asuitable wavelength. The FraunhoferILT is developing a tool to test and calibrate the IMIKRID sensors at single-molecule level. This device consists of a confocal single molecule detectorwith integrated optical tweezers. Theoptical tweezers permit the controlledtransport of a nanoparticle to the sen-sor surface of the transducer to triggera reproducible single-molecule response.The optical tweezers can also be usedto position a nanoparticle in the fluidicstream as a specific capture probe, en-abling direct detection of the bindingof the analyte molecule of interest

using the confocal single-molecule de-tector. The use of single nanoparticlesas reactive sensor surfaces in the fluidstream of a microfluidic system mini-mizes surface effects such as the non-specific adsorption of proteins, whichlimit the sensitivity of any diagnosticsystem. The combination of opticaltweezers and single-molecule detectionis expected to provide a highly sensitivediagnostic tool for detection of markerconcentrations in the single-moleculerange down to below 10-12 mol/l.


The ability to detect serum proteins on the basis of their specific binding to nanoparticles will permit preventiveearly diagnosis of cardiovascular di-seases and cancer. This is not possibleat present, due to the detection limitof 1 ng/ml (10-11 mol/l) in state-of-the-art, antibody-based serological tests.IMIKRID offers a means of implement-ing large-scale integrated sensors withsingle-molecule sensitivity for applica-tions at the point of care. The R&Dactivities of the IMIKRID project aresupported by the BMBF and are beingimplemented together with partner in-s-titutes of the Fraunhofer-Gesellschaftand the Institute for Micro Sensors inErfurt.

Contacts



Integrated microfluidic diagnostic systems - IMIKRID

Above: Branching of the micro-fluidic channels in an integratedsensor chip. Source: FraunhoferInstitute for Applied InformationTechnology FIT, BiomolecularOptical Systems department.Below: Optical tweezers systemfor integration in a confocal detection system for single-mo-lecule diagnostics.

Task

The resection of intracranial tumors involves opening a hole in the craniumof the same size as the tumor to be rejected. Endoscopic removal of braintumors by means of keyhole surgerywould represent a significant improve-ment in neurosurgical practice since it would reduce the »patient trauma«.With this objective in mind, the Fraun-hofer ILT and partners in industrial andresearch fields are developing an en-doscope for use in plasma-induced»cold« laser neurosurgery.

Method

The main component of the surgicalintervention system is an endoscopemeasuring 5.5 mm in outer diameterhousing a micro-optical channel of 2.8 mm in width. The endoscope’s micro-optics guide the laser beam intothe surgical cavity and focus it ontothe tissue to be ablated. The tip of the endoscope is fitted with a tilted mirrorto decouple the ablation laser at a per-pendicular angle to the endoscope’saxis of symmetry. The laser employedfor ablation is a Nd:YVO4 picosecondlaser connected in series with an INNO-SLAB amplifier having the followingspecifications: output power P = 10 W,pulse energy Ep = 1 mJ, pulse durationtp = 25 ps, wavelength λ = 532 nm.The pulse repetition rate can be variedbetween f = 1 kHz and 10 kHz. Theablation process is automated, and thelaser focus can be set to scan any geo-metry within a cylindrical volume mea-suring 5 cm in diameter and 12 cm inheight by rotating the tilted mirror, displacing the focusing lens, and altering the depth of the endoscope.The ablated tissue is removed from thesurgical cavity by an integrated rinsing

and suction system. Ablation experi-ments were performed in the laboratory on tissue samples of pigs’ hearts andbrains in order to determine the laserparameters providing the greatest ab-lation efficiency. During these experi-ments, the samples were placed in a flow cell through which water waspumped at flow velocities varying from0.2 l/min to 2 l/min. This water washedablated fragments of tissue out of theablation zone to prevent laser lightfrom being absorbed by debris in thepath of the ablation laser beam. Theflow rate was regulated to produce themaximum ablation efficiency at a con-stant pulse repetition rate.


The ablation experiments on pig’s hearttissue enabled an energy threshold value of Ep = 30 µJ to be establishedfor plasma-induced laser ablation. Thediameter of the ablation crater at apulse energy of 200 µJ lay between 50 µm and 100 µm. The edges of theablation craters were sharply definedand exhibited no thermal effects of the laser light on the adjacent tissue.

The development of the endoscope is supported by the BMWI and is beingcarried out together with partnersfrom industry and clinical research.

Contacts



Endoscope for »cold« laser neurosurgery

Above: Endoscope for »cold« laser ablation with a stereotacticalframe. Source: MRC-SystemsGmbH, Heidelberg.Middle: Cross-section through asquare-shaped ablation crater inthe muscle tissue of a pig’s heart.Below: The sharp edges of the ab-lation geometry are clearly visiblein the plan view.

1 mm

1 mm

Below: Endoscope for use withOCT, consisting of:A micro-optical channel andB rotating mirror tube.C Assembled endoscope.The micro-optical channel andmirror tube are assembled in a coaxial arrangement and eachcan be moved with respect to the other. Diameter of themicro-optical channel 3.0 mm;diameter of the assembled system 5.5 mm.

Above: OCT cross-sectionimage of two blood vesselsdownstream of a bifurcation,measured using the endoscope.The vessels have a diameter of420 µm and 440 µm respectively.Middle: A horizontal sectionthrough the three-dimensionalOCT dataset showing the bifur-cation point.

Task

Therapeutic techniques involving en-doscopy call for new diagnostic me-thods that provide surgeons with in-formation on intraoperative events. Asan alternative to white-light and fluo-rescence endoscopy, optical coherencetomography (OCT) is a high-resolution,interferometric measuring techniquewith which it is possible to obtainimage data of tissue morphologies without the use of marker molecules.The main medical application envisagedfor OCT is the online monitoring of lasersurgery processes. The Fraunhofer ILT is developing an OCT module for theendoscopic detection and measure-ment of blood vessels. Its purpose is to monitor the cauterization of bloodvessels by laser coagulation using high-energy laser light during keyholesurgery.

Method

To obtain the maximum possible pene-tration depth into the tissue of approx.2 mm, a beam source with a centerwavelength in the region of 1300 nmis employed. Light is introduced intothe surgical cavity via an optical fiberand a rigid endoscope. The parallelmeasuring beam is decoupled by a deflection mirror mounted on the tipof the endoscope at 90° to its longitu-dinal axis and focused on the tissue tobe examined by means of a microlens.The surface of a three-dimensional tar-get volume can be scanned point bypoint through this lens by sliding theendoscope along its own axis, rotatingthe deflection mirror and adjusting thefocusing lens. A scan performed usingthe OCT system delivers depth cues extending from the surface into the tissue at each measuring point. This isachieved by periodically varying the

optical distance of a reference beamon which the measuring beam is super-imposed. This interferometric measure-ment (A-scan) is performed at a fre-quency of 200 Hz and a digital resolu-tion of 1.6 µm per pixel. The resultingimage data can be processed to obtaina 3-D image.


The endoscopic OCT diagnostic has anaxial resolution of approx. 25 µm at alateral resolution of 20 µm. In a seriesof validation experiments, cross-sectionimages were taken of vessels ex vivo inthe vascular system of a porcine heart.The images were recorded with theprobe in a static position while the en-doscope mirror was rotated to movethe measuring beam across the cross-section of the vessel. A clear contrastcould be observed between the vesselsand the tissue surrounding them. With the help of a software programspecially developed for OCT diagnosis,the measurement data can be displayedas 2-D sections. Image sequences canbe used to evaluate changes in thevessels' position and geometry, forexample after thermal interaction dueto irradiation with laser light.

Contacts

Dipl.-Phys. S. Hölters, Tel.: [email protected]. R. Noll, Tel.: [email protected]


Optical coherence tomography (OCT) in endoscopy

1 mm

5 mmA

B

C

Task

During production, variations can occur in the wall thickness of loosegoods made of plastic, such as trans-lucent bottles or the preforms fromwhich they are manufactured. To pre-vent these variations from exceedingthe defined tolerance range, randomsamples are taken from the productionline at hourly intervals, sawn apart,and examined under a light microscope.For greater process reliability and in order to improve product quality, anautomated system for measuring wallthickness is required that will provide a100-percent monitoring capability. Theenvisaged system involves the use ofoptical coherence tomography (OCT),an imaging technique based on inter-ferometric measurements that produ-ces high-resolution 3-D tomographicimages. By recording reflected andscattered light signals, this techniquepermits the non-contact measurementof the layer thickness of plastic bottlesand preforms during the productionprocess. The same technique can alsobe used to determine the thickness ofindividual layers of laminate compositematerials to a resolution of approxima-tely 25 µm.

Method

Data obtained by measuring selectedsubsets of the geometry of symmetri-cally round plastic bottles or preforms,such as the longitudinal profile orcross-section, can be extrapolated toprovide the distribution of layer thick-ness over the entire geometry. At a cycle rate of up to 10,000 bottles perhour, it is possible to provide 100-per-cent online monitoring of wall thick-ness and individual layer thicknessesduring the production process. BecauseOCT is based on single-point measure-

ments, a pair of scanner mirrors has tobe used to move the OCT measuringbeam across the surface of interest inorder to measure the surface or layergeometries.


The existing OCT system has an axialmeasuring range in air of 9 mm at ascanning frequency of 200 Hz and aresolution of approx. 25 µm. Unlikeabsorptive measuring techniques, OCTpermits the use of an epitaxial mea-surement setup in which the sourceand receiver are located in the external environment of the measured object.This measurement setup was used todetermine the position and thicknessof multilayer preforms and bottles witha minimum layer thickness of approx.50 µm. The project team is currentlyworking on the design of special op-tical systems to compensate for the differences in the path length of themeasuring light that occur when usingOCT to take measurements at two different sites on the path described bya moving object. Optical path lengthcompensation is a necessary prerequi-site for the use of OCT techniques tomeasure moving samples, because themeasurements are based on the diffe-rence between optical distances. TheOCT measuring system is being vali-dated in the laboratory on moving pre-forms guided around a circular path ona turntable, to simulate their transporton a centrifugal conveyor in the pro-duction plant.

Contacts

Dipl.-Phys. S. Hölters, Tel.: [email protected]. R. Noll, Tel.: [email protected]


Optical coherence tomography (OCT) for layer thickness measurement of loose goods

Above: Preforms employed inthe manufacture of PET bottles.Below: Recording of the cross-section of a multilayerPET preform made using theOCT measuring system.Overall wall thickness approx.4.3 mm; thickness of the inter-facial layer at the midpoint approx. 410 µm.

Task

Measurements of the refractive indexcan provide a variety of important information about the structure andmaterial properties of microscopic ob-jects. In materials research, micro-op-tical or crystal-optical components canbe qualified using measurements ofthe refractive index and dispersion.One of the main difficulties encounteredwhen examining thin, transparent ob-jects under a light microscope is thatof generating image contrast. Whenobserving living cells in a dye-free me-dium, optical techniques alone are ca-pable of quantifying cells on the basisof their refractive index and translatingthis into contrast. This measurementpermits the dry mass of the cells to be determined, thereby opening thedoor to new applications in biologyand medical diagnostics.

Method

The Horn design of the Mach-Zehnderinterference microscope offers the bestphase resolution for measurements of the refractive index coupled withmaximum enlargement of the light microscope images. This is achieved byintegrating two complete microscopeoptics with identical wavelength cha-racteristics in the interferometer arms.Modern optomechanical concepts derived from laser technology can beused to automate the highly sensitivesystem and make it more user-friendly.


Various experimental approaches werepiloted in partnership with collaborat-ing cell biologists, pathologists, envi-ronmental scientists and crystallogra-phers. The cell movement of living cells and the associated mass transportprocesses were observed and recordedover several hours. Measurements ofthe dry mass of cells were successfullyemployed to identify tumor cells as dis-tinct from healthy cells in streak culturesand microscopic sections. This methodwill serve as the basis for new applica-tions in tumor diagnostics, where realphysical measurements will help toprovide a more reliable diagnosis. Measurements of the dry mass of cells were also employed to determine thecarbon content of various types of algae, for subsequent use in environ-mental model calculations. The resultsshowed a significant deviation fromthe tabulated values currently in use.

The aim of the project is to develop acommercial version of an interferencemicroscope offering not only a uniquemeans of performing high-precisionmeasurements but also featuring ex-ceptional user-friendliness.

Contacts

Dipl.-Phys. D. Mahlmann, Tel.: [email protected]. Dr. P. Loosen, Tel.: [email protected]


White-light Mach-Zehnder interference microscopy in transmission

Above: Combined arrangementof Mach-Zehnder interferometerand matching microscope optics.Middle: Interference contrastimage of neurons. Unstained cells can be observed in detailedcontrast and quantified.Below: Interference fringe pattern of an optical waveguide. The refractive index profile can be measured to sub-nanometeraccuracy as a function of the cur-vature of the interference fringes.

Patents Germany

DE 197 80 124 B4Anordnung zur Formung des geometrischen Querschnitts mehrerer Festkörper- und/oderHalbleiterlaser

DE 101 06 474 B4Verfahren sowie Vorrichtung zum Aufbringen einer Korrosions-schutzschicht auf Kantenflächenvon Blechen

DE 10 2005 026 968 B4Einbringen von Mustern in matteOberflächen durch moduliertesLaserstrahlpolieren

DE 10 2005 010 381 B4Verfahren zur Vermessung von Phasengrenzen eines Werkstoffesbei der Bearbeitung mit einemBearbeitungsstrahl sowie zuge-hörige Vorrichtung

DE 10 2005 022 095 B4Verfahren und Vorrichtung zur Bestimmung einer lateralen Relativbewegung zwischen einemBearbeitungskopf und einem Werkstück

DE 10 2005 000 840 B4Verfahren und Vorrichtung zur Elementanalyse mittels Laser-Emissionsspektrometrie

Patents Europe

EP 1 399 287 B1Verfahren zum Schneiden von zu fügenden Bauteilen mit Laser-strahlung

Patents USA

US 7,176,408 B2Method for laser-cutting structuralcomponents to be joined

Patents Australia

2003249876Method and device for carrying out emission spectroscopy

Patents China

ZL02807825.XVerfahren und Vorrichtung zumErzeugen von extrem ultravioletterStrahlung und weicher Röntgen-strahlung

Patent Applications National

10 2007 002 888.3Anordnung mit einem fest-stehenden Festkörpermedium

10 2007 002 821.2Verfahren und Anordnung zur Freqenzkonvertierung kohärenteroptischer Strahlung

10 2007 003 759.9Verfahren zur Frequenzstabilisierunggütegeschalteter Laser

10 2007 014 665.7Verfahren zur Herstellung laser-aktiver Wellenleiterschichten

10 2007 018 400.1Optisches System für einen Lasermaterialbearbeitungskopf

10 2007 024 701.1Verfahren zur Materialabtragungsowie Vorrichtung zur Durch-führung des Verfahrens

10 2007 024 700.3Verfahren zur Materialbearbeitungmit Laserstrahlung sowie Vor-richtung zur Durchführung des Verfahrens

10 2007 029 052.9Verfahren und Vorrichtung zumHerstellen eines Bauteils auf drei-dimensionalen Daten des Bauteils

10 2007 028 789.7Verfahren zum Fügen von Hybrid-bauteilen

10 2007 031 244.1Vorrichtung und Verfahren zurDurchführung statischer und dynamischer Streulichtmessungenin kleinen Volumina

10 2007 038 502.3Verfahren zum Fügen von mindestens zwei Bauteilen mittels Laserstrahlung

10 2007 039 035.3Verfahren zur Herstellung einesBauteils sowie Verwendung desnach dem Verfahren hergestelltenBauteils

10 2007 041 939.4Vorrichtung und Verfahren für dieXUV-Mikroskopie

Patent Applications International

PCT/DE2007/001856Verfahren und Vorrichtung zur Feinpositionierung eines Werkzeugsmit einer Handhabungseinrichtung

PCT/EP2007/009094Anordnung mit einem fest-stehenden Festkörpermedium

PCT/DE2007/000341Vorrichtung und Verfahren zum Fügen von wenigstens zwei aus thermoplastischem Material bestehenden Fügepartnern mittelsLaserstrahlung

Trademark Applications

307 58 327.9/42TWIST

307 61 417.4/42LIFTEC


Patents

Fuhrmann, C. - 19.03.2007Laser-Lichtbogen-Hybridschweißenbis zu Blechdicken von 25 mm

Scholz, C. - 23.05.2007Themal and Mechanical Optimisationof Diode Laser Bar Packaging

Trippe, L. - 03.09.2007Reduzieren erstarrter Schmelze inder Bohrung beim Einzelpuls- undPerkussionsbohren mit Nd:YAG-Laserstrahlung

Baatzsch, AndreasUntersuchung zur Stirnflächen-kopplung von Large-Mode-Area-Fasern

Beck, MatthiasUntersuchungen zur Schweiß-barkeit des Chrom-Nickel-Stahls1.4305 am Beispiel der Faser-rohrspitze eines endoskopischenInstrumentes

Biermann, TimLaserstrahlschweißen und -schneidenmit dem Kombikopf: Verfahrens-und Systemoptimierung

Binder, MarkusVersuchsumgebung und Grundlagenzur Ultrapräzisionstriangulation mitblauen Lasern

Bock, MarioUntersuchung der elektrischen und optischen Eigenschaften kurz-gepulster Diodenlaser

Buchbinder, DamienKonzeption und Erprobung einesPulverdosiersystems zur definiertortsaufgelösten Deposition unter-schiedlicher Pulverwerkstoffe fürdas Selective Laser Melting

Dietrich, JensUntersuchung der Effizienzsteige-rung beim Bohren mit zeitlich undräumlich überlagerter Laserstrahlungdurch Hochgeschwindigkeitsfoto-grafie

Fitzau, OliverVergleichende Untersuchungen zur Erzeugung polarisierter Laser-strahlung mit Faserlasen

Funck, Max ChristianAuslegung einer miniaturisiertenBearbeitungsoptik für das Laser-strahl-Mikrofügen

Geffers, ChristophUntersuchung zur Ausweitung von Laseranwendungen in derindustriellen Produktion

Goldner, AndreasKonstruktion eines optischen Sensormoduls für die lasergestützteSchichtdickenmessung

Groebner, MarioLaseranalyse von Einschlüssen inMetallen

Hamad, EyadMessung der Temperatur in biologischem Gewebe während der Laserkoagulation

Hammer, PhilippTemperaturabhängigkeit der optischen Eigenschaften von Thermoplasten

Hauck, SebastianMöglichkeiten und Grenzen bild-rotatorischer Lichtstrahldrehung

Hoerstmann-Jungemann, Maren ChristineWeißlichtinterferometer zur Bestimmung der Dispersion der Gruppenlaufzeit dielektrischer Spiegel im sichtbaren und ultra-violetten Spektralbereich

Jedrzejczyk, DanielSimulation und Experimente zurnichtlinear optischen Frequenz-konversion in periodisch gepoltemMgO:LiNbO3 Kristall mit Wellenleiter

Kochem, GerdKonstruktion und Aufbau eines singlemodefasergekoppelten Trapezlaser-Moduls

Küpper, FelixErzeugung weicher Röntgen-strahlung in einer gepulsten Gasentladung für den Einsatz ineinem Laborröntgenmikroskop

Kuhlen, TobiasAnalyse von Feinstaub auf Filter-substraten mittels Laser-Emissions-spektrometrie

Langer, TorstenThermische Auslegung einer Fasereinkopplung für Hochleistungs-diodenlaser

Lu, XinLaserstrahl-Auftragschweißen aufTitanaluminiden mit artähnlichenWerkstoffen

Ostholt, RomanAuslegung und Konstruktion eines optischen Systems für eineSLM-Anlage zur variablen Einstellung des Fokusdurchmessers

Roth, PeterSpektroskopische Analyse laser-induzierter Plasmen beim Mikro-Materialabtrag mit ns-Pulsgruppen

Schleifenbaum, HenrichErhöhung der Aufbaurate beimSLM

Soeryanto, DennyErarbeitung von Verfahrensgrund-lagen zur Reparatur von einkristallinenShroud-Segmenten eines Flugzeug-triebwerks durch Laserstrahl-Auf-tragschweißen

Temmler, AndréPhysikalische Ursachen und Grenzendes Strukturierens metallischerOberflächen durch Umschmelzenmit Laserstrahlung

Volkmer, Niels-ChristianMikrostanzen mit lokal angepassterBauteiltemperatur

Weitenberg, JohannesYtterbiumdotierte Kristalle beihohen Pumpleistungsdichten


Dissertations Diploma Theses

S. Kaierle, W. Fiedler, B. Regaard, M. DahmenAnwendung brillianter Dioden-laser beim Schweißen von Alu-minium-DünnblechenLaser Technik Journal 2, 35-38, 2007

S.Kaierle, M. Dahmen, S. Mann, R. PopraweAutonomous Production Cell for Laser Beam WeldingProc. Int. Conf. on CompetitiveManufacturing »COMA 07«, Stellenbosch, Südafrika6 S., 2007

R. Noll, M. KrauhausenAutoteile unter LaseraugenLaser + Photonik 2, 30-33, 2007

C. Johnigk Berührungslos - präzise - steuerbarMO Metalloberfläche 61, 24-27,2007

J. Geiger, B. Erben, D. Hoffmann,S. AltmeyerCharacterization of high powermultimode combinersCLEO Europe 2007, Munich, Germany, June 18-21 1 S., 2007

C. Franz, S. Mann, S. KaierleComparison of process moni-toring strategies for laser transmission welding of plasticsProc. of ICALEO October 29 -November 1, 2007, Orlando, Fl. 602-606, 2007

M. Dahmen, W. Fiedler, B. Regaard,S. KaierleContinuous process controlduring laser beam welding ofsmall section aluminium sheetProc. of the 4th Int. WLT Conf. onLasers in Manufacturing, Munich,June 2007 5 S., 2007

R. Noll, M. Krauhausen Den Bewegungszustand desBlechs einfrierenQZ Qualität und Zuverlässigkeit 52,36-40, 2007

B. Jungbluth, M. Vierkoetter, M. Hoefer, J. Loehring, D. Ober-beckmann, D. HoffmannDesign and characterization of a rugged and compact setup forwidely tunable harmonic gene-ration in the ultravioletProc. SPIE 6455, 1-10, 2007

J. Loehring, K. Nicklaus, N. Kujath,D. HoffmannDiode pumped Nd:YGG laser for direct generation of pulsed935 nm radiation for watervapour measurementsProc. SPIE 6451, in print, 2007

B. Zintzen, A. Emmerich, J. Geiger,D. Hoffmann, P. LoosenEffective cooling for high-powerfiber lasersProc. of the 4th Int. WLT-Conf. onLasers in Manufacturing, Munich,June 2007 5 S., 2007

B. Regaard, W. Fiedler, S. KaierleError detection in lap weldingapplications using on-line meltpool contour analysis by coaxialprocess monitoring with exter-nal illuminationProc. of the 4th Int. WLT Conf. onLasers in Manufacturing, Munich,June 2007 5 S., 2007

M. Haverkamp, K. Wieching, M. Traub, K. BouckeFiber-coupled diode laser mo-dules with wavelengths around2 µmProc. SPIE 6456, 9 S., 2007

C. Wessling, M. Traub, D. HoffmannFiber coupled diode laser ofhigh spectral and spatial beamquality with kW class outputpowerProc. SPIE 6456, 1-7, 2007

I. Miyamoto, A. Horn, J. Gottmann,D. Wortmann, F. YoshinoFusion Welding of Glass UsingFemtosecond Laser Pulses withHigh-repetition RatesJ. Laser Micro/Nanoeng. 2, 57-63,2007

B. Zintzen, T. Langer, J. Geiger, D. Hoffmann, P. LoosenHeat transport in solid and air-clad fibers for high-power fiberlasersOpt. Expr. 15, 16787-16793, 2007

E. W. Kreutz, K. Walther, R. Poprawe, S. Angel, E. Ratte, W. Bleck, K. Bobzin, E. Lugscheider, R. Nickel, K. Richardt, N. BagcivanHigh-temperature turbine applications using open porousmetallic foams with thermalbarrier coatings and coolinghole arraysISCORMA-4, Calgary/Alberta,Canada, August 27-31, 200711 S., 2007

K. Walther, M. Brajdic, I. Kelbassa Increase of drilling velocity byuse of superposed laser radiationProc. of the 4th Int. WLT-Conf. onLasers in Manufacturing, Munich,June 20074 S., 2007

H. Schinkel, P. Jacobs, S. Schillberg,M. Wehner Infrared picosecond laser forperforation of single plant cellsBiotechnol. Bioeng. 99, 244-248,2007

D. PetringIntegriertes Laserstrahlschneidenund -schweißen: Reduzierungvon Nebenzeiten und System-aufwandEALA 2007, Bad Nauheim15 S., 2007

P. Albus, B. Burbaum, I. KelbassaLaser cladding of mesh structureson HPT liner and NGV partsProc. of the 4th Int. WLT-Conf. onLasers in Manufacturing, Munich,June 20073 S., 2007

J. Gottmann, L. Moiseev, D. Wort-mann, I. Vasilief, L. Starovoytova,D. Ganser, R. WagnerLaser deposition and laser structuring of laser active planar waveguides of Er:ZBLAN,Nd:YAG and Nd:GGG for integrated waveguide lasersProc. SPIE 6459, 10 S., 2007

M. Wehner, P. Jacobs, D. Esser, H. Schinkel, S. SchillbergLaser-mediated perforation of plant cellsProc. SPIE 6632, 9 S., 2007

M. Wehner, T. Mans, W. Meiners,A. Lenenbach, C. Wessling, R.PopraweLasertechnik für die ZahnmedizinLaserzahnheilkunde 3, 191-198,2007

R. NollLasertriangulationIn: Handbuch zur Industriellen Bildverarbeitung. Hrsg.: N. Bauer Stuttgart: Fraunhofer IRB Verl.56-60, 2007

R. Noll, M. KrauhausenLasertriangulation für die Online-Messung geometrischerGrößen in der ProduktionIn: Handbuch zur Industriellen Bildverarbeitung. Hrsg.: N. BauerStuttgart: Fraunhofer IRB. Verl 260-275, 2007

I. Miyamoto, A. Horn, J. GottmannLocal Melting of Glass Materialand Its Application to DirectFusion Welding by Ps-laser PulsesJ. Lasermicro/Nanoeng. 2, 7-14,2007

J. Gottmann, D. Wortmann, I. Vasilief, L. Moiseev, D. Ganser Manufacturing of Nd:Gd3Ga5O12ridge waveguide lasers by pulsedlaser deposition and ultrafastlaser micromachiningAppl. Surf. Sci. 254, 1105-1110,2007

L. Peter, R. Noll Material ablation and plasmastate for single and collineardouble pulses interacting withiron samples at ambient gaspressures below 1 barAppl. Phys. B 86, 159-167, 2007

T. Jambor, K. WissenbachMicro laser cladding with high quality fibre lasersProc. 4th Int. WLT-Conf. on Lasersin Manufacturing, Munich, June2007 193-197, 2007

Scientific Publications



R. Schmitt, B.E. Damm, L. JuschkinMit weicher Röntgenstrahlunghochgenau messenIn: Optische Messung technischerOberflächen in der PraxisDüsseldorf: VDI-Verl.VDI-Berichte. 1996329-337, 2007

M. Hoefer, M. Traub, R. Klein-dienst, H. Sipma, H.-D. Hoffmann,P. Wessels, P. BurdackMulti ten-watt, ultra-stable, and tuneable Innoslab-basedsingle frequency MOPAProc. SPIE 6451, 7 S., 2007

D. Petring, H. DicklerMultifunktionaler Laser-bearbeitungskopfMM Maschinenmarkt 22, 34-36, 2007

D. Petring, H. DicklerNebenzeiten senken und Flexibilität steigernTechnica 56, 72-74, 2007

P. Albus, A. Boglea, B. Burbaum, J. Holtkamp, I. Kelbassa, V. Nazery-Goneghany, A. Olowinsky, D. Petring, M. Poggel, F. Schmitt, F. Schneider, N. Wolf, R. PopraweNeue Schweißtechnologien mit neuen LasernProc. of the 10th Int. Aachen Welding Conf. iASTK'07229-242, 2007

M. Leers, C. Scholz, K. Boucke, M. OudartNext generation heat sinks for high-power diode laser barsSemiconductor Thermal Measurement and Management Symposium, 2007 SEMI-THERM 2007, 23. Annual IEEE105-111, 2007

M. Leers, K. Boucke, C. Scholz, T. WestphalenNext generation of coolingapproaches for diode laser barsProc. SPIE 6456, 10 S., 2007

M. Traub, M. Bock, H.-D. Hoffmann,M. BartramNovel high peak current pulseddiode laser sources for directmaterial processingProc. SPIE 6456, in print, 2007

V. Sturm, A. Brysch, R. Noll Online Multielement Analysis of the Top Gas of a Blast Furnaceby Laser-induced BreakdownSpectroscopy (LIBS) Berg- und HüttenmännischeMonatsh. 1, 28-32, 2007

R. Noll, M. KrauhausenOnline-Lasermesstechnik für Walzproduktestahl und eisen 127, 99-105, 2007

S. Angel, E. Ratte, W. Bleck, K. Bobzin, E. Lugscheider, R. Nickel, K. Richardt, N. Bagcivan, K. Walther, E.W. Kreutz, I. Kelbassa,R. PopraweOpen porous metallic foamswith thermal barrier coatingand cooling hole array for hightemperature turbine applicationsHigh Temp. Mat. Proc. 11, 321-344, 2007

V. SturmOptical micro-lens array forlaser plasma generation in spectrochemical analysisJ. Anal. Atom. Spectr. 22, 1495-1500, 2007

E. WillenborgPolieren mit LaserstrahlungKunststoffe 97, 63-66, 2007

I. Kelbassa, K. Walther, L. Trippe,W. Meiners, C. OverPotentials of manufacture andrepair of nickel base turbinecomponents used in aero engines and power plants bylaser metal deposition and laser drillingJ. Aerospace Power 22, 739-748,2007

W. Fiedler, M. Dahmen, S. KaierleProcess control of laser beamwelded small section aluminumsheetsProc. of ICALEO, October 29 -November 1, 2007, Orlando, Fl. 271-276, 2007

E.W. Kreutz, L. Trippe, K. Walther,R. PopraweProcess development and con-trol of laser drilled and shapedholes in turbine componentsJ. Lasermicro/Nanoeng. 2, 123-127, 2007

D. Petring, C. Fuhrmann, N. Wolf,R. PopraweProgress in Laser-MAG hybridwelding of high-strength steelsup to 30 mm thicknessProc. of ICALEO, October 29 -November 1, 2007, Orlando, Fl.300-307, 2007

J. Wilkes, K. WissenbachRapid Manufacturing of ceramiccomponents by selective lasermeltingProc. of the 4th Int. WLT-Conf. onLasers in Manufacturing, Munich,June 2007207-211, 2007

D. Buchbinder, W. Meiners, K. Wissenbach, K. Müller-Lohmeier,E. BrandlRapid manufacturing vonAluminiumbauteilen für dieSerienproduktion durch Selec-tive Laser Melting (SLM)Euro-uRapid2007, Frankfurt/M.,December 3-4, 20076 S., 2007

D. Wortmann, M. Ramme, J. GottmannRefractive index modificationusing fs-laser double pulsesOpt. Expr. 15, 10149-10153, 2007

S. Höges, W. MeinersSelective Laser MeltingProc. 41. Jahrestagung Dt. Ges. f. Biomed. Technik im VDE, Aachen,Germany, September 2007 2 S., 2007

M. Traub, H.-D. Plum, H.-D. Hoff-mann, T. SchwanderSpaceborne fiber coupled diode laser pump modules forintersatellite communicationsProc. SPIE 6736, in print, 2007

R. Wagner, J. GottmannSub-wavelength ripple formationon various materials induced by tightly focused femtosecondlaser radiation8th Int. Conf. on Laser AblationJ. Phys.: Conference Series 59,333-337, 2007

D. Wortmann, L. Moiseev, I. Vasilief, D. Ganser, L. Starovoytova,J. GottmannWaveguide lasers of Er:ZBLANand Nd:GGG by pulsed laserdeposition and fs-laser micro-structuringProc. 4th Int. WLT-Conf. on Lasersin Manufacturing 2007, Munich,June 2007821-826, 2007

C. Schnitzler, S. Hambuecker, O. Ruebenach, V. Sinhoff, G. Steckman, L. West, C. Wessling,D. HoffmannWavelength stabilization ofHPDL array: fast-axis collimationoptic with integrated VHGProc. SPIE 6456, 1-7, 2007

W. Meiners, A. WeisheitWerkstoff-Kompromisse passé?Form + Werkzeug 5, 78-81, 2007

M. Haverkamp, G. Kochem, K.Boucke, E. Schulze, H. Roehle1.1 W Four-wavelength Raman pump using BH lasersOptical Fiber Communication andthe National Fiber Optic EngineersConf. OFC/NFOEC 2007 1-3, 2007

Scientific Publications


Lectures

20.01.2007 - M. Hoefer Multi ten-watt, ultra-stable andtuneable INNOSLAB-based singlefrequency MOPAPhotonics West 2007, San Jose,CA, USA

20.01.2007 - M. TraubNovel high-peak current pulseddiode laser sources for directmaterial processingPhotonics West 2007, San Jose,CA, USA

21.01.2007 - J. GottmannLaser deposition and laser structuring of laser active planar waveguides of Er:ZBLAN,Nd:YAG and Nd:GGG for integrated waveguide lasersPhotonics West 2007, San Jose,CA, USA

21.01.2007 - M. LeersNext generation of coolingapproaches for diode laser barsPhotonics West 2007, San Jose,CA, USA

22.01.2007 - H.-D. HoffmannThe INNOSLAB laser, extendingthe parameter range for indu-strial and scientific applicationsPhotonics West 2007, San Jose,CA, USA

22.01.2007 - J. LöhringDiode pumped Nd:YGG laser for direct generation of pulsed935 nm radiation for watervapour measurementsPhotonics West 2007, San Jose,CA, USA

22.01.2007 - M. WehnerRapid prototyping of micro-fluidic components by laserbeam processingPhotonics West 2007, San Jose,CA, USA

23.01.2007 - B. JungbluthDesign and characterization of a rugged and compact setupfor widely tunable harmonicgeneration in the ultravioletPhotonics West 2007, San Jose,CA, USA

23.01.2007 - C. WesslingFiber coupled diode laser ofhigh spectral and spatial beamquality with kW class outputpowerPhotonics West 2007, San Jose,CA, USA

23.01.2007 - K. WiechingFiber-coupled diode laser modules with wavelengths around 2 µmPhotonics West 2007, San Jose,CA, USA

24.01.2007 - K. NicklausFrequency stabilization of q-switched Nd:YAG oscillatorsfor airborne and spaceborneLIDAR systemsPhotonics West 2007, San Jose,CA, USA

30.01.2007 - D. PetringIntegriertes Laserstrahlschneidenund -schweißen: Reduzierungvon Nebenkosten und System-aufwand8th EALA »Automotive Circle International« Conference, BadNauheim

02.02.2007 - S. KaierleAutonomous production cell for laser beam weldingCOMA 2007, Stellenbosch, Südafrika

04.02.2007 - A. HornOrts- und zeitaufgelöste Diagnosevon Prozessen induziert durchultrakurz gepulste LaserstrahlungSeminarvortrag, Universität Kassel,Kassel

13.02.2007 - A. GillnerLasers and photonics for industrial manufacturingPhotonics 2007, Eindhoven, Niederlande

13.02.2007 - R. NollLaser scanning methods for verification tasksIAEA, Wien, Österreich

23.02.07 - W. Schulz, Schneiden mit LaserstrahlungKolloquium Fraunhofer SCAI, Birlinghofen

06.03.2007 - A. L. Boglea, Mikro-Kunststoffschweißen mitLaserstrahlung - Schweißen imSekundentakt bei Geometrien < 100 µmAachener Laserseminar »Laserschweißen von Kunststoffen«,Fraunhofer ILT, Aachen

06.03.2007 - A. GillnerLaserstrahlquellen zum KunststoffschweißenAachener Laserseminar »Laserschweißen von Kunststoffen«,Fraunhofer ILT, Aachen

06.03.2007 - M. PoggelLaser und Kunststoff - eine festeVerbindungAachener Laserseminar »Laserschweißen von Kunststoffen«,Fraunhofer ILT, Aachen

06.03.2007 - M. PoggelTransparent und ArtungleichAachener Laserseminar »Laser-schweißen von Kunststoffen«,Fraunhofer ILT, Aachen

06.03.2007 - A. GasserAnlagen- und Systemtechnik fürdie LaseroberflächentechnikAachener Laserseminar »Vorsprungdurch Laser-Oberflächentechnik«,Fraunhofer ILT, Aachen

06.03.2007 - C. JohnigkReinigen mit LaserstrahlungAachener Laserseminar »Vorsprungdurch Laser-Oberflächentechnik«,Fraunhofer ILT, Aachen

06.03.2007 - G. VitrRandschichthärten und Wärmebehandeln von Stählenmit LaserstrahlungAachener Laserseminar »Vorsprungdurch Laser-Oberflächentechnik«,Fraunhofer ILT, Aachen

06.03.2007 - A. WeisheitLaserstrahl-Auftragschweißenvon Funktionsschichten für denVerschleiß- und KorrosionsschutzAachener Laserseminar »Vorsprungdurch Laser-Oberflächentechnik«,Fraunhofer ILT, Aachen

06.03.2007 - E. WillenborgPolieren und Strukturieren mitLaserstrahlungAachener Laserseminar »Vorsprungdurch Laser-Oberflächentechnik«,Fraunhofer ILT, Aachen

06.03.2007 - K. WissenbachLasereinsatz in der Oberflächen-technik - Ein ÜberblickAachener Laserseminar »Vorsprungdurch Laser-Oberflächentechnik«,Fraunhofer ILT, Aachen

07.03.2007 - A. L. BogleaMikroschweißen von Kunststoffen- mit hoher Geschwindigkeit inMikrodimensionenAachener Laserseminar »Mikrover-bindungstechnik«, Fraunhofer ILT,Aachen

07.03.2007 - A. GillnerAktuelle Entwicklungen zu neuen Laserstrahlquellen für die MikroverbindungstechnikAachener Laserseminar »Mikrover-bindungstechnik«, Fraunhofer ILT,Aachen

07.03.2007 - A. OlowinskyMikroschweißen mit Laserstrah-lung - Neue Verfahrenskonzeptemit optimiertem EnergieeintragAachener Laserseminar »Mikrover-bindungstechnik«, Fraunhofer ILT,Aachen

07.03.2007 - F. SariLasermikrofügen von Halbleiternund KeramikenAachener Laserseminar »Mikrover-bindungstechnik«, Fraunhofer ILT,Aachen

08.03.2007 - A. GillnerAktuelle Entwicklungen zu neuen Laserstrahlquellen für das MikrobohrenAachener Laserseminar »Mikroboh-ren mit Laser«, Fraunhofer ILT,Aachen

08.03.2007 - C. A. HartmannHochgeschwindigkeits-mikrobohrenAachener Laserseminar »Mikroboh-ren mit Laser«, Fraunhofer ILT,Aachen

08.03.2007 - S. KaierleProzessüberwachung beimLaserstrahlbohrenAachener Laserseminar »Mikroboh-ren mit Laser«, Fraunhofer ILT,Aachen

08.03.2007 - W. WawersMikrobohren mit LaserstrahlungAachener Laserseminar »Mikroboh-ren mit Laser«, Fraunhofer ILT,Aachen

19.03.2007 - M. BenkPinchplasma für den Spektral-bereich des WasserfenstersFrühjahrstagung der DeutschenPhysikalischen Gesellschaft, Düssel-dorf

19.03.2007 - M. HermansEntwicklung einer Methode zurBeobachtung der Dampf- undPlasmadynamik innerhalb derBohrung beim LaserstrahlbohrenFrühjahrstagung der DeutschenPhysikalischen Gesellschaft, Düsseldorf

Lectures

19.03.2007 - A. MaderTime-resolved EUV images of a tin vapour discharge plasmafor future lithographyFrühjahrstagung der DeutschenPhysikalischen Gesellschaft, Düsseldorf

19.03.2007 - I. MingareevUntersuchungen zur Schmelz-dynamik bei der Materialbear-beitung mit ultrakurzen Laser-pulsenFrühjahrstagung der DeutschenPhysikalischen Gesellschaft, Düsseldorf

19.03.2007 - A. WerthGlasschweißen mit ultrakurzgepulster LaserstrahlungFrühjahrstagung der DeutschenPhysikalischen Gesellschaft, Düsseldorf

20.03.2007 - S. MeyerZeitaufgelöste Plasmabeob-achtung bei der Mikrostruk-turierung von Metallen mitps-DoppelpulsenFrühjahrstagung der DeutschenPhysikalischen Gesellschaft, Düsseldorf

20.03.2007 - M. LeersNext generation heat sinks forhigh power diode laser barsSEMI-THERM 2007, San Jose, CA,USA

21.03.2007 - E. Bremus-Koebber-lingNeurite growth on micro-patterned polymer surfaces with complex topographies (Posterpräsentation)Biomedica, Aachen

22.03.2007 - C. D. GehlenZeit- und ortsaufgelöste Untersuchung laserinduzierterPlasmen beim präzisen Mikro-Materialabtrag mit Pulsgruppen (Posterpräsentation)Frühjahrstagung der DeutschenPhysikalischen Gesellschaft, Düsseldorf

23.03.07 - M. Nießen Charakterisierung von Verfahrens-parametern beim SchneidenKolloquium Fraunhofer SCAI, Birlinghofen

23.03.2007 - M. Haverkamp1.1 W four wavelength Ramanpump using BH-lasersOFC / NFOEC 2007, Anaheim, CA,USA

27.03.2007 - A. GillnerLaser structuring of metals andhard materialsTagung Mikrobearbeitung, Leuven,Belgien

16.04.2007 - G. BackesLaserbearbeitung im Triebwerk-bauSeminarvortrag »Laserbearbeitungim Triebwerkbau«, Berlin

18.04.2007 - R. Poprawe The consequences of societaldemands for industrial inno-vation and the future of lasermaterials processingALAW 2007, Orlando, FL, USA

23.04.2007 - A. HornInvestigations on melting andwelding of glass by ultra-shortpulsed laser radiationLPM 2007, Wien, Östereich

23.04.2007 - F. SariLaser transmission bonding and welding - Introduction andexperimental resultsLPM 2007, Wien, Östereich

25.04.2007 - D. GanserFabrication of NdGGG planarwaveguide laser by pulsed laserdepositionLPM 2007, Wien, Östereich

26.04.2007 - C. JohnigkCleaning of technical surfaceswith laser radiationIDC 2007, Düsseldorf

02.05.2007 - A. OlowinskyAdvances in polymer laser microweldingSPIE Microtechnologies for the NewMillennium, Maspalomas, Spanien

05.05.2007 - H.-D. HoffmannHigh power solid state lasers forLPP EUV Sematech »Source Workshop«, Baltimore, MD, USA

05.05.2007 - H.-D. HoffmannRod-slab-disc-fiber, design andperformance comparison of highpower laser architecturesCLEO / PHAST 2007, Baltimore,MD, USA

05.05.2007 - D. WortmannHighspeed production of periodical nanostructures usingfemtosecond laser radiationCLEO / PHAST 2007, Baltimore,MD, USA

05.05.2007 - D. WortmannWaveguide lasers of Er:ZBLANand Nd:GGG by pulsed laserdeposition and fs-lasermicrostructuringCLEO / PHAST 2007, Baltimore,MD, USA

28.05.2007 - A. L. BogleaFiber laser welding for packaging of disposable polymeric microfluidic-biochipsEMRS 2007 Spring Meeting, Strasbourg, Frankreich

31.05.2007 - J. Gottmann Manufacturing of Er:ZBLAN ridge waveguides by pulsedlaser deposition and ultrafastlaser micromachining for greenintegrated lasersEMRS 2007 Spring Meeting, Strasbourg, Frankreich

31.05.2007 - J. GottmannManufacturing of Nd:Gd3Ga5O12ridge waveguide lasers by pulsed laser deposition andultrafast laser micromachiningEMRS 2007 Spring Meeting, Strasbourg, Frankreich

31.05.2007 - R. Poprawe Tailored Light - Neue Laser fürneue AnwendungenBundesanstalt für Materialforschungund -prüfung, Berlin

01.06.2007 - W. Schulz Nichtlineare Dynamik der Laser-FertigungsverfahrenKolloquium BAM, Berlin

06.06.2007 - S. KaierleBasics for common laser applicationsUniversity of Technology, Peking,China

12.06.2007 - J. GottmannPulsed Laser Deposition und fs-Laser Strukturierung für WellenleiterlaserSeminar TU Braunschweig

13.06.2007 - S. PfeifferProzesssimulation für das LaserstrahltiefschweißenFOSTA ForschungsvereinigungStahlanwendungen, Arbeitskreissit-zung P708: Untersuchung derstrukturellen Stabilität von Model-len zur Schweißverzugssimulationbei Stahlwerkstoffen, Düsseldorf

18.06.2007 - R. Poprawe Societal demands determine the industrial innovation andthe future of laser materials processingLasers in Manufacturing - LIM2007, München

18.06.2007 - D. WortmannWaveguide lasers of Er:ZBLANand Nd:GGG by pulsed laserdeposition and fs-laser micro-structuringLasers in Manufacturing - LIM2007, München

19.06.2007 - M. BrajdicIncrease of drilling velocitiy byuse of superposed laser radiationLasers in Manufacturing - LIM2007, München

19.06.2007 - J. GeigerCharacterization of high powermultimode combinersCLEO Europe / Laser 2007, München

19.06.2007 - M. WehnerLaser processing of medical andbio-analytical devicesIndustry Workshop - Medical devicemanufacturing, Laser 2007, München

19.06.2007 - M. WehnerLaser-mediated perforation of plant cellsEuropean Conference on BiomedicalOptics - ECBO 2007, München

20.06.2007 - H.-D HoffmannRecent developments and perspectives of high-brightnessslab-, fiber- and diodelasersIndustrial Workshop »AdvancedSolid State Lasers«, Laser 2007,München

20.06.2007 - P. AlbusLaser cladding of mesh structureson HPT liner and NGV partsLasers in Manufacturing - LIM2007, München

20.06.2007 - T. JamborMicro laser cladding with highquality fibre lasersLasers in Manufacturing - LIM2007, München

20.06.2007 - M. PoggelWelding of transparent thermoplastics with fibre lasersLasers in Manufacturing - LIM2007, München


Lectures

20.06.2007 - J. WilkesRapid manufacturing of ceramiccomponents by selective lasermeltingLasers in Manufacturing - LIM2007, München

20.06.2007 - S. KaierleProcess basics and their influence on process stabilityand diagnosticsLASER INDUSTRY WORKSHOP,München

21.06.2007 - B. ZintzenEffective cooling for high-powerfiber lasersLasers in Manufacturing - LIM2007, München

21.06.2007 - A. GillnerLaser micro and nano structuringfor functional surfaces on poly-mer partsLasers in Manufacturing - LIM2007, München

21.06.2007 - A. OlowinskyLaser beam micro joining - newprocesses and applicationsLasers in Manufacturing - LIM2007, München

21.06.2007 - A. L. BogleaMicrowelding of polymericmaterials with fibre lasersLasers in Manufacturing - LIM2007, München

21.06.2007 - W. SchulzDiagnosis and simulation of high speed drillingLasers in Manufacturing - LIM2007, München

22.06.2007 - D. WortmannHighspeed production of periodical nanostructures usingfs-laser radiationLasers in Manufacturing - LIM2007, München

22.06.2007 - M. DahmenRepair of blade integrated disks by laser beam welding -weldability aspects and approachSeminar »Laser application in turbomachinery«, München

22.06.2007 - K. KowalickQuality assurance for laser applications in turbo machinerySeminar »Laser application in turbomachinery«, München

22.06.2007 - K. WaltherManufacture of shaped holes in multilayer systems by laserdrilling and laser structuring:From theory to applicationSeminar »Laser application in turbomachinery«, München

22.06.2007 - W. MeinersTechnological basics and eco-nomical advantages of additivemanufacture and repair by LaserMetal DepositionSeminar »Laser application in turbomachinery«, München

27.06.2007 - J. HoltkampLaser assisted micro sheet formingFLAMN 2007, St. Petersburg, Russland

27.06.2007 - L. StarovoytovaFabrication of Nd:Gd3Ga5O12planar waveguide laser by pulsed laser depositionFLAMN 2007, St. Petersburg, Russland

19.07.2007 - R. NollLaserspektroskopische Verfahrenfür SicherheitsanwendungenWorkshop »Optische Mikrosystemefür Sicherheitsanwendungen«, Goslar

08.08.2007 - R. PopraweFrontiers of advanced lasermanufacturing technology for 2015National Natural Science Foun-dation of China, Peking, China

28.08.2007 - E. W. KreutzHigh temperature turbine appli-cations using open parvus me-tallic foams with thermal barriercoatings and cooling hole arraysISCORMA 2007, Calgary, Kanada

05.09.2007 - J. GottmannDiode pumped ridge waveguidelaser by pulsed laser depositionand ulftrafast laser microma-chiningAdvanced Laser Technologies, Levi,Finland

05.09.2007 - J. GottmannManufacturing of periodicalnanostructures by fs-laser directwritingAdvanced Laser Technologies, Levi,Finland

07.09.2007 - M. WehnerMultimodal laser sources for surgery and device fabricationPhotonics 21 Workshop »Life Science and Health«, Jena

11.09.2007 - K. WissenbachDMD and SLM activities at ILT4. European Summer School »RapidManufacturing for Competitiveness«,St. Etienne, Frankreich

11.09.2007 - C. Fricke-BegemannLaser-based measurementsystems for size-dependent particle compositionEAC 2007, Salzburg, Österreich

11.09.2007 - C. D. GehlenTime and spatially resolved investigations of laser-inducedplasmas produced by ns- and ps-bursts in the milli- and sub-millijoule regime (Posterpräsentation)EMSLIBS 2007, Paris, Frankreich

11.09.2007 - Ü. AydinAnalysis of limestone and dolo-mite samples by laser-inducedbreakdown spectroscopy formineral processing (Posterpräsentation)EMSLIBS 2007, Paris, Frankreich

11.09.2007 - Ü. AydinLIBS identification of movingaluminium scrap particles bycleaning contamination layerswith new tailored laser system (Posterpräsentation)EMSLIBS 2007, Paris, Frankreich

11.09.2007 - M. HöhneDetermination of metals andnon-metallic inclusions by rapidLIBS analysis in steel samples (Posterpräsentation)EMSLIBS 2007, Paris, Frankreich

11.09.2007 - A. LamottReadout electronics for spec-trometers used in laser-inducedbreakdown spectroscopy (Posterpräsentation)EMSLIBS 2007, Paris, Frankreich

11.09.2007 - N. StraussLIBS-based measurement system for size-dependent particle composition (Posterpräsentation)EMSLIBS 2007, Paris, Frankreich

11.09.2007 - V. SturmFast vacuum slag analysis in a steel works by laser-induced breakdown spectroscopy (Posterpräsentation)EMSLIBS 2007, Paris, Frankreich

11.09.2007 - Q. WangComparison of NIR and UV excitation of LIBS plasma for the detection of explosives (Posterpräsentation)EMSLIBS 2007, Paris, Frankreich

12.09.2007 - R. NollLIBS - from research to industry,new frontiers for process controlEMSLIBS 2007, Paris, Frankreich

12.09.2007 - J. VrenegorTesting of a LIBS machine in a steel works laboratory for process controlEMSLIBS 2007, Paris, Frankreich

20.09.2007 - M. TraubSpaceborne fiber coupled diode laser pump modules forintersatellite communicationsSecurity and Defense 2007, Florenz,Italien

23.09.2007 - D. Ganser,Laser deposition of laser active planar waveguides forintegrated waveguide lasersCOLA 2007, Teneriffa, Spanien

24.09.2007 - A. HornTime-resolved investigations onultra-fast welding of glass-glass and glass-silicon non-interfero-metric time-resolved quantitivephase microscopy for ultrafastengineeringCOLA 2007, Teneriffa, Spanien

24.09.2007 - D. WortmannFS-laser structuring of ridgewaveguidesCOLA 2007, Teneriffa, Spanien

24.09.2007 - D. WortmannWaveguidelasers by pulsed laser deposition and fs-laserstructuringCOLA 2007, Teneriffa, Spanien

24.09.2007 - R. PopraweHigh speed precision laser ablationCOLA 2007, Teneriffa, Spanien

26.09.2007 - M. DahmenHybrid laser beam welding of structural parts13th IIW WG Shipbuilding Meeting,Odense C., Dänemark


Lectures

26.09.2007 - M. DahmenAutonomous joint tracking andapplications to robot control13th IIW WG Shipbuilding Meeting,Odense C., Dänemark

26.09.2007 - S. HoegesSLM-Generative Fertigung vonindividuellen Knochenersatz-implantaten41. DGBMT-Jahrestagung BMT2007, Aachen

27.09.2007 - R. PopraweFestvortrag41. DGBMT-Jahrestagung BMT2007, Aachen

05.10.2007 - E. W. KreutzEvolution of laser sourcesLASERAP 2007, Saint Léger Beuvray, Frankreich

06.10.2007 - R. NollLIBS - R&D projects at Fraunhofer ILTNASLIBS 2007, New Orleans, LA,USA

08.10.2007 - C. HinkeIndividualized serial productionfor mass customization andopen innovationMCPC 2007, Boston, DC, USA

17.10.2007 - R. PopraweFuture high power lasers and new applicationsMassachusetts Institute of Technology, Boston, USA

24.10.2007 - R. PopraweNew welding technologies by new lasers10. Internationales AachenerSchweißtechnik Kolloquium,Aachen

24.10.2007 - J. GeigerTutorial on fiber laser pumpingBRIGHTER-Treffen, Madrid, Spanien

29.10.2007 - R. PoprawePhotonics in the 21st century -The European Technology Platform Photonics 21ICALEO® 2007, Orlando, FL, USA

29.10.2007 - S. KaierleFrom flexible to adaptive manu-facturing: an approach for lasermaterials processing (plenary talk)ICALEO® 2007, Orlando, FL, USA

30.10.2007 - C. A. HartmannInvestigation on laser microablation of steel using ps-IR pulse burstsICALEO® 2007, Orlando, FL, USA

30.10.2007 - D. PetringProgress in laser-MAG hybridwelding of high-strength steelsup to 30 mm thicknessICALEO® 2007, Orlando, FL, USA

31.10.2007 - A. L. BogleaTWIST - A new method for themicro-welding of polymers withfibre lasersICALEO® 2007, Orlando, FL, USA

31.10.2007 - C. ChaminadeLaser-based glass soldering forMEMS packagingICALEO® 2007, Orlando, FL, USA

31.10.2007 - S. KaierleComparison of process moni-toring strategies for laser trans-mission welding of plasticsICALEO® 2007, Orlando, FL, USA

01.11.2007 - S. KaierleProcess control of laser beamwelded small section aluminumsheetICALEO® 2007, Orlando, FL, USA

08.11.2007 - W. SchulzModelling and simulation of laser processingSeminar Graduiertenschule AICES -Cluster of Excellence, RWTHAachen University

15.11.2007 - H.-D. HoffmannDesignaspekte robuster undkompakter Faserlaser mit Aus-gangsleistung im kW- BereichIWS Faserlaser Workshop, Dresden

15.11.2007 - E. WagenaarsA tin-based plasma source forextreme ultraviolet lithographyWELTPP-10, Kerkrade, Niederlande

20.11.2007 - E. Bremus-KoebberlingSelektive Laser-Oberflächen-funktionalisierung medizin-technischer KunststoffbauteileAachener Laserseminar »Laserver-fahren in der Medizintechnik«,Fraunhofer ILT, Aachen

20.11.2007 - A. GillnerLasersysteme und Laserverfahrenin der Medizintechnik - Etabliertund trotzdem nicht abgehakt,Ideen für die ZukunftAachener Laserseminar »Laserver-fahren in der Medizintechnik«,Fraunhofer ILT, Aachen

20.11.2007 - A. GillnerNeue Laserstrahlquellen für die Präzisionsbearbeitung vonMedizinprodukten - Eigenschaftenund Potentiale von Kurzpuls-lasern, UV-Lasern bis zu Faser-lasernAachener Laserseminar »Laser-verfahren in der Medizintechnik«,Fraunhofer ILT, Aachen

20.11.2007 - S. HoegesPatientenspezifische Fertigungmedizinischer Implantate durchSelective Laser MeltingAachener Laserseminar »Laser-verfahren in der Medizintechnik«,Fraunhofer ILT, Aachen

20.11.2007 - M. PoggelLaserstrahlfügen medizintech-nischer Kunststoffbauteile - vontransparent über flexibel bis zuultrafeinAachener Laserseminar »Laser-verfahren in der Medizintechnik«,Fraunhofer ILT, Aachen

20.11.2007 - S. KaierleModerne Systemtechnik für diesichere und effiziente Material-bearbeitung mit LaserstrahlungAachener Laserseminar »System-technik«, Fraunhofer ILT, Aachen

20.11.2007 - S. KaierleAutonomes Laserstrahlschweißendurch optische Geschwindig-keitsmessung und NahtfolgeAachener Laserseminar »System-technik«, Fraunhofer ILT, Aachen

21.11.2007 - S. KaierleProzessüberwachung und Qua-litätssicherung für die Material-bearbeitung mit LaserstrahlungAachener Laserseminar »System-technik«, Fraunhofer ILT, Aachen

21.11.2007 - S. MannProzessüberwachung mit koaxialer FremdbeleuchtungAachener Laserseminar »System-technik«, Fraunhofer ILT, Aachen

21.11.2007 - A. LamottOnline Überwachung vonSchweißprozessen mit Emissions-spektrometrieAachener Laserseminar »Lasermess-technik für die metallverarbeitendeIndustrie«, Fraunhofer ILT, Aachen

21.11.2007 - R. NollGrundlagen und Methoden der Lasermesstechnik - Stand der Technik und neue Entwick-lungenAachener Laserseminar »Lasermess-technik für die metallverarbeitendeIndustrie«, Fraunhofer ILT, Aachen

21.11.2007 - F. SchmittEntwicklung und Einsatz miniaturisierter Scanner für das Laserstrahl-MikrofügenKolloquium Mikroproduktion, Aka-demie-Hotel Karlsruhe, Karlsruhe

22.11.2007 - F. SariAnwendungsmöglichkeiten vonLaserdurchstrahlverfahren fürdas Fügen von MikrobauteilenKolloquium Mikroproduktion, Aka-demie-Hotel Karlsruhe, Karlsruhe

28.11.2007 - S. PfeifferProzesssimulation zur Nutzungals Wärmequelle in FEM-Simu-lationen des Verzugs beimSchweißenFOSTA Forschunsvereinigung Stahl-anwendungen, ArbeitskreissitzungP708: Untersuchung der struktu-rellen Stabilität von Modellen zurSchweißverzugssimulation beiStahlwerkstoffen, Düsseldorf

01.12.2007 - D. PetringPresent status and future researchand development of laser ma-terial processing on sheet metalin Europe20th Anniversary of Amada Foun-dation for Metal Work Technology,Isehara, Japan

03.12.2007 - D. BuchbinderRapid Manufacturing von Aluminiumbauteilen für die Serienproduktion durch Selective Laser Melting (SLM)Euro-uRapid 2007, Frankfurt/Main

04.12.2007 - A. GillnerFunctional surfaces on polymers for medical products and microoptics by laser based embossingand micro structured toolsEuro-uRapid 2007, Frankfurt/Main

10.12.2007 - F. SariLaser assisted transmission bondingInternational Conference on»Wafer Bonding for MEMS Techno-logies and Wafer Level Integration«,Halle



11.01.2007Chair for Laser Technology LLT at RWTH AachenLecture in association with the RWTH Colloquium on LaserTechnologyProf. Alan H. Epstein, Massachusetts Institute of Technology, Cambridge, MA»Chip-based gas turbine generators,rocket engines and chemical lasers«

25.01.2007Chair for Laser Technology LLT at RWTH AachenLecture in association with the RWTH Colloquium on LaserTechnologyDr. Joseph Pankert, Philips LightingB.V., Eindhoven, NL»EUV Lithographie für die Herstel-lung hochintegrierter Halbleiter-Chips«

13.02.2007, AachenUnihits for KidsForum organized by the Chair for Laser Technology LLT and theFraunhofer ILT to give advice onscientific careers to students at theGeschwister-Scholl-Gymnasium inPulheim.

06.03.2007, AachenAachen Laser Seminar »Advanceby laser surface engineering - deposition welding, repairs, cleaning and polishing«Seminar organized by Carl HanserPublishers, Munich in associationwith the Fraunhofer Institute forLaser Technology ILT, Aachen. Additional information: www.aachenerlaserseminare.de.

06.03.2007, AachenAachen Laser Seminar »Laserwelding of plastics - precisionand flexibility in the micro tomacro range«Seminar organized by Carl HanserPublishers, Munich in associationwith the Fraunhofer Institute forLaser Technology ILT, Aachen. Additional information: www.aachenerlaserseminare.de.

07.03.2007, Aachen Aachen Laser Seminar»Micro bonding by laser«Seminar organized by Carl HanserPublishers, Munich in associationwith the Fraunhofer Institute forLaser Technology ILT, Aachen. Additional information: www.aachenerlaserseminare.de.

08.03.2007, Aachen Aachen Laser Seminar »Microdrilling by laser - from basic re-search to industrial application«Seminar organized by Carl HanserPublishers, Munich in associationwith the Fraunhofer Institute forLaser Technology ILT, Aachen. Additional information: www.aachenerlaserseminare.de.

23.03.2007, Aachen 27th seminar of the »Aix-Laser-People« Alumni club meeting of the Fraun-hofer ILT and the Chair for LaserTechnology LLT at the laser process-ing and consulting center LBBZGmbH in Geilenkirchen, featuring a lecture by Dipl.-Ing. Ulrich Bernerson »Laser processing à la carte - thechallenges faced by laser contrac-tors, as exemplified by LBBZGmbH«, a tour of the LBBZ GmbHfacilities in Geilenkirchen, and a pre-sentation of the Neumann & EsserGroup with a subsequent tour of the company in Übach Palenberg.

03.05.2007Chair for Laser Technology LLT at RWTH AachenLecture in association with theRWTH Colloquium on Laser TechnologyDr. Thomas Riedl, TU Carolo-Wilhelmina, Braunschweig»Organic semiconductor lasers -from the visible to the UV«

24.05.2007Chair for Laser Technology LLT at RWTH AachenLecture in association with the RWTH Colloquium on Laser TechnologyDr. Götz Erbert, Ferdinand-Braun-Institut für Höchstfrequenztechnik,Berlin»Hochleistungslaser - Schlüsselbau-elemente moderner Lasertechnologie«

14.06.2007Chair for Laser Technology LLT at RWTH AachenLecture in association with theRWTH Colloquium on Laser TechnologyDr. Holger Schlüter, Trumpf Photonics Inc., Cranbury, NJ, USA»Scheibenlaser in Produktion undEntwicklung«

14.06.2007, AachenUnihits for KidsForum organized by the Chair for Laser Technology LLT and theFraunhofer ILT to give advice onscientific careers to students at theInda Gymnasium in Aachen.

20.06.2007, Munich28th seminar of the »Aix-Laser-People« Alumni club meeting of the Fraun-hofer ILT and the Chair for LaserTechnology LLT with a stage debateon the topic of »Living and workingas entrepreneur«. Participants in thedebate: • Dipl.-Ing. Ulrich Berners, manag-

ing director, Laser Bearbeitungs- und Beratungszentrum GmbH, Geilenkirchen

• Dr. Keming Du, managing director,EdgeWave GmbH, Aachen

• Dipl.-Ing. Jürgen Jannsen, manag-ing director, RJ Lasertechnik GmbH,Übach-Palenberg

• Dr. Reinhard Kramer, managing director, PRIMES GmbH, Pfung-stadt

• Dipl.-Phys. Axel Bauer, Arbeits-kreis Lasertechnik e.V., Aachen (who chaired the debate).

22.06.2007, Munich LASER 2007 - Seminar »Laserapplication in turbo machinery« Immediately following LASER 2007,a seminar on »Laser application inturbo machinery« was held in theNH Hotel at the new Munich tradefair center on June 22, 2007. Theseminar was organized by theFraunhofer ILT and the Chair forLaser Technology LLT. Led by Akad.Rat Dr.-Ing. Ingomar Kelbassa, theseminar was aimed primarily atsystems manufacturers, suppliersand service providers in the engineconstruction sector. It was attendedby approximately 40 people, whocame to learn about the latest deve-lopments in component repair foraircraft engines.

Conventions and Conferences

Above: Meeting of the Alumni club»Aix-Laser-People« on March 23,2007. Middle: Aachen Laser Seminar.Below: LASER 2007 - Seminar »Laserapplication in turbo machinery« onJune 22, 2007.

18.07.2007Chair for Laser Technology LLTat RWTH AachenLecture in association with the RWTH Colloquium on LaserTechnologyProf. Dr. Karl Leo, Institut für Angewandte Photophysik (IAPP),Dresden»Organische Halbleiter: Physik undBauelementanwendungen«

16.08.2007, AachenUnihits for KidsForum organized by the Chair for Laser Technology LLT and theFraunhofer ILT to give advice onscientific careers to students at theSt. Ursula Gymnasium in Aachen.

27. - 28.09.2007, Thun, Switzerland 29th seminar of the »Aix LaserPeople«Alumni club meeting of the Fraun-hofer ILT and the Chair for LaserTechnology LLT, featuring a tour ofthe Birr plant of Alstom AG in Swit-zerland on September 27, 2007. A presentation on Alstom Power,one of the world’s leading providersof comprehensive power generationsolutions, was given by Dr.-Ing.Markus Oehl, process developmentmanager in the hot gas partsdepartment. The tour of the plantincluded a visit to the productionline for generators and rotors usedin gas and steam turbines. On September 28, 2007, the seminarcontinued with a trip to lasermanufacturer LASAG AG in Thun,Switzerland, including a presen-tation by Managing Director Dr.Dietmar Wagner and Dr. Ulrich Dürr.

18.10.2007Chair for Laser Technology LLTat RWTH AachenLecture in association with the RWTH Colloquium on LaserTechnologyDipl.-Ing. Stefan Irrgang, IPG LaserGmbH, Burbach»Faserlaser für die industrielleAnwendung«

25.10.2007Chair for Laser Technology LLTat RWTH AachenLecture in association with the RWTH Colloquium on LaserTechnologyProf. Dr. Karl-Friedrich Klein, Fachhochschule Gießen-Friedberg,Friedberg»Mikrostrukturierte Faser für neueAnwendungen«

08.11.2007Chair for Laser Technology LLTat RWTH AachenLecture in association with the RWTH Colloquium on LaserTechnologyProf. Dr. T. Baumert, UniversitätKassel, Institut für Experimental-physik, Kassel»Ultraschnelle Laserkontrolle«

20.11.2007, Aachen Aachen Laser Seminar»Lasers in the field of medicaltechnology«Seminar organized by Carl HanserPublishers, Munich in associationwith the Fraunhofer Institute forLaser Technology ILT, Aachen. Additional information:www.aachenerlaserseminare.de.

20. - 21.11.2007, Aachen Aachen Laser Seminar»Laser systems engineering -quality assurance and processmonitoring, beam sources andhandling systems«Seminar organized by Carl HanserPublishers, Munich in associationwith the Fraunhofer Institute forLaser Technology ILT, Aachen. Additional information:www.aachenerlaserseminare.de.

21.11.2007, Aachen Aachen Laser Seminar»Laser measuring technologiesfor the metalworking industry«Seminar organized by Carl HanserPublishers, Munich in associationwith the Fraunhofer Institute forLaser Technology ILT, Aachen. Additional information:www.aachenerlaserseminare.de.

29.11.2007Chair for Laser Technology LLTat RWTH AachenLecture in association with the RWTH Colloquium on LaserTechnologyV. K. Tikhomirov, Chemistry Department, Catholic UniversityLeuven, Belgium»Rare-earth doped nano-crystals intransparent glass-ceramics and theirapplications«

20.12.2007, Aachen 30th seminar of the »Aix Laser People«Alumni club meeting of the Fraun-hofer ILT and the Chair for LaserTechnology LLT, featuring lecturesby Dr. Jochen Stollenwerk on »Newdevelopments in surface engineer-ing at the Fraunhofer ILT«, andDipl.-Ing. Volker Cremer ofengineering service provider Bertrandt Ingenieurbüro GmbH inCologne on »Project managementat Bertrandt - Tier 1 partner to theautomotive industry«. The lectureswere followed by a tour of theindustrial research association GIFGesellschaft für IndustrieforschungmbH at the industry and businesspark IGA in Alsdorf.


Conventions and Conferences

Meeting of the Alumni club »Aix-Laser-People« on September27 and 28, 2007 in Thun, Switzerland.

23.01. - 25.01.2007San Jose, USAPhotonics West 2007International trade fair for opticsand photonicsParticipation by the departmentsfor laser components and for solid-state and diode lasers of the Fraun-hofer ILT and the Chair for LaserTechnology LLT at the German pavilion.ILT/LLT topics: assembly of diodelasers, characterization of diodelaser bars, laser systems based onlaser bars, high-energy diode lasermodules for space-based applica-tions, and solid state lasers.

16.04. - 20.04.2007HannoverHannover Messe 2007International industry fairParticipation by the micro techno-logy department of the FraunhoferILT at the IVAM joint stand.ILT topic: Lasers in micro engineer-ing, Highlights: micro drilling athigh drilling rates and micro weld-ing of plastics.

08.05. - 11.05.2007SinsheimControlInternational trade fair for qualityassuranceParticipation by the department forlaser measurement and testingtechnology of the Fraunhofer ILT at the joint stand hosted togetherwith LSA - Laser Analytical Systems+ Automation GmbH in Hall 4.ILT topics: laser measuring productsand systems for process monitoringand quality assurance, including acompact laser measuring device forspectral element analysis, a systemfor rapid, locally resolved elementanalysis, and non-contact lasermeasuring systems for chemicalanalysis and for determining thedimensional accuracy and geometryof products.

18.06. - 21.06.2007MunichLASER 2007LASER 2007 World of Photonicsand World of Photonics Congress2007Participation by the Fraunhofer ILTat the joint Fraunhofer stand in Hall B3.ILT topics: component repair foraircraft engines by laser cladding;development of customized diode,fiber and YAG lasers for medicalengineering, materials processingand satellite communications; rapidmanufacturing of aircraft, tool andmedical components by selectivelaser melting (SLM); modeling andsimulation software for optimizingprecision drilling processes; microdrilling of silicon components forthe production of solar cells; microstructuring and micro generation;joining of transparent plastic parts;integrated laser-beam welding andcutting without retooling, using acombi-head; coaxial process control(CPC) system for online monitoringof welding and cutting processes;laser-beam cutting at outputs over5 kW using a robust mirror cuttinghead.

18.06. - 24.06.2007Le Bourget, FranceSalon International de l’Aéro-nautique et de l’EspaceInternational Paris Air ShowParticipation by the CLFA at theexhibition in Hall 4.CLFA topics: rapid manufacturingand repair by laser cladding.

24.10. - 31.10.2007DüsseldorfK 2007International trade fair for plasticsand rubberParticipation by the micro techno-logy department of the FraunhoferILT at the joint Fraunhofer stand inHall 3.ILT topic: welding of plastics.

29.10. - 01.11.2007Orlando, FloridaICALEO26th International Congress onApplications of Lasers & Electro-OpticsParticipation by the Fraunhofer ILT in the lecture sessions and theICALEO Vendor Program. The Ven-dor Program involved 86 exhibitorsfrom nine countries, including theFraunhofer ILT in collaboration withthe Fraunhofer CLT, Plymouth, USA.

13.11. - 16.11.2007MunichProductronica 2007International trade fair for electronics productionParticipation by the micro techno-logy department of the FraunhoferILT at the joint Fraunhofer stand inHall B5.ILT topic: flexible manufacturing cell for laser micro processing.

05.12. - 08.12.2007FrankfurtEuroMoldWorld fair for moldmaking and tooling, design and applicationdevelopmentParticipation by the surface treat-ment department of the FraunhoferILT at the joint Fraunhofer stand»Innovations in toolmaking« in Hall 8.ILT topic: High-performance moldinserts for tool construction.


Above: Joint Fraunhofer stand atthe EuroMold 2007 in Frankfurt.Middle and below: Joint Fraun-hofer stand at the LASER 2007 in Munich.

Trade Fairs

»Your partner for innovation«(German/English)This brochure provides a concise over-view of the Fraunhofer ILT. In additionto presenting a summary of EuropeanR&D projects conducted by the ILT, thebrochure also contains a short profileof the institute as well as a list of refe-rence customers.

»Services and Contacts« (German/English)This brochure gives an overview of current services offered and contactswithin the Institute. It also introducesfocal points of each division of theFraunhofer ILT.

Annual Report 2007(German/English)The annual report presents a compre-hensive look at the R&D activities ofthe Fraunhofer ILT for the respectivebusiness year. Lists of scientific publi-cations and lectures as well as patents,dissertations, conferences and tradefairs are also included. The English ver-sion can only be found on our websiteat: www.ilt.fraunhofer.de.

Proceedings of the Aachen Collo-quium for Laser Technology AKL’06The technical proceedings of theAachen Colloquium for Laser Techno-logy AKL’06 (May 3 - 5, 2006) containsreports from 34 laser manufacturersand users outlining the latest develop-ments and technology trends in in-dustries such as optics, automobile,metal production, tool and die makingas well as electrical and electronicengineering. Practical case studies highlight various laser processes suchas laser beam welding and cutting,laser surface technology as well aslaser micro engineering.

Proceedings of the TechnologyBusiness day TBT’06The proceedings of the TechnologyBusiness Day, which took place on03.05.2006 in Aachen with a panel of 13 experts in financial services,technology marketing, law, sales andbusiness consulting, are addressed pri-marily toward managers of expandinghigh-tech firms and newly establishedsmall companies. The publication pro-vides a succinct overview of the emerg-ing trends and opportunities offered bylaser technology, mechanical and auto-motive engineering. At the same time,it also sheds light on many financial,legal and marketing questions confront-ing businesses at various stages of theirevolution.

Technical Brochure: »High-Power Diode Lasers« This technical brochure outlines thevarious development activities of theFraunhofer ILT in the area of high-power diode lasers. Included aredevelopments such as the design ofspecial components for laser cooling,diode laser bar packaging, diode laserburn-in characterization and the opticaldesign and development of completediode laser modules.

Technical Brochure: »Laser Tech-nology for Surface Modificationand Forming« This technical brochure provides anoverview of how lasers are employedin the area of surface modification andforming. Included are processes suchas deburring, melting and forming,polishing, roughening, structuring andactivation, re-crystallization, annealingand fine pearlitizing.


Publications

ILT

InstitutLasertechnik

Fraunhofer

TAGUNGSBAND

03 . - 05 . MAI 2006

EUROGRESS AACHEN

Technical Brochure: »Laser Technology for Wear and Corrosion Protection« Wear and corrosion protection can becreated by various laser processes. Thistechnical brochure provides insightsinto processes such as martenistic sur-face hardening, remelting, depositionwelding, alloying and dispersion.

Technical Brochure: »Laser BeamDeposition Welding« This technical brochure provides anintroduction to the processes andsystems used in laser beam depositionwelding. It also elucidates the differen-ces between conventional powderfeed nozzles and those used in laserbeam deposition welding.

Technical Brochure: »Rapid Proto-typing and Rapid Manufacturing« This brochure describes the selectivelaser melting process developed at theFraunhofer ILT which enables complexmetal parts to be manufactured directlyfrom 3D CAD data. It also providesexamples of applications of the laserbeam generation technique.

Technical Brochure: »Lasers in Microstructuring« This technical brochure describes processes such as laser ablation, precision cutting, drilling and laser-assisted microforming.

Technical Brochure: »Laser Ablation, Cleaning and Marking«This technical brochure outlines the advantages of the different laserprocesses and the wealth of potentialapplications.

Technical Brochure: »Systems and Equipment for Laser MaterialsProcessing«This technical brochure highlights thesystems engineering solutions availableto Fraunhofer ILT customers. Theyencompass the planning, developmentand installation of complete laser facilities and process monitoring andcontrol systems, complemented by fea-sibility studies, training and educationseminars and consulting services.

Technical Brochure: »Quality Assu-rance in Laser Materials Processing«This technical brochure explains thepotential for process monitoring andcontrol in laser materials processing. Italso outlines the services available fromthe Fraunhofer ILT for the developmentof such monitoring systems.

Technical Brochure: »Lasers in Mounting and ConnectingTechniques«This technical brochure gives an over-view of the use of laser technology inmounting and connecting techniques.Micro joining processes such as laserbeam bonding and laser beam solder-ing are demonstrated.

Technical Brochure: »Lasers in Plastics and Paper Processing« This technical brochure describes theuse of lasers in the processing of plastics,composite materials, paper and glass.

Technical Brochure: »Lasers in Life Science« This technical brochure deals withapplications of laser technology inmedical engineering. It also describesthe use of lasers as tools in microreac-tion processes and biotechnology.


Publications

Laser in der Kunststoff-und Papiertechnik

Laser in Life Science

Technical Brochure: »Modeling and Simulation« Written by experts, this brochure pro-vides an overview of the activities andcore competencies of the projectgroup on modeling and simulation. ILTspecialists and researchers at the Chairfor Laser Technology LLT of RWTHAachen University devise models tosimulate resonator design conceptsand beam-guiding and focusingsystems, and a variety of machiningprocesses including cutting, weldingand drilling.

Technical Brochure: »Laser Microscopy«A brochure offering insights intoadvanced techniques of laser scanningmicroscopy developed at the Fraun-hofer ILT.

Technical Brochure: »Polishing with Laser Radiation«This technical brochure describes the process of laser polishing and itspossible applications.

Technical Brochure: »Heat Treat-ment with Laser Radiation«This brochure provides an insight intolaser-assisted hardening, softening,annealing and forming.

Technical Brochure: »Material Analysis and Process Monitoringwith Laser« This technical brochure provides anoverview of materials analysis systemsand their possible applications.

Technical Brochure: »Design of Diode Laser Heat Sinks«This brochure describes the structureof diode laser heat sinks, illustrated by prototypes.

Technical Brochure: »CustomizedServices for Diode Lasers«This technical brochure provides aninsight into research and developmentactivities and customer-specific solu-tions in the field of high-power diodelasers.

Information Brochure:»Optical Technology Courses at RWTH Aachen«This brochure summarizes the lasertechnology courses available at RWTHAachen and is designed specifically for students of mechanical and electricalengineering as well as physics. The brochure details the courses and lectureson laser technology available to studentswithin their major field of study that aretaught by the individual RWTH chairsunder the auspices of the Fraunhofer ILT.

Information Brochure: »Networks of Competence« »Networks of Competence« was setup on the initiative of the BMBF andserves as an international marketinginstrument and presentation showcasefor the most highly skilled networks ofcompetence in Germany. Its Internetportal, at: www.kompetenznetze.de,with its efficient search engine andmany useful links, provides an idealinformation source and communica-tion platform for individuals and orga-nizations in Germany and elsewherelooking for information and potentialworking partners.

Information Brochure: »European Laser Institute ELI« This brochure provides information onthe European network of recognizedcenters of R&D in laser technologycoordinated by the Fraunhofer ILT. The members of this network have setthemselves the goal of making existinglaser know-how in Europe accessibleto all interested parties in industry and science. The project is sponsoredby the European Commission. Furtherinformation can also be found at:www.europeanlaserinstitute.org.

Product and Project DataDescriptions of projects from theFraunhofer ILT annual reports and specific product information can bedownloaded from our website at:www.ilt.fraunhofer.de.


Publications

StudieninfoOptische Technologienan der RWTH Aachen

ILT

CD-ROM »Laser Technology« (German only)

This CD-ROM is a collection of graphics,pictures and videos from the lecturesLaser Technology I and II by Prof. Dr. rer. nat. Reinhart Poprawe M.A.and a new revised version was producedin 2003.

It was produced by the Department for Laser Technology LLT in the machinefaculty at the RWTH Aachen Universityin close cooperation with the Fraun-hofer Institute for Laser Technology ILT.

It contains the basics of laser technologyas well as physical and technical pro-cesses for modern manufacturing pro-cesses. Furthermore, the current stateof economic use of laser and industrialapplications is demonstrated in nume-rous examples.

The program runs using Acrobat Reader5.0 on computers with Microsoft Windows 95 OSR 2.0, Windows 98 SE,Windows Millenium Edition, WindowsNT 4.0 with Service Pack, Windows2000, Windows XP and MacOSX (64 MB Ram (random access memory)as well as 30 MB free fixed-disk storage).

The printing and use of unaltered graphics and pictures is only allowedfor educational purposes.

Further information and order formsfor the CD-ROM »Laser Technology«are available through the laser technology association AKL e.V., Steinbachstraße 15, 52074 Aachen.

ContactDiana HeinrichsPhone +49 241 8906-122Fax +49 241 [email protected]


CD-ROM »Laser Technology«

»Laser Technology for Manu-facturing« by Reinhart Poprawe

Principles, prospects and examples for the innovative engineer.

Applied laser technology is too wide-ranging a topic to be covered in asingle volume. For this reason, thebook places special emphasis on lasertechnology as used in manufacturingapplications, particularly present-daymachining processes used in produc-tion technology. The phenomenaoccurring in laser-based materials pro-cessing are quantified by formulae andillustrated with corresponding modelsthat are readily understood by the trained engineer or physicist. Thesebasic principles enable the differenttypes of machining operations to besystematically characterized, permittingthe various applications to be illustra-ted using a common scientific basis. Of more practical significance are theprocesses described for various machin-ing operations, which explain in simpleterms the basic principles and keyquantitative interrelationships betweenthe process parameters. The numerousexamples are intended to spark thereader’s creativity and help to inspirenew applications.

ContentsIntroduction, behavior of electromag-netic radiation at interfaces, absorptionof laser radiation, energy transfer andthermal conduction, thermomechanics,phase transformation, melting poolflows, laser-induced ablation, plasmaphysics, laser radiation sources, surfacetechnologies, forming, rapid prototyp-ing, rapid tooling, joining, ablation anddrilling, cutting, systems engineering,laser measuring technologies.Appendices: A: optics, B: continuummechanics, C: laser-induced ablation,D: plasma physics, E: explanation of symbols and constants, F: color images, index

2005. XVII, 526 pages, 353 illustrations(VDI publication), ISBN 3-540-21406-2

The book can be ordered from:Springer KundenserviceHaberstraße 769126 HeidelbergTelefon +49 6221 345-0Fax +49 6221 [email protected]


Technical Book »Laser Technology for Manufacturing«


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If you would like more informationabout the research and developmentat the Fraunhofer Institute for LaserTechnology please go to our website at www.ilt.fraunhofer.de. Informationcan also be ordered using this form.

Brochure: »Your partner for innovation«GermanEnglish

Brochure: »Services and Contacts« (German/English)

Annual Report 2007 (English version only available online at www.ilt.fraunhofer.de)




Proceedings of the Aachen Colloquium for Laser Technology AKL’06 (only German)

Proceedings of the TechnologyBusiness Day TBT’06 (only German)

Proceedings of the International Laser Technology CongressAKL’08 (only English)

Technical Brochure: »High-Power Diode Lasers« GermanEnglish

Technical Brochure: »Lasertechnik für die Oberflächenmodifikation und das Umformen« (Laser Tech-nology for Surface Modification and Forming) (only German)

Technical Brochure: »Lasertechnik für den Verschleiß- und Korrosions-schutz« (Laser Technology for Wear and Corrosion Protection) (only German)

Technical Brochure:»Laserstrahlauftragschweißen«(Laser Beam Deposition Welding)(only German)

Technical Brochure:»Rapid Prototyping and Rapid Manufacturing« GermanEnglish

Technical Brochure:»Lasers in Microstructuring«GermanEnglish

Technical Brochure:»Abtragen, Reinigen und Markieren mit Laserstrahlung« (Laser Ablation, Cleaning and Marking) (only German)

Technical Brochure: »Systems andPlant for Laser Materials Processing« (only German)

Technical Brochure: »Quality Assurance in Laser Materials Processing« GermanEnglish

Technical Brochure: »Lasers in Mounting and Connecting Techniques«GermanEnglish

Technical Brochure: »Lasers in Polymer and Paper Technology« GermanEnglish

Technical Brochure: »Lasers in Life Science«GermanEnglish

Technical Brochure: »Modellie-rung und Simulation« (Modeling and Simulation) (only German)

Technical Brochure: »Laser-mikroskopie« (Laser Microscopy) (only German)

Technical Brochure: »Polieren mit Laserstrahlung« (Polishing with Laser Radiation) (only German)

Technical Brochure: »Wärme-behandlung mit Laserstrahlung« (Heat Treatment with Laser Radiation) (only German)

Technical Brochure: »Material Analysis and Process Monitoring with Laser«GermanEnglish

Technical Brochure: »Design of Diode Laser Heat Sinks«(only English)

Technical Brochure: »Customized Services for Diode Lasers«(only English)

Information Brochure: »Optische Technologien an der RWTH Aachen« (Optical Technology Courses at RWTH Aachen) (only German)

Information Brochure: »Networks of Competence«(German/English)

Information Brochure: »European Laser Institute ELI« (only English)

CD-Rom »Lasertechnik« (Laser Technology) (only German)

Technical Book »Lasertechnik fürdie Fertigung« (Laser Technologyfor Manufacturing) (only German)


Information Service

Editorial staffDipl.-Phys. Axel Bauer (responsible)Stefanie Flock

Design and ProductionDipl.-Des. Andrea Croll

PrintDruckspektrumHirche-Kurth GbR, Aachen

PaperThis Annual Report was printed on environment-friendly, unchlorinatedand acid-free bleached paper.

Contact Dipl.-Phys. Axel BauerTelephone +49 241 8906-194Fax +49 241 [email protected]

Subject to alterations in specificationsand other technical information.

All rights reserved. Reprint only withwritten permission of the editorial office.

© Fraunhofer-Institut für Lasertechnik ILT, Aachen 2008

Fraunhofer-Institutfür Lasertechnik ILT

Steinbachstraße 1552074 AachenPhone +49 241 8906-0Fax +49 241 8906-121

[email protected]

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Documents

Performance and Results Annual Report 2007 · which utilize selected technology net-works. Customers are offered laser-specific solutions that encompass design engineering, material