Ultrafast laser written active devices

Laser & Photon. Rev. 3, No. 6, 535–544 (2009) / DOI 10.1002/lpor.200810050 535

Abstract Direct-write optical waveguide device fabrication is

probably the most widely studied application of femtosecond

laser micromachining in transparent dielectrics at the present

time. Devices such as buried waveguides, power splitters, cou-

plers, gratings, optical amplifiers and laser oscillators have all

been demonstrated. This paper reviews the application of the

femtosecond laser direct-write technique to the fabrication of

active waveguide devices in bulk glass materials.

White light diffraction from waveguide Bragg gratings fabri-

cated in doped phosphate glass using the femtosecond laser

direct-write technique. Such a waveguide Bragg grating was in-

strumental to the first demonstration of a monolithic waveguide

laser using this technique.

© 2009 by WILEY-VCH Verlag GmbH & Co.KGaA, Weinheim

Ultrafast laser written active devicesMartin Ams*, Graham D. Marshall, Peter Dekker, James A. Piper and Michael J. Withford

MQ Photonics Research Centre, Centre for Ultrahigh bandwidth Devices for Optical Systems (CUDOS), Department of Physics,

Macquarie University, North Ryde, NSW2109, Australia

Received: 5 September 2008, Revised: 28 October 2008, Accepted: 29 October 2008

Published online: 12 December 2008

Key words: Femtosecond, direct-write, waveguide, optical glass, Bragg grating, laser.

PACS: 42.55.-f, 42.60.Da, 42.65.Re, 42.70.Ce, 42.82.Et

1. Introduction

The worldwide market for optical components is grow-ing exponentially. In particular, rare-earth doped opticalamplifiers are emerging as the predominant optical signalamplification device for every aspect of optical commu-nication networks from repeaters, pre-amplifiers, signalconditioners and power boosters to in-line amplifiers forwavelength-division-multiplexed (WDM) systems [1]. Op-tical amplifiers can amplify light signals of multiple wave-lengths simultaneously, independent of the signal data rate,providing a powerful benefit when upgrading a system asonly the launch/receive terminals in a network would re-quire changing. Such an optical amplifier is the ErbiumDoped Fibre Amplifier (EDFA) in which the core regionof an optical fibre is doped with Er3+ ions. EDFAs pro-

duce high gain with relatively little noise, demonstrate po-larisation independency, and operate at wavelengths thatminimise dispersion effects in silica, i.e. the telecommuni-cations C-band. However, EDFAs are quite bulky and henceare difficult to incorporate into confined spaces, and arecertainly not amenable to circuit-board-level or chip-levelintegration. Furthermore, as the optical network nears theend user at the Metropolitan Area Network (MAN) andLocal Area Network (LAN) stages, the network is charac-terised by numerous splitting of the input signal into manychannels. This feature represents a fundamental problemfor optical networks. Each time the input signal is split, thesignal strength per channel is reduced. As optical telecom-munication networks push further and further toward theend user, there is thus an ever-growing need for compactand low cost integrated optical amplification devices [2].

* Corresponding author: e-mail: [email protected]

© 2009 by WILEY-VCH Verlag GmbH & Co.KGaA, Weinheim

536 M. Ams, G.D. Marshall, et al.: Ultrafast laser written active devices

Figure 1 (online color at: www.lpr-journal.org) The femtosec-

ond laser direct-write technique.

A possible solution to this problem is the rare-earth dopedwaveguide amplifier which is similar to an EDFA exceptthat it provides high gain in a short length of doped waveg-uide rather than several metres of fibre [3]. For telecomapplications, it is also extremely important to fabricate acompact laser source able to generate, in parallel, all thechannels used in WDM signal transmission, i.e. a compacttelecom transmitter (waveguide laser array) emitting on theITU grid. Such laser sources can also be used, for example,in various switching designs that would ultimately formpart of an integrated chip to be used in MANs.

Various technologies are available for the fabricationof active integrated optical devices: ion exchange [4, 5],silicon-on-insulator [6–8] and silica-on-silicon [6,7,9]. Thelatter category can be subdivided into thermal oxidationand nitridation [10,11], sputtering [12–14], flame hydrol-ysis deposition [15–17], chemical vapour deposition andplasma-enhanced chemical vapour deposition [18–20] andthe sol-gel process [21–26]. A relatively new fabricationmethod that also shows good promise in this field is ultra-fast laser direct-writing of guided wave devices. In 1996, itwas shown that tightly focussed femtosecond infrared laserpulses can create a permanent refractive index modificationinside bulk glass materials [27, 28]. Although investiga-tions into understanding the nature of this modification andthe conditions that produce it are ongoing, it is widely ac-cepted that the modification process is initiated by the rapidabsorption of laser energy through nonlinear excitationmechanisms [29]. The subsequent dissipation of this en-ergy into the lattice causes modification inside the material.This result led to a new field in Photonics in which opticaldevices, functioning in the same way as optical fibres, couldbe directly written into many bulk materials, active or pas-sive, simply by moving the sample through the focus of thefemtosecond laser beam (Fig. 1). The material surrounding

the focal volume remains largely unaffected by the writingbeam passing through it, allowing structures to be written atarbitrary depths and in a three-dimensional fashion [30,31].Another key advantage of the femtosecond laser direct-write technique is that the glass sample is essentially a selfcontained clean room offering device fabrication withoutthe need for a controlled environment1. Ultrafast laser writ-ten devices are also tolerant of changing environmentalconditions by virtue of their being embedded in a bulk ma-terial. The femtosecond laser direct-write technique has al-ready been used to fabricate waveguides [27,32–38], powersplitters [30,39,40], couplers [31,41–44], gratings [45–51],computer generated holograms [52] and optical storagedevices [53–55] inside a large host of bulk materials. Al-though this field is still in its infancy, compared to the wellestablished techniques mentioned above, researchers arenow benchmarking ultrafast laser direct-written devicesagainst those made by the standard methodologies and aredemonstrating comparable performance. In this paper wereview work in the area of direct-write femtosecond lasermodification of doped materials with an emphasis on thefabrication of active waveguide devices, namely waveguideamplifiers and waveguide laser sources.

2. Experimental

Optical waveguide devices have been produced using thesetup shown in Fig. 1 together with either (i) regenera-tively amplified Ti:Sapphire laser systems that providehigh pulse energies (μJ-mJ) at kHz repetition rates, (ii)oscillator-only Ti:Sapphire systems with low energy (nJ)and high repetition rates (MHz) or (iii) high pulse energy(nJ–μJ) ytterbium-doped fibre lasers at high repetition rates(100 kHz–MHz) as well as cavity dumped Yb:KYW laseroscillators. Typically, the infrared femtosecond laser pulsesare focussed into the sample using a microscope objective.A variety of objectives with different numerical aperture(NA) and working distances have been used by researchersin the field so that the size and shape of the fabricated struc-tures could be tailored to a certain degree. Usually highNA objectives are used in conjunction with high repeti-tion rate systems as a tight focus is required in order toachieve sufficient intensities to modify the sample substrate.Such a tight focus is not required when using low repetitionrate systems and low NA objectives are typically used inthose cases. However, employing low NA objectives pro-duces challenges in achieving circularly symmetric localarea index changes in bulk materials because the depthof field of the focal spot in these cases is larger than thelateral dimensions. In these cases simple beam shapingtechniques including asymmetric focussing using a slit aper-ture [56, 57] or two-dimensional deformable mirror [58],astigmatic cylindrical telescope arrangements [59,60], the

1 Application of the femtosecond laser direct-write technique

to glass samples does, however, require the sample to be optically

polished before fabrication.

© 2009 by WILEY-VCH Verlag GmbH & Co.KGaA, Weinheim www.lpr-journal.org

Laser & Photon. Rev. 3, No. 6 (2009) 537

multiscan method [61–63] and spatial light modulatorscan recover this symmetry. Another variable used by re-searchers is the incident pulse energy. Indeed, differentpulse energies will result in different peak index changesand associated variations in the guided mode field diameter.In addition, the output of the writing beam can be square-wave modulated in intensity thereby creating a waveguidestructure formed by segments of exposed glass with a de-sired period. This technique has been used, for example, tofabricate waveguide Bragg gratings [64–66].

Other parameters which affect the writing properties,and thus the resulting device, include the sample translationspeed and direction [67], focussed beam shape, beam po-larisation [68], pulse repetition rate, wavelength and pulseduration. Resulting devices are not only dependant on thesefabrication parameters but are also heavily influenced by theproperties of the actual material in which the device is to becreated in; for example, bandgap energy, whether the sam-ple is crystalline or amorphous, thermal characteristics andfracture strength. Active waveguide devices fabricated us-ing the femtosecond laser direct-write technique have onlybeen reported in five different materials: Nd-doped silicateglass [69], Er/Yb co-doped phosphate glass [65,66,70–77],LiF crystal [78], Nd-doped YAG crystal [79] and Er-dopedand Er/Yb co-doped oxyfluoride silicate glass [61,80,81].These samples were specifically chosen due to their targetapplication, region of wavelength emission and ease of dop-ing with rare-earth ions. Of these materials, the phosphateglass hosts are best suited to active device fabrication foruse in telecommunications as tens of percent by weight ofrare-earth ions can be held in solution offering the highestgain-per-unit length value (4 dB/cm) in the C-band withoutdetrimental effects such as ion-clustering.

3. Waveguide amplifier

Example absorption spectra of the Ytterbium and Erbiumions in a commonly employed phosphate glass host areshown in Fig. 2a and b, respectively. The Ytterbium ab-sorption spectrum is characterised by a single dominantpeak at 975 nm due to the 2F7/2 to

2F5/2 transition of the

Yb3+ ion which is used to optically pump the waveguidedevice. The Er3+ absorption spectrum displays two broadabsorption curves that are the result of the many host-fieldStark split 4I13/2 to

4I15/2 transitions.

Differential interference contrast (DIC) microscope im-ages of waveguides written in Er/Yb Kigre QX phosphateglass are shown in Fig. 3. In this case the waveguides werewritten 300 μm below the glass surface using circularly po-larised radiation, a translation speed of 25 μm/s, a 20×(0.46NA) microscope objective and a 500 μm slit. After fabrica-tion, the input and output facets of the sample were groundand polished to expose the waveguides because the direct-write process cannot easily access the final few microns ofglass near the edge of the target substrate. The exposed endfacets are also shown.

Figure 2 (online color at: www.lpr-journal.org) Absorption

spectra of Kigre co-doped QX glass. a) Absorption due to the

Yb3+ ions (pump wavelength) and b) Absorption due to the Er3+

ions (signal wavelength).

Figure 3 (online color at: www.lpr-journal.org) (Top) DIC top-

view images of a number of linear structures written with different

pulse energies in Kigre QX glass. (Bottom) Respective end-on

transmission DIC images.

www.lpr-journal.org © 2009 by WILEY-VCH Verlag GmbH & Co.KGaA, Weinheim


Figure 4 (online color at: www.lpr-journal.org)

Active waveguide device configuration and

characterisation setup. DUT – Device Under

Test. OSA – Optical Spectrum Analyser.

For different glass types and direct-write systems thereexists a range of parameters, sometimes very narrow [77],that are compatible with the fabrication of low-loss waveg-uides. Fig. 3 demonstrates this point. For pulse energiesbelow 1.0 μJ, there is no clear evidence of modificationof the glass sample. For pulse energies above 2 μJ, visi-ble signs of damage along the structures were evident andcracking of the glass is seen in the corresponding end-onimages. In some cases the cracking seen end-on did notcontinue along the length of the structure, thereby eitherrepresenting stress created during polishing or stress re-lief of the modified region produced after polishing. Thestructures written with pulse energies between these two ex-tremes showed a smooth modification of the glass had beencreated. In this case the optimal waveguide was fabricatedusing a pulse energy of 1.5 μJ.

The typical active device characterisation setup isshown in Fig. 4. Using a properly attenuated tunable laseras the signal source, the relative gain versus total pumppower characteristic (of the optimal waveguide above) wasmeasured at the wavelength corresponding to the peak ofthe gain curve, i.e. 1534.6 nm. The resulting plot is shownin Fig. 5 in terms of gain per unit length, dB/cm. The absorp-tion coefficient for the QX phosphate glass in the C-band,taken from the spectra in Fig. 2, is also shown. Maintainingthe input signal well below 0.5mW revealed little changein the relative gain, indicating all measurements were con-ducted in the small-signal regime2.

It can be seen that although the gain did not saturate3,the maximum relative gain has more than compensatedfor the absorption resulting in a maximum internal gain of

2 The small-signal gain is the gain obtained for an input signal

which is so weak that it does not cause any gain saturation, i.e.

reduced gain for high input signal powers.3 Gain saturation was not reached because the sample was either

too long or not enough pump power was being supplied.

Figure 5 (online color at: www.lpr-journal.org) (Top) Signal

enhancement at 1534.6 nm versus total pump power. (Bottom)

Internal gain of a waveguide amplifier fabricated in an Er/Yb

co-doped Kigre QX phosphate glass.

2.37 dB/cm. This internal gain, as a function of wavelength,is presented in Fig. 5. The results show amplification acrossthe whole C-band, typical for devices of this type. To date,internal gains of 3.18 dB/cm in the C-band have been re-ported for Er/Yb doped systems [61, 71, 74, 76, 81] anda gain of 1.5 dB/cm at 1054 nm for a femtosecond laserwritten waveguide amplifier fabricated in Nd-doped silicateglass [69].

Accurate alignment of the probe fibres used to get lightinto and collect light out of the waveguide amplifier iscrucial to achieving the maximum amount of available gainin the system. Typically, a visible green emission can beseen along the length of the waveguide amplifier (Fig. 6)during pump propagation in an Er/Yb co-doped sample.This green emission is due to cooperative up-conversionof Er3+ ions in the 4I13/2 manifold to the

4I9/2 manifold.

When an Er3+ ion in the 4I9/2 manifold decays it releasesa green photon. Although the up-conversion process isknown to hamper the waveguide amplifier’s performance,it provides a very useful tool for precise alignment of theinput and output probe fibres during characterisation.



Figure 6 (online color at: www.lpr-journal.org) Green fluorescence along a waveguide amplifier written in Kigre QX glass indicating

cooperative up-conversion of Er3+ ions in the 4I13/2 manifold.

There is still potential for further improvement of thegain of these devices by optimising the doping concentra-tions of the Er3+ and Yb3+ ions, optimising the waveguideamplifier length and optimising the pump power configu-ration. Furthermore, there is scope to develop glasses thatare engineered for the direct-write process, as the dopedglasses typically used are those developed for use in fibrepreforms and ion exchange processes. Examples of activ-ity in this area include research into oxyfluoride silicateglass [61, 81], in which thermal shock due to high pumppowers may be reduced due to its structural stability whilstalso raising the prospect of an increased gain bandwidthbecause of its dopant compatibility. It is worth noting thatthe waveguide amplifiers reported to date, created using thefemtosecond laser direct-write technique, can reach a per-formance level (net gain of 2.7 dB/cm [74]) allowing themto be considered for telecommunication applications and bedirectly compared to devices fabricated with conventionaltechniques (net gain of 3 dB/cm [3]).

4. Waveguide laser oscillator

To turn these amplifiers into laser oscillators, appropriatefeedback of the particular amplified frequency must beapplied. In the laser, positive feedback may be obtainedby placing the gain material between a pair of suitablemirrors which, in fact, form an optical cavity or resonator.Lasing emissions in the cavity build up to a steady state,effectively as stationary EM oscillations in the cavity, whensaturation is reached. Saturation is reached when the gainprovided by the medium exactly matches the losses ofthe mirror cavity and ancillary optics incurred during acomplete round-trip of an EM wave. With guided wavedevices, the cavity usually takes the form of a DistributedBragg Reflector (DBR) geometry or a Distributed Feedback

(DFB) design, although external dielectric mirrors on theamplifier’s end facets can also be used.

4.1. DBR waveguide lasers

The laser cavity employed by two different research groupsin the field [72, 76, 82] is identical to the active devicecharacterisation setup (Fig. 4) but with the signal sourceremoved and the probe fibres butt-coupled to the waveguideamplifier replaced with two fibre Bragg gratings (FBGs)which act as cavity mirrors. The FBGs were centred at thesame wavelength but had a different reflectivity and band-width. This enabled a laser cavity to be created with a highreflector at one end and an output coupler at the other (theOSA end). This configuration with respect to discrete mir-rors or dielectric coatings allows for efficient pumping withstandard pigtailed diode lasers with no additional lossesto the system. A simple change of laser wavelength andoutput coupling is achieved by substitution of the FBGs.

Such a cavity led to the demonstration of femtosecondlaser written waveguide lasers (WGLs) able to provide tun-ability in the whole C-band, single longitudinal mode andstable mode-locking operation. In particular, recent reportshave indicated that using a cavity length of 5.5 cm and a57% output coupler, WGLs with threshold pump power of124mW and slope efficiency of 21% are achievable [75].Furthermore, a mode-locked WGL source based on carbonnanotubes technology (used to create a saturable absorber)has been reported [76]. This WGL had a repetition rate of16.7MHz and a pulse duration of 1.6 ps. These results notonly confirm that the femtosecond laser direct-write tech-nique is capable of fabricating practical devices, with qual-ity comparable to that obtained with standard techniques,but also that active waveguide devices can find applicationin optical telecommunication networks.



4.2. DFB waveguide lasers

In conventional laser oscillators, the feedback of radiationinto the active medium (to build up the photon concentra-tion) is accomplished by reflection at the surface of theresonator mirrors. A serious handicap of the feedback pro-vided by mirror resonators is that many longitudinal modesmay fit under the system’s gain bandwidth thus impedingsingle mode operation, i.e. a really short laser cavity is re-quired to generate a single mode laser. This obstacle can beovercome by replacing the resonator mirrors with a periodiclaser structure, i.e. by periodic modulations of refractiveindex and/or gain of the laser medium.In 1971, Kogelnik et al. [83] removed the resonator

mirrors of a typical dye laser and used the Bragg effect toprovide frequency-selective feedback that was distributedover the entire length of the laser medium instead of beinglocalised on laser mirrors, i.e. the active region of the devicewas structured as a diffraction grating, a DBR, providing op-tical feedback for the laser due to Bragg scattering from thestructure. This type of laser was thus named a ‘distributedfeedback’ (DFB) laser. The DBR in a DFB laser is con-structed so as to reflect only a narrow band of wavelengths,thus producing a very narrow linewidth laser output. Thefrequency selectivity of the Bragg effect predestinates thedistributed feedback for mode selection in lasers with broad-band gain media. Furthermore, altering the temperature ofthe device causes the pitch of the grating to change due tothermal expansion. This alters the reflection wavelength ofthe grating structure, and thus the wavelength of the laseroutput, producing a tunable laser4.When a DFB laser is formed with a uniform grating

and no end reflectors, it oscillates simultaneously on twowavelengths spaced symmetrically about the Bragg wave-length of the grating. This is a consequence of the round-tripphase criterion associated with a DFB laser in which thephase shift of one round-trip must be an integer multipleof 2π [84–86]. Single frequency operation can still be ob-tained from a DFB laser by introducing an additional phaseshift in the cavity, which forces the laser to oscillate at theBragg wavelength. This can either be done by perturbingthe Bragg structure that forms the cavity or by using an endreflector to change the cavity round-trip phase shift. Bothapproaches were studied by Kringlebotn et al. [87] who, in1994, produced the first fibre laser variant of a DFB laser.It was shown that the most effective way of ensuring singlemode operation was to introduce a π/2 phase shift intothe grating. This work represented a major breakthrough infibre laser technology at the time, as only a single gratinghad to be written into the fibre to form the cavity.Several experimental techniques have been reported

that enable the realisation of Bragg grating structures insidefemtosecond laser written waveguides to create such a cav-ity [64,78,88]. Kawamura et al. [78] developed a hologramtechnique to encode grating structures inside a LiF crystal

4 Alteration of the modulation rate of the current powering the

laser also tunes the device.

Figure 7 (online color at: www.lpr-journal.org) (a) Schematic of

a waveguide Bragg grating (WBG) fabricated using the modulated

writing beam method and (b) DIC top-view image of the WBG

structure fabricated in a Kigre QX sample.

by a single interfered femtosecond laser pulse. The result-ing periodic refractive index contrast was contributed tothe formation of F2 colour centres. When side-pumping thegrating with 450 nm light, a DFB laser oscillator at 707 nmwas created. The grating structure, however, is weak andnot permanent as the colour centres can be eliminated by an-nealing. In addition, the linewidth was significantly broaderthan that normally expected of DFB lasers.

More recently, by square-wave modulating a low repeti-tion rate femtosecond laser’s output, a first order permanentwaveguide Bragg grating (WBG) directly written insideEr/Yb co-doped phosphate glass in a single fabrication stepwas demonstrated [65,66]. A 20mm long modulated WBG,fabricated in a Kigre QX glass sample, across the completelength of the waveguide region (see Fig. 7) was used tocreate a DFB waveguide laser oscillator.

The output fibres from the two WDMs in the amplifi-cation characterisation setup (Fig. 4) were butt-coupled tothe modulated WBG end facets with index matching gel inthe interstitial gap. 976 nm and 980 nm laser diodes wereused to pump the modulated WBG structure from oppositeends. In a manner similar to that described by Kringlebotnet al. [87], an external point-heater was positioned in thecentre of the WBG and adjusted to produce an approximateπ/2 phase shift in the grating. Laser emission was coupledequally out of both ends of the waveguide and was detectedon the OSA.

The laser output spectrum (from one end) when pumpedwith the maximum available pump power (710mW com-bined from both pump diodes) is shown in Fig. 8. Theapparent linewidth of the laser in Fig. 8 is limited by the slitwidth of the OSA (10 pm). Measurements using a scanning



Figure 8 (online color at: www.lpr-journal.org) 10 pm resolution

bandwidth OSA spectrum of the waveguide laser output.

Michelson wavemeter (Agilent HP 86120B) indicated thatthe actual laser linewidth was in fact less than 4 pm. Thewavelength drift of the laser was measured over a period of5 minutes and was observed to be 6 pm. This drift was mostlikely due to variations in the temperature of the waveg-uide Bragg grating/laser structure due to the external heaterand/or pump lasers or gradual misalignment with time. Thewavelength of the laser was 1537.624 nm and could beadjusted by changing the temperature of the sample. Theoutput power of the laser emanating from each facet wasestimated to be −7.3 dBm or 0.19mW (measured afterwaveguide/fibre coupling losses) giving a total of 0.37mWavailable output power. The threshold pump power for laseraction was 639mW resulting in a slope efficiency of 0.5%.In order to achieve a comparable performance with waveg-uide lasers using external reflectors (previous section), it isclear that both the active characteristics of the modulatedWBG and the design of the laser cavity (DFB structure)must be enhanced. Although it is known that the WBGstructure contributes to an increase in the propagation lossof the waveguide amplifier device [64], the WBG producedby the ultrafast laser direct-write technique can still be ofhigh enough quality that the internal gain in the system stillexceeds this increase.Devices of this type open the possibility for creating

a variety of narrow linewidth laser designs in bulk glasseswithout the use of external mirrors, for example, laser ar-rays, coupled lasers and more sophisticated waveguide andpump delivery technologies, all of which have significantimportance in the field of laser physics and optical commu-nication networks.

5. Conclusion

We reviewed the femtosecond laser direct-write techniqueas a technology capable of producing active waveguide de-vices inside bulk transparent materials without the need for

lithography, etching, a controlled environment or much sam-ple preparation. The application of the femtosecond laserdirect-write technique to doped phosphate glass hosts wasdemonstrated. The devices outlined in this paper, namelywaveguide amplifiers and waveguide laser oscillators, raisethe prospect of creating optical devices for the use in aidingall-optical access communication networks.

Acknowledgements This work was produced with the assistanceof the MQ Photonics Research Centre and the Australian Research

Council under the ARC Centres of Excellence&LIEF programs.

Martin Ams received the B. Sc. de-gree in physics and the Ph.D. de-gree in optical laser physics fromMacquarie University, Sydney, NSW,Australia, in 2001 and 2008, respec-tively. He is currently a ResearchAssociate at the MQ Photonics Re-search Centre and the Centre for Ul-trahigh Bandwidth Devices for Op-

tical Systems (CUDOS), Macquarie University. Hiscurrent research interests include femtosecond laserdirect-writing of photonic waveguide devices for usein telecommunication, sensing and biophotonic applica-tions. He has over six years of photonics experience. Heis the author or co-author of more than 25 journal andconference papers.

Graham D. Marshall received theD. Phil. degree in 2002 from OxfordUniversity, UK. His dissertation con-cerned the plasma kinetics of variousmetal vapour laser systems. In 2003,he joined the Centre for UltrahighBandwidth Devices for Optical Sys-tems (CUDOS) at Macquarie Univer-sity in Sydney, Australia. His present

research interests include the application of ultrafastlasers to optical materials processing and the develop-ment of optical devices for telecommunication, sensing,and information processing applications.

Peter Dekker received the Ph.D.degree in physics from MacquarieUniversity, Sydney, NSW, Australia,in 2005. He is currently with theCentre for Ultrahigh Bandwidth De-vices for Optical Systems (CU-DOS), Macquarie University. Hiscurrent research interests includediode-pumped solid-state lasers, in-

cluding visible Raman lasers based on crystalline mate-rials, and doped glass waveguide lasers for telecommu-nications applications.



James A. Piper received the B. Sc.and Ph.D. degrees in physics fromthe University of Otago, Dunedin,New Zealand, in 1968 and 1971, re-spectively. In 1971 he accepted a Re-search Fellowship at Oxford Univer-sity for four years before moving toAustralia and taking up a position atMacquarie University, Sydney, NSW,

Australia as Senior Lecturer and Associate Professorin Physics. He became a Professor of Physics in 1984and is currently the Deputy Vice Chancellor (Research)at Macquarie University. His research has been con-cerned with copper vapour lasers, dye lasers, excimerlasers, all-solid-state lasers, including self-frequency-doubling lasers and intracavity crystalline Raman lasers,and applications in microfabrication and biomedicine.Throughout his career, he has received many distin-guished awards including the Pawsey Medal (1982),the Australian Optical Society Medal (1997) and morerecently the Carnegie Centenary Professorship from theCarnegie Trust Universities of Scotland (2004). Prof.Piper is a Fellow of the Optical Society of America.

Michael J. Withford received thePh. D. degree on the effects of gas ad-ditives on copper vapour laser perfor-mance from Macquarie University,Sydney, NSW, Australia, in 1995. Hecurrently leads both the MacquarieUniversity node of Australian Re-search Council (ARC) Centre of Ex-cellence: Ultrahigh Bandwidth De-

vices for Optical Systems (CUDOS) and the NationalCollaborative Research Infrastructure Strategy (NCRIS)Node OptiFab. His work led to the development of a newsubclass of metal vapour, termed kinetically enhancedcopper laser, in 1998. His current research interests in-clude laser micromachining and fabrication of a range ofphotonic devices such as fibre Bragg gratings, periodi-cally poled ferroelectric materials, guided wave devices,and self-assembled photonic crystals. Assoc. Prof. With-ford is a member of the Australian Optical Society andthe Optical Society of America.

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Ultrafast laser written active devices