FRISNO 10

February 8-13, 2009

Ein Gedi, Israel

PROGRAM AND ABSTRACTS

Ein Gedi, February 8, 2009 Dear Participant, Welcome to FRISNO-10, the Tenth French Israeli Symposium on Nonlinear and Quantum Optics, part of a series that had started almost 20 years ago on the shores of the Sea of Galilee, and alternated every other year between tall Mountains in France and deep valleys in Israel. In particular, we appreciate the “Frisno Spirit” which led ALL of our invited speakers and ALL of those who had submitted abstracts to stick with the original plans even at uncertain times. This year, the program includes over 120 oral and poster presentations, covering a very wide spectrum of topics in the fields of Nonlinear and Quantum optics. As in previous years, French and Israeli groups, as well as groups from other countries are present in this conference, and we hope that future collaborations will continue to emerge from these conferences. We wish to thank all the people who have helped with the organization of the conference, members of the organizing committees, our sponsors (listed separately on the next page), and all contributors who have submitted many interesting research results for presentation in this meeting. We followed the FRISNO tradition, and most oral presentations were selected by the committees from amongst the submissions, thus securing “new faces” and introducing new groups and younger people. We wish all participants a pleasant week, indoors at the lecture and poster halls, and outside, on the shores of the Dead Sea, on top of Massada, or elsewhere in Israel. Thank you all for your participation, Yehiam Prior Robert Kuszelewicz Weizmann Institute of Science CNRS – Laboratoire de Photonique et

Nanostructures

We gratefully acknowledge the financial support of:

• The French Embassy in Israel and the French Ministry of Foreign Affairs

• Société Française d'Optique

• The Weizmann Institute of Science Goldschleger Foundation

• The Weizmann Institute of Science Crown Family Photonics Center

• Newport Corporation, USA

• Newport Corporation, Spectra Physics Lasers Division, USA

• New Technology, Israel

• Coherent Inc., USA

• Ammo Engineering, Israel

z The Weizmann Institute of Science

Laser Systems Product Overview

Scientific Committee

Yehiam Prior, Chair, Weizmann Institute of Science, Israel Robert Kuszelewicz, Co-Chair, LPN/CNRS, France

Israel

Yehuda Band, Ben Gurion University of the Negev, Beer Sheva

Michael Rosenbluh, Bar Ilan University, Ramat Gan

Bruno Sfez, Soreq Nuclear Center, Yavne

Yaron Silberberg, Weizmann Institute of Science, Rehovot

Shammai Speiser, Technion, Israel Institute of Technology, Haifa

Moshe Tur, Tel-Aviv University, Tel-Aviv

Arie Zigler, Hebrew University, Jerusalem

France

Izo Abram, (CNRS-DIR)

Alain Bathélémy (XLIM - Univ. Limoges)

Claude Boccara (ESPCI-Paris)

Georges Boulon (PCML -Univ. Lyon1)

Claude Cohen-Tannoudji (LKB/ENS - Paris)

Eric Freysz (CPMOH-Univ. Bordeaux1)

Hervé Rignault ( Institut Fresnel Marseille) )

Isabelle Robert-Philip (LPN-CNRS Marcoussis)

Joseph Zyss (Institut D’Alembert-ENS Cachan)

PROGRAM

Sunday February 8, 2009 15:00 16:00-19:00

Arrival Registration (Hotel Lobby) Dinner

20:30 Wine and Beer Reception (Mitzpe Arugot)

Monday February 9, 2009 8:15 Opening Remarks: Yehiam Prior

Mo-A Chair : Yehiam Prior

8:30 Claude Cohen-Tannoudji, Measuring Time with Ultracold Atoms: Achievements and Perspectives

9:15 R. Folman, Atom Chips: Where Materials Engineering Meets Atom Optics

9:45 V. Klimov , D. Bloch, M. Ducloy, J.R. Rios Leite, Detection of Spiral photons in Quantum Optics

10:15 Coffee

Mo-B Chair : Martial Ducloy

10:45 Firstenberg O., M. Shuker, A. Ron, N. Davidson, Non-diffraction of Slow Light

11:15 S. Gigan, F. Ramaz, E. Bossy, A. Claude Boccara, Controlling Wavefront in Optics, Acousto-Optics, and Photoacoustics

11:45 Tasgal R. S. R. Shnaiderman Y. B. Band, Slowing and Stopping Light with Gap- Acoustic Solitons

12:15 M. Hamamda, M. J. Grucker, G. Dutier, F. Perales, J. Baudon, M. Ducloy, Atom optics versus photon optics: similarities and differences

13:00 Lunch

Mo-C Chair : Nir Davidson

15:00 Rudolf Grimm, Few-body physics with ultracold atoms: Efimov states and beyond

15:40 J. Chabé, G. Lemarié, B. Grémaud, D. Delande, P. Szriftgiser, J. C. Garreau, Experimental observation of the Anderson transition with atomic matter waves

16:10 Coffee

Mo-D Chair : Shammai Speiser

16:40 S. Singha, Z. Hu Y. Liu and R. J. Gordon , Controlling Light with Light: Efficient Energy Transfer between Laser Beams by Stimulated Raman Scattering.

17:10 J. Szeftel, N. Sandeau, Fluorescence versus laser effect : towards a unified picture

19:00 Dinner

Mo-PS1

20:30 Poster session 1

Tuesday February 10, 2009 Tu-A Chair : Yaron Silberbnerg

8:30 Serge Haroche, Exploring the quantumness of light in a Cavity

9:10 P.-F. Cohadon, P. Verlot, A. Tavernarakis, T. Briant, A. Heidmann, A scheme to probe optomechanical correlations between 2 optical beams down to the quantum level

9:40 A.E.Kaplan, S. N. Volkov, Laser-driven atoms in a finite lattice stage a nano-riot against uniformity

10:10 Coffee

Tu-B Chair: Claude Boccara

10:40 C. Rotschild, A. Barak, Y. Lamhot, E. Greenfeld, M. Saraf, R.A. El-Ganainy, E. Lifshitz, D.N. Christodoulides and M. Segev, Complex Nonlinear Opto-Fluidity

11:20 M.I. Stockman, Nanoplasmonics from Attoseconds to Terahertz

11:50 L. Xuan, A, Slablab, C. Zhou, D. Chauvat, Y.De Wilde, S. Perruchas, C. Tard, T. Gacoin, P. Villeval, J-F. Roch, Single KTiOPO4 nanocrystals for nonlinear probing of local optical fields and interaction with a metallic nanostructure

12:45 Lunch

Transportation to Jerusalem-Rehovot-Tel Aviv (and back) may be arranged for those participating in the Israeli Elections.

14:00 EXCURSION Massada and/or Nahal David

19:00 Dinner

20:30 Lecture

Wednesday - February 11, 2009 We-A Chair : Dan Oron

10:30 Paul Corkum, Extreme Nonlinearity: Attosecond-Attosecond Science

11:10 M. Schultze , E. Goulielmakis, M. Hofstetter, M. Uiberacker, J. Gagnon, V. Yakovlev, U. Kleineberg, F. Krausz, 80 attosecond soft-X-ray pulses

11:40 Coffee

We-B Chair : Michael Rosenbluh

12:00 A. Shalit, Y. Paskover, Y. Prior , Combined Time Frequency Detection by Single Shot Four Wave Mixing

12:30 E. Shumakher, A. Willinge,r G. Eisenstein , Narrow Band Raman Assisted Fiber Parametric Amplification: The Issue of Fiber Imperfections

13:00 P. Sebbah, U. Bortolozzo, S. Residori, Speckle Instability in Strongly Scattering Kerr Random Media

13:45 Lunch

We-C Chair : Oren Cohen

15:15 Stephen R. Leone , Ultrafast X-ray probing of electron dynamics to the attosecond limit

15:55 D. Shafir, D.Mairesse, B. Fabre, J. Higuet, E. Mével, E. Constant, D. M. Villeneuve, P. B. Corkum, N. Dudovich , Probing Atomic Wavefunctions via Strong Field Light-Matter Interaction

16:25 Coffee

We-D Chair : Claude Fabre

17:00 Nimrod Moiseyev , Photo induced conical intersections in molecular optical lattices: the phenomenon and its consequences

17:30 TBD

19:00 Dinner

W-PS2

20:30 Poster session 2

Thursday February 12, 2009 Th-A Chair : Daniel Bloch

8:30 Mark G. Raizen , Towards Comprehensive Control of Atomic and Molecular Motion

9:10 C. Parthey , Matveev A. Alnis J. Kolachevsky N. Udem T. Hansch T. , Towards High Precision Spectroscopy of a Supersonic Beam of Atomic Hydrogen

9:40 TBD

10:10 Coffee

Th-B Chair : Barak Dayan

10:40 M. Zielinski, D. Oron, D. Chauvat, J. Zyss, Polarization resolved second-harmonic generation from a single CdTe quantum dot with record dimensions

11:10 Aviad Y. I. Reidler W. Kinzel I. Kanter M. Rosenbluh , Phase synchronization in mutually coupled chaotic diode lasers

11:40 R. Kuszelewicz , Fundamentals Functionalities and Applications of Cavity Solitons: Review on the achievements of the FunFACS FET-Project

12:10 F. Billard, D. Gachet, H. Rigneault, Coherent anti-Stokes Raman scattering (CARS) in a microcavity

13:00 Lunch

Th-PS3

14:30 Poster Session 3

16:00 Coffee

Th-D Chair : Ilya Averbukh

16:40 C. Fabre, N. Treps, G. De Valcarcel, G. Patera, O. Pinel, B. Chalopin, B. Lamine, High accuracy space-time positioning beyond the standard quantum noise limit

17:20 L. Vaidman , How a photon can be inside a Mach-Zehnder interferometer without ever being on any path which leads towards it?

17:50 Y. Bromberg, Y. Lahini E. Small, and Y. Silberberg , Hanbury Brown-Twiss Interferometry with Interacting Photons

19:30 Conference Dinner

Friday February 13, 2009 Fr-A Chair : Reuven Kuszelewicz

8:30 Gerard Mourou , Extreme Light Physics

9:10 S. Eisenmann, A. Pukhov, J. Peñano, P. Sprangle, A. Zigler, High Intensity Laser filamentation and Plasma Lensing

9:50 Malka V. J. Faure Y. Glinec C. Rechatin A. Norlin A. Lifschitz Laser plasma accelerator: towards a high quality electron beam

10:30 Concluding Remarks

10:35 Coffee

11:15 DEPARTURE

POSTER PRESENTATIONS

POSTER SESSION 1 Monday February 9, 2009 Mo-1 Afek I., A. Natan, O. Ambar, Y. Silberberg, Photon-number-resolving detection using

a detector array for use in quantum optic

Mo-2 Akkermans E., A. Gero, R. Kaiser, Photon Localization and Dicke Superradiance in

Atomic Gases

Mo-3 Alfassi B., C. Rotschild, M. Segev, Incoherent Surface-Solitons in Effectively-

Instantaneous Nonlinear Media

Mo-4 Barmashenko B.D., S. Rosenwaks, Diode-pumped alkali vapor lasers: the next

generation of high power lasers?

Mo-5 Belabas N., J.A. Levenson, C. Minot, J. Moison, Nonlinear optics in structured

functionalized waveguide array

Mo-6 Bruner B., H. Suchowski, Y. Silberberg, Strong Field Coherent Control Using 2D

Spatio-Temporal Mapping

Mo-7 Clow Stephen D., C. Trallero-Herrero, T. Bergeman, T. Weinacht, Strong Field

Atomic Population Transfer

Mo-8 Dallal Y., N. Akerman, Y. Glickman, S. Kotler, A. Weksler, R. Ozeri, Towards high

fidelity single ion-qubit gates

Mo-9 David T., Y. Japha, V. Dikovsky, R. Salem, C. Henkel, R. Folman, Magnetic

Interactions of Cold Atoms with Anisotropic Conductors

Mo-10 Ellenbogen T., N. Voloch, A. Ganany-Padowicz, A. Arie, Generation of Airy Beams

with Quadratic Nonlinear Photonic Crystals

Mo-11 Elsass T., S. Barbay, K. Gauthron, G. Beaudoin, I. Sagnes, R. Kuszelewicz,

Monolithic vertical cavity laser with a saturable absorber: towards an integrated cavity

soliton laser

Mo-12 Fabre C., N. Treps, G. De Valcarcel, G. Patera, O. Pinel, B. Chalopin, High accuracy

space-time positioning beyond the standard quantum noise limit

Mo-13 Golan B., Z. Fradkin, T. Markus, D. Oron, R. Naaman, Ultrafast electron dynamics

at the DNA-Au interface studied by time-resolved two-photon photoemission and

femtosecond pulse shaping

Mo-14 Gross N., Z. Shotan, L. Khaykovich, Inelastic collisions near Feshbach resonances in

ultra-cold 7Li

Mo-15 Gurgov H., O. Cohen, Spatiotemporal Pulse-Train Solitons

Mo-16 Helml W., G. Marcus, Y. Deng, V. S. Yakovlev, K. Schmid, X. GU, R. Kienberger,

F. Krausz, Generation of intense keV attosecond pulses

Mo-17 Huppert D., I. Presiado, A. Uritski, Indication of a very large proton diffusion in ice Ih

Mo-18 Japha Y., O. Arzouan, Y. Avishai, R. Folman, Phase rigidity and incoherent operation

of guided matter-wave Sagnac interferometers

Mo-19 Japha Y., O. Entin-Wohlman, T. David, R. Salem, R. Folman, S. Aigner, L. Della

Pietra, J. Schmiedmayer, Long-Range Order in Electronic Transport through

Disordered Metal Films

Mo-20 Katz O., A. Natan, S. Rosenwaks, Y. Silberberg, Shaped Femtosecond Pulses for

Standoff Detection of Chemical Traces

Mo-21 Katzir Y., M. Levin, S.Eisenman, A.Zigler, Optical Generation and Control of Plasma

Lens System

Mo-22 Kinzel D., S. Alfalah, J. González-Vázquez, L. González, Photoisomerization Versus

Photodissociation; Quantum Dynamical Simulations on a Chiral Olefin

Mo-23 Neve-Oz Y., Y. Saado, T. Pollok, M. Golosovsky, S. Burger, D. Davidov, Wave

focusing by plano-concave lenses based on 2D photonic quasicrystal and 2D photonic

crystal super-lattice

Mo-24 Owschimikow N., J. Maurer, F. Königsmann, B. Schmidt, N. Schwentner, Rotational

dephasing and depopulation rates measured via nonadiabatic alignment

Mo-25 Petrov P. G., S. Younis, R. Macaluso, S. Machluf, T. David, B. Hadad, Y. Japha, M.

Keil, A Novel Atom Trap Based on Carbon Nanotubes

Mo-26 Rezek Y., T. Feldmann, R. Kosloff, The Minimal Temperature of Quantum

refrigerators

Mo-27 Rohrlich D., Y. Japha, R. Folman, How to produce “high-N00N” atom states via RF

pulses on a (1μm)2 flux qubit

Mo-28 Rosenblit M., Y. Japha, P. Horak, R. Folman, High-Quality Micro-Resonator for

Trapping and Detecting a Single Atom on a Chip

Mo-29 Rybak L., L.Chuntonov, A. Gandman, N. Shakour, Z. Amitay, Multiphoton

Femtosecond Control of Resonance-Mediated Generation of Short-Wavelength Coherent

Broadband Radiation

Mo-30 Salem R., Y. Ben-Hayim, J. Chabé, R. Szmuk, M. Keil, Y. Japha, R. Folman,

Engineered Fragmentation: Generating a 1D Magnetic Lattice

Mo-31 Shahmoon E., S. Levit, R. Ozeri, Qubit Coherent Control with Squeezed Light Fields

Mo-32 Fridman M., V. Eckhouse, N. Davidson, A. Friesem, Synchronization and Quantum

Noise in Coupled Laser Oscillators

POSTER SESSION 2 Wednesday February 11, 2009

We- 1 Baruch G., Numerical Solution of the Nonlinear Helmholtz Equation

We-2 Belabas N., S. Bouchoule, I. Sagnes, J.A. Levenson, C. Minot, J. Moison, arrays to

tailor discrete and extended modes and control the light flow

We-3 Ben Aroya I., M. kahanov, G. Eisenstein, On The Locking problem of a Chip Scale

Atomic Clock: The Use of Double Field FM Spectroscopy

We-4 Dikovsky V., A. Gershanik, D. Grosswasser, R. Folman, Superconducting Atom Chip

We-5 Eilam A., A. D. Wilson-Gordon, H. Friedmann, Slow and stored light in an amplifying

double Λ system

We-6 Eilam A., A. D. Wilson-Gordon, H. Friedmann, Efficient light storage due to coupling

between lower levels of Λ system

We-7 Fleger Y., Y. Mastai, M. Rosenbluh, D. H. Dressler, Surface-Enhanced Raman

spectroscopy as a Probe for Adsorbate Orientation on Silver Nanoclusters

We-8 Fleischer S., Y. Khodorkovsky, I. Sh. Averbukh, Y. Prior, Field-free unidirectional

molecular rotation

We-9 Gachet D., F. Billard, H. Rigneault, Focused Field Symmetries for Background-Free

Coherent Anti-Stokes Raman Spectroscopy

We-10 Gandman A., L. Chuntonov, L. Rybak, Z. Amitay, Observation and Coherent Control

of Transient Two-Photon Absorption: The Bright Side of Dark Pulses

We-11 Gershnabel E., I. Sh. Averbukh, Laser Induced Alignment of Water Spin Isomers

We-12 Gilary I., N. Moiseyev, Suppression of photo-ionization by a static field

We-13 Givon M., A. Waxman, D. Groswasser, R. Folman, Walks on the Bloch sphere:

Coherent manipulations of an atomic two-state system

We-14 Glickman Y., N. Akerman, S. Kotler, Y. Dallal, A. Weksler, R. Ozeri, Quantum

Information studies with trapped ions and flying photons

We- 15 Klaiman S., N. Moiseyev, Visualization of Branch Points in PT -Symmetric Waveguides

We-16 Königsmann F., N. Owschimikow, D. T. Anderson, N. Schwentner, Dynamics of

elementary excitations in para-hydrogen crystals: long living, coherent phonons, rotons

and stimulated rotational Raman beats

We-17 Kuyanov-Prozument K., A. F. Vilesov, Hydrogen clusters that remain liquid at low

temperature

We-18 Lahini Y., R. Pugatch, F. Pozzi, M. Sorel, R. Morandotti, N. Davidson, Y.

Silberberg, Direct Observation of a Localization Transition in Quasi-periodic Photonic

Lattices

We-19 Lindner N. H., T. Rudolph, A photonic cluster state machine gun

We-20 Milner A. A., Y. Prior, AFM tip Assisted Laser Induced Surface Modification

We-21 Mojzisova H., J. Olesiak, M. Zielinski, K. Matczyszyn, D. Chauvat, J. Zyss,

Nonlinear polarimetric analysis of DNA in liquid crystalline phases

We-22 Schwartz O., D. Oron, Plasmon-enhanced third harmonic generation in gold nanorods

We-23 Shuker M., O. Firstenberg, A. Ron, Coherent Storage of Three-dimensional Light-

Fields in Atomic Vapor

We-24 Singha S., Z. Hu, Y. Liu, R.J. Gordon, Controlling Material Transformation and

Plasma Emission with Trains of Ultrafast Laser Pulses

We-25 Streltsov A. I., O.E. Alon, L.S. Cederbaum, Attractive Phenomena in Attractive BECs:

Fragmentation and Collapse

We-26 Suchowski H., D. Oron, A. Arie, Y. Silberberg, Bloch Sphere Representation of SFG

and Efficient Adiabatic Conversion

We-27 Vilensky M. Y., Y. Prior, I. S. Averbukh, Feedback-Controlled Radiation Pressure

Cooling

We-28 Waxman A., M. Givon, G. Aviv, D. Grosswasser, R. Folman, Modulation

Enhancement of a Laser Diode in an External Cavity

POSTER SESSION 3 Thursday February 12, 2009

Th-1 Avidan A., D. Oron, A Large Blue Shift of the Biexciton State in Tellurium

Doped CdSe Colloidal Quantum Dots

Th-2 Aviv G., M. Givon, A. Waxman, D. Grosswasser, R. Folman, Bloch Q-bit:

Multiphoton Coherent Manipulations of an Atomic Two-State System

Th-3 Baer M., O. Deeb, S. Jabour, M. Leibscher, J. Manz, S. Zilberg, Molecular

Symmetries of Non-adiabatic Couplings and Quantum Dynamical Simulations for

Intramolecular Torsion Switched by Laser Pulses

Th-4 Bahat-Treidel O., O. Peleg, M. Grobman, M. Segev, Zero Backscattering in

Honeycomb Photonic Lattice

Th-5 Barak A., M. Segev, L. Friedland, Autoresonant Optics and Many-Body Random-Phase

Autoresonance

Th-6 Barbay S., T. Elsass, X. Hachair, I. Sagnes, R. Kuszelewicz, Cavity solitons in a

Vertical Cavity Semiconductor Optical Amplifier: from single to cluster states

Th-7 Bar-Gill N., E. Rowen, G. Kurizki, N. Davidson, Many-Body Excitations and their

Decay in a BEC Th-8 Towards selective heat transfer between a hot surface and an atom

Th-8 Bloch D., T. Passerat de Silans, I. Maurin, Ph. Ballin, A. Laliotis, P. Chaves de

Souza Segundo, S. Saltiel, M.-P. Gorza, M. Ducloy, D. de Sousa Meneses, P.

Echegut, Towards selective heat transfer between a hot surface and an atom

Th-9 Dayan B., T. Aoki, A. S. Parkins, D. J. Alton, C. A. Regal, S. Kelber, H. J. Kimble,

E. P. Ostby, K. J. Vahala, A photon turnstile with single atoms coupled to chipbased

microcavities

Th-10 Gavra N., V. Ruseva, M. Rosenbluh, Enhancement in microwave modulation efficiency

of vertical cavity surface-emitting laser by optical feedback

Th-11 Grinvald E., G. Lasovski, S. Levit, A. A. Friesem, Exploiting Symmetry Selection

Rules for Strong Evanescent Fields in Resonant Photonic Crystal Slabs

Th-12 Grohmann T., J. Floß, M. Leibscher, Control of Molecular Torsion by Intense Laser

Pulses: Two-Dimensional Model Studies

Th-13 Haakh H., F. Intravaia, C. Henkel, S. Spagnolo, R. Passante, B.Power, F. Sols,

Magnetic Casimir-Polder force near superconductors and metals

Th-14 Leshem A., O. Gat, Breakdown of Macroscopic Realism in the Dynamics of a Harmonic

Oscillator

Th-15 Lev U., V. S. Prabhudesai, A. Natan, A. Diner, O. Heber, B. Bruner, D. Strasser, Y.

Silberberg, D. Zajfman, Effect of linear chirp on strong field photodissociation of H2+

Th-16 Levi L., T. Schwartz, M. Segev, S. Fishman, Breakdown of Anderson Localization due

to Dynamic Disorder

Th-17 Lifshitz E., Multiexcitons in colloidal semiconductor nanocrystals

Th-18 Margalit L., T. Zigdon, A. D. Wilson-Gordon, S. Rochester, D. Budker, Visualization

of coherent population trapping

Th-19 Marom R., C. Levi, T. Weis, S. Rosenwaks, Y. Zeiri, R. Kosloff, I. Bar, Quantum

tunneling of hydrogen atoms in dissociation of photoexcited methylamine and

methylamine-d 3

Th-20 Mayteevarunyoo T., B. A. Malomed, Two-dimensional spatial solitons and vortices in

photonic crystals

Th-21 Pugatch R., O. Firstenberg, M. Shuker, N. Davidson, Universal Electromagnetically

Induced Transparency Spectra of Random Coherent Recurrence

Th-22 Residori S., U. Bortolozzo, J.P. Huignard, Slow and Fast Light through nonlinear

Wave Mixing in Liquid Crystals

Th-23 Shafir D., Y. Mairesse, B. Fabre, J. Higuet, E. Mével, E. Constant, D. M. Villeneuve,

P. B. Corkum, N. Dudovich, Probing the spatio-temporal properties of a re-collision

process

Th-24 Sidorenko P., A. Bahabad, T. Popmintchev, M. Murnane, H. Capteyn, O. Cohen,

Sawtooth grating-assisted-phase-matching

Th-25 Sindelka M., Matter-Laser Interaction: Derivation of coupled Maxwell-Schr¨odinger

equations from the first principles of quantum electrodynamics

Th-26 Stern M., V. Garmider, E. Segre, M. Rappaport, V. Umansky, Y.Levinson, I. Bar-

Joseph, Photoluminescence Ring Formation In Coupled Quantum Wells: A

Manifestation Of The Mott Transition

Th-27 Yurovsky V. A., A. Ben-Reuven, Observable effects of non-integrability on three-body

one-dimensional collisions

Th-28 Zadok A., E. Zilka, A. Eyal, L. Thévenaz, M. Tur, Polarization Dragging Phenomena

in Stimulated Brillouin Amplification/Attenuation in Standard Single-Mode Fibers

Th-29 Zigdon T., A. D. Wilson-Gordon, H. Friedmann, Pump-probe spectroscopy in

degenerate two-level atoms with arbitrarily strong fields

Monday February 9, 2009

Session Mo-A Chair: Yehiam Prior

Mo-B Chair: Martial Ducloy

Mo-C Chair: Nir Davidson

Mo-D Chair: Shammai Speiser

Measuring Time with Ultracold Atoms Achievements and Perspectives

Claude Cohen-Tannoudji Collège de France and Laboratoire Kastler Brossel

Ecole Normale Supérieure, Paris, France Institut Francilien de Recherche sur les Atomes Froids

Ultracold atoms, which move with very low velocities, allow longer

observation times which increase considerably the precision of the

measurement of the frequency of atomic transitions used in frequency

standards. Recent progress in the realization of cesium atomic clocks using

microwave transitions of laser cooled cesium atoms will be described,

leading to relative frequency stability in the range of 10-16, which corresponds

to an error less than one second in 3×108 years. The perspective of putting

these clocks in a microgravity environment, and in particular in the

International Space Station, is very attractive. In the optical domain, new

atomic clocks using optical transitions of trapped ions or of atoms trapped in

optical lattices are developed by several groups. They lead to leading to

higher precision than microwave clocks. Several applications of these ultra

precise atomic clocks are also being investigated and will be briefly

reviewed.

Mo-A

Atom Chips: Where Materials Engineering Meets Atom Optics

Ron Folman, Atom Chip Group, Ben Gurion University, Israel www.bgu.ac.il/atomchip Cold isolated atoms offer a unique system for quantum operations, both for technology and fundamental studies. To maintain a high level of control over the external and internal degrees of freedom of such atoms, and to enable robust miniaturization and enhanced complexity, a system named the atom chip began to be utilized in 1999. Here, fields originating from the chip − magnetic, electric, and electromagnetic − trap, guide, manipulate, and measure the atoms, which are positioned microns away from the chip surface in ultra-high vacuum. In this presentation I will describe two drawbacks of this system, namely, static magnetic potential corrugations arising from electron scattering in the surface, and spin flips and decoherence of the atomic state originating from thermally activated electron current fluctuations in the surface giving rise to noise. Several recent experimental and theoretical observations will be detailed [1-4].

Two hindering effects in atom-surface coupling on the atom chip: (left) experimental results [1] of magnetic potential corrugations due to electron scattering in a gold wire; (right) calculation [3] of decoherence due to fluctuating magnetic fields originating from Johnson noise on the atom chip surface.

[1] S. Aigner et al. Science 319, 1226 (2008). [2] Y. Japha et al. Phys. Rev. B77, 201407(R) (2008). [3] T. David* et al. Euro. Phys. Jour. D48, 321, (2008). [4] V. Dikovsky et al. arXiv 0808.1897 (2008). *This paper was chosen by the editors of EPJ as a “Highlight Paper”, and Tal David, the author, has just been chosen for a Graduate Student Award by the U.S. Materials Research Society.

Mo-A

Detection of Spiral photons in Quantum Optics

V.V. Klimov1, D. Bloch2, M. Ducloy2, J.R. Rios Leite3

1 P.N. Lebedev Physical Institute, Russian Academy of Sciences, Moscow 119991, Russia

2 Laboratoire de Physique des Lasers, UMR 7538 du CNRS et de l’Université Paris13, 93430 Villetaneuse, France

3 Departamento de Fisica, Universidade Federal de Pernambuco,50670-901 Recife, PE, Brazil e-mail : daniel.bloch@univ-paris13.fr

We establish that numerous "hollow" beams such as Bessel beams and Laguerre-Gauss

beams –which result from a summation of Bessel beams in the paraxial approximation [1]- are not true hollow beams in spite of their null electric field on-axis: when the phase factor of a (spiral) electric field evolves like exp imϕ, with ϕ the azimuthal phase, the magnetic field is not null on-axis for m= ± 2. Rather, it exhibits a circular polarization, and a transverse structure. Such an original situation is also found for the gradient of the electric field. It can be extended, for ⎜m⎜> 2, to higher orders derivative of the electromagnetic field. Differing structures for the electric and magnetic fields have already been found for some specific fields with a complex spatial structure [2], but our results here apply to fields freely propagating in vacuum, making simpler the concept of a photon.

For such spiral beams, a standard photon detector, based upon the detection of the electric field is blind to the field if located on the beam axis, while a similarly located detector of the magnetic field (M1 process) or a gradient detector (based upon a quadrupole transition) will detect light from the spiral beam. Hence, the mapping of the electromagnetic field, and the possibility to detect a photon through an energy exchange, appears to depend on the nature of the photon detector. Such a point has not been exploited in Quantum Optics, which generally assumes detector based upon an electric dipole (E1) transition (extension of Quantum Optics to magnetic detector was briefly considered in [3]).

The resonant irradiation with Laguerre-Gauss (LG) beams of systems involving these nearly forbidden E2 or M1 transitions could be of a special interest in quantum optics: in a classical approach [4], LG beams carry more than one unit of orbital angular momentum (OAM) per photon, but a quantized exchange of this OAM induces specific effects only on a non E1 transition; it is hence expected that this specific transfer should be spatially selective. In the same way, selective manipulation of chiral molecules with LG beams has been considered: although an experimental attempt, averaged over a large irradiation region, turned to be ineffective [5], a key to an effective manipulation could lie in the playing with the spatial selectivity.

Note that quantitatively, it is only for strongly focussed beams that the on-axis transferable energy compares to the one associated with the maxima of the electric field [6]. Our results do not require the paraxial approximation, and extensions to nano-optics is considered.

[1] S.M. Barnett and L. Allen, Opt. Comm.110, 670 (1994) [2] W.T.M. Irvine and D. Bouwmeester, Nature Physics 4, 716 (2008) [3] R.J. Glauber, Phys. Rev., 130, 2529 (1963). [4] L. Allen et al., Phys. Rev. A 45, 8185 (1992). [5] F. Araoka et al., Phys.Rev. A 71,055401(2005) [6] V. Klimov, D. Bloch, M. Ducloy, J.R. Rios Leite, arXiv:0802.0560 [quant-ph] and arXiv:0805.1697

Mo-A

Non-diffraction of Slow Light

O. Firstenberg, M. Shuker, A. Ron

Physics Department, Technion, Israel (oferfir@tx.technion.ac.il)

N. Davidson Department of Physics of Complex Systems, Weizmann Institute of Science, Israel

Classical wave fields are subjected to diffraction throughout their propagation. In many

systems, a reduction or elimination of the diffraction spreading of beamlike fields are obtained by manipulating the susceptibility in real space and inducing a gradient of the index of refraction. Similarly to wave-guiding, only specific modes may propagate in the induced wave-guides without diffraction or, equivalently, arbitrary images are revived after a certain self-imaging distance. However in these schemes, diffraction is not suppressed for an arbitrary image and for any distance along the propagation direction.

Here, we present a scheme to achieve slow-light propagation without diffraction for any arbitrary paraxial image, with both the intensity and phase information of the image completely maintained [1]. We utilize Dicke narrowing in electromagnetically induced transparency (EIT), in a vapor atomic medium with buffer gas, to obtain a susceptibility that is quadratic in the transverse momentum space [2]. By carefully tuning the EIT parameters and a specific negative Raman-detuning, the refraction induced by atomic motion completely counterbalances the paraxial optical-diffraction and by that eliminates the effect of diffraction. For negative detuning, the moving atoms drag the transverse momentum components towards the center, resulting in a Doppler trapping of light by atoms in two dimensions (Fig. 1).

The experimental conditions for a realization of our method are readily available. A unique manifestation of the scheme is the ability to suspend the expansion of narrow beams regardless of their position (Fig. 2). Other applications may include high-resolution imaging, slowing and storage of images, and nonlinear optics.

FIG 1. Pump-Probe geometry and an illustration of the Doppler trapping of light: EIT in the medium depends on the wave-vector k⊥, such that atoms that move oppositely to k⊥ drag the respective fileld's component more efficiently back to the main axis.

FIG 2. An incident beam of two Gaussians (dashed black) propagating one Rayleigh length. The normalized transmitted images and cross-sections (blue) are shown for: free-space diffraction (left), on-resonance EIT (center), and negative detuning (right), exhibiting no diffraction and no diffusion.

1. O. Firstenberg, M. Shuker, N. Davidson, A. Ron, Accepted to PRL (2008). 2. O. Firstenberg, M. Shuker, R. Pugatch, D. R. Fredkin, N. Davidson, A. Ron, PRA 77, 043830 (2008).

Mo-B

ProbePump

k⊥

z

x

y

CONTROLLING WAVEFRONT IN OPTICS, ACOUSTO-OPTICS,

AND PHOTOACOUSTICS

Sylvain Gigan, François Ramaz, Emmanuel Bossy and A. Claude Boccara

Institut Langevin, Laboratoire d’Optique Physique ESPCI-CNRS-UPMC-INSERM

Although optical waves do not exhibit the same ability to be manipulated as e.g.

electromagnetic waves up to a few GHz or acoustic waves, for which field emitters-detectors are available, a number of controls are nevertheless possible in the optical domain. Indeed deformable mirrors led to adaptive optics, real time holography to complex wavefront synthesis, phase conjugation is in certain conditions equivalent to time reversal, matrices of spatial light modulators allow to control light not only spatially but also in the frequency domain etc.. We have been able to measure and correct wavefront distortions induced by biological tissues such as the lymph nodes as shown in the images below where the optimum is the left one.

This set of images has been obtained by OCT (optical coherence tomography) about 150 µm

below the sample surface where “ballistic” photon detection is still possible. At much larger depths (a few cm) we use a combination of optical and acoustic waves to get the

optical contrast and the acoustic resolution. As an example we took advantage of time reversal of acoustic wave to refocus a photoacoustic signal through a scattering medium in the presence of a strong wavefront aberrator such as the

scull.

The left part of the image corresponds to the distorted wavefront whereas the corrected one

corresponds to the right one. We will show other situations where wavefronts can be controlled over a few modes to millions

of modes and discuss a few applications and perspectives offered by these new methods and devices to the field of biomedical imaging

Mo-B

Mo-B

Slowing and Stopping Light with Gap-Acoustic Solitons

Richard S. Tasgal <tasgal@bgu.ac.il>, R. Shnaiderman <shnaibor@bgu.ac.il>, and Y. B. Band <band@bgu.ac.il>

Departments of Chemistry and Electro-Optics and the Ilse Katz Center for Nano-Science, Ben-Gurion University of the Negev, Beer-Sheva 84105, Israel

Abstract

Gap-acoustic solitons (GASs), which make use of the nearly universal electrostrictive light-sound interaction, offer promising new avenues for slowing light. Optical gap solitons exist inside the frequency region of the band gap created by a Bragg grating. The Bragg grating, which may be considered as a distributed mirror for wavelengths in phase with it, keeps low-intensity light out of the gap. But nonlinearities can distort the optical band structure, and an intense pulse can punch a hole for itself in the band gap, in which it can then reside. The resulting localized structure, called an optical gap soliton, can be stable, with velocities from zero (i.e., stopped light) up to the group-velocity of light in the medium. When one also considers the effects of electrostriction, or the dependence of the index of refraction on the density of the material, optical gap solitons become GASs. GASs share many of the properties of standard gap-solitons, but they have many interesting properties of their own, especially when their velocities are close to the speed of sound and they interact strongly with the acoustic field [1]. For example, GASs which are moving at supersonic velocities may experience instabilities which leave the GAS whole, but bring the velocity abruptly to close to zero. This is illustrated at right, with the light intensity on top and the material density (i.e., acoustic field) below, versus distance in the fiber and time. In the process of stopping, the GAS spins off acoustic waves forward and backward, which balances the decreased GAS momentum. Relatedly, GASs can be made to change velocity by collisions with acoustic pulses. By these effects, the GASs may be stopped and manipulated.

Two moving GASs may collide. In the illustration at the left, the GASs begin with zero velocity, and accelerate towards each other by a mutual attraction (which depends on the relative phase, and which decreases exponentially with soliton separation). The solitons merge during the collission, emitting energy into the acoustic field. Over a longer time-scale, the remaining excited energy is dissipated into the acoustic field.

Also, phonon damping decelerates GASs, as shown at the left. The soliton velocity decreases approximately exponentially. During this retardation process, the GAS emits acoustic waves moving in the same direction as the soliton. Using this effect in a recirculating loop, a GAS may be decelerated from a high velocity to low velocity.

In summary: We shall show that acousto-optical interactions of gap-acoustic solitons provides a toolbox by which light may be slowed, and by which slowed and stopped light may be manipulated.

[1] R. S. Tasgal, Y. B. Band and B. A. Malomed, Phys. Rev. Lett. 98, 243902 (2007).

Atom optics versus photon optics: similarities and differences

M. Hamamda, J. Grucker, G. Dutier, F. Perales, J. Baudon, M. Ducloy

Laboratoire de Physique des Lasers, UMR CNRS 7538 Institut Galilée, Université Paris 13

93430 Villetaneuse, France

With the fast development of matter-wave optics, many of the functions previously operated in light optics have been realised: atom diffraction, atom mirrors, beam splitters, atom interferometry, atom holography, quantum reflection, quantum atom statistics, etc. Their similarities and differences originate in the properties of the associated particle: non-zero atom mass, vacuum dispersion for the “de Broglie” waves (implying the wave packet spreading), scalar character of the atomic wave function, influence of the internal atomic degrees of freedom…

Along this viewpoint, recent developments in the field of atom optics will be discussed, including atom interferometry at the nanoscale (“atomic nanoscope”), non-diffracting atom waves and negative-index ‘meta-material’ for atom optics.

The development of an atomic nanoscope based on a Fresnel-type biprism atom interferometer is in progress [1]. An analysis of the influence of gravity on this type of atom interferometer has been performed. Non-diffracting atomic nano-beams can be generated by use of specially designed transverse Stern-Gerlach interferometers [2]. The non-diffracting character is linked to the special shape of the resulting transverse profile (of the Lorentz type), and can be compared with Bessel beams in light optics. The actual implementation of an experimental set-up making use of “Campargue-type” nozzle beams will be described. Finally the extension of “left-handed” optical meta-materials to negative-index media for matter waves will be analysed. This includes the devising of atomic “meta-lens” by means of co-moving magnetic fields [3], and the analysis of the propagation of evanescent atomic waves.

[1] J. Grucker et al, “Schlieren imaging of nano-scale atom-surface inelastic transition using a Fresnel biprism atom interferometer”, Eur. Phys. J. D 47, 427 (2008) [2] F. Perales et al, “Ultra thin coherent atom beam by Stern-Gerlach interferometry”,

Europhys. Lett., 78, 60003 (2007)

[3] J. Baudon et al, “Negative-index media for matter-wave optics”, arXiv:0811.2479

Mo-B

Few-body physics with ultracold atoms: Efimov states and beyond

Rudolf Grimm

Institute of Experimental Physics, University of Innsbruck, and

Institut for Quantum Optics and Quantum Information, Austrian Academy of Sciences,

Innsbruck, Austria

Few-body physics is an emerging sub-field of research with ultracold atoms, facilitated by the

unique possibility to widely control the two-body interactions via Feshbach resonances [1].

Efimov states in three-body systems with large scattering lengths are the paradigm of few-body

physics [2, 3]. More than 35 years after their prediction, we could observe the first experimental

signatures of Efimov states in an optically trapped, ultracold gas of cesium atoms [4, 5]. The

Efimov states manifest themselves in zero-energy resonances in three-body recombination [4]

and inelastic atom-dimer scattering [5]. We have recently extended our studies into the four-body

sector by exploring collisions of weakly bound “halo” dimers as an elementary four-body process

[6]. We observe a decay minimum with variable atomic scattering length and a remarkable

temperature dependence, which cannot be explained in terms of the usually valid threshold law.

Recent theoretical progress on the four-boson system [7] provides deeper insight into the four-

body system and leads to the prediction of a new four-body recombination resonance. In ongoing

experiments we focus on the latter feature. Preliminary results do already confirm the prediction.

[1] C. Chin, R. Grimm, P. Julienne, E. Tiesinga, subm. to Rev. Mod. Phys.; arXiv:0812.1496.

[2] V. Efimov, Phys. Lett. B 33, 563 (1970).

[3] E. Braaten and H.-W. Hammer, Phys. Rep. 428, 259 (2006).

[4] T. Kraemer et al., Nature 440, 315 (2006).

[5] S. Knoop et al., arXiv:0807.3306.

[6] F. Ferlaino et al., Phys. Rev. Lett. 101, 023201 (2008).

[7] J. von Stecher, J. P. D’Incao, C. H. Greene, arXiv:0810.3876.

Mo-C

Experimental observation of the Anderson transition with atomic matter waves Julien Chabé1,*, Gabriel Lemarié2, Benoît Grémaud2, Dominique Delande2, Pascal Szriftgiser1 and Jean Claude Garreau1 1 Laboratoire de Physique des Lasers, Atomes et Molécules, Université des Science et Technologies de Lille, F-59655 Villeneuve d’Ascq cedex, France 2 Laboratoire Kastler-Brossel, Université Pierre et Marie Curie-Paris 6, ENS, CNRS; 4 Place Jussieu, 75005 Paris, France Phase transitions are major phenomena in physics, where a small change in a parameter may induce a dramatic change in physical properties of a system. Of particular interest in modern physics is the metal-insulator Anderson transition in disordered systems, ultimately due to the interplay between quantum interference and disorder. Here we present the first experimental observation of the Anderson transition using atomic matter waves. The Anderson model [1] describes the effect of random impurities on the quantum properties of a particle in a crystal lattice. The model predicts the existence of a quantum phase transition between an insulator phase where the wavefunction is exponentially localized at long times and a metallic phase, where the wavefunction is delocalized and displays diffusive transport. The metal-insulator transition is a fundamental quantum process whose applicability goes much beyond the original. It plays a central role in the study of quantum disordered systems, and has progressively been extended from its original solid-state physics scope to many different fields, including dynamical systems, optics, acoustics, biology and even cosmology. Many studies have pointed out strong analogies between cold atoms trapped in optical lattices and the physics of condensed matter. Using an atom-optics system formally equivalent to the Anderson model in three dimensions [2]

we unambiguously demonstrate the Anderson transition. Sensitive measurements of the dynamics of the atomic wavefunction and the use of finite-size scaling techniques make it possible to extract both the critical disorder strength and the critical exponent of the transition [3]. [1] Anderson, P. W. Phys. Rev. 109, 1492-1505 (1958); Anderson, P. W. Rev. Mod. Phys. 50, 191-201(1978). [2] G. Casati, I. Guarneri, and D. L. Shepelyansky, Phys. Rev. Lett. 62, 345 (1989). [3] Julien Chabé, Gabriel Lemarié, Benoît Grémaud, Dominique Delande, Pascal Szriftgiser and Jean-Claude Garreau. Accepted to Phys. Rev. Lett. Preprint availaible on ArXiv 0709.4320 * present address: Atom Chip Group, Department of Physics, Ben-Gurion University, P.O. Box 653 Be'er Sheva 84105 Israel

Mo-C

Figure: (left) Phase diagram of the transition. The insets show momentum distributions of the atomic cloud in the “insulator” localised state and in the “metallic” delocalised state. We follow the dashed curve to demonstrate the crossover between these states. (right) Experimental localisation length determined by finite-size scaling as a function of disorder strength. It diverges around K=6.4 with a critical exponent ν =1.4±0.3, signature of the 3-D

Anderson transition.

Controlling Light with Light: Efficient Energy Transfer between Laser Beams by Stimulated Raman Scattering

Sima Singha, Zhan Hu, Yaoming Liu, and Robert J. Gordon Department of Chemistry, University of Illinois at Chicago

Laser transformation of materials is a highly complex process involving multiple time

and length scales. One way of separating and possibly controlling such processes is to excite the material with trains of sub-ps pulses separated by the characteristic times of the processes of

interest. Here we describe experiments performed on two such time scales. In the first experiment, we irradiated a crystal in air with a pair of 50fs, 800nm pulses having delays of up to 100ps. A typical result is shown in Fig. 1 for Si(111), where the ratio of the plasma fluorescence produced by the pulse pair to that produced by a single pulse of the same total energy is plotted

as a function of delay and fluence. At constant fluence, the enhancement ratio grows to a plateau with a time constant of 30-40ps, whereas at a fixed delay the ratio passes through a maximum and falls off at high fluence. We interpret this as an incoherent effect in which the first pulse

melts the surface and the second pulse interacts more strongly with the liquid phase, as the melt front propagates into the bulk.1,2

Figure 1. Fluorescence enhancement at 505.6nm produced by double pulse

ablation of Si(111). Left panel: enhancement ratio vs. pulse delay at a

fixed fluence of 10.4J/cm2. Right panel: 3D plot showing both time and

fluence dependence of the enhancement ratio.

In a second set of experiments, trains of three or more pulse were generated with a spatial light modulator, with separations on the order of 1 ps. Figure 2 shows the enhancement ratio for GaAs. The peak spacing corresponds approximately to the LO phonon period of the crystal and

is highly suggestive of a coherent effect.

Figure 2. Fluorescence enhancement of GaAs produced by a 3-pulse train. Left: Enhancement ratio at a

fluence of 15.3 J/cm2. The arrows indicate multiples of the phonon period. Right: 3D plot of enhancement vs. pulse delay and total fluence.

1 Z. Hu, S. Singha, Y. Liu, and R. J. Gordon, Appl. Phys. Lett. 90, 131910 (2007). 2 S. Singha, Z. Hu, and R. J. Gordon, J. Appl. Phys. (in press).

Mo-D

Fluorescence versus laser effect: towards a unified picture

Jacob Szeftel

ENS Cachan, LPQM, 61 avenue du Président Wilson, 94230 Cachan, France

Nicolas Sandeau

Université ParisVI, UMR 7033 BioMoCeTi, 4 place Jussieu F-70005 Paris France

Light is generated through a two-stage process : first an electron is excited from its groundstate

up to an excited state and then light is emitted through radiative recombination. At low pumping

intensity, a sequence of fluorescence wave-packets is observed, while above some pumping

threshold, a coherent and powerful output is achieved thanks to the laser effect. Fluorescence and

laser emissions have been ascribed to spontaneous and stimulated emission. Besides, both

processes, albeit unrelated, tend to describe the electromagnetic field in terms of emitted photons.

However because there is no one to one correspondence between the amplitude of the

electromagnetic field and the photon number, the observed field pattern cannot be reproduced by

the available theory. This inconsistency was first noticed by Lamb[1]. In our work, the motion of

the electric dipole under the action of the electromagnetic field is governed by the Bloch

equations. The field is characterized classically by its time-dependent amplitude. An additional

relation between the dipole and the field is needed. Rather than resorting to the Maxwell equation

to this purpose, as done by all authors following Lamb, it is derived by taking advantage of the

conservation of the total energy of the coupled system, comprising the electromagnetic field and

the resonant dipole. The resulting nonlinear differential equation is shown to sustain two fixed

points associated with fluorescence and laser emission, respectively. The existence of a pumping

threshold is confirmed for the laser effect. The pumping rate conditions solely whether light will

be emitted by fluorescence or laser effect and convergence toward the relevant fixed point is

obtained in all cases. The initial conditions, chosen to integrate the differential equation, assume

a nonvanishing electric polarization of the emitting dipole rather than a nonvanishing

electromagnetic field. The distribution function accounting for the thermal fluctuations of the

random initial polarization has been worked out.

References [1] W.E. Lamb, Phys.Rev., 134, A1429 (1964)

Mo-D

Tuesday February 10, 2009

Session Tu -A Chair: Yaron Silberbnerg

Tu -B Chair: Claude Boccara

Exploring the quantumness of light in a Cavity

Serge Haroche

ENS and Collège de France, Paris We describe Cavity QED experiments in which a beam of Rydberg atoms is used to manipulate and probe non-destructively microwave photons trapped in a very high Q superconducting cavity. We realize an ideal quantum non-demolition (QND) measurement of light, observe the radiation quantum jumps due to cavity relaxation and prepare non-classical fields such as Fock and Schrödinger cat states. Combining QND photon counting with a homodyne mixing method, we reconstruct the Wigner functions of these non-classical states and, by taking snapshots of these functions at increasing times, obtain movies of the decoherence process. We also observe that the coherent evolution of the field in the cavity is frozen when we measure non-destructively its photon number and we realize in this way a simple demonstration of the quantum Zeno effect. These experiments open the way to the implementation of quantum feed back procedures aimed at preserving over long time intervals the quantum coherence of non-classical states of radiation in a cavity.

Tu-A

A scheme to probe optomechanical correlations between two optical beams down to the quantum level

P.-F. Cohadon, P. Verlot, A. Tavernarakis, T. Briant, and A. Heidmann

Laboratoire Kastler Brossel, UPMC-ENS-CNRS, Case 74, 4 place Jussieu, F75252 Paris Cedex 05, France

Quantum effects of radiation pressure are expected to limit the sensitivity of second-generation gravitational-wave interferometers. Though ubiquitous, such effects are so weak that they haven’t been experimentally demonstrated yet. Using a high-finesse optical cavity and a classical intensity noise [1], we have demonstrated radiation-pressure induced correlations between two optical beams sent into the same moving mirror cavity. The intensity fluctuations of the first, high-power, signal beam are imprinted onto the mirror motion by radiation pressure, whereas the resulting position fluctuations are monitored through the phase of the second, weaker, meter beam. As the intensity fluctuations of the signal beam are unchanged by reflection upon the cavity, the intensity-phase correlations observable between the two reflected beams provide a direct measurement of the optomechanical correlations.

The figure presents the trajectories in phase-space of both the reflected signal beam intensity and the reflected meter beam phase (calibrated as mirror displacement). The two trajectories are very similar, the small differences being due to the thermal noise which partly drives the mirror motion. Our results therefore demonstrate optomechanical correlations [2] between the mirror motion, proportional to the phase fluctuations of the meter beam, and the intensity fluctuations of the reflected signal beam. Such correlations are still at the classical level but we note that for our system, for quantum noise and a cryogenic temperature of 4 K, averaging the experimental signal should enable to retrieve the corresponding quantum correlations and hence demonstrate radiation-pressure noise. With an upgrade of our experimental setup, one can also envision radiation-pressure induced quantum optics experiments, such as optomechanical squeezing or QND measurements. [1] T. Caniard, P. Verlot, T. Briant, P.-F. Cohadon, and A. Heidmann, Phys. Rev. Lett. 99, 110801 (2007) [2] P. Verlot, A. Tavernarakis, T. Briant, P.-F. Cohadon, and A. Heidmann, arXiv:0809.2510

Tu-A

Laser-driven atoms in a finite lattice stage a nano-riot against uniformity

A. E. Kaplan and S. N. Volkov

Johns Hopkins University, 21218, Baltimore, USA

A crystal, i. e. an ordered lattice of atoms or moleculesis normally assumed to be almost uniformly excited by an incident light, at least on a sub-wavelength scale. An interatomic interaction produces then a uniform local field (different from that of incident laser) at each atom as well. This is a major assumption in the Lorentz-Lorenz theory of interaction of light with dense matter. We showed [1] that at certain critical conditions on the atomic density and dipole strength, a previously unexpected phenomenon emerges: the interacting atoms break the uniformity of interaction, and in a violent switch to a strong non-uniformity, their excitation and local field form nanoscale strata with a spatial period much shorter than that of laser wavelength, thus changing the entire paradigm of light-matter interaction. The most interesting effects can be observed for relatively small 1D-arrays or 2D lattices if the laser is almost resonant to an atomic quantum transition. The effects include huge local field enhancement at size-related resonances at the frequencies near the atomic line, so that the strata are readily controlled by laser tuning. A striking feature is that for the shortest strata, the nearest atomic dipoles counter-oscillate, which is reminiscent of anti-ferromagnetism of magnetic dipoles in Ising model. Our results also show the formation of "hybrid" modes, whereby at certain atoms in the lattice, their excitation and local field get completely suppressed. Due to those modes, at certain "magic" array size or configuration, the absorption of light at the exact resonant is almost fully canceled. The simplest magic 2D-shape is a six-point star made of 13 atoms (with one atom at the center). The resonant amplitude enhancement enables optical hysteresis and bistability at low light intensities; the tiniest known optical switch can be made of just two atoms. The new phenomenon promises a potential for nanoscale non-conductive computer elements, sensors for detecting bio-molecules, etc. [1] A. E. Kaplan and S. N. Volkov, "Nanoscale stratification of local optical fields in low-dimensional atomic lattices", Phys. Rev. Lett., v. 101, 133902 (2008)

Tu-A

Complex Nonlinear Opto-Fluidity

C. Rotschild1, A. Barak1, Y. Lamhot1, E. Greenfeld1, M. Saraf2, R.A. El-Ganainy3, E. Lifshitz2, D.N. Christodoulides3 and M. Segev1

1. Physics Department and Solid State Institute, Technion, Haifa 32000, Israel

2. Chemistry Department and Solid State Institute, Technion, Haifa 32000, Israel 3.College of Optics and Photonics, CREOL, University of Central Florida, Orlando, Florida

Abstract: We demonstrate symbiotic dynamics of light and nano-particles suspended in liquid. Light-force varies the local particle density, modifies the fluid properties (surface-tension, viscosity), inducing motion/rotation in the fluid, causing synergetic nonlinear-dynamics of light and fluid.

Opto-Fluidity describes systems where optics and fluids operate in synergy, resulting in functional devices such as liquid lenses of variable foci, liquid mirrors, liquid-crystal displays, and electro-wetting lenses. Thus far, however, all of these are means to control optical properties of devices by manipulating fluids, while light does not affect the dynamics of fluid itself. Here, we experimentally study a complex system, were the optical propagation dynamics and the fluid dynamics are strongly coupled: light modifies the properties of the fluid, causing motion and rotation within the fluid, and in turn, the fluid affects the propagation dynamics of the optical beam. We demonstrate momentum transfer from light to fluid and back, using light force as Archimedes Pump to pull and push droplets in a controlled fashion, optically-induced variations of surface tension, and self-focusing within the fluid down to single-wavelength scales. Our system includes high-index dielectric nano-particles, suspended in low-index liquid. Light exerts force on the particles, inducing macroscopic flow of particles towards the high-intensity region of the beam, which changes the fluid properties such as viscosity, and surface tension. The optical forces are transferred to the liquid due to drag forces on the particles, causing flow in the fluid. This light-induced flow also modifies the optical properties of the liquid, changing the local refractive index, thus affecting light propagation. We begin with experiments on transferring angular motion from light to the fluid and back, in the regime of laminar flow in the fluid. We use a motor to construct an intensity structure that spirals (in time) about its center, at a constant angular velocity, and focus this spiraling beam on the top interface between the liquid and air. The beam rotates the fluid in the cell, about the beam center (Fig. 1a). That is, light transferred angular momentum and kinetic energy to the fluid. Next, we stop the motor. The fluid continues to rotate (because it has inertia), rotating the region of high particle density with it. Because the particles have a higher refractive index, these regions channel the light within them, and the rotating fluid is now rotating the (now otherwise stationary) light beam in the cell, (Fig. 1b). That is, the fluid has now transferred angular momentum to the light. We have therefore completed a cycle: transferred angular momentum and kinetic energy from light to the fluid and back. Finally, we restart the motor and cause high speed rotation of the light beam. The result is an overwhelming light-induced fountain effect: the liquid is propelled upwards into the air, with the rotating light beam acting as an “optical drill” (Fig. 1c). We now focus the rotating beam on a liquid droplet inside a horizontal pipette. A clockwise rotating beam pulls the droplet (Fig. 1d), whereas a counterclockwise rotating beam pushes the droplet away: an Optical Archimedes Pump. Finally, we use a vertical pipette and demonstrate that the height of fluid within it varies with light intensity: at low intensity the fluid level is high (Fig. 1e), whereas increasing the intensity makes the fluid level do down considerably (Fig. 1f). The optical beam controls the surface tension of the fluid.

Figure1: Transfer of momentum from the beam to the liquid and back, and optically-induced surface tension

Finally, we study the symbiotic interaction between light and the upper surface of the liquid, where nonlinear optics is coupled to nonlinear fluid dynamics. We launch the beam close to the surface, attracting particles from the surface to the beam center, thus changing surface tension, and causing deformation of the surface. Increasing the intensity deforms the surface more, until a break point occurs: the deformation collapses, deflecting the beam, and the system evolves again, in self-oscillating (possibly chaotic) fashion.

Tu-B

Nanoplasmonics from Attoseconds to Terahertz Mark I. Stockman, Department of Physics and Astronomy, Georgia State University, Atlanta,

GA 30302, USA, e-mail: mstockman@gsu.edu, web site: www.phy-astr.gsu.edu/stockman Abstract: We present recent ideas in nanoplasmonics regarding precise control of the optical localization energy on femtosecond-nanometer scale. Among these are SPASER, attosecond plasmonic field microscope, coherent control by time reversal, and plasmonic renormalization of Coulomb interactions. SPASER was proposed as a quantum generator of coherent ultrafast and intense optical fields localized on the nanoscale [1], see also [2]. SPASER is a missing active device in nanoplasmonics, greatly needed to build nanoplasmonic circuits. It will allow compensation of losses, active modulators, logical elements and ultrafast memory elements. Recently, there has been a great interest and progress in both understanding fundamentals of SPASER and demonstrating a working device. We expect to present recent results showing nonlinear control and switching in SPASER.

We continue with the idea of attosecond nanoplasmonic field microscope [3]. So far, the spatiotemporal dynamics of optical fields localized on the nanoscale has been hidden from direct access in the real space and time domain. Here, we describe an approach that will, for the first time, provide direct, non-invasive access to the nanoplasmonic collective dynamics, with nanometer-scale spatial resolution and temporal resolution on the order of 100 attoseconds. This offers a valuable way of probing nanolocalized optical fields that will be interesting both from a fundamental point of view and in light of the existing and potential applications of nanoplasmonics.

While ideas of the coherent control are well developed and tested at the present time, a formidable problem remains of finding the shape of a controlling pulse that localizes the optical excitation at a given site of the nanosystem with a nm resolution at the required time with a fs precision. To radically solve this problem, we have proposed [4] an efficient method. based on a general idea of time reversal where the nanosystem itself plays the role of an optical antenna and resonator. It is wireless and noninvasive. This method will open up many more fundamental and engineering applications of nanoplasmonics, in particular, to ultrafast computations and information storage on the nanoscale and ultrafast nanoscale spectroscopy.

Another new development is a study of the ultimate concentration of THz energy on the nanoscale [5]. Here we establish the principal limits for the nanoconcentration of the THz radiation in metal/dielectric waveguides and determine their optimum shapes required for this nanoconcentration. We predict that the adiabatic compression of THz radiation from the initial spot size of a hundred microns to the final size of R = 100− 250 nm can be achieved,. This will find a wide spectrum of applications in science, engineering, biomedical research, environmental monitoring, and defense.

Finally, we consider a very general and important process occurring on the nanoscale spatial scale and the temporal scale of tens femtoseconds. It is nanoplasmonic renormalization of Coulomb interactions [6]. We illustrate this theory by computing the dressed interaction explicitly for an important example of metal–dielectric nanoshells which exhibits a rich resonant behavior in magnitude and phase. This in a combination with the recently discovered [7] efficient nonlinear control of the transmission will lead to new nanoplasmonic circuits with functionalities of switches and modulators. [1]. D. J. Bergman and M. I. Stockman, Phys. Rev. Lett. 90, 027402 (2003). [2]. M. I. Stockman, Nature Photonics 2, 327 (2008). [3]. M. I. Stockman, M. F. Kling, U. Kleineberg, et al., Nature Photonics 1, 539 (2007). [4]. X. Li and M. I. Stockman, Phys. Rev. B 77, 195109 (2008). [5]. A. Rusina, M. Durach, K. A. Nelson, et al., Opt. Expr. 16, 18576 (2008). [6]. M. Durach, A. Rusina, V. I. Klimov, et al., New J. Phys. 10, 105011 (2008). [7]. K. F. MacDonald, Z. L. Samson, M. I. Stockman, et al., arXiv:0807.2542 (2008).

Tu-B

Single KTiOPO4 nanocrystals for nonlinear probing of local optical fields and interaction with a metallic nanostructure

L. Le Xuan1

, A. Slablab1

, C. Zhou1

, D. Chauvat1

, Y. De Wilde2

, S. Perruchas3

, C. Tard3

, T. Gacoin

3

, P. Villeval4

and J-F. Roch1

1

ENS de Cachan, Laboratoire de Photonique Quantique et Moléculaire UMR 8537, Cachan, 94235, France 2

ESPCI,

Laboratoire Photons Et Matière -UPR A0005, Paris, 75005, France. 3

Ecole Polytechnique, Laboratoire de Physique de la

Matière Condensée, Palaiseau Cedex, 91128, France. 4

Cristal Laser S.A, Messein, 54850, France. email : aslablab@lpqm.ens-cachan.fr

The finding of nonlinear nanometric-sized probes is of key importance for the development of nonlinear microscopy in physical as well as biological sciences. We isolate nonlinear KTiOPO4 (KTP) nanocrystals and study them by second-harmonic generation (SHG) microscopy and atomic force microscopy (AFM). With both polarization analysis and defocused imaging of the emitted second harmonic field, we extract the Euler angles of the crystalline axes of a single nanocrystal. The nonlinear features of a single KTP nanocrystal make it a good candidate for a vectorial probe of electromagnetic near-fields and coherent imaging. We also investigate the interaction of such a well-characterized nanocrystal with a single gold nanostructure which is approached in the vicinity of the KTP nanocrystal using an AFM tip. A colloidal solution of KTP nanocrystals with polymer is obtained either from centrifugation of KTP powder [1] or by direct chemical synthesis, resulting in a nanocrystal size of a few tens of nanometers. This solution is spin-coated on a glass cover slip. It results in a thin layer of polymer with isolated nanocrystals that can be precisely located using structuration of the polymer film. Thus a single nanocrystal can be studied using SHG and AFM scannings. The nano KTPs are excited by a femtosecond laser with 986 nm wavelength to generate 493 nm SHG signals. Scanning the excitation beam by tilting a mirror mounted on a piezoelectric transducer, we obtain an SHG image of the sample, in which nearly all these emitters can also be found unambiguously in the AFM image. By analyzing the polarization state of the SHG signal against the rotation of the excitation beam using a half wave plate, we obtain the projection of the nanocrystal c-axis on the cover slip surface (x,y) plane. With the recently developed defocused imaging technique adapted to SHG [2], we can deduce the three-dimension orientation for one certain nonlinear emitter. The results infer the possibility of obtaining vectorial information at nanometric scale on the distribution of an electromagnetic field, simply using an asymmetric SHG nano-emitter [3]. Finally we investigate the interaction of the KTP nanocrystal and a metallic nanostructure (gold nanosphere). The AFM tip is functionalized with a gold sphere which size is about 100 nm. When the gold sphere is brought to the focus of the microscope objective by the AFM tip, its interaction with the laser excitation field creates intense localizations of the field at the two poles. By scanning a KTP nanocrystal with a size of about 60 nm at the vicinity of the nanosphere, we can clearly see these lobes with resolution far beyond the optical one. This experiment demonstrates the ability of the KTP nanocrystal as vectorial probes for optical near-fields. References and notes [1] KTP powder provided by D. Lupinski and Ph. Villeval at Cristal Laser S. A., Nancy, France. [2] N. Sandeau, L. Le Xuan, D. Chauvat, C. Zhou, J.-F. Roch, and S. Brasselet, « Defocused imaging of second harmonic generation from a single nanocrystal », Optics Express, 15, 16052 (2007). [3] L. Le Xuan, C. Zhou, A. Slablab, D. Chauvat, C. Tard, S. Perruchas, T. Gacoin, P. Villeval, and J.-F. Roch « Photostable second-harmonic generation from a single KTiOPO4 nanocrystal for nonlinear microscopy », Small 4, 1332 (2008).

Tu-B

Wednesday February 11, 2009

Session We-A Chair: Dan Oron

We-B Chair: Michael Rosenbluh

We-C Chair: Oren Cohen

We-D Chair: Claude Fabre

Extreme Nonlinearity: Attosecond-Attosecond Science Paul Corkum

Joint Laboratory for Attosecond Science 100 Sussex Drive

Ottawa, Canada K1A 0R6 Abstract:

During the past six years the minimum duration of optical (XUV) pulses has fallen from 5 femtoseconds (5x10-15 sec) to about 100 attoseconds (~10-16 sec)—less than the classical period of a ground-state electron in a hydrogen atom. Intense short laser pulses drove this revolution by forcing electron wave packets to tunnel from the atom or molecules, move under the force of the time dependent electric field and then re-collide with their parent ions. From the ion’s perspective, an attosecond electron wave packet re-collides. Attosecond XUV pulses are the byproduct of this collision. The attosecond electron, controlled by light, is something unique in science. With wavelength ~ 0.5-3 Ångstrom, it allows us to measure Angstrom-scale spatial information -- as in a photograph. The “shutter speed” can be attoseconds. I illustrate three ways that electron created in this highly nonlinear interaction gives give us spatial images. Tunneling. The lateral momentum distribution of electrons that tunnel measures a filtered

projection of the momentum wave function of the ionizing orbital. Rotating the molecule, we gain all information about the orbital. We show that tunneling from HCl occurs from both the HOMO and the HOMO-1 orbital [1]. Therefore, the act of tunneling creates a superposition of hole-states in the ion.

Laser Induced Electron Diffraction: The re-collision electron elastically scatters from its parent molecular ion. The diffraction pattern gives the position of a molecule’s atoms [2].

Orbital Tomography: Attosecond pulses arise from the interference between the re-collision electron and the initial orbital from which it separated. The amplitude and phase of the XUV radiation contains all information to recreate the orbital image [3] and to observe attosecond dynamics when multiple orbitals simultaneously ionize [4].

[1] Hiroshi Akagi, T. Otobe, A. Staudte, A. Shiner, F. Turner, R. Dörner, D.M. Villeneuve and

P.B. Corkum, “Angular distribution of tunnel ionization probability from HOMO-1 of HCl”, unpublished results.

[2] M. Meckel, D. Comtois, D. Zeidler, A. Staudte, H.C. Bandulet, D. Pavicic, H. Pepin, J. C. Kieffer, R. Dörner, D. M. Villeneuve and P. B. Corkum, “Laser Induced Electron Tunneling and Diffraction”, Science 320, 1478 (2008).

[3] J. Itatani, J. Levesque, D. Zeidler, H. Niikura, H. Pepin, J. C. Kieffer, P. B. Corkum and D. M. Villeneuve, “Tomographic Imaging of Molecular Orbitals”, Nature 432, 867 (2004).

[4] O. Smirnova, S. Patchkovskii, Y. Mairesse, N. Dudovich, D. Villeneuve, P. B. Corkum, and M Y. Ivanov, “Time and Space Resolved High Harmonic Imaging of Electron Tunneling from Molecules” submitted to Nature.

We-A

80 attosecond soft-X-ray pulses [1]

M. Schultze1, E. Goulielmakis1, M. Hofstetter2, M. Uiberacker2, J. Gagnon1, V. Yakovlev2, U. Kleineberg2, F. Krausz1,2

1Max-Planck-Institut für Quantenoptik, Hans-Kopfermann-Strasse 1, D-85748 Garching, Germany 2 Department für Physik, Ludwig-Maximilians-Universität, am Coulombwall 1, Germany

martin.schultze@mpq.mpg.de

Abstract: We demonstrate the generation of powerful sub-100-as soft-x-ray pulses by means of 1.5-cycle waveform-controlled laser fields. Our new tool opens the door for exploring electronic processes on a time scale approaching the atomic unit.

Attosecond pulses are emitted when energetic electron wavepackets, created by the interaction of intense-laser fields with atoms, recollide with the atomic core and radiate soft-x-rays. Spectral filtering of radiation emerging from a single recollision event comprises the cornerstone of isolated attosecond pulse technology [2]. Indeed, light wavepackets emitted within the most intense half-cycle of a few-cycle laser pulse have allowed for generation of powerful attosecond pulses in the sub 200-as regime [3]. The duration of these pulses has been limited by the spectral width of the emitted soft-x-ray continuum, which is inextricably related to the intensity contrast between adjacent half-cycles of the driving pulse. Here we demonstrate a new regime of attosecond pulse generation where waveform-controlled pulses comprising merely 1.5 field oscillations are employed to drive soft-x-ray emission from atoms. Adjusting the phase setting to enhance the contribution of a single, most-powerful electron trajectory, we generate a supercontinuum that extends over more than ~28 eV in FWHM. From the temporal characterization of the emitted soft-x-rays, pulses were ascertained to have a duration of 80±5 attoseconds. Soft-X-rays are generated by gently focusing (f=600 mm) sub-4-fs laser pulses into a quasi-static gas cell filled with Neon. A double-mirror assembly, consisting of a Mo/Si multilayer mirror supporting a bandwidth of ~35 eV FWHM (centered at 80 eV) and an outer concentric perforated mirror focus the soft-x-rays and the laser beam respectively into a second Ne target. The delay between laser and soft-x-ray pulse can be varied with attosecond resolution. Electrons ejected in the polarization direction of the laser are collected by a time-of-flight (TOF) electron spectrometer. Figure 1.A shows a recorded spectrogram of our soft-x-ray attosecond pulse. We analyze our spectrogram utilizing a version of the FROG technique [2] optimized for attosecond streaking. The algorithm renders the temporal intensity and phase of the attosecond pulse as depicted in figure 1.B.

Fig.1. (A) Atomic-transient-recorder spectrogram of a sub-100-as soft-x-ray pulse. (B) Temporal intensity profile and phase of the pulse retrieved from the data for the spectrogram depicted in (A).

We believe that our powerful sub-100-as pulses precisely synchronized to their cause (laser fields) offer a dramatic improvement of the temporal resolution and hold promise for real time tracking of ultrafast dynamics on the time scale of electron correlation [4]. References [1]. E. Goulielmakis, M. Schultze, M. Hofstetter, V. S. Yakovlev, J. Gagnon, M. Uiberacker, A. L. Aquila, E. M. Gullikson, D. T. Attwood, R. Kienberger, F. Krausz, U. Kleineberg, Science 320, 5883 (2008) [2]. R. Kienberger, E. Goulielmakis, M. Uiberacker, A. Baltuska, V. Yakovlev, F. Bammer, A. Scrinzi, T. Westerwalbesloh, U. Kleineberg, U. Heinzmann, M. Drescher, and F. Krausz, "Atomic transient recorder, Nature 427, 817 (2004). [3] M. Schultze , E. Goulielmakis, M. Uiberacker , M. Hofstetter, J. Kim J, Kim D, Krausz F, Kleineberg U., Powerful "170-attosecond XUV pulses generated with few-cycle laser pulses and broadband multilayer optics", New. J. Phys 9, 243 (2007) [4] J. Breidbach, and L. Cederbaum, "Universal attosecond response to the removal of an electron," Phys. Rev. Lett. 94, 033901 (2005)

We-A

Combined Time Frequency Detection by Single Shot Four Wave Mixing Andrey Shalit, Yuri Paskover, and Yehiam Prior

Department of Chemical Physics, Weizmann Institute of Science, Rehovot, Israel 76100 yehiam.prior@weizmann.ac.il, phone +972-8-934-4008, fax +972-8-934-4126

Time Resolved Four Wave Mixing (TR-FWM) is an excellent method for probing molecular vibrational dynamics on the femtosecond time scale [1]. Recently we discussed a 3-Dimensional forward propagating Boxcars geometry of three well collimated beams intersecting within a sample. We have shown that the arrival time of each of the pulses to a particular location within the intersection region determines the time delay between the pulses such that an image of the FWM signal generated in the different locations provides full information on the TR-FWM signal within a single laser shot [2]. Thus, each single shot experiment provides a time resolved signal, which in turn is Fourier Transformed to provide the frequency dependence of the FWM signal. We further showed [3] that the well collimated beams impose strict phase matching conditions on the generated FWM signal, thus enabling Phase Matching Spectral Filtering within the broad spectral width of the ultrashort pulses by varying the angle of the Stokes beam. A full spectrally and time resolved FWM signal was achieved when the experiment was repeated for different angles. The next step, presented here for the first time, is the amalgamation of these multiple experiments (each for a different tuning of the phase matched filter) into a single one. The experimental geometry was modified, such that instead of changing the input Stokes angle δ, now the Stokes beam was gently focused by a cylindrical lens to the interaction region. Thus, the different directions (angles) were all present simultaneously, each giving rise to a signal centered at a different frequency and phase matched in a slightly different geometrical direction. The picture of the FWM signal as captured directly on the CCD camera (Fig. 1a) contains the entire range of input frequencies hitherto necessitating a series of different experiments with individually tuned input angles. The method is demonstrated on liquid neat dibromomethane (CH2Br2).

a) b)

Fig 1 a) Image of the captured signal. Different vibrational modes are spread out on the CCD camera. b) Power spectra of time and frequency resolved images

The simultaneous observation of the entire spectrum allows not only the assignment of the observed beats to specific vibrational modes but also the identification of distinct contributions from various spectroscopic pathways. In conclusion, the ability to carry out fully time and frequency resolved measurement within a single laser shot opens the road to the addressing and spectral interpretation of complex molecules undergoing rapid photo-bleaching as is the case for many biological molecules.

References

[1] S. Ruhman , A Joly, K. Nelson, IEEE J. Quantum Elect. 24 (1988) 460

[2] Y. Paskover, I. S. Averbukh Y. Prior, OE 15 (2007) 1700

[3] Y. Paskover, A Shalit Y. Prior, (2008) submitted

We-B

Y pixels

Z p

ixle

s

200 400 600 800800

0

200

400

600 Δ= 0

Y pixels

Z p

ixle

s

200 400 600 800800

0

200

400

600 Δ= 0

Narrow Band Raman Assisted Fiber Parametric Amplification : The Issue of Fiber Imperfections

Evgeny Shumakher, Amnon Willinger, Gadi Eisenstein

Electrical Engineering Dept. Technion

Narrow band parametric amplification occurs in optical fibers when the pump propagates in the

normal dispersion regime. Phase matching conditions are satisfied then in two spectral regions

which are widely detuned from the pump. The wavelengths where gain takes place and the width

of the gain spectra are determined by the spectral detuning between the pump and the zero

dispersion wavelength of the fiber. The detuning between pump and the gain is usually larger

than 100 nm and therefore the parametric process is strongly coupled to Raman scattering. The

large detuning requires that the complete complex susceptibility of the Raman scattering process

be considered and therefore it affects both the gain and the phase matching conditions.

Narrow band Raman assisted fiber parametric amplifiers have been used in recent years

as slow and fast light elements. The relatively wide bandwidth (on the scale of electrical

bandwidths) as well as the ability to tune the delay using the pump power enabled to demonstrate

with these amplifiers the widest tuning range for a room temperature optical delay line and the

capability to delay fast data signals with no distortion.

Detailed examinations reveal however that conventional modeling of these amplifiers

fails to fit experimental results. Proper theoretical modeling of experiments which also allows

optimization requires considering the role of fiber imperfections the two most important ones are

random birefringence (also known as PMD) and longitudinal variations of linear and nonlinear

propagation parameters.

These imperfections have been modeled in a detailed statistical formalism which yields

superb agreements with experiments. Moreover, it was demonstrated that the narrow band

parametric amplification process can be a superb tool for the extraction of the longitudinal

parameter distribution yielding resolutions of the order of single meters and a very high

sensitivity.

We-B

Speckle Instability in Strongly Scattering Kerr Random Media

Patrick Sebbah1, Umberto Bortolozzo2, Stefania Residori2

1Laboratoire de Physique de la Matière Condensée - CNRS UMR 6622 Université de Nice-Sophia Antipolis, Parc Valrose, 06108 Nice Cedex 02, France

2Institut Non Linéaire de Nice INLN – CNRS UMR 1361 Université de Nice Sophia-Antipolis, route des Lucioles, 06560 Valbonne, France

Email : sebbah@unice.fr Large intensity fluctuations of light diffusing through random media originates from the interference of the multiply scattered waves. The resulting speckle pattern can be viewed as a fingerprint of the disorder configuration of the medium and therefore is highly sensitive to scatterer motion. In the presence of a non linearity, the speckle may become instable as a results of the positive feedback provided by the scattering medium, even in absence of scatterer motion. This instability was predicted for nonlinearities exceeding a certain threshold value and demonstrated by Skypetrov and Maynard [1] using a stationary self-consistent theory. Its experimental observation however has never been reported.

In this paper, we demonstrate speckle instability in a scattering two dimensional nonlinear disorder system. We consider a photorefractive liquid crystal light valve (LCLV), which combines a nematic liquid crystal (LC) layer with a thin monocrystalline photorefractive crystal (BSO) in the form of a cell wall [2]. A controlled random orientation of the LC layer is obtained by projecting the computer-generated random pattern of a spatial light modulator (SLM) onto the BSO film. The beam of a HeNe laser crossing the LCLV is transversely scattered by the randomly modulated nematic refractive index, as it bounces back and forth between the glass plates surrounding the LCLV, as shown in the figure. The nonlinearity is provided here by the reorientational Kerr effect of the LC. Above a threshold intensity, the HeNe

speckle pattern starts to blink at a specific frequency. The threshold is found to be disorder dependent. At higher intensities, several frequencies appear and the instability eventually develops into chaos. We confirm numerically the existence of a threshold and investigate the dynamical behavior of wave in nonlinear random media below and above threshold in the particular regime of very strong disorder, where interference effects may result in Anderson localization. In this regime where solutions of the wave equation are spatially localized, we show that the amplitude modulation observed in the speckle pattern in the presence of a Kerr nonlinearity results from the beating between the excitation frequency and the eigenfrequency of a localized mode of the random medium. The nonlinearity preferentially transfers the energy from the pump light into the localized modes of the system, which provide natural resonant cavities. This is analogous to random lasing, where the gain selects naturally the modes of the passive system [3]. [1] S. E. Skypetrov and R. Maynard, Phys. Rev. Lett. 85, 736 (2000). [2] U. Bortolozzo, S. Residori, A. Petrosyan, and J.P. Huignard, Opt. Commun. 263, 317 (2006). [3] C. Vanneste and P. Sebbah, Phys. Rev. Lett., 87, 183903 (2001).

We-B

Ultrafast X-ray probing of electron dynamics to the attosecond limit

Stephen R. Leone

Departments of Chemistry and Physics, 209 Gilman Hall and Lawrence Berkeley National Laboratory

University of California, Berkeley, CA 94720 USA srl@berkeley.edu, 510-643-5467, fax 510-643-1376

Pulses of soft x-rays produced by high harmonic generation are used to probe atomic and molecular processes through core level spectroscopy and to create isolated attosecond pulses to study the timescales of electronic dynamics. Ultrafast transient absorption is a new, versatile experimental platform, whereby the high harmonics are the probe, following a visible pulse that initiates the dynamics. The high harmonics are spectrally resolved after the sample to reveal the spectral transitions at various short delay times, to the attosecond limit. The high field ionization of Xe atoms at 800 nm is investigated by transient core level absorption probing on femtosecond timescales[1]. Measurements of both the spin-orbit population ratio and the alignment of the ground state of Xe ions are obtained and a breakdown of the adiabatic assumption is found. Electromagnetically induced transparency is of great interest for such properties as the slowing of the speed of light. Here, two states in He atoms, both of which undergo autoionization, are investigated by coupling the two levels with a high field 800 nm light pulse, while probing one of the transitions with soft X-ray transient absorption. The results show a small degree of both induced absorption and induced transparency [2]. Dibromomethane is ionized to the +1and +2 ionic charge states by a high field at 800 nm, and the time-resolved dissociative processes are observed by femtosecond transient X-ray absorption on the neutral and ionic molecules and atomic species containing Br atoms [3]. In a collaboration with the group of Ferenc Krausz in Munich, attosecond transient absorption measurements are performed on the high field ionization of Kr, revealing both half-cycle production of Kr ions and spin-orbit wave packet dynamics [4]. Wavelength-tunable attosecond pulses are generated on the leading edge of an 800 nm driver pulse by varying the focus intensity and carrier-envelope phase [5]. [1] Z.-H. Loh, M. Khalil, R. E. Correa, R. Santra, C. Buth, and S. R. Leone, “Quantum state-resolved probing of strong-field-ionized xenon atoms using femtosecond high-order harmonic transient absorption spectroscopy,” Phys. Rev. Lett. 98, 143601 (2007). [2] Z.-H. Loh, C. H. Greene, and S. R. Leone, "Femtosecond induced transparency and absorption in the extreme ultraviolet by coherent coupling of the He 2s2p (1Po) and 2p2 (1Se) double excitation states with 800 nm light," Chem. Phys. 350, 7 (2008). [3] Z.–H. Loh, and S. R. Leone, "Ultrafast strong-field dissociative ionization dynamics of CH2Br2 probed by femtosecond soft x-ray transient absorption spectroscopy," J. Chem. Phys. 128, 204302 (2008). [4] Z.-H Loh, E. Goulielmakis, A. Wirth, S. Zherebtsov, N. Rohringer, R. Santra, F. Krausz, and S. R. Leone (in preparation). [5] A. Jullien, T. Pfeifer, M. J. Abel, P. M. Nagel, M. J. Bell, D. M. Neumark and S. R. Leone, "Ionization phase-match gating for wavelength-tunable isolated attosecond pulse generation," Appl. Phys. B Lasers and Optics, 93, 433 (2008).

We-C

Probing Atomic Wavefunctions via Strong Field Light-Matter Interaction

D. Shafir 1, Y. Mairesse 2, B. Fabre2, J. Higuet 2, E. Mével 2, E. Constant2 , D. M. Villeneuve 3, P. B. Corkum 3, N. Dudovich1

1. Department of Physics of Complex Systems, Weizmann Institute of Science, Rehovot 76100, Israel. 2. CELIA, Université Bordeaux I, UMR 5107, 351 Cours de la Lib\'eration, 33405 Talence Cedex, France. 3. National Research Council of Canada, 100 Sussex Drive, Ottawa, Ontario K1A 0R6, Canada.

We will present an approach to perform correlated measurements of electronic wavefunctions

and will describe how the correlated properties of the measurement can be applied to probe

atomic states. The approach relies on the manipulation of an electron ion recollision process in a

strong laser field. We apply a two color field to direct the free electron's motion during one

optical cycle (see Fig. 1A). Manipulating a recollision process allows us to resolve the symmetry

of the atomic wavefunction with notably high contrast (see Fig. 1B).

The measurement, dictated by the strong laser field, provides a direct insight into its interaction

with the atom. This approach will have an important impact on molecular tomography and

extend it to more complex molecular orbitals. Since the method is closely related with attosecond

technology, time and space will combine in the future allowing dynamic imaging of a broad

range of atomic and molecular processes.

A. Schematic drawing of attosecond pulse generation with a two color field. The motion of the electron is

schematically described by the blue dashed line. The recollision projects the ground state into the optical frequencies

of the emitted pulse. B. Retrieved Neon mixed 2p orbital.

We-C

Photo induced conical intersections in molecular optical lattices: the phenomenon and its consequences

Nimrod Moiseyev

Schulich Faculty of Chemistry and Minerva Center of Nonlinear Physics in Complex Systems,

Technion - Israel Institute of Technology, Haifa 32000, Israel

Abstract

Conical intersections appear in the potential energy surfaces (PES) of molecules which consist of

more than two atoms. For principal reasons, no conical intersections exist in the case of free

diatomic molecules. We will show that diatomic molecules which interact with the standing laser

waves produce periodic arrays of laser induced conical intersections, such that the rovibrational

and the translational molecular motions are strongly coupled to each other. Similarly as for the

usual conical intersections in field free polyatomic molecules, also the laser induced conical

intersection introduces infinitely strong local non-adiabatic couplings between the involved

nuclear degrees of freedom. An effect of the laser induced conical intersections on trapping of

cold diatomic molecules by light and on the spectrum of the trapped molecules will be discussed.

Based on N. Moiseyev, M. Sindelka and L.S. Cederbaum, Fast Track Communication in J. Phys. B 41, 221001 (2008).

We-D

Imaging through a discrete system E. Suran1, F. Louradour1, A. Barthelemy1,

A. Kudlinski2, G. Martinelli2, Y. Quiquempois2, M. Douay2, A. Szameit3, T. Pertsch3

1 XLIM photonic department, UMR CNRS 6172, Limoges, 87 000, France 2 PhLAM Laboratory, UMR CNRS 8523, Villeneuve d’Ascq, 59 655, France

3 Institute of Applied Physics, Jena, 07743, Germany Email: eric.suran@xlim.fr

We present the first experimental realization of self-imaging in a discrete system. The device is made of two identical weakly coupled waveguide arrays with segmentation in between the two [1]. It is shown that the device operation is not perturbed by the boarder of the array so that the full array can serve for an image relay [2]. For the fabrication of the segmented waveguide arrays we used the femtosecond direct-writing technique. The total length of the arrays is 50 mm with a waveguide spacing of 16 µm and 20 µm in the one- and two-dimensional case, respectively. The length of the segmented area was 2.6 mm, while the period of the segmentation was chosen to be 16 µm. This results in a complete inversion of the global phase of the travelling field inside the array, so that the evolution dynamics is reversed and the input field is imaged onto the sample output facet. In future research we will also investigate the experimental implementation of 3D discrete imaging with coherent optical fiber bundles of larger length and larger number of optical cores. In this case the major limitation comes from a lack of perfect periodicity of the discrete array. That’s why we numerically investigate the impact of slight inhomogeneities upon discrete imaging. We show that transverse inhomogeneities strongly affect the propagation. However imaging is still possible.

Arrays of coupled waveguides with mid-span phase inversion open a real new opportunity for imaging with femtosecond excitations. The powers that can be transmitted before the onset of nonlinearity can be significantly higher than those compatible with single core or uncoupled multicore fibers. That advantage comes from the power sharing between several guides on the major part of the light path between the input face and output face of the component. We present numerical simulations of non linear propagation of femtosecond pulses inside the discrete imaging device and show a large reduction of nonlinear distortions. References [1] S. Longhi, Opt. Letters, 33, 473-475, 2008. [2] A. Szameit, Appl. Phys; Lett. 93, 181109, 2008. E. Suran, F. Louradour and A. Barthelemy thank Agence Nationale de la Recherche for its financial support in the frame of the SYDIMEN project.

We-D

Thursday February 12, 2009

Session Th-A Chair: Daniel Bloch

Th-B Chair: Barak Dayan

Th-D Chair: Ilya Averbukh

Towards Comprehensive Control of Atomic and Molecular Motion

Mark G. Raizen Center for Nonlinear Dynamics and Department of Physics The University of Texas at Austin, Austin, TX 78712, USA

The control of translational motion of all atoms and molecules has been a major scientific goal for many years, and its success would enable a wide range of fundamental and applied research. The most successful method to date has been laser cooling, as recognized by a Nobel Prize in 1997. Despite the enormous success of this method, it has been limited to a small set of atoms in the periodic table and excluded any molecules due to the basic requirement of a two-level cycling transition. In the past few years, we have developed in my group new approaches to the general challenge of trapping and cooling. Our starting point is the supersonic beam, which creates a very monochromatic but fast beam. This device, developed and used primarily by chemists, serves as a universal platform for atoms or molecules that are entrained in a noble gas carrier. Further developments of the supersonic beam by the group of Prof. Uzi Even now make it a compact and practical source of cold but fast atoms and molecules. To stop the beam, we developed a series of electromagnetic field coils, an atomic coilgun. This method can work on any paramagnetic species which includes 95% of the periodic table (in the ground or first metastable state). We have applied this approach to stop metastable atomic neon and molecular oxygen [1]. In parallel, the group of F. Merkt (ETH Zurich) has stopped atomic hydrogen. After the atoms or molecules are stopped, they can be stored in a magnetic quadrupole trap. The next challenge is to find a way to cool the atoms or molecules in the trap. Typical densities preclude the use of evaporative cooling which is also often limited by inelastic collisions, so a new approach is needed. We have developed a general method, based on the concept of a “one-way wall of light” that we first proposed in 2005. We realized this concept experimentally and have used it to compress atomic phase [2]. We showed that our method, single-photon cooling, is an exact realization of informational cooling as proposed by Leo Szilard in 1929. We create a Maxwell’s demon where each scattered photon corresponds to an atom that is trapped in an optical tweezer, and show that we operate near maximal efficiency limited only by trap dynamics [3]. We have shown theoretically that this method will work on any multi-level atom or molecule that can be magnetically trapped [4]. We therefore have developed a general two-step approach that should enable trapping and cooling of most of the periodic table and many molecules. We are now applying these methods towards trapping and cooling of hydrogen isotopes. The main scientific goal in my group is to trap atomic tritium for precision measurement of beta decay. This system could be used to determine the rest mass of the neutrino, one of the outstanding questions in contemporary physics. References 1. E. Narevicius, A. Libson, C. Parthey, I. Chavez, J. Narevicius, U. Even, and M. G. Raizen, Phys. Rev. Lett. 100, 093003 (2008). 2. G. N. Price, S. T. Bannerman, K. Viering, E. Narevicius, and M. G. Raizen, Phys. Rev. Lett. 100, 093004 (2008). 3. S. T. Bannerman, G. N. Price, K. Viering, and M. G. Raizen, submitted for publication, arXiv:0810.2239 4. E. Narevicius and M. G. Raizen, submitted for publication, arXiv:0808.1383

Th-A

Towards High Precision Spectroscopy of a Supersonic Beam of

Atomic Hydrogen

Christian G. Parthey*, Arthur Matveev*,#, Janis Alnis*, Nikolai Kolachevsky*,#, Thomas Udem*, and Theodor W. Hänsch*,&

*Max-Planck-Institut für Quantenoptik, Garching, Germany #P.N: Lebedev Physical Institute, Moscow, Russia &Ludwig-Maximilians-Universität, München, Germany

High-precision spectroscopy of the 1S-2S transition in atomic hydrogen and deuterium provides an essential contribution to the determination of the Rydberg constant, the Lamb shift, and the 2S hyperfine interval. Furthermore, it allows for studies of nuclear properties of the proton and the deuteron and has been amongst the various tests of QED [1]. Although the Q factor of the transition is about 2×10-15, the experimental uncertainty has not reduced below the level of 1.4×10-14, yet. The accuracy has been limited by the control of systematic effects. Among these, the dynamic Stark effect, the second order Doppler effect, and time of flight broadening are the most prominent ones. All mentioned systematics can be targeted by using hydrogen at lower velocities. Therefore, it has been a long time dream to use hydrogen at subkelvin temperatures. Unfortunately, no lasers are available to laser cool hydrogen. Although buffer gas cooling can be applied to hydrogen, the high collision rates with the background gas needed for cooling do not offer an environment suited for precision spectroscopy. Recent developments in controlling supersonic beams with pulsed magnetic fields [2-5] have been proven to provide an excellent source of cold hydrogen. We will implement the atomic coilgun to improve our precision spectroscopy experiment. [1] F. Biraben, arXiv: 0809.2985v1 [2] N. Vanhaecke, U. Meier, M. Andrist, B.H. Meier, and F. Merkt, Phys. Rev. A 75,

031402(R) (2007). [3] E. Narevicius, A. Libson, C.G. Parthey, J. Narevicius, I. Chavez, U. Even, and M.G.

Raizen, Phys. Rev. Lett. 100, 093003 (2008). [4] E. Narevicius, A. Libson, C.G. Parthey, I. Chavez, J. Narevicius, U. Even, and M.G.

Raizen, Phys. Rev. A 77, 051401(R) (2008). [5] S. D. Hogan, A.W. Wiederkehr, H. Schmutz, and F. Merkt, Phys. Rev. Lett. 101, 143001

(2008).

Th-A

Polarization resolved second-harmonic generation from a single CdTe quantum dot with record dimensions

Marcin ZIELINSKI,1,3 Dan ORON,2,3 Dominique CHAUVAT,1,3 and Joseph ZYSS1,3

(1) Laboratoire de Photonique Quantique et Moléculaire, Ecole Normale Supérieure de Cachan, 61, avenue du Président Wilson, 94230 Cachan CEDEX, France

(2) Department of physics of complex systems, Weizmann institute of science, Rehovot, 76100, Israël.

(3) D’Alembert Institute, Laboratoire Européen Associé NABI CNRS-Weizmann

Second-harmonic generation (SHG) microscopy has developed into a new field to investigate

noncentrosymmetry occurring in biological macromolecules. Recently, new nonlinear

nanoparticles, active in second-harmonic generation, have been synthetized both for probing

biological phenomena in cells or to develop new scanning microscopy configurations, based on

the functionalization of an AFM tip with a nonlinear nanoparticle. Among the material used to

make the nanoparticles are KTiOPO4, KnbO3, Li(FeO3)3, ZnO. The intrinsic nonlinearity of

these materials allow to detect nanoparticles with size above 30 nm and typically of the order of

100 nm. However, semiconductor materials are known to exhibit larger nonlinearities. Under the

same microscope, using non-centrosymmetric semiconductors should thus allow us to detect

smaller nanoparticles, within or below the 10 nm size range, which is well adapted to ultrahigh

resolution tip-based scanning microscopy, but which is also closer to the characteristic scale of

cellular biology. Here we present results on core/shell CdTe/CdS quantum dots of size less or

equal to 15 nm. We are not only able to detect SHG from a single nanoparticle, but also to

optimize the excitation wavelength for the Ti-Sa wavelength range and to check its crystalline

symmetry using nonlinear polarimetry (Figure 1).

Figure 1: Polarization response along two analysis directions of the second harmonic generation from a single

CdTe nanoparticle of size 15 nm.

Th-B

Phase synchronization in mutually coupled chaotic diode lasers

Y. Aviad1, I. Reidler1, W. Kinzel2, I. Kanter1, M. Rosenbluh1

1The Jack and Pearl Resnick Institute for Advanced Technology, Department of Physics, Bar-Ilan University, Ramat-Gan 52900,

Israel 2 Institut fur Theoretische Physik Universitat Wurzburg, Am Hubland 97074 Wurzburg, Germany

Semiconductor lasers with optical feedback have chaotically pulsating output behavior.

When two similar chaotic lasers are optically coupled, they can become synchronized in their

optical fluctuations. Our experimental work show that the synchronization is not only in the

amplitude and in the timing of the pulses but that the short pulses are also phase coherent with

each other. This is true even when the lasers are separated by distances much larger than their

coherence length. The synchronization of the optical phase of two mutually coupled chaotic

diode lasers is experimentally examined under isochronal and achronal conditions. We show that

the emergence of full or partial correlations in the chaotic laser intensities is accompanied by

similar optical phase correlations. The chaotic lasers are thus coherent with each other either

instantaneously (isochronal) or with a time delay between them equal to an integer multiple of

the optical propagation time between the lasers (achronal). Such synchronization is expected to

play an important role in cryptography and secure communications based on mutual coupled

chaotic lasers.

Phase coherence, as measured by fringe visibility of two isochronally synchronized semiconductor lasers.

Inset: The time-shifted intensity cross correlation of the two lasers.

Th-B

Fundamentals Functionalities and Applications of Cavity Solitons : Review on the achievements of the FunFACS FET-Project

R. Kuszelewicz Laboratoire de Photonique et de Nanostructures, CNRS-UPR20,

Route de Nozay, 91460 Marcoussis, France email : robert.kuszelewicz@lpn.cnrs.fr

Abstract : Cavity Solitons were demonstrated six years ago in semiconductor microresonators [1] in the frame of the European FET-project PIANOS. They consist in localized optical states, writable and erasable at arbitrary positions of the transverse plane of the resonator. As such they can be used as binary elements of optical information. They have the unique property of being sensitive to phase or amplitude gradients of the field under which they can drift and therefore introduce the property of motility and malleability of 2D binary information arrangements. This talk will give an extended review of the main results obtained during the course of the European FunFACS FET-STREP project [2]. It will discuss the challenges at stake and tend to give a reasonable perspective of possible applications. This project has run between 2005 and 2008. It aimed at greatly enhancing the scope of cavity soliton science and technology by realizing scientific breakthroughs with a large potential impact in opto-electronics. The key-demonstration was that of self-sustained cavity soliton lasers operating in the continuous as well as in the pulsed regime resulting from a 3-dimensional, longitudinal + transverse, localization of light. The objectives of FunFACS were organized so as to cover a large panel of theoretical and experimental studies ranging from fundamental light-matter non linear dynamics in microresonators to the demonstration of embryonic all-optical functionalities such as soliton-based all optical delay line, sources of pulse trains on demand or disorder mapping in photonic devices by using cavity solitons.

Fig. 1 : Scheme of an all-optical delay line based on CS.

The principal schemes were retained under the conditions of meeting the requested criteria for the observation of CS : bistability is introduced either by the simultaneous presence of gain and saturable absorption, or by reinjection via a frequency-selective element ; a large Fresnel number is met by either using microresonators or extended cavities close to the self-imaging configuration ; longitudinal localization is obtained via the classical Q-switching or mode-locking mechanisms. The consortium was composed of many of the most active European groups working on the field with theoretical, experimental and material expertise and realizing the state-of the-art on the subject : INFM (CNR), Univ. of Strathclyde- Glasgow, INLN-Nice (CNRS/UNSA), Univ. Libre de Bruxelles LAAS-Toulouse (CNRS), ULM-Photonics (Philips), and LPN-Marcoussis (CNRS) [1] S. Barland et al., Nature,. 419. , 689 (2002) [2] http://www.funfacs.org

Th-B

Coherent anti-Stokes Raman scattering (CARS) in a microcavity

F. Billard1, D. Gachet2 and H. Rigneault* Institut Fresnel, Mosaic group, CNRS UMR 6133, Université Paul Cézanne, Aix-Marseille III, Domaine

universitaire St Jérôme, 13397 Marseille cedex 20, France * Corresponding author: herve.rigneault@fresnel.fr

Coherent Coherent anti-Stokes Raman scattering (CARS) is a powerful tool for molecular label-free analysis even if it still lacks sensitivity. Several strategies have been proposed to enhance the CARS signal and most of them are based on local enhancement of the density of states. Thus, single molecule sensitivity has even recently been claimed1. Nonetheless, due to the locality of enhancement, these approaches are poorly compatible with imaging as such applications require delocalization of the field enhancement. Resonators such as a Fabry-Perot cavity are good candidates to increase CARS sensitivity in this purpose. We have theoretically and experimentally investigated coherent anti-Stokes Raman scattering (CARS) in a Fabry-Perot cavity. We focused on design where the cavity is transparent for pump and Stokes beams but reflective for the generated anti-Stokes beam. Such configuration has great interest for spectroscopic studies. The theoretical part has been carried on by implementing the so-called “Image dipole method”2,3. This method cannot predict any signal enhancement due to enhanced molecular emission rate since it can only predict signal enhancement due to radiation pattern modification. It does not matter as dipole confinement and density of states modifications are weak in studied cases. The cavity modifies CARS far-field radiation patterns in two ways. First, the patterns are now ring shaped. In particular, the CARS emission is more directive than in free-space. Second, for bulk media, symmetry between Epi and Forward emission is found. These two features allow the use of low numerical aperture collection objectives and Epi detection. The CARS signal stability as a function of the cavity detuning is highly dependent on the cavity width. Two main regimes are found. For a large cavity, the signal is stable in respect of the cavity length and/or wavelength but only low enhancement is expected. For a small cavity, the signal is highly unstable but higher enhancement can be reached4. Experimentally, Forward far-field radiation pattern modification by the cavity has been demonstrated. Moreover, experimental modulation of the Forward/Epi signal as a function of the cavity detuning has been shown, in accordance with theoretical predictions. In a last study, we demonstrate that no parametric gain is reached. The signal modification is only due to spatial redistribution of the signal5. Such a cavity could find applications in microscopy to improve signal collection or to work with Epi detection for instance. Moreover, this study illustrates the influence of electromagnetic environment on photonic emission processes. References [1] T.-W. Koo, S. Chan and A. A. Berlin, Opt. Lett. 30, 1024 (2005). [2] J. P. Dowling, M. O. Scully and F. de Martini, Opt. Comm. 82, 415 (1991). [3] M. Marrocco, Laser Physics 17, 935 (2007). [4] F. Billard, D. Gachet and H. Rigneault, submitted. [5] D. Gachet, F. Billard and H. Rigneault, manuscript in preparation. 1. Current address: Institut Carnot de Bourgogne, UMR CNRS 5209, Département « Optique, interaction Matière-

Rayonnement», Université de Bourgogne, 9, Avenue Savary, B.P. 47 870, 21078 Dijon cedex, France 2. Current address: Department of Physics of Complex Systems, Weizmann Institute of Science, Rehovot 76100, Israel

Th-B

High accuracy space-time positioning beyond the standard quantum noise limit

C. Fabre, N. Treps, G. De Valcarcel, G. Patera, O. Pinel, B. Chalopin, B. Lamine

Laboratoire Kastler Brossel

Université Pierre et Marie Curie-Paris6, ENS, CNRS 4 Place Jussieu, CC74, 75252 Paris cedex 05, France

fabre@spectro.jussieu.fr Accurate space-time positioning is an important issue of physics, both from a fundamental perspective and for its numerous practical applications. Considering successively the spatial and temporal positioning methods using optical methods, we demonstrate that there is a basic quantum limit to their accuracy, independent of the measurement protocol, when one uses shot noise limited light. We will then show how to reach this standard quantum noise limit. Finally we will show that his limit can be circumvented using a specifically designed quantum-entangled non-classical light beam, resulting from the superposition of a coherent state and a vacuum squeezed state in two different spatial or temporal modes. An OPO synchronously pumped by a mode-locked laser (the OPO cavity length is equal to the spatial distance between successive pulses) turns out to be a very efficient device to produce squeezed states when the pump intensity is slightly less than the oscillation threshold. Squeezing is effective not in a single frequency mode, as usual, but instead in a whole set of "super-modes", which are well defined linear combinations of signal modes of different frequencies, i.e. of trains of pulses of well defined shapes. Such modes are precisely the ones needed to improve time positioning measurements. We will also report on the progress of the experiment that we are currently developing to produce such squeezed and/or entangled frequency combs.

We finally describe a scheme that allows us to beat the standard quantum limit in clock synchronisation and ranging measurements, which could be used in space experiments where losses are small and high precision needed. It is based on the use of a homodyne technique with squeezed frequency combs and local oscillator pulses in appropriately shaped super-modes, and turns out to be less sensitive to phase noise than other proposed techniques based on few-photon entangled states. N. Treps, N. Grosse, C. Fabre, H. Bachor, P.K. Lam, “The "Quantum Laser Pointer"", Science 301, 940 (2003) V. Delaubert, N. Treps, C. Fabre, H. Bachor, P. Réfrégier, “Quantum limits in image processing” Europhys. Letters 81 44001 (2008) B. Lamine, C. Fabre, N. Treps, “Quantum improvement of time transfer between remote clocks” Phys. Rev. Letters 101 123601(2008)

Th-C

How a photon can be inside a Mach-Zehnder interferometer without ever being on any path which leads towards it?

L. Vaidman, Raymond and Beverly Sackler School of Physics and Astronomy,Tel-Aviv University, Tel-Aviv 69978, Israel A controversy about counterfactual computation [1,2] reveals a paradoxical feature of a pre- and post-selected quantum particle: it can reach a certain location without being on the path that leads to and from this location. Hosten proposed a counterfactual computater (CFC), i.e. a device which yields the outcome of a computation without running. This is an improvement of the previous proposal [3], which used an interaction-free measurement (IFM) scheme [4] for constructing a CFC computer, but only in the case of one particular outcome. The core of the controversy is that it is possible to perform counterfactual computation CFC when the process of computation is just the passage of the photon through the device without any change in the device and without absorption of the photon. The scheme, described in the figure, consists of one Mach-Zehnder interferometer nested inside another, with the computer placed in one arm of the inner interferometer. The inner interferometer is tuned by a π-phase shifter in such a way that if the outcome is 0, i.e., the computer is transparent, there is destructive interference towards the output beam splitter of the large interferometer. If the outcome is 1, the photon can reach the output beamsplitter of the external interferometer, which is tuned in such a way that there is then destructive interference toward detector D1. Consider now a run of the device in which a single photon enters the interferometer and is detected by D1. In this case we get the information that the result of the computation is 0 and apparently the photon did not pass through the computer. On the other hand, this setup is an implementation of an arrangement usually known as the “three-box paradox” [5]. The paradox is that according to a counterfactual analysis, at the intermediate time the particle would be found with certainty inside the computer if it were searched for there. Using weak measurements [6,7] one can directly measure whether or not the photons actually do pass through the computer and they show that the photon did not enter the interferometer, the photon never left the interferometer, but it was there!

[1] O. Hosten et al., Counterfactual quantum computation through quantum interrogation, Nature 439, 949 (2006). [2] L. Vaidman, Impossibility of the counterfactual computation for all possible outcomes. Phys. Rev. Lett. 98, 160403

(2007). [3] G. Mitchison and R. Jozsa, Counterfactual Computation. Proc. Roy. Soc. Lond. A 457, 1175 (2001). [4] A. C. Elitzur and L. Vaidman, Quantum Mechanical Interaction-Free Measurements, Found. Phys. 23, 987 (1993). [5] Y. Aharonov and L. Vaidman, Complete description of a quantum system at a given time, J. Phys. A 24, 2315

(1991). [6] Y. Aharonov and L. Vaidman, Properties of a quantum system during the time interval between two measurements,

Phys. Rev. A 41, 11 (1990). [7] K.J. Resch, et al., Experimental realization of the quantum box problem, Phys. Lett. A 324, 125 (2004).

Th-C

Hanbury Brown-Twiss Interferometry with Interacting Photons

Y. Bromberg, Y. Lahini, E. Small and Y. Silberberg Department of Physics of Complex Systems, The Weizmann Institute of Science, Rehovot, Israel

Five decades ago Hanbury Brown and Twiss (HBT) have shown that the angular size of stars can be measured by correlating the intensity fluctuations of two detectors at different locations [1]. Since then, intensity correlation measurements have been extended to many other particles beyond photons, such as electrons [2], atom matter-waves [3], and pions [4]. An implicit and important assumption in the analysis of HBT interferometry is that the particles involved are interaction free. Here we study the effects of interactions between the propagating particles on the intensity correlation. Specifically, we consider optical HBT interferometry in a nonlinear medium which induces interactions between the photons.

Since the HBT effect is essentially a wave phenomenon, it can be analyzed adequately in the optical domain by classical wave theory. Interactions between the photons are introduced by considering the propagation of light in a medium with intensity-dependent index of refraction. Here we experimentally study the HBT correlations in the presence of focusing nonlinearity (attractive interactions) and defocusing nonlinearity (repulsive interactions). In general, we find that focusing nonlinearity tends to sharpen the intensity correlation function g(2)(Δ), i.e. the correlation peak grows and its width decreases with nonlinearity (Fig. 1a). Most importantly, the width of the correlation function is no longer a measure for the size of the source, but is purely determined by the properties of the medium. For a defocusing nonlinear medium the correlation profile flattens: the width of g(2)(Δ) remains fixed and its peak decreases with increasing nonlinearity (Fig. 1b). Repulsive interactions therefore tend to diminish the HBT correlation enhancement.

Fig 1. The measured intensity correlation function g(2)(Δ) of light propagating in a nonlinear medium, for different input powers. (a) In a two dimensional (1+1) slab with focusing (Kerr) nonlinearity. (b) In a three dimensional medium with defocusing (thermal) nonlinearity. In the nonlinear regime, g(2)(0)>2 for the focusing nonlinearity and g(2)(0)<2 for the defocusing nonlinearity.

The setup studied in this work is a prototype for a variety of systems described by the

nonlinear Schrödinger equation (or equivalently the Gross-Pitaevskii equation), such as Bose-Einstein condensates. We believe that the role of interactions on intensity correlations described here are general, and may apply to such systems. [1] R. Q. Twiss and R. Hanbury Brown, "Correlations between photons in two coherent beams of light." Nature, 177, 27–29, 1956. [2] W. D. Oliver, J. Kim, R. C. Liu and Y Yamamoto, "Hanbury Brown and Twiss-type experiment with electrons." Science 284, 299–301 (1999) [3] I. Bloch, J. Dalibard, W. Zwerger, "Many-Body Physics with Ultracold Gases." arXiv:cond.mat/0704.3011 [4] G. Baym, "The physics of Hanbury Brown-Twiss intensity interferometry: from stars to nuclear collisions." Acta Phys.Polon. B29 (1998)

1839-1884, arXiv:nucl-th/9804026v2.

Th-C

−150 −100 −50 0 50 100 150

1

1.5

2

2.5

3

Δ

g(2) (Δ

)

Focusing Nonlinearity

(a) 0.5mW2mW4mW7mW

−100 −50 0 50 100

1

1.2

1.4

1.6

1.8

2

2.2Defocusing Nonlinearity

Δ

g(2) (Δ

)

(b) 10mW300mW600mW1520mW ( ) 2

)2( )()(I

xIxIg

Δ+=Δ

Friday February 13, 2009

Session Fr-A Chair: Reuven Kuszelewicz

Extreme Light Physics

by Gérard A. Mourou

Institut de la Lumière Extrême ENSTA Palaiseau 91761

ELI (Extreme Light Infrastructure) will be the first infrastructure dedicated to the

fundamental study of laser-matter interaction in a new and unsurpassed regime of

laser intensity: the ultra-relativistic regime (IL>1023 W/cm2). At its centre will be

an exawatt-class laser ~1000 times more powerful than either the Laser

Mégajoule in France or the National Ignition Facility (NIF) in the US. In

contrast to these projects, ELI will attain its extreme power from the shortness of

its pulses (femtosecond and attosecond). The end goal will be the investigation of

the structure of matter from atom to vacuum. It will serve to study a new

generation of compact accelerators delivering energetic particle and radiation

beams of femtosecond (10-15 s) to attosecond (10-18 s) duration. Relativistic

compression offers the potential of intensities exceeding IL>1025 W/cm2, which

will challenge the vacuum critical field as well as provide a new avenue to

ultrafast attosecond to zeptosecond (10-21 s) studies of laser-matter interaction.

ELI will afford wide benefits to society ranging from improvement of oncology

treatment, medical imaging, fast electronics and our understanding of aging

nuclear reactor materials to development of new methods of nuclear waste

processing.

Fr-A

High Intensity Laser filamentation and Plasma Lensing Shmuel Eisenmann1, Anatloly Pukhov1, Joe Peñano2, Phil Sprangle2 and Arie Zigler1

1Racah Institute of Physics, Hebrew University, Jerusalem, Israel 91904 2Plasma Physics Division, Naval Research Laboratory, Washington, DC 20375

One of the remarkable properties of the ultrashort filaments propagating in ambient air is that

they can travel tens or even hundreds of meters producing fine and as often assumed relatively uniform ionized channels on their wake. The ability to generate in this way very long thin plasmas is clearly of significant interest for the use of ultrashort pulses to guide and trigger electric discharges in large systems. Moreover, the generated plasma plays a substantial role in the dynamics of the propagating light filament.

Here we report the first mapping of the longitudinal fine structure of plasma generated by a single high-intensity filament. Using our recently developed method of filament stabilization [1], we create a single, spatially-stable from shot to shot filament and measure its profile at different locations along the propagation direction [2]. Our measurements reveal that the electron density in the channel varies by more than three orders of magnitude along a distance of several meters. Moreover it exhibits a post-ionization regime, where filament does not diverge although almost no plasma is present. This is in agreement with recent theoretical predictions [3].

We have also observed the effect of an energy reservoir [4]. We do so by allowing only the core of filament to pass through a pin-hole and monitor the plasma density after it. These measurements demonstrated that filament propagation is sustained by the surrounding laser energy reservoir. It was also observed in simulations that the critical power for self-focusing is effectively increased relative to that of a Gaussian pulse. The increase in self-focusing power is mainly due to the non-Gaussian shape of the filament and not the presence of a plasma. Termination of the filament occurred when ionization loss reduced the laser power below this effective self-focusing power.

Figure 1: Simulated (solid black curve) and experimentally measured (dashed red curve) normalized electron density as a function of distance. (a) shows the result of un-apertured propagation, i.e., no primary pinhole. (b) shows the result for apertured propagation for a primary pinhole.

[1] G. Fibich, S. Eisenmann, B. Ilan, A. Zigler , Opt. Lett. 29, 1772 (2004) [2] S. Eisenmann, A. Pukov and A. Zigler, Phys. Rev. Lett., 98, 155002 (2007) [3] S. Champeaux and L. Bergé, Phys. Rev. E 71, 046604 (2005) [4] S. Eisenmann, Joe Peñano, Phil Sprangle and Arie Zigler, Phys. Rev. Lett. 100 155003 (2008)

Fr-A

Laser plasma accelerator: towards a high quality electron beam

V. Malka, J. Faure, Y. Glinec, C. Rechatin, A. Norlin, A. Lifschitz Laboratoire d'Optique Appliquée, EP, ENSTA, CNRS, , 91761 Palaiseau, France

Email : victor.malka@ensta.fr

Compact accelerators based on the use of lasers and plasmas produced today high quality and quasi mono-energetic electron beams [1,2]. The efficient bubble regime of acceleration that we have demonstrated few years ago is now currently working in many laboratories over the world. More recently stable and quasi mono-energetic electron beams have been demonstrated at LOA using by colliding two laser pulses in under-dense plasma [3]. This last approach seems very promising for future applications because of the stability of the electron beam and the easy control of its parameters. I will present the different regimes of acceleration and relevant applications that have been recently considered at LOA : For medicine to treat the cancer by radiotherapy, for fundamental studies in radiobiology (short-time-scale), for chemistry (radiolysis in the femtosecond range), for material science in automobile and aeronautic industries (for non-destructive dense matter inspection by radiography), and finally for accelerator physics.

Figure 1 : scheme of principle of the bubble regime. The laser pulse evacuates electrons creating a bubble structure which accelerates electrons during a very short time and in a very small area.

Figure 2 : scheme of principle of the colliding laser pulses. The beating of the two laser pulses which counter propagates heats electrons. Electrons are then trapped by the wakefield driven by the pump laser beam

References [1] Dream Beams issue of Nature 431, 38 - 544 (2004). [2] A.Pukhov, J.Meyer-ter-Vehn, Appl. Phys. B74,355(2002). [3] J. Faure et al., Nature 444, 737 (2006).

Fr-A

Monday February 9, 2009

POSTER SESSION 1

Mo-1 - Mo32

Photon-number-resolving detection using a detector array for use in quantum optics

I. Afek, A. Natan, O. Ambar and Y. Silberberg

Many experiments in quantum optics require knowledge of the exact number of photons in a

pulse of light. Such experiments include the proposal for linear optics quantum computation and various suggestions for obtaining the Heisenberg Limit with multi-photon entangled states. A number of approaches have been taken to construct detectors with photon number resolution, these include cryogenic devices such as the VLPC [1] a superconducting bolometer [2] and time multiplexing [3]. Here we present an experimental study of the use of a Multiple Pixel Photon Counter (MPPC) (Hamamatsu) for photon number resolved single photon measurements. We show that the MPPC is an attractive candidate for use in quantum optics.

The MPPC consists of an array of Avalanche Photo Diode (APD) pixels operating in Geiger mode. Each APD pixel outputs a pulse signal when it detects a photon. The signal output of the MPPC is the total sum of the outputs from all APD pixels. To evaluate the MPPC we used a pulsed laser (Tsunami, Spectra-Physics) λ = 810 nm with a rep rate of 1 MHz reduced from 80 MHz using a pulse picker (Pulse Select, APE).

The MPPC has very good photon number resolution up to N=10 as can be seen in Fig 1. In addition it can be operated at the relatively high rep rate of ~1MHz. The MPPC does not require any type of cooling or additional optical auxiliary setup, making it much simpler and cheaper than the other available photon number resolving solutions. We obtained a dark count rate of ~0.003 photons per pulse using gated detection. In addition, the MPPC pixels exhibit a small degree of cross-talk which may be easily compensated for by using a method which we have developed, see Fig 2.

The main limitation of the MPPC is that its peak detection efficiency is currently at 400 nm

with an efficiency of only ~10 % at 800 nm. We expect that the MPPC will be shortly available with peak efficiency at 800 nm making it an invaluable tool for quantum optics in the near future. [1] J. Kim, S. Takeuchi, Y. Yamamoto and H.H. Hogue 1999, Appl. Phys. Lett.,74 902 [2] B. Cabrera et. al. 1998, Appl. Phys. Lett.,73 735 [3] D. Achilles et. al. 2004, J. Mod. Opt. ,51 1499

Mo-1

Fig 1: Pulse height histogram measured with MPPC for average photon number nav = 2.3.

Fig 2: Measured photon number distribution (bars) and best fit for coherent state (squares)

for nav = 1.65. Left pane: raw data. Right pane: data corrected for cross-talk.

Photon Localization and Dicke Superradiance in Atomic Gases§

E. Akkermans1,2, A. Gero1, and R. Kaiser3

1Department of Physics, Technion—Israel Institute of Technology, Haifa 32000, Israel 2Department of Applied Physics and Physics, Yale University, USA

3Institut Non Line´aire de Nice, UMR 6618 CNRS, France We study photon emission rates from an atomic gas while taking into account cooperative effects, such

as superradiance and subradiance, between the scatterers. To this purpose we consider N identical

atoms, placed at random positions in an external radiation field. The photon escape rates from the

atomic gas are derived by diagonalizing an N×N Euclidean random matrix U for a broad range of

sample size and disorder strength. For a three-dimensional geometry Uij = sin(xij) / xij , while for a one-

dimensional gas Uij = cos(xij), where xij is the dimensionless random distance between any two atoms.

A scaling function, which measures the relative number of states having vanishing escape rates, is

introduced. We find out that for a large sample of three-dimensional gas the photons undergo a

crossover from delocalization towards localization rather than a disorder-driven phase transition as for

Anderson localization. By using a stochastic Markov model, we show that photon localization is

primarily determined by cooperative effects and not by disorder, and a disorder-induced phase

transition is unlikely to take place. For one dimensional geometry, due to the periodic nature of the

coupling matrix, the single atom limit is never reached and the photons are always localized.

This crossover from delocalization towards localization also provides an interesting link to the recently

studied "small world networks" which exhibit a crossover, rather than a phase transition, between

regular (ordered) lattices and random networks.

§E. Akkermans, A. Gero, and R. Kaiser, Phys. Rev. Lett. 101, 103602 (2008)

Mo-2

Incoherent Surface-Solitons in Effectively- Instantaneous Nonlinear Media Barak Alfassi, Carmel Rotschild, and Mordechai Segev

Physics Department and Solid State Institute, Technion, Haifa 32000, Israel eorddba@tx.technion.ac.il

Surface waves, propagating at the interface between two media with different optical properties, are intriguing phenomena. Optical surface wave were studied both in the linear domain [ 1, 2, 3], and in the nonlinear domain, [ 4, 5, 6]. However, until recently, it was believed that incoherent spatial solitons can exist only in a non-instantaneous nonlinearity whose the response time τ is much slower than the fluctuation time tc of the incoherent field (τ >>tc). However, nonlocal nonlinearities can overcome this obstacle, as was recently proposed and demonstrated [ 7 8].

Here, we present the first experimental and theoretical study of incoherent surface-solitons in instantaneous nonlocal nonlinear media: self-trapped incoherent beams propagating between linear and a nonlocal effectively-instantaneous nonlinear medium. As a model system for a long-range nonlocal nonlinear medium, we use the thermal nonlinearity of lead glass [ 8]. Figure 1 shows a sketch of a sample of width 2d with all the relevant boundary conditions [ 6]. We first neglect the interference terms and find the modes forming an incoherent solitons in non-instantaneous nonlinearities (Fig. 2a,b). The linear diffraction of such beam is depicted in (Fig 2c). Then, we use those modes (Fig.2a) as the initial condition to simulate surface soliton in our instantaneous nonlinearity. Under these conditions, one can think of an incoherent beam as an ensemble average over a sequences of different realizations r =1,2… , each of a duration ct . Fig. 2d shows the simulated propagation of three random realizations. Although each realization has a different initial intensity distribution and is propagating at a different trajectory, all of them are self trapped near the interface. The ensemble average over 200 realizations is depicted in Fig. 2e-f, the time-averaged beam is self-trapped, forming a incoherent surf-soliton that showing no evidence of broadening or statistical nonlinear diffraction, as is the case for incoherent bulk soliton [ 7, 8]. Experimentally, we pass an 80µm FWHM 488nm coherent laser beam through a diffuser and then launch it into a lead-glass sample of dimensions 2x2x80 mm3. The experimental results, depicted in Fig 3, show (a) an incoherent (ensemble-averaged) surface soliton, (b) an incoherent input beam attracts to the surface, (c) linear diffraction of such beam, and (d) a single realization of the multimode surface waves.

To conclude, we presented the first experiments & theory of surface-solitons in instantaneous nonlocal nonlinearities. 1. W. L. Barnes, A. Dereux, and T.W. Ebbesen, Nature 424, 824 (2003) 2. P. Yeh, A. Yariv, and A.Y. Cho, Appl. Phys. Lett. 32, 104 (1978). 3. D. Artigas, and L. Torner, Phys. Rev. Lett. 94, 013901 (2005). 4. G. S. Garcia Quirino et al., Phys. Rev. A 51, 1571 (1995); M. Cronin-Golomb, Opt. Lett. 20, 2075 (1995). 5. S. Suntsov, et al., Phys. Rev. Lett. 96, 063901 (2006). 6. B. Alfassi, et al., Phys. Rev. Lett. 98, 213901 (2007); A. Barak, et al., Opt. Lett. 32, 2450 (2007). 7. O. Cohen, H. Buljan, T. Schwartz, J. W. Fleischer, and M. Segev, Phys. Rev. E, 73, 015601 (2006). 8. C. Rotschild, T. Schwartz, O. Cohen, and M. Segev, Nature Photonics 2, 371 - 376 (2008).

Mo-3

Fig. 2.

Fig. 1.

Fig. 3.

Diode-pumped alkali vapor lasers: the next generation of high power lasers?

B. D. Barmashenko and S. Rosenwaks

Department of Physics, Ben-Gurion University of the Negev, Beer-Sheva 84105, Israel Diode-pumped alkali lasers (DPALs) convert un-phased low beam quality radiation from diode laser arrays into coherent, high quality ~ 800 nm wavelength radiation of alkali (Cs, Rb) atoms. The diode laser in-band pumping of the higher fine-structure level 2P3/2, via the D2 (2S1/2 → 2P3/2) transition, is followed by rapid relaxation of 2P3/2 to the 2P1/2 fine-structure level and lasing on the D1 (2P1/2 → 2S1/2) transition. DPALs developed during the last several years have attracted increasing attention because of their potential to achieve high power with a high quality beam.

For currently developed low power (< 100 W) DPALs there is no need to replenish the gas mixture. However, at higher, e.g., ~ 100 kW powers, the heat release due to relaxation between the fine-structure levels of the alkali atoms reaches several kW and there is a need to flow or at least transport the gas in a closed system to decrease the temperature.

We are currently developing a model of a gas flow DPAL with the flow direction either transverse (perpendicular) or parallel to the optical axis of the resonator. The gain g and the available lasing power Pav in such systems are strongly non-uniform in the transverse direction due to the following reasons: Firstly, in the currently used systems the pumping beam is focused into the alkali-vapor cell so that the diameter of the pumping beam waist (< 100 μm) is smaller than both the mirror aperture and the laser beam waist. As a result the pumping rate and population inversion strongly change in the transverse direction. Secondly, in transverse flow DPALs the temperature increases in the flow direction. Due to the quasi-equilibrium between the fine-structure levels of the alkali atoms the temperature strongly affects the population of the upper laser level 2P1/2. This effect is especially important in Cs where the spin-orbit splitting EΔ is 800 K, the initial temperature T = 450-500 K and in a static cell it might be a few hundreds K higher. As a result, even if the cell is pumped by many diodes and the pumping is spatially uniform, both g and Pav strongly change in the transverse direction and depend on the flow velocity.

For the simplest case of the spatially uniform pumping we derived the following expression for the small signal gain on the lasing D1 transition

Athbb

bthstim n

IITkETkETkE

IIg)/)](/exp(3[1)/exp(

1)/exp()1/(

Δ++−Δ−Δ

−= σ , (1)

where stimσ is the stimulated emission cross section, I the intensity of the pumping beam,

1)/exp()/exp(2

−ΔΔ+

≡TkE

TkEhIb

b

absth τσ

ν , the threshold pumping intensity and nA the density of the alkali atoms.

It is seen that for small EΔ , due to the factor 1)/exp( −Δ TkE B , g strongly decreases and Ith strongly increases with increasing T. Hence it is indeed very important to avoid the excessive heating of the system, i.e., to flow the alkali vapor.

We calculated the small signal gain and temperature spatial distributions for transverse flow DPALs and their dependence on the power and diameter of the pumping beam and the flow velocity, and found the optimal beam and flow parameters corresponding to the maximum gain and minimum temperature gradients. The optimal system geometry and pumping parameters for high power operation are predicted.

Mo-4

Nonlinear optics in structured functionalized waveguide array

Nadia Belabas*1, Juan Ariel Levenson1, Christophe Minot2,1 and Jean-Marie Moison1 1 Laboratory of Photonics and Nanostructures -UPR20 CNRS, Route de Nozay, Marcoussis, F-91460, France

2Institut Telecom / Telecom ParisTech, 46 rue Barrault, 75634 Paris Cedex 13, France *Corresponding author: nadia.belabas@lpn.cnrs.fr

Manipulation of light propagation in the guided regime has been pursued for a long time [1] to combine the best of two worlds (the control of propagation of the guided regime with the flexibility of free-space design).

Fig 1 Coupling in homogeneous arrays (grey frame, left) enables diffraction engineering and soliton creation and steering in the non linear regime. Structuring the coupling constant (green frame, right) opens a whole world of signal processing functions. We show how patterning the coupling constant between neighboring waveguides leads to a complete set of signal processing functions such as redirecting, guiding, focusing, and routing (Fig 1 right) in contrast with demonstration of stimulating effects in the literature [2] involving mostly propagation in homogeneous and infinite arrays (Fig 1 left). We detail how discrete photonics in such a functionalized space are similar but not identical to their continuous counterparts. Building blocks for discrete photonics device are thus simulated and open new routes to develop alloptical signal processing in the linear and non-linear regime. Finally we exemplify the benefit of patterning the coupling constant on the paradigmatic problem of commuting and modulating light flow via a controlling beam (Fig 2). 1) The pump power threshold associated to usual schemes [3,4] involving homogeneous waveguide arrays can be significantly lowered when divergence of the pump is suppressed using a channel of higher coupling constant between two semi-infinite barrier of lower coupling constant [5]. 2) One conceptual step further, tuning the resonances of a double barrier structure is demonstrated to yield a threshold-less device whose transmission curve can be, in addition, inverted by tuning the incidence angle on the device (Fig 2).

Fig 2 Combining a structured functionalized space with non linear optics in coupled waveguide arrays. The red arrow represents the pump field. Orange curve and corresponding input field arrow of the device sketched in the gray frame: homogeneous array approach in the literature. Blue curves and arrow in the corresponding sketch: structuring the coupling constant to suppress the divergence of the pump. Green curves and arrows in the corresponding sketch: accessing the levels of discrete Fabry-Perot for a controllable threshold-less modulator.

Mo-5

1. A. L. Jones J. Opt. Soc. Am. 55, 261 (1965). S. M. Jensen, IEEE J. Quantum Electron. QE-18, 1580 (1982). A. B. Aceves and M. Santagiustina Phys. Rev. E 56, 1113 (1997). I. Garanovich, A. Sukhorukov, and Y. Kivshar Opt. Express 13, 5704-5710 (2005) 2. D. N. Christodoulides, F. Lederer and Y. Silberberg, Nature 424, 817-823 (2003). J. Fleischer, G. Bartal, O. Cohen, T. Schwartz, O. Manela, B. Freedman, M. Segev, H. Buljan, and N. Efremidis, Opt. Express 13, 1780-1796 (2005) 3. D. N. Christodoulides and E. D. Eugenieva Phys. Rev. Lett. 87, 233901 (2001). 4. J. M. Moison and C. Minot, French Patent n° 07 54872 (2007). Nadia Belabas, Sophie Bouchoule, Isabelle Sagnes, Juan Ariel Levenson, Christophe Minot and Jean-Marie Moison submitted (2008) 5. J. M. Moison and C. Minot, French Patent n° 08 05307 (2008). J. M. Moison, N. Belabas, C. Minot, and J. A. Levenson to be submitted (2008)

Strong Field Coherent Control Using 2D Spatio-Temporal Mapping

B. D. Bruner, H. Suchowski, and Y. Silberberg Dept. of Physics of Complex Systems, Weizmann Institute of Science, Rehovot, 76100 Israel e-mail: Barry.Bruner@weizmann.ac.il

Strong field multiphoton excitation in a three level resonant system was controlled by a 2D spatio-temporal scheme, in which quadratic phase and a second, arbitrary phase parameter are scanned using a pulse shaper. The parameter space is mapped onto a two-dimensional landscape, as described in detail in our earlier work [1]. In the present experiment, a 100 fs ultrashort laser pulse laser centred at 780 nm covered both the 5S1/2 5P3/2 (780 nm) and the 5P3/2 5D1/2 (776 nm) resonant transitions in Rb85. A π-step phase was scanned across the spectral envelope using a programmable liquid crystal Spatial Light Modulator (SLM), aligned in a standard 4-f configuration.

Fig. 1. (left) 2D spatio-temporal maps of Rb85. The excited state fluorescence (from the 5D1/2 level) is plotted in a 2D grid as a function of π-step position (vertical axis) and the quadratic spectral phase (GDD) of the excitation pulse (horizontal axis). The peak intensities at zero GDD are (a) 130, (b) 60, (c) 24, (d) 10 GW/cm

2

. (right) Population transfer in a dressed three level system using chirped pulses. Several key features emerge in the weak-to-strong field mappings. The maximum enhancement does not occur at zero GDD, but rather for combinations of specific π-step and GDD values (also seen from dressed state picture in Ref. [2]). For strong fields, the adiabatic population transfer occurs for at negative GDD via a process that is analogous to the counterintuitive pathway in STIRAP. The resonant transition frequencies are strongly dependent on the fluence. As the fluence is increased, the resonant enhancement features broaden and shift from their intensity independent values and acquire a pronounced curvature for small GDD. These spatio-temporal mappings should be an effective method for strong field coherent control in a variety of multilevel systems. [1] H. Suchowski, A. Natan, B. D. Bruner, Y. Silberberg, J. Phys. B. 41 (7), 074008/1-9 (2008). 2] M. Wollenhaupt, A. Praekelt, C. Sarpe-Tudoran, D. Liese, T. Baumert, Appl. Phys. B 82 (2), 183-188 (2006

Mo-6

Strong Field Atomic Population Transfer Stephen D. Clow1, Carlos Trallero-Herrero2, Thomas Bergeman1, and Thomas Weinacht1

1Department of Physics, Stony Brook University, Stony Brook, NY, 11794, USA 2National Research Council of Canada, 100 Sussex Drive, Ottawa, Canada

There is significant interest in controlling atomic and molecular dynamics using shaped ultrafast laser pulses, an important aspect of which is selectively populating a particular target state with high efficiency. To achieve this beyond the limits of single-photon excitation, one has to consider multiple interfering pathways and dynamic Stark shifts (DSS), which make resonance conditions time-dependent and substantially modify the phase advance of the bare states during the atom/molecule-field interaction1. In this work, we demonstrate strong-field atomic population transfer in a three-level system via three-photon absorption from a single shaped ultrafast laser pulse. The optimal pulse shape for efficient population transfer is discovered using closed-loop learning control (Fig. 1) and interpreted via pulse shape parameter scans and numerical integration of the Schrodinger equation (Fig. 2). In Fig. 2b the solid, dashed, dashed-dot, and red curves represent the pulse envelope, ground, intermediate, and excited states, respectively. We show a population inversion can be achieved and measured using a combination of spontaneous and stimulated emission2. Our interpretation of the pulse shape dependence illustrates the advantages of sequential population transfer over adiabatic rapid passage with multiphoton coupling between levels3. We are currently applying strong-field control over single atom dynamics to the collective emission from ensembles of atoms (i.e. superfluorescence ). 1. C. Trallero-Herrero, et.al. Phys. Rev. A 74, 051403 (2006) 2. C. Trallero-Herrero, et.al. J. Phys. B: At. Mol. Opt. Phys. 41, 074014 (2008) 3. S. Clow, et.al. Phys. Rev. Lett. 100, 233603 (2008)

Mo-7

Figure 2: (a) Calculated Wigner distribution for the experimentally

determined chirp rate. (b) Corresponding electronic dynamics and pulse envelope.

Figure 1: Wigner distribution of an experimentally retrieved optimal pulse.

(a)

(b)

Towards high fidelity single ion-qubit gates

Yoni Dallal, Nitzan Akerman, Yinnon Glickman, Shlomi Kotler, Ana Weksler and Roee Ozeri

Weizmann Institute of Science, Rehovot 76100, Israel

Fault tolerant quantum error-correction schemes requires the implementation of high fidelity quantum

gates. The fidelity of a quantum gate is defined as ˆ| |F ψ ρ ψ=< > where |ψ > is the ideal final state

and ρ is the density operator of the real final (mixed) state. We designed and built a system that will

implement high fidelity stimulated Raman gates on single trapped 88Sr+ ion-qubits. Our qubit levels

are the two Zeeman states of the 1 25S electronic ground level, separated by 2.8MHz G . Raman

transitions are induced by an External Cavity Diode Laser, where the Laser diode used is a violet LD

of 405nm, off-resonance with the transitions to the 1 25P and 3 25P levels at 422 and 408 nm

respectively. The two, co-propagating, Raman beams are the two polarization components of the

405nm light where one polarization component phase modulated at the qubit Level separation by an

EOM. The Rabi frequency is directly monitored by mixing down the beat-note of the two Raman

beams and actively stabilized using feedback control. A Field Programmable Gate Array card is used

to implement the control electronics with the advantage of flexibility and better integration with the

experiment. Classical noises were suppressed such that the expected error ( 1 Fε = − ) is expected to be

quantum limited due to spontaneous scattering of photons and smaller than 410− .

Mo-8

Magnetic Interactions of Cold Atoms with Anisotropic Conductors

T. David1, Y. Japha1, V. Dikovsky1, R. Salem1, C. Henkel2 and R. Folman1 1Atom Chip Group, Ben Gurion University, Israel: www.bgu.ac.il/atomchip

2Universität Potsdam, Germany An atom chip is an apparatus where isolated cold atoms are trapped microns above the chip surface, creating a solid state device with long coherence times. One of the limitations on the lifetime and coherence of atoms trapped above the surface is the interaction of the atoms with current fluctuations in the wire, which is usually not ideal and held in room temperature. This work is focused on extending these coherence times so that the atom chip may offer new experimental opportunity to investigate the foundations of quantum mechanics (e.g. interferometry and decoherence) as well as serve as a base for quantum technology including clocks, sensors and quantum information processing and communications. We analyze atom-surface magnetic interactions on atom chips where the magnetic trapping potentials are produced by current-carrying wires made of electrically anisotropic materials. We present a theory for time-dependent fluctuations of the magnetic potential, arising from thermal noise originating from the surface. It is shown that using materials with a large electrical anisotropy results in a considerable reduction of heating and decoherence rates of ultra-cold atoms trapped near the surface, of up to several orders of magnitude, also at room temperature. We also show that spatial fluctuations of the currents in the wire, which cause static perturbations in the magnetic potential along the wire, may be significantly reduced by replacing conventional wires with wires made of electrically anisotropic materials. This improvement may allow use of these wires to generate smooth potentials for guiding and trapping ultracold atoms very close to the surface. Materials, fabrication, and experimental issues are discussed, and specific candidate materials are suggested.

Figure. Lines: spin decoherence rate as a function of electrical anisotropy r = σxx/σyy, for layered and quasi-1D conducting materials. For these lines, the good conductivity along the wire was assumed to be identical to that of Au. For layered materials having the badly conducting axis along the wire thickness (dashed red) the dependence on the anisotropy is negligible.

References: T. David et al., Euro. Phys. Jour. D48, 321, (2008). This paper was chosen by the editors of EPJ as a “Highlight Paper”, and Tal David, the author, has just been chosen for a Graduate Student Award by the U.S. Materials Research Society.

Mo-9

Generation of Airy Beams with Quadratic Nonlinear Photonic Crystals

Tal Ellenbogen, Noa Voloch, Ayelet Ganany-Padowicz, Ady Arie Dept. of Physical Electronics, Faculty of Engineering, University of Tel-Aviv, Tel-Aviv 69978

e-mail address: ellenbog@post.tau.ac.il Last year Siviloglou et al [1] reported the first experimental observation of a new class of optical beams with non-diffracting wave packets that accelerate in free space. Up until now, these beams were generated by linear reflection from a spatial light modulator. We demonstrate a new method for generating Airy beams by a three-wave mixing process in a quadratic nonlinear photonic crystal. The nonlinear generation enables to obtain Airy beams at new wavelengths, and opens new possibilities for switching and manipulating these beams. To generate the Airy beam we designed a quadratic nonlinear photonic structure with the following poling function of the quadratic coefficient: χ(2)(x,y)=signcos[2π(fxx+fcy3)], where fx is the spatial frequency of the modulation in the beam’s propagation direction and fc controls the strength of the cubic modulation in the transverse direction. The structure is illustrated in Fig. 1 (a). We manufactured the proposed structure in a 0.5mm thick z-cut stoichiometric lithium tantalite crystal and designed it to generate an Airy beam at the second harmonic of a single mode Gaussian Nd:YLF pump laser. We performed an optical Fourier transform to the output of the nonlinear photonic crystal, using a lens of 100 mm focal length, and recorded the propagation dynamics of the Fourier transformed pump and second harmonic waves. Figure 1 (b) shows a profile photograph of the green second harmonic Airy beam and Fig. 1 (c) and (d) shows the propagation dynamics of the output pump wave and the output second harmonic wave respectively. The output pump wave has a Gaussian beam propagation dynamics with slight intensity modulations which might be caused by small linear variations in the crystal due to the poling process. The output second harmonic beam shows the propagation dynamics of a truncated Airy beam, i.e., nearly non-diffracting and “freely accelerating” to one side. In addition to generating Airy beams at new wavelengths as shown here, the nonlinear interaction enables new exciting possibilities, e.g., to all-optically control the acceleration rate and the acceleration direction of the Airy beam.

ω 2ωFar field

χ(2)ω 2ω

Far field

χ(2)

FH p

rofil

e [m

m]

Propagation direction [mm]0 100 200 300 400

-3-2-10123

SH

pro

file

[mm

]

Propagation direction [mm]0 100 200 300 400

-3-2-10123

(a) (b)

(c) (d)

Fig. 1. (a) Illustration of the nonlinear structure. (b) Photograph of green Airy beam at the second harmonic. Propagation dynamics of (c) output fundamental wave and (d) output second harmonic wave. [1] G. A. Siviloglou, J. Broky, A. Dogariu, and D. N. Christodoulides, Phys. Rev. Lett. 99, 213901 (2007).

Mo-10

Monolithic vertical cavity laser with a saturable absorber : towards an integrated cavity

soliton laser T. Elsass, S. Barbay, K. Gauthron, G. Beaudoin, I. Sagnes and R. Kuszelewicz

Laboratoire de Photonique et de Nanostructures, CNRS-UPR20, Rte de Nozay, 91460 Marcoussis, France.

email : tiffany.elsass @lpn.cnrs.fr Summary Cavity solitons in semiconductor systems have been first demonstrated in optical amplifiers, and recently in a laser with external grating feedback. We propose an original design of a monolithic and integrated vertical cavity laser with saturable absorber and discuss experimental results showing the formation and control of bistable laser spots. Cavity solitons (CSs) are self-localized spots appearing in the transverse plane of a nonlinear cavity. Their existence is now well established, in particular in semiconductor systems [1,2] where most of the potential applications reside. They have also been recently found in a laser system [3] consisting in a vertical cavity surface emitting laser (VCSEL) with an external feedback grating and two mutually-coupled VCSELs [4] in presence of saturable absorption. One of the main advantages of a CS laser relies on the fact that it is a source and not an amplifier, thus making it easier to cascade several CS devices for optical information processing, while being generally simpler to operate. Indeed there is no need anymore for a coherent injection making it much more attractive and cost effective. We have designed and fabricated a monolithic, optically pumped VCSEL structure with intracavity gain and saturable absorber sections [5].We show experimental results obtained in different samples with different gain-to-saturable absorber lifetime ratios. Several regimes are identified close to threshold. One of them is a stationnary regime with the appearance of bright spots (Fig.1 left). These spots appear sub-critically (Fig.1 center) and can be excited and erased repetitively with externally addressed local excitation pulses as short as 60ps, at a maximum repetition rate of 80MHz. These pulses act principally as a kink on the carrier density distribution. Another regime corresponds to self-pulsing (Fig.1 right). We shall discuss the observed temporal dynamics in relation with the spatial response.

Fig. 1: Left : Average near-field intensity image of the system in the bistable regime. Center : Bistable output vs pump characteristics. Right : Pulsing regime of period 9ns. We ackowledge support from the European project IST-STREP FunFACS. References [1] S. Barland et al., Nature 445, 699 (2002). [2] S. Barbay et al., Optics Letters 31, 1504 (2006). [3] Y. Tanguy et al., Physical Review Letters 100, 013907 (2008). [4] P. Genevet et al., Physical Review Letters, 101, 123905 (2008). [5] S. Barbay et al., report on the FunFACS IST-FET-STREP Project #4868

Mo-11

High accuracy space-time positioning

beyond the standard quantum noise limit

C. Fabre, N. Treps, G. De Valcarcel, G. Patera, O. Pinel, B. Chalopin, B. Lamine

Laboratoire Kastler Brossel Université Pierre et Marie Curie-Paris6, ENS, CNRS 4 Place Jussieu, CC74, 75252 Paris cedex 05, France

fabre@spectro.jussieu.fr Accurate space-time positioning is an important issue of physics, both from a fundamental perspective and for its numerous practical applications. Considering successively the spatial and temporal positioning methods using optical methods, we demonstrate that there is a basic quantum limit to their accuracy, independent of the measurement protocol, when one uses shot noise limited light. We will then show how to reach this standard quantum noise limit. Finally we will show that his limit can be circumvented using a specifically designed quantum-entangled non-classical light beam, resulting from the superposition of a coherent state and a vacuum squeezed state in two different spatial or temporal modes. An OPO synchronously pumped by a mode-locked laser (the OPO cavity length is equal to the spatial distance between successive pulses) turns out to be a very efficient device to produce squeezed states when the pump intensity is slightly less than the oscillation threshold. Squeezing is effective not in a single frequency mode, as usual, but instead in a whole set of "super-modes", which are well defined linear combinations of signal modes of different frequencies, i.e. of trains of pulses of well defined shapes. Such modes are precisely the ones needed to improve time positioning measurements. We will also report on the progress of the experiment that we are currently developing to produce such squeezed and/or entangled frequency combs.

We finally describe a scheme that allows us to beat the standard quantum limit in clock synchronisation and ranging measurements, which could be used in space experiments where losses are small and high precision needed. It is based on the use of a homodyne technique with squeezed frequency combs and local oscillator pulses in appropriately shaped super-modes, and turns out to be less sensitive to phase noise than other proposed techniques based on few-photon entangled states. N. Treps, N. Grosse, C. Fabre, H. Bachor, P.K. Lam, “The "Quantum Laser Pointer"", Science 301, 940 (2003) V. Delaubert, N. Treps, C. Fabre, H. Bachor, P. Réfrégier, “Quantum limits in image processing” Europhys. Letters 81 44001 (2008) B. Lamine, C. Fabre, N. Treps, “Quantum improvement of time transfer between remote clocks” Phys. Rev. Letters 101 123601(2008)

Mo-12

Ultrafast electron dynamics at the DNA-Au interface studied by time-resolved two-photon

photoemission and femtosecond pulse shaping

B. Golana , Z. Fradkina , T. Markusa , D. Oronb , and R. Naamana*

a) Dept. of Chemical Physics

b) Dept. of Complex Matter Physics

The Weizmann Institute of Science, Rehovot 76100, Israel

The dynamics of electronic excitations at molecule-metal interfaces is crucial for understanding

interfacial charge transfer at molecular electronic based devices. In addition, the electronic properties

of oxidized DNA bases and their interaction with low energy electrons are important for understanding

radiation related DNA damage.

Using an experimental set up that combines photoelectron imaging, two-photon photoemission

(2PPE), and spectral phase and polarization pulse shaping we investigated the dynamics of electron

transfer through self assembled single strand DNA monolayers containing oxidized bases on gold

films.

By imaging of the photoelectrons angular distribution, it was found that the organic DNA monolayer

filters the electron emission angles, permitting mainly emission normal to the surface. In addition,

chirped-pulse 2PPE validates that upon adsorption of DNA a two photon absorption process which

involves high energy intermediate states is preferred. The electronic dispersion of these states was

investigated using angle-resolved 2PPE, and a difference has been observed between the electron

localization in the DNA-induced surface states and states on bare Au.

By applying time-resolved 2PPE measurements, we obtained the population dynamics in transiently

populated electronic states in the DNA-induced surface.

Mo-13

Inelastic collisions near Feshbach resonances in ultra-cold 7Li

Noam Gross, Zav Shotan and Lev Khaykovich Department of Physics, Bar-Ilan University, Ramat Gan, 59200 Israel

Recently we reported on a successful achievement of 7Li Bose-Einstein condensate (BEC) by means of forced evaporation in a crossed-beam optical trap [1]. The method requires the use of Feshabch resonances in order to tune elastic collision rate. However, the inelastic processes such as dipole relaxation and three-body recombination show dramatic enhancement in the vicinity of Feshabch resonances and may limit atom densities and trap lifetime [2]. Indeed we obtained only a few hundreds of atoms in the BEC and its lifetime was extremely short. We inveatigate two- and three-body losses in the vicinity of two Feshbach resonances on the |F=1,mF=0> state. Fig. 1 shows the remaining atoms after preliminary evaporation that was performed at different magnetic fields for two durations (1.4 s and 6 s). Two minima indicate the location of Feshabch resonances. For short evaporation time maximum of remaining atoms is achieved between the resonances while for long evaporation time it appears before the first resonance. Thus, inelastic processes are very strong in-between the resonances despite the presence of a zero crossing point where scattering length vanishes. In the region of strong inelastic losses short lifetimes and quick drop in density are obtained (Fig. 2). Fig. 2a shows the atom density after 100 ms (empty squares) and 10 s (filled circles) of waiting time at a given magnetic field. By measuring lifetime of atoms in the trap (Fig 2b) we extract two- and three-body loss coefficients. At a magnetic field of 870 Gauss (empty circles) two-body loss coefficient is measured to be β = 1.16*10-13 cm3/sec, an order of magnitude higher than at 824 Gauss (filled triangles) where it already returns to its zero field value of β = 1*10-14 cm3/sec. The upper limit for three-body loss at 870 Gauss is K=9.5*10-26 cm6/sec. The investigation of the inelastic losses allows us to find an optimal magnetic field for evaporation and increase the number of atoms in the BEC by a factor of 10. [1] N. Gross and L. Khaykovich, Phys. Rev A 77, 023604 (2008). [2] S. Inouye et.al., Nature 392, 151 (1998); J. Stenger et.al. Phys. Rev. Lett. 82, 2422 (1999) ; J.L. Roberts, et.al., Phys. Rev. Lett. 85, 728 (2000).

Mo-14

Spatiotemporal Pulse-Train Solitons Hassid C. Gurgov and Oren Cohen

Solid state institute and physics department, Technion – Israel Institute of Technology, Haifa, Israel gurgov@tx.technion.ac.il

We propose spatiotemporal solitons that consist of trains of short pulses. The pulses are collectively trapped in the

transversal directions by a slow nonlinearity and each pulse is selftrapped temporally by a fast nonlinearity. A spatiotemporal optical soliton is a self-localized entity that maintains its shape in the longitudinal (temporal) direction as well as in its transversal direction(s) through a robust balance between diffraction, group velocity dispersion and nonlinearity.1,2 However, spatialtemporal pulses in Kerr media are unstable. Several possibilities to allow the existence of spatiotemporal solitons were considered, yet, the only successful experiment in this field was the creation of (1+1+1)D spatiotemporal solitons through the process of phase-mismatched second harmonic generation in quadratic nonlinear media.3 The experimental demonstration of selflocalized entity in three dimensions is still considered a ‘grand challenge’ in nonlinear optics [1]. We propose a new kind of spatiotemporal solitons: pulse-train solitons. This soliton consists of short pulses that are collectively trapped in the spatial (transversal) domain by a slow selffocusing nonlinearity (e.g. thermal) whose nonlinear response time is much larger than the time between adjacent pulses, T, and each pulse is self-trapped in the temporal domain by an instantaneous (e.g. Kerr) nonlinearity (Fig. 1a). We solved theoretically and demonstrate numerically (1+1+1)D pulse-train solitons in a medium with both the optical Kerr nonlinearity and a slowly-responding and highly-nonlocal self-focusing nonlinearity. Figure 1b show the intensity of a single pulse in the train where x and t are the dimensionless transverse direction and time, respectively. The pulse is much more confined in x than in t because the slow nonlinearity is much stronger that the Kerr nonlinearity. The slow nonlinearity, which is transparent to the fact that the beam consists of pulses, leads to the formation of a spatial soliton. Each pulse is injected into a waveguide that was induced in the medium by former pulses in the train and can self-tapped temporally by the Kerr nonlinearity, similarly to temporal solitons in fibers. We verified the stability of this pulse-train soliton by simulating the propagation with 5% initial noise in amplitude and phase (Fig. 2b).

Figure 1: (a) schematic of pulse-train solitons. (b,c) Numerical example of (1+1+1)D pulse-train soliton in medium with both Kerr nonlinearity and with slow and highly nonlocal self-fucusing nonlinearity. (b) Intensity of a pulse in a pulse-train solitons © Peak intensity as a function of the propagation distance. The pulse train soliton consist of pulses shown in plot (a). The dispersion length (the distance in which the width of the pulse is broaden by a factor of 2) is z=103. The pulse propagates over 100 dispersion lengths with only small variations in its shape. The periodic variations in the peak intensity result from beating between multiple modes of the induced waveguide. Higher order modes are slightly populated because the initial beam includes 5% noise in the amplitude and phase. References [1] F.Wise, P. Trapani, “Spatiotemporal optical solitons,” OPN 13, 28-32 (2002) [2] Y. Silberberg, “Collapse of optical pulses,” Opt. Lett. 15, 1282 (1990). [3] R. Chiao, E. Garmire, C.Townes, “Self-trapping of optical beams,” Phys. Rev. Lett. 13, 479 – 482 (1964)

Mo-15

Generation of intense keV attosecond pulses

W. Helml¹, G. Marcus¹, Y. Deng¹, V. S. Yakovlev², K. Schmid¹, X. Gu¹, R. Kienberger¹,³, F. Krausz¹,²

¹ Max-Planck-Institut für Quantenoptik, Hans-Kopfermann-Str. 1, D-85748 Garching, Germany

² Department für Physik, LMU München, Am Coulombwall 1, D-85748 Garching, Germany ³ Physik Department, Technische Universität München, James Franck Str., 85748 Garching, Germany

We investigate the possibility of increasing the harmonic yield in the keV-region by using a freely adjustable multi-gas-jet array to modulate the target density for quasi-phasematching during the harmonic build-up process [1]. To push attosecond-pulse generation towards higher photon energies compared to HHG driven by the conventionally used Ti:Sa lasers [2], we developed a 2.1 µm few-cycle OPCPA system [3] to extend the energetic cut-off (Ecutoff ~ λ2

driv). Coherent growth of soft x-ray radiation during HHG is primarily restricted by the increasing ionization of the gas, which gives rise to dephasing between the fundamental laser and the generated harmonic field. A fundamental limit of the build-up process is reached when this phase-mismatch equals π, at which point there evolves destructive interference between different contributions to the harmonic wave. It has recently been demonstrated [4] that already the use of two gas nozzles can increase the effective coherence length by a factor of four (Figure 1.a).

Our approach of quasi-phase-matching in the multi-jet gas target has two main advantages (Figure 1.b). On the one hand each source can be optimized individually for the best high harmonic yield and also positioned independently of the others, such that the density modulation can be adjusted to the changing field of the driving laser as it propagates through the gas, on the other hand it is possible, by setting up the multi-jet-system to enhance the contribution from a specific electron trajectory, to efficiently control the spectral and temporal structure of the generated harmonic field. This would lead to the generation of extremely short single attosecond pulses with tunable photon energy. References [1] V. Tosa, V. S. Yakovlev, F. Krausz, New J. of Phys. 10, 025016 (2008) [2] A. L. Cavalieri, E. Goulielmakis, B. Horvath, W. Helml, M. Schultze, M. Fieß, V. Pervak, L. Veisz, V. S. Yakovlev, M. Uiberacker, A. Apolonski, F. Krausz, R. Kienberger, New J. Phys. 9 , 242 (2007) [3] X. Gu, G. Marcus, Y. Deng, T. Metzger, C. Teisset, N. Ishii, T. Fuji, A. Baltuska, H. Ishizuki, T. Taira, T. Kobayashi, R. Kienberger, F. Krausz, Generation of carrier-envelope phase-stable two-cycle 740-μJ pulses at 2.1 μm carrier wavelength, accepted by Opt.Express [4] J. Seres, V. S. Yakovlev, E. Seres, Ch. Streli, P. Wobrauschek, Ch. Spielmann, F. Krausz, Nature Physics 3, 878 (2007)

Mo-16

Figure 1.a Figure 1.b Fig. 1.a Harmonic intensity depending on atomic densities

for 1, 2 or 3 subsequent nozzles.

Fig. 1.b Build-up of harmonic intensity

in multi-jet-systems designed for

enhancement of 2 different electron

trajectories

Indication of a very large proton diffusion in ice Ih

by Dan Huppert, Itay Presiado and Anna Uritski

Raymond and Beverly Sackler Faculty of Exact Sciences, School of Chemistry, Tel Aviv University, Tel Aviv 69978, Israel

The physics of ice has been studied1 for a long time, posing many questions that still puzzle us today. We studied the proton diffusion in ice by a chemical reaction of several molecules in their excited-state with a proton added to the ice as a small concentrations of the strong mineral acid HCl. We used a time-resolved emission technique to monitor the excess by excess protons reaction in both liquid water and in ice. The electrical conductivity measurements of Eigen2 in the early sixties of the 20th

century resulted in a surprisingly large mobility value for the proton in ice. The results of the present study and of our previous one3,4 indicate that the proton mobility in ice is indeed larger than in water, at least on a nanometric distance scale. Already in 1983 Nagle advocated the existence of proton wires in ice and in enzymatic systems in which the proton transport is carried out via a concerted mechanism (Grotthuss mechanism) on a limited length scale. Under certain assumptions and approximations, we deduced the proton diffusion constant in bulk ice from the experimental data fit by using the irreversible diffusion-assisted recombination model based on the Debye-Smoluchowski equation. We found that the proton diffusion in ice Ih at 240 - 263 K is about 10 times larger than in liquid water at 295 K. Ice conductance has been extensively studied for more than four decades. Our findings are in accord with the electrical measurements of Eigen and deMaeyer, but contradict conductivity measurements of ice from 1968 to this day. We explained the large difference between the results of the present study and the conductivity measurements by the proton diffusion length in the two types of measurements. In our measurements, we monitored a small diffusion sphere of about 50 nm around the excited photoacid molecules, whereas in the conductance measurements the distances between electrodes were in the range of 1 mm. 1 Petrenko, V. F.; Whitworth, R. W. The Physics of Ice; Oxford University, Press: 1999. 2 (a) Eigen, M. Proton Transfer, Angew. Chem., Int. Ed. 1964, 3,1. 3 Uritski, A.; Presiado I.; Huppert, D. J. Phys. Chem. C 2008, 112, 11991. 4 Uritski, A.; Presiado, I.; Huppert, D. J. Phys. Chem. C accepted for publication

Mo-17

Phase rigidity and incoherent operation of guided matter-wave Sagnac interferometers

Yonathan Japha, Ofir Arzouan, Yshai Avishai and Ron Folman Physics Department, Ben Gurion University, Israel

www.bgu.ac.il/atomchip Sagnac interferometry is based on the effect of rotation or acceleration on the phase difference between counter-propagating waves in a closed loop. The effect of these rotations on matter waves of massive particles is many orders of magnitude larger than on light waves, which are usually used in navigation systems. We present a theory of the transmission of Sagnac interferometers based on guided matter waves. An interferometer of this type consists of one or more input and output channels connected by beam splitters and waveguides serving as the interferometer arms. In analogy to mesoscopic solid-state electron interferometers, we find phase rigidity in configurations with only one input and one output port. Phase rigidity, namely the fact that the transmission depends mainly on the Sagnac phase shift and not on arm-length differences, is due to time-reversal symmetry. It allows incoherent operation which is robust to arm-length differences. This sensitivity makes possible the operation of highly sensitive interferometers with high-flux atom sources, which are available for laser-cooled atoms. High-finesse configurations offer very high rotation sensitivity even for miniature loops on an atom chip.

aout

ain

a+

a−

b+

b−

Ωβ

α

i

i’

β’

α’

o

o’

(a)

ain a

out

a+

b+

a−

b−

Ω

α

βi

o’’α’

β’o

o’

(c)

ain

aout

a+

b+

a−

b−

Ω

α

βi

o

(d)

ain

aout

a+

b+

a−

b−

Ωα

βi

α’

β’o

(b) Figure: Geometries of guided matter-wave Sagnac interferometers: (a) Mach-Zehnder. Horizontal lines represent 50-50% beamsplitters. Open squares indicate controllable reflectivity. When fully reflecting, the interferometer displays phase rigidity. (b) High-finesse 2-port loop. Closed squares are fully reflecting mirrors. Vertical lines are low-transmission beam-splitters. (c) 4-port loop. No phase rigidity. (d) High-finesse single-junction loop. For this loop it is shown that high sensitivity is possible even with multimode operation.

Reference: Y. Japha, O. Arzouan, Y. Avishai and R. Folman, Phys. Rev. Lett. 99, 060402 (2007).

Mo-18

Long-Range Order in Electronic Transport through Disordered Metal Films

Y. Japha1, O. Entin-Wohlman1, T. David1, R. Salem1, R. Folman1, S. Aigner2, L. Della Pietra2 and J. Schmiedmayer2

1Atom Chip Group, Ben Gurion University, Israel: www.bgu.ac.il/atomchip 2Heidelberg University, Austria

Ultracold-atom magnetic-field microscopy permits probing of electron transport patterns in planar structures with unprecedented sensitivity and resolution. In polycrystalline metal (gold) films we observe long-range correlations, forming organized patterns oriented at ±45 relative to the mean current flow, even at room temperature and at length scales orders of magnitude larger than the diffusion length or the grain size. The tendency to form patterns at these angles is a direct consequence of universal scattering properties at defects. The observed amplitude of the current-direction fluctuations scales inversely to that expected from the relative-thickness variations, the grain size and the defect concentration, all determined independently by standard methods. A careful comparison of the different measurements with our theoretical models, assuming bulk and surface long-range disorder in the wire structure, offers new insight into the structure and the nature of electron transport in polycrystalline metal films. The theoretical model also provides predictions regarding the dependence of current fluctuations on the geometry of the wires. The results indicate that ultracold atom magnetometry provides new insight into the interplay between disorder and transport.

x (μm)

Figure 1. Atomic density fluctuations, 3.5μm above a thin gold film, due to current-directional deviations in the wire. The simulation (b) regenerates patterns similar to those measured (a). Figure 2. Microscopic and macroscopic models for the 45 effect. A-B: a microscopic conductivity-changing defect repels or attracts the current lines, thus generating a field of vertical current component oriented at 45. C: current scattering by a step-like defect. Maximum transverse current is generated by steps oriented by 45.

References: S. Aigner et al., Science 319, 1226 (2008)

Y. Yapha et al., Phys. Rev. B77, 201407(R) (2008)

Mo-19

Shaped Femtosecond Pulses for Standoff Detection of Chemical Traces O. Katz 1, A. Natan 1 , S. Rosenwaks 2 , Y. Silberberg 1

1 Department of Physics of Complex Systems, Weizmann Institute of Science, Rehovot, 76100 Israel 2 Department of Physics, Ben Gurion University of the Negev, Beer Sheva 84105, Israel.

E-mail: yaron.silberberg@weizmann.ac.il, Remotely detecting and identifying traces of hazardous materials at standoff distances is one of the recent concerns at the focus of current research activities. The vibrational spectrum of molecules provides an excellent fingerprint for chemical species identification, and can be harnessed for this task. We have experimentally utilized one of our group's femtosecond coherent-control techniques1 for remote detection and identification of minute amounts of solids and liquids at a standoff (>10m) distance. In this Coherent Anti-Stokes Raman Scattering (CARS) technique, a single ultrashort pulse supplies both the broadband pump and Stokes photons, and a narrow-band portion of the same pulse is phase-shifted to serve as the probe beam using a pulse shaper (Fig. 1c). Furthermore, we exploited the strong nonresonant four-wave mixing background for amplification of the weak backscattered resonant CARS signal through a homodyne detection scheme. We have succeeded in rapidly resolving the vibrational spectrum of trace amounts of contaminants such as explosives and nitrate samples, from the weak backscattered photons under ambient light conditions 2. This highly sensitive single-beam spectroscopic technique has a potential for hazardous materials standoff detection applications.

Fig. 1: (a) Resolved femtosecond CARS vibrational spectra of two trace samples obtained at a standoff distance of 12m (<1000μg crystallized KNO3 particle, and RDX explosive particles with a total mass of <4mg); Each spectrum was resolved from a single measurement with an integration time of <3 seconds. The known vibrational lines of the samples are plotted in gray bars. (b) Image of the KNO3 contaminant sample, placed 12m from the measuring apparatus. (c) The experimental setup. The laser source is an amplified femtosecond Ti:Sapphire laser (0.5mJ, 30fs, 1KHz repetition rate). The pulses are phase-shaped in a pulse shaper using an electronically controlled liquid-crystal spatial light modulator. The beam is focused on a distant sample through a telescope, and the backscattered radiation is collected to a spectrometer with a 7.5" diameter lens. 1 D. Oron, N. Dudovich, and Y. Silberberg, Phys. Rev. Lett. 89 (2002) 273001. 2 O. Katz, A. Natan, S. Rosenwaks, Y. Silberberg , Appl. Phys. Lett. 92, 171116 (2008).

Mo-20

Optical Generation and Control of Plasma Lens System

Y.Katzir, M.Levin, S.Eisenman, A.Zigler

Racah Institute of Physics, Hebrew University, Jerusalem, 91904 Israel

Abstract: We present a novel approach for focusing and collimating a NIR femtosecond laser

pulse, by use of a plasma lens system. The plasma lens was created at the entrance of a polyethylene

capillary by another nanosecond laser which was used to ablate the capillary entrance in a

configuration which focuses the femtosecond laser pulse and allows it to pass through the capillary at

higher transmittance. This configuration offers versatility in the plasma lens f-number for extremely

tight focusing of high power lasers with no damage threshold restrictions of regular optical

components.

Experimental setup:

Results:

Mo-21

Experimental setup

The igniting laser (pink) was

focused approximately 3cm from

the capillary entrance and was

used to ablate the capillary

entrance, which generated a

plasma plume in a configuration

that created a plasma lens.

According to measurements of

plasma density, the guided pulse

(red) was focused 1cm before the

capillary entrance, and its

transmittance was measured at

the capillary exit.

Results:

Guided laser train pulses

intensity as a function of

time. The instance of

igniting laser hitting the

capillary (20mJ) is marked

by the dotted line at t=0.

An increase by a factor of

three in guided laser

transmittance was detected

after 45ns.

PHOTOISOMERIZATION VERSUS PHOTODISSOCIATION; QUANTUM DYNAMICAL SIMULATIONS ON A CHIRAL OLEFIN

Daniel Kinzel,1 Sherin Alfalah,2 Jesús González-Vázquez, 1 Leticia González1

1Institut für Physikalische Chemie, Friedrich-Schiller Universität Jena, Helmholtzweg 4, Jena, Germany

2Faculty of Pharmacy, Al-Quds University, Jerusalem, Palestine E-mail: Daniel.Kinzel@uni-jena.de

The (4-methylcyclohexylidene) fluoromethane (4MCF) system is a chiral molecule whose R/S enantiomers are obtained upon photoisomerization around the olefinic double bond [1,2], see Scheme 1. Recently, it has been suggested that 4MCF might serve as a substrate for a laser-induced molecular rotor [3]. As it is well-known in olefins, 4MCF presents several conical intersections (CI) between the lowest singlet excited state and the electronically ground state [4]. Moreover, besides the “typical” twisted, pyramidalized, and H-migration CIs found in ethylenic systems, here a CI for HF dissociation has been located [5]. This CI is expected to be populated in gas phase, competing then with the R/S photoisomerization pathway. In this contribution, the competition of R/S photoisomerization against HF dissociation is investigated. For that purpose, two-dimensional potential energy surfaces (PES) have been calculated for both the ground and lowest excited states along the isomerization and dissociation degrees of freedom using multiconfigurational CASSCF methods. Additionally, nonadiabatic couplings and permanent-, as well as, transition- dipole moments are also obtained at the same level of theory. The PESs show two degeneracy points with a strong coupling out of the Franck-Condon region, which correspond to the CIs between the ground and first excited states.

Based on this PESs and ab initio couplings, quantum dynamical simulations in the diabatic representation have been performed in order to evaluate whether this chiral rotor is destroyed upon excitation. S R

Scheme 1. The R and S enantiomers of 4MCF

[1] D. Kröner, M. F. Shibl and L. González, Chem. Phys. Lett. 372, 242 (2003). [2] D. Kröner and L. González, Chem. Phys. 298, 55 (2004). [3] Y. Fujimuro, L. González, D. Kröner, J. Manz, I. Mehdaoui and B. Schmidt, Chem. Phys. Lett. 386, 248 (2004). [4] M. Schreiber, M. Barbatti, S. Zilberg, H. Lischka and L. González, J. Phys. Chem. A 111, 238 (2007). [5] S. Zilberg, S. Cogan, Y. Haas, O. Deeb and L. González, Chem. Phys. Lett. 443, 43 (2007). Acknowledgements: We are grateful for the support by the DFG, project Nr. GO 1059/5-2.

Mo-22

FH

H3C

HF

H3C

Wave focusing by plano-concave lenses based on 2D photonic quasicrystal and 2D photonic crystal super-lattice

Y. Neve-Oz1, Y. Saado1 , T. Pollok2, M. Golosovsky1, S. Burger2 and D. Davidov1

1The Racah Institute of Physics, the Hebrew University of Jerusalem, Israel

2Zuse Institute Berlin, Germany

We report on microwave focusing by a plano-concave lens based on planar array of dielectric rods arranged in a crystalline or quasicrystalline (QC) configuration.

We designed a 2D photonic crystal superlattice from the dielectric rods of two different diameters. This device was designed for the operation in the microwave range. The composite unit cell of the superlattice results in a narrow transmission subband inside the photonic stop-band. Due to Brillouin zone folding in the superlattice, this transmission band is characterized by a negative refractive index. This was verified experimentally by constructing a plano-concave lens that focused the microwave radiation into a subwavelength spot.

Another way to achieve focusing by the plano-concave lens was to use aperiodic, quasicrystalline arrangement of the dielectric rods. We studied microwave propagation in such arrays using JCM-Wave software that is based on a time-harmonic, adaptive, higher-order finite-element method. We found that in specially designed dielectric rod arrays based on Penrose tilings with 5- and 10-fold symmetry, there is light localization, resulting from multiple scattering. This results in a very small refractive index (fast light). We showed by numeric simulations that a plano-concave lens built from such material exhibits focusing (Figure 1). Figure 1. A plano-concave quasicrystalline lens. The phase distribution shows almost constant phase inside the lens and a uniform phase front on the concave face. The intensity distribution shows focusing.

Mo-23

Rotational dephasing and depopulation rates measured via non-adiabatic alignment

Nina Owschimikow1, Jochen Maurer1*, Falk Königsmann1, Burkhard Schmidt2,

and Nikolaus Schwentner1

1 Institut für Experimentalphysik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany 2 Institut für Mathematik, Freie Universität Berlin, Arnimallee 6, 14195 Berlin, Germany

Ambient conditions, i.e. temperatures of order of 100 K and pressures of order of 1 atm, are standard for studies of physical and chemical properties of molecules in the gas phase. Under these conditions, bimolecular collisions, and therefore decoherence and dissipation, typically occur on a picosecond time scale. The dynamics in experiments on non-adiabatic alignment covers exactly this time range. We show that laser induced alignment of diatomic molecules can be used to quantitatively study relaxation processes of both phase and population.

Figure 1. Figure 2.

We use a Ti:Sa amplified fiber laser with a pulse length of 160 fs focused to an intensity of 1013 W/cm2 to induce alignment in a sample of N2 at pressures of 100 to 900 mbar and temperatures between 80 and 300 K. The excitation is followed by recurrent transient bursts of molecular alignment reflecting the phase coherence (Fig. 1), which are monitored in a homodyne detected optical Kerr effect experiment. Random bimolecular collisions result in a loss of phase coherence and thus an exponential decay of intensity of the revivals. The collision rate is connected with thermal equilibration via the collision number Zr, which describes the number of collisions necessary to re-establish equilibrium between translational and rotational degrees of freedom. A mean free path analysis of the experimental decay rates, after weighting with Zr, yields rotational relaxation cross sections that are in excellent agreement with values from the literature (Fig. 2, black: our results; grey: literature data from Ref. 1). Additionally, at high intensities, a non-equilibrium population of M quantum numbers is created upon excitation and is reflected in a weak structureless offset in the detected signal. By decomposing the theoretically calculated signal into a coherence part and a population part according to Ref. 2 and fitting to our data, we show that the slower thermalization of population compared to phase relaxation is contained in a change of revival shape over time (inset Fig.1), and thus both times can be extracted directly from an alignment experiment. [1] F. J. Aoiz et. al., J. Phys. Chem. A 103, 823 (1999), and references therein [2] S. Ramakrishna and T. Seideman, Phys. Rev. Lett. 95, 113001 (2006)

Mo-24

A Novel Atom Trap Based on Carbon Nanotubes

Plamen G. Petrov, Saeed Younis, Roberto Macaluso, Shimi Machluf*, Tal David, Benyamin Hadad, Yoni Japha, Mark Keil, Ernesto Joselevich, and Ron Folman

Department of Physics, Atom Chip Group, Ben Gurion University, Be’er Sheva, Israel

* machlufs@bgu.ac.il The recent realization of micron-scale magnetic potentials through standard microelectronic fabrication techniques has led to the development of miniature atom traps near surfaces, in what are widely known as atomchips. Bringing atoms ever closer to the source of the magnetic potentials enables tighter traps and opens new avenues for quantum manipulation (e.g., control of tunneling barriers on the order of 1μm, the atomic deBroglie wavelength). The motivation to use carbon nanotube (CNT)-based devices ranges from improving atom optics technology to fundamental studies of CNTs. Atom-surface interactions due to the Casimir-Polder force become important at sub-micron distances; the resulting trap losses caused by tunneling to the surface can be controlled for CNT-based traps since the amount of matter near the atoms can be very small. CNT-based traps are also expected to exhibit ballistic electron transport, thereby reducing electron scattering and improving the smoothness of the magnetic potential. Thermally induced electromagnetic noise will be improved, reducing trap loss and decoherence. Relative to normal conductors, CNTs offer sharp absorption peaks and hence may serve as useful electrodes near high-finesse resonators since they will not absorb resonator photons. They may also serve as mechanical oscillators, leading to atom-oscillator coupled systems in which the laser-cooled atom can cool the CNT oscillatory motion. Finally, once the trap is realized, atoms may serve as extremely sensitive probes of electron transport and other aspects of CNT science. We present a feasibility study for loading cold atomic clouds into magnetic traps created by CNTs grown directly onto dielectric surfaces (submitted to Phys. Rev. A). We show that atoms may be captured for experimentally sustainable nanotube currents, generating trapped clouds whose densities and lifetimes are sufficient to enable detection by simple imaging methods.

Mo-25

general view of the BGU atomchip

schematic view of the carbon nanotube trap

simulated isopotential surface for ultracold atoms hovering ~1 μm above the carbon nanotube

BEC transition for 87Rb at BGU

The Minimal Temperature of Quantum Refrigerators

Tova Feldmann, Yair Rezek and Ronnie Kosloff

Institute of Chemistry the Hebrew University, Jerusalem 91904, Israel

A first principle reciprocating quantum refrigerator is investigated with the purpose of determining the limitations of cooling to absolute zero. We find that if the energy spectrum of the working medium possesses an uncontrollable gap, then there is a minimum achievable temperature above zero. The reason is that such a gap, combined with a negligible amount of noise, prevents adiabatic following during the expansion stage which is the necessary condition for reaching Tc =0. For the case where the gap can be forced to close, the scaling of the optimal cooling power of a reciprocating quantum refrigerator is sought as a function of the cold bath temperature as Tc approaches zero. In this case the working medium consists of a gas of noninteracting particles in a harmonic potential. Two closed-form solutions of the refrigeration cycle are analyzed, and compared to a numerical optimization scheme, focusing on cooling toward zero temperature. The optimal cycle is characterized by a linear relation between the heat extracted from the cold bath, the energy level spacing of the working medium and the temperature. The scaling of the optimal cooling rate is found to be proportional to

Tc^3/2 giving a dynamical interpretation to the third law of thermodynamics.

Mo-26

How to produce “high-N00N” atom states via RF pulses on a (1μm)2 flux qubit

D. Rohrlich, Y. Japha and R. Folman

Atom Chip Group, Ben Gurion University, Israel: www.bgu.ac.il/atomchip “High-N00N” states are maximally entangled states of a high number N of identical two-level systems: if 0N represents all of the N systems in one of the states and N0 represents all of them in the other,

then ( ) 2/00 NN + is a high-N00N state. High-N00N states can beat the shot noise limit N/1≥Δφ for the detection of the quantum phase φ of the systems and can, in principle, saturate [1] the “Heisenberg limit” N/1≥Δφ . We propose to use a “flux qubit” – a mesoscopic superconducting ring – for efficient preparation of high-N00N states of two-level atoms. For example, the flux qubit shown in the micrograph was fabricated by a group at Delft University of Technology [2]. It is roughly (1 μm)2 in area and couples to a SQUID. Rabi oscillations generated by the flux qubit appear on the schematic diagram. This flux qubit supports superposed fluxes B1, B2 that differ by half a flux quantum, B2–B1= hc/2e, with coherence lasting from 0.5 μs to 4 μs at 25 mK. We show how to transfer the superposition from such a superposed magnetic field to the two-level atoms. First, we toggle the atoms selectively using an RF (radio frequency) pulse that addresses only the B2 term: Since B2–B1 = (hc/2e )/(1 μm)2 = (2 x 10–7 cm2 G )/(1 μm)2 = 20 G, the frequency splitting ν = (B2–B1)(μB/h) for the RF pulse is (20 G)(1.4x106 Hz/G) ≈ 30 MHz, and there is no problem addressing only the B2 term. Next, a π/2-pulse on the superconducting ring, followed by a measurement of the magnetic field, reduces the atoms to a high-N00N state. A (1 μm)3 box in the superconducting ring could contain 100 atoms, assuming a BEC cloud with a density of 1014 atoms/cm3. Thus, our challenge is to produce high-N00N states with N=100.

[1] J. J. Bollinger, W. M. Itano, D. J. Wineland and D. J. Heinzen, Phys. Rev. A54, R4649 (1996). [2] I. Chiorescu et al., Science 299, 1869 (2003).

Mo-27

( ) ( ) . 002

1 02

12121 BNBNBBN ⊗+⊗→+⊗

High-Quality Micro-Resonator for Trapping and Detecting a Single Atom on a Chip Michael Rosenblit1, Yonathan Japha1, Peter Horak2 and Ron Folman1

1Atom Chip Group, Ben Gurion University, Israel: www.bgu.ac.il/atomchip. 2Optoelectronics Research Centre, University of Southampton, U.K. We describe the use of whispering gallery modes (WGM) of a microdisk resonator for the optical detection of single rubidium and cesium atoms near the surface of a substrate. Light is coupled in two high-Q whispering-gallery modes of the disk which can provide attractive and/or repulsive potentials, respectively, via their evanescent fields. The sum potential, including van der Waals/Casimir-Polder surface forces, may be tuned to exhibit a minimum at distances on the order of 100 nm from the disk surface. We discuss the possibility of simultaneously optically trapping and detecting atoms, when the back-action of an atom held in this trap on the light fields is sufficiently strong to provide a measurable effect. The goal is to enable state preparation, manipulation and probing of single atoms, molecules, or clusters using the spectral properties of a monolithically fabricated high-quality micro-resonator. Expected applications, for example, will be quantum state preparation and manipulation as well as detection e.g. for matter-wave interferometry, and for quantum information processing. We have shown that a single atom can be detected near the surface of a microdisk resonator with and without trapping, such that it can be detected with negligible heating. The atom is detected via a blue-detuned WGM of the resonator, while trapping at a fixed position is achieved by a second, red-detuned WGM. The two light fields create a trapping potential at a distance of 100-150 nm from the disk surface. At this distance, the atom-surface attractive interaction (van der Waals force) is much weaker than the light force, while the optical potential is sufficiently strong to create a deep trap for the atom. The atom is then confined in the radial direction and in the z direction (perpendicular to the chip surface). For trapping in the tangential direction, we suggest that the red-light WGM be coupled to the microdisk from both sides, such that a red-detuned standing wave is formed along the disk perimeter and the atom may be trapped in any of the maxima of the red detuned light.

Figure. Scheme of the detection and trapping system: An optical waveguide (1) is coupled to the microdisk (2). Adiabatic tapers (3) couple light into and out of the waveguide. An atom (4) initially trapped by a magnetic field generated by a wire (5) is then loaded into the bichromatic optical trap created by the light coupled into the disk. The atom causes a detectable phase shift of the light at the output port.

References: M. Rosenblit et al., Phys. Rev. A73, 063804 (2006). Rosenblit et al., J. Nanophotonics 1, 011670 (2007). U.S. Patent approved; patent number due January 2009.

Mo-28

Multiphoton Femtosecond Control of Resonance-Mediated Generation of Short-Wavelength Coherent Broadband Radiation

Leonid Rybak, Lev Chuntonov, Andrey Gandman, Naser Shakour and Zohar Amitay Schulich Faculty of Chemistry, Technion, Haifa, Israel (rleo@tx.technion.ac.il)

We introduce a new scheme for generating short-wavelength coherent broadband radiation with well-controlled spectral characteristics. It is based on shaping long-wavelength femtosecond pulse to coherently control atomic resonance-mediated (2+1) three-photon excitation to a broad far-from-resonance continuum (see Fig. 1). Here, the spectrum (central frequency and bandwidth) of deep-ultraviolet (UV) coherent broadband radiation generated in Na vapor is experimentally controlled by tuning the linear chirp that we apply to the driving phase-shaped near-infrared femtosecond pulse. Figure 2 presents the complete set of the experimentally generated chirp-controlled UV spectra as a function of the applied NIR chirp. The results are presented as a color-coded map, with each UV spectrum normalized independently by its maximal intensity. This is a first step in implementing the full scheme for producing shaped femtosecond pulses at wavelengths down-to the vacuum-ultraviolet (VUV) range, which currently is inaccessible by the present pulse shaping techniques. Inspired by past demonstrations of narrowband coherent VUV generation via resonance-mediated threephoton atomic excitation, the extension to the VUV range can be achieved by a proper change of the excited atomic species and the driving pulse wavelength. Such shaped pulses will make many VUV-absorbing molecular species newly available for coherent control.

Mo-29

Fig. 2: The experimentally generated chirp-controlled UV spectra as a function of the applied NIR chirp.

Fig. 1: The excitation scheme of Na for the generation of deep-ultraviolet (UV) coherent broadband radiation by shaped NIR femtosecond pulse via resonance-mediated (2+1) three-photon

i i

Engineered Fragmentation: Generating a 1D Magnetic Lattice Ran Salem, Yenon Ben-Hayim, Julien Chabé, Ramon Szmuk, Mark Keil, Yonathan Japha and Ron Folman Atom Chip Group, Ben Gurion University, Israel www.bgu.ac.il/atomchip In this work, we use the atom chip to investigate the tunneling and interference of matter waves (ultracold atoms) which are released from a chain of magnetic traps in one dimension (1D). Atoms are extremely sensitive to directional deviations of the current in the wire. We propose to exploit this sensitivity by engineering a novel 1D magnetic lattice. We have already fabricated a gold wire with a periodic sinusoidal center shift on the chip. (See Fig. 1.) Next, we will load an atomic Bose-Einstein condensate into the periodic 1D waveguide potential generated a few microns from the wire by the current in the chip wire. By controlling the height of the waveguide potential from the chip wire we will be able to generate many-body atomic states of either separate condensates in many traps or a coherently correlated Bose gas extending over many traps. By releasing the potential and observing the interference pattern of the atoms we may be able to characterize their ground state properties and dynamics. Figure 1: An SEM image of the periodically perturbed gold wire fabricated on the chip (left) and an isopotential plot of the trapping potential at 1.5µK.

Figure 2: Simulation of the atomic density creating an interference pattern 10 msec after release from a coherent state in a chain of 4 traps. The details of the interference pattern in a real measurement will permit characterization of the initial atomic state and dynamics.

Mo-30

Qubit Coherent Control with Squeezed Light Fields

Ephraim Shahmoon1, Shimon Levit1 and Roee Ozeri2

1Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot, 76100, Israel 2Department of Physics of Complex Systems, Weizmann Institute of Science, Rehovot, 76100, Israel

(ephraim.shahmoon@weizmann.ac.il)

Quantum control fields that operate on a qubit in a single quantum gate may become entangled with the qubit and thus contribute to the gate error [1,2]. For coherent state control fields the error was shown to be exactly the one due to atomic radiative decay in free space with a classical and deterministic control field [3]. Here, we study the use of squeezed light for qubit coherent control and compare it with coherent light control field. We calculate the entanglement between a short pulse of resonant squeezed light and a two-level atom in free space during the π pulse operation and the resulting operation error. We find that for squeezed light, the interplay of three phases - the squeezing phase, the phase of the light field and the atomic superposition, determines the error and the entanglement magnitude. In fact, in comparison with coherent control using coherent light state, the error and the entanglement can be either enhanced or suppressed depending on the above phase relations [see Fig. 1]. These results are explained intuitively by using the Bloch sphere picture and quantitatively by quantum interference effects in the evolution of the atom-pulse quantum state. For quantum information processing purposes the relevant error is that averaged over all possible initial states. To this end, the use of squeezed light would not reduce the average error compared with the coherent light case by a practicably useful amount. In fact, in most cases the average error increases as a result of the enhancement of atom-pulse entanglement by squeezing. We discuss the possibility of measuring the increased gate error as a signature of this entanglement.

FIG. 1: The atom-pulse entanglement vs squeezing. In this specific calculation, the atom coupling to the rest of the free space field modes is neglected. Results are shown for four atomic initial states and for the squeezing phases φ=0,π/2 (|g› and |e› denote the atom's ground and excited states repectively). Compared with the coherent light case (r=0), one obtains a squeezing phase dependent suppression and enhancement of the entanglement as squeezing gets larger. The error probability follows similar trends.

[1] S. J. van Enk and H. J. Kimble, Quantum Inf. Comput. 2, 1 (2002) [2] A. Silberfarb and I. H. Deutsch, Phys. Rev. A 69, 042308 (2004) [3] W. M. Itano, Phys. Rev. A 68, 046301 (2003)

Mo-31

Wednesday February 11, 2009

POSTER SESSION 2

We-1 - We-28

Numerical Solution of the Nonlinear Helmholtz Equation Guy Baruch, Tel Aviv University, Israel The nonlinear Helmholtz equation models the propagation of intense continuous-wave laser beams in Kerr media such as water, silica and air. Mathematically, it is a semilinear elliptic equation which requires non-selfadjoint radiation boundary-conditions, and remains unsolved in many configurations. Its commonly-used paraxial approximation, the nonlinear Schrodinger equation (NLS), is known to possess singular solutions wherein the beam collapses to zero radius, and infinite amplitude. We therefore consider the question, which has been open since the 1960s: do nonlinear Helmholtz solutions exist, under conditions for which the NLS solution becomes singular? In other words, is the collapse arrested in the elliptic, nonparaxial model? In this work we develop a numerical method which produces such solutions in some cases, thereby showing that the collapse is indeed arrested in the elliptic nonparaxial model. We also consider the (1+1)D case, which models propagation in planar waveguides, wherein the NLS has stable solitons. For beams whose width is comparable to the optical wavelength, the NLS model becomes invalid, and so investigation of such nonparaxial solitons requires solution of the Helmholtz model. Joint work with Gadi Fibich and Semyon Tsynkov.

We-1

Structured waveguide arrays to tailor discrete and extended modes and control the light flow Nadia Belabas*1, Sophie Bouchoule1, Isabelle Sagnes1, Juan Ariel Levenson1, Christophe Minot2,1 and Jean-Marie Moison1

1 Laboratory of Photonics and Nanostructures -UPR20 CNRS, Route de Nozay, Marcoussis, F-91460, France 2Institut Telecom / Telecom ParisTech, 46 rue Barrault, 75634 Paris Cedex 13, France

*Corresponding author: nadia.belabas@lpn.cnrs.fr Light propagation in homogeneous arrays of weakly coupled waveguides, i.e. identical waveguides identically coupled, has been studied extensively [1]. In these periodic discrete systems diffraction follows a specific band diagram [2]. Manipulating light with light in this homogeneous meta-material can be achieved by the control of solitonic propagation [3]. We propose an alternative/complementary route towards molding and controlling the flow of light in waveguide arrays: inscribing signal processing functions in matter by structuring the coupling constant C, one key parameter of those arrays. Similarly to what brought success to conventional and photonic-band-gap optics (resp. electronics) through optical index (resp. bandgap) patterning we show that narrow features in the density of modes can thus be engineered in the band diagram using very simple schemes and exploited towards the conception of sensitive devices. We present here two possible designs where localized or extended modes can be put to good use: 1) We demonstrate confinement of light in designated areas of one-dimensional semi-conductor waveguide arrays (Fig 1) where the coupling constant map is engineered to create the analog of a confining structure in the photonic (waveguide) or electronic (quantum well) domains [4]. The spatially localized modes can then be used for example to confine a pump/control beam and improve homogeneous space designs

Fig1 Theoretical (left) and experimental (right) confinement of light in appropriate III-V semiconductor patterned waveguide arrays, analogs of optical waveguide or quantum wells. (a) Schematics of a channel (b) kz(kx) band diagram for the canal involving four (c channel = 1) inter-guide couplings, surrounded by large dams with c barrier = 0.5 (c) corresponding density of modes.

2) We simulate an heterostructure (Fig 2) that allows for example to tailor and suppress divergence in any desired direction by an adequate design of the miniband. [5]

. 1. D. N. Christodoulides, F. Lederer and Y. Silberberg Nature 424, 817- 823 (2003). J. Fleischer, G. Bartal, O. Cohen, T. Schwartz, O. Manela, B. Freedman, M. Segev, H. Buljan, and N. Efremidis, Opt. Express 13, 1780-1796 (2005) 2. S. Eisenberg , Y. Silberberg, R. Morandotti, and J. S. Aitchison, Phys. Rev. Lett. 85, 1863 (2000). D. Mandelik, H. S. Eisenberg, and Y. Silberberg R. Morandotti and J. S. Aitchison Phys. Rev. Lett. 90, 0353902 (2003). 3. A. B. Aceves and M. Santagiustina, Phys. Rev. E 56, 1113 (1997). D. N. Christodoulides and E. D. Eugenieva, Phys. Rev. Lett. 87, 233901 (2001). I. Garanovich, A. Sukhorukov, and Y. Kivshar Opt. Express 13, 5704-5710 (2005) 4. J. M. Moison and C. Minot, French Patent n° 07 54872 (2007). Nadia Belabas, Sophie Bouchoule, Isabelle Sagnes, Juan Ariel Levenson, Christophe Minot and Jean-Marie Moison submitted (2008) 5. J. M. Moison, N. Belabas, C. Minot, and J. A. Levenson to be submitted (2008) J. M. Moison and C. Minot, French Patent n° 08 05307 (2008).

We-2

Fig 2 A coupled waveguide heterostructure (b) folded band diagram for the stack with 4 high (cchannel = 1) inter-guide couplings and 4 low (cbarrier = 0.5) ones. (c) corresponding density of modes. The transmission T (kz) obtained by numerical simulation is shown as a red

On The Locking problem of a Chip Scale Atomic Clock: The Use of Double Field FM Spectroscopy

Ido Ben Aroya, Matan kahanov, Gadi Eisenstein

Electrical Engineering Dept. Technion

Chip scale atomic clocks are frequency standards based on coherent population trapping (CPT) in a

hot vapor of an Alkali atom such as Rb or Cs. The CPT process in those clocks is induced by a

modulated semiconductor laser usually a low power VCSEL. The CPT resonance obtained in those

systems are rather narrow offering Q values of about 20 million however, their contrasts are low

ranging from 1% to 5%. Such low contrasts require that the frequency locking loop make use of a

sensitive spectroscopic scheme such as FM spectroscopy.

The only way to imprint the FM modulation on the optical spectrum is to drive the diode laser with an

microwave current which is itself FM modulated. This means however that both AM modulation

sidebands, which serve as the two fields driving the CPT process, include low frequency FM side

bands. When the microwave signal is swept during the frequency locking process, the two sets of side

bands shift in opposite directions so that every two lines in the complex spectrum which are separated

by the hyper fine splitting frequency of the atom contribute to the CPT signal. The total CPT response

is a sum of many such contributions.

A detailed analysis of this double field FM spectroscopy enables optimization of the FM parameters

(FM modulation rate and index). Under optimized conditions, the error signal in the locking loop has

the largest possible signal to noise ratio and consequently leads to the best clock performance with

state of the art performance.

We-3

Superconducting Atom Chip V. Dikovsky, A. Gershanik, D. Groswasser and R. Folman Atom Chip Group, Ben Gurion University, Israel; www.bgu.ac.il/atomchip Atom chips are solid state devices with isolated cold atoms held in states with long coherence times. To reduce dephasing fields originating in nearby chip current-carrying structures, we intend to use superconductors for these structures. As is known, the magnetic noise of a superconductor in the Meissner state is many orders of magnitude reduced from that of normal metal. This reduction yields longer atomic lifetimes in the magnetic trap (no spin flips), reduced heating, and long coherence times. In addition to improved atom optics, we expect that trapping atoms close to superconductors will enable us to probe with extreme sensitivity some superconducting phenomena. For example, we expect to be able to image vortex motion and the power spectrum of the noise produced by the vortices. We also intend to measure the Casimir-Polder force, which is predicted to have different values near superconducting and normal-metal surfaces. For the first experiments we have developed a niobium-based superconducting chip design. This design is intended to keep the guiding wires in the Meissner state during the atom loading. A continuous-flow cryostat that cools the superconducting chip to a working temperature of about 5 K has been created and tested. References: V. Dikovsky et al., arXiv 0806.1897, accepted for publication in Euro. Phys. Jour. D. V. Dikovsky et al., Euro. Phys. Jour. D35, 87 (2005). T. David et al., Euro. Phys. Jour. D48, 321 (2008). This paper was chosen by the editors of EPJ as a “Highlight Paper”, and Tal David, the author, has just been chosen for a Graduate Student Award by the U.S. Materials Research Society.

We-4

Slow and stored light in an amplifying double Λ system A. Eilam, A. D. Wilson-Gordon, and H. Friedmann,

Department of Chemistry, Bar-Ilan University, Ramat Gan 52900, Israel

We have shown [1], both analytically and numerically, that a probe pulse stored in the lower Λ system

of a double Λ system in an electromagnetically induced transparency (EIT) configuration can be

amplified on retrieval by introducing a small perturbation, due to the addition of an off-resonance

pump field on the upper Λ system of the double Λ system. This leads to the creation of a pulse at the

four-wave mixing (FWM) frequency that is strongly coupled to the restored probe pulse, so that both

the probe and FWM pulses experience gain that is one of the characteristics of the medium in this

configuration. The propagation of the probe and FWM pulses is shown in Fig. 1. The enhancement

compensates for the losses that result from the narrowing of the EIT transparency window as the

writing field is switched off, and the decay of the coherence during the storage time. Moreover, this

system can compensate for the broadening processes that usually occur due to the absorption of the

Fourier components in the wings of the probe pulse. All these unique phenomena are achieved without

destroying the coherent properties of the medium.

0

1020

3040

0

200

4000

3

6

x 10−6

γ32

t’α

0 z

|Ωij|2

Ω32

Ω41

Fig. 1. Propagation of the probe (red) and FWM (blue) pulses as a function of time and propagation

length

[1] A. Eilam, A. D. Wilson-Gordon, and H. Friedmann, Opt. Lett. 33, 1605 (2008).

We-5

Efficient light storage due to coupling between lower levels of Λ system

A. Eilam, A. D. Wilson-Gordon, and H. Friedmann,

Department of Chemistry, Bar-Ilan University, Ramat Gan 52900, Israel

The phenomenon of stored light in atomic systems [1,2] has created considerable attention in the

optical communications field. This process is based on electromagnetically induced transparency (EIT)

in a three-level Λ system. The EIT process is characterized by a very narrow transparency window

and high dispersion of the active medium. One of the main problems in stored light processes is the

losses that occur due to decay of the coherence between the lower levels (LLs) and due to the

narrowing of the transparency window as the control field is switched off. Many attempts have been

made to prevent these losses [3-5]. We propose a new method of circumventing these difficulties [3]

by conserving or even enhancing the LL coherence, and consequently the retrieved probe pulse. The

method involves applying a perturbative field that couples the LLs during the storage time when

neither the control or probe fields are present. We have shown both analytically and numerically that

this LL coupling field can improve the efficiency and yield of the stored light process. Typical results

are shown in Fig. 1.

25 40

0

0.6

1.2

zΓ/c

|Vp(t

,z)/

Vp(0

,z)|

2

10 250

0.8

1.6x 10

−3

zΓ/c

|ρ21

|2

a b

Figure 1. (a) The LL coherence and (b) the relative intensity of the retrieved probe, at a particular

time, as a function of the propagation distance, for different intensities of the LL coupling field. Red –

no, green – very weak, and red – stronger coupling field. [1] M. Fleischhauer, and M. D. Lukin, Phys. Rev. Lett. 84, 5094 (2000).

[2] D. F. Phillips, A. Fleischhauer, A. Mair, and R. L. Walsworth, Phys. Rev. Lett. 86, 783 (2001).

[3] A. Eilam, A. D. Wilson-Gordon, and H. Friedmann, to be published.

[4] I. Novikova, D. F. Phillips, and R. L. Walsworth, Phys. Rev. Lett. 99, 3604 (2007).

[5] D. Stepanenko, G. Burkard, G. Giedke, and A. Imamoglu, Phys. Rev. Lett. 96, 136401 (2006).

We-6

Surface-Enhanced Raman spectroscopy as a Probe for Adsorbate

Orientation on Silver Nanoclusters

Y. Fleger1,2 Y. Mastai2,3 M. Rosenbluh1,2 and D. H. Dressler2,3

1The Jack and Pearl Resnick Institute for Advanced Technology, Department of Physics, Bar-Ilan University, Ramat-Gan, Israel

2Institute of Nanotechnology and Advanced Materials, Bar-Ilan University, Ramat-Gan 52900, Israel

3Department of Chemistry, Bar-Ilan University, Ramat-Gan 52900, Israel

Abstract

Surface enhanced Raman spectroscopy (SERS) has been used to characterize multilayers of three

isomeric aromatic compounds adsorbed on silver nanoclusters. The three structural isomers, which all

adsorb as carboxylate species, onto the silver nanoclusters, bind in two different geometries on the

silver surface. Different surface geometries, correlate to differences in bonding strength of these

molecules to the silver surface, which can be probed by SERS. For Ortho-hydroxybenzoic acid

(salicylic acid), the steric hindrance between the adjacent carboxylate and hydroxyl groups causes the

carboxylate group to rotate from the common flat geometry of benzene substituents on surfaces, and

bond directly through one of the oxygen atoms to the surface. In this case, strong coordinative bonding

between the carboxylate and metal surface promotes significant down shifts of major SERS peaks in

the molecule in comparison to the normal Raman vibrations of the respective crystalline material.

Whereas, for Para, and Meta hydroxybenzoic acid, steric hindrance is less likely since the two

functional groups are not at adjacent positions, and therefore these molecules adsorb on the silver

surface in a totally flat geometry. For these molecules, the CO2 interacts, weakly, with the surface

through an extended π bond, when the aromatic rings are physically adsorbed in the common flat

position. Therefore, for the meta and para substituents, we do not observe significant downshifts of

major Raman peaks, in their SERS spectrum.

Raman and SERS spectra of A. o-Hydroxybenzoic acid, B. p-Hydroxybenzoic acid and C. m-Hydroxybenzoic acid

We-7

600 800 1000 1200 1400 1600 1800

Inte

nsit

y (a

.u)

Raman spectra for p-Hydroxybenzoic acid

Raman shift (cm-1)

1360 cm-1850 cm

-1

1160 cm-1

1600 cm-1

SERS spectra for p-Hydroxybenzoic acid

600 800 1000 1200 1400 1600 1800

Raman spectra for m-Hydroxybenzoic acid

Inte

nsit

y (a

.u)

Raman shift (cm-1)

997 cm-1

1603 cm-1

SERS spectra for m-Hydroxybenzoic acidA.

600 800 1000 1200 1400 1600 1800

990 cm-1

1565 cm-1

1600 cm-1

1025 cm-11580 cm

-11630 cm-1

Raman spectra for Salicylic

Inte

nsit

y (a

.u)

Raman shift (cm-1)

SERS spectra for Salicylic B. C.

600 800 1000 1200 1400 1600 1800

Inte

nsit

y (a

.u)

Raman spectra for p-Hydroxybenzoic acid

Raman shift (cm-1)

1360 cm-1850 cm

-1

1160 cm-1

1600 cm-1

SERS spectra for p-Hydroxybenzoic acid

600 800 1000 1200 1400 1600 1800

Raman spectra for m-Hydroxybenzoic acid

Inte

nsit

y (a

.u)

Raman shift (cm-1)

997 cm-1

1603 cm-1

SERS spectra for m-Hydroxybenzoic acidA.

600 800 1000 1200 1400 1600 1800

990 cm-1

1565 cm-1

1600 cm-1

1025 cm-11580 cm

-11630 cm-1

Raman spectra for Salicylic

Inte

nsit

y (a

.u)

Raman shift (cm-1)

SERS spectra for Salicylic B. C.

Field-free unidirectional molecular rotation

Sharly Fleischer, Yuri Khodorkovsky, I. Sh. Averbukh and Yehiam Prior Department of Chemical Physics, Weizmann Institute of Science, Rehovot, Israel 76100

yehiam.prior@weizmann.ac.il, phone +972-8-934-4008, fax +972-8-934-4126 The essence of coherent control is to drive a molecular system towards specific behavioral goal. The goals are usually set as the enhanced population of a specific vibrational or electronic state and the tools are ultrashort laser pulses which are modulated either in the time or frequency domains. Here we present a double pulse scheme for controlling the sense (clockwise / counterclockwise) of molecular rotation. In the context of laser induced molecular alignment much progress was achieved, mostly due to the increasing availability of strong ultrashort pulses. Various applications based on the time-dependent alignment of molecules were suggested, ranging from optical gating [i] and alignment-dependent strong field ionization [ii] to molecular phase modulators for the compression of ultrashort light pulses [iii]. We have recently demonstrated selective alignment of close molecular species in mixtures, including molecular isotopes and isomers [iv,v]. In practically all previous works in this field, with the exception of [vi], the rotational motion is enhanced, but the net total angular momentum delivered to the molecules remained zero, and for a good reason. For a single pulse schemes, as well as for techniques using multiple pulses polarized in the SAME direction, no preferred sense of rotation exists due to the axial symmetry of excitation. In our scheme (figure 1) we apply the first pulse, linearly polarized (red arrow) along the z axis and let the molecules rotate until they reach an aligned state. At the time of maximal alignment, the molecules are confined in a narrow cone around the polarization direction of the first pulse. At this moment, a second pulse, linearly polarized at 45 degrees to the first pulse, is applied, and thereby induces unidirectional (clockwise) molecular rotation. An interesting feature of this unidirectional rotational excitation is the confinement of the molecules to rotate mostly in the plane defined by the two polarizations. We present a new observable 2cos ϕ which is correlated with the azimuthal distribution

of the molecules (see figure 2).

The time-averaged value 2cos 0.63ϕ ≈ found in this simulation, indicates to persistent highly anisotropic

angular distribution which, in turn, may offer an efficient way to control kinetic and optical properties of the gas medium. Detailed numerical simulations using analytical and numerical (FDTD) approaches, as well as potential applications of the presented technique will be discussed. [i M. A. Duguay and J. W. Hansen, Appl. Phys. Lett. 15, 192 (1969). [ii] I.V. Litvinyuk et.al., Phys. Rev. Lett. 90, 23 (2003). [iii] R.A.Bartels et.al. , Phys. Rev. Lett 88, 019303 (2002). [iv] Sharly Fleischer, Ilya Sh. Averbukh and Yehiam Prior, PRA 74, 041403 (2006). [v] Sharly Fleischer, Ilya Sh. Averbukh and Yehiam Prior, PRL 99, 093002 (2007) [vi] J. Karczmarek, J.Wright, P.Corkum, and M.Ivanov, Phys. Rev. Lett. 82, 3420 (1999).

We-8

Figure 1: Schematic representation of the molecular response to the double pulse sequence.

Figure 2: Deviation of 2cos ϕ from its

isotropic value (0.5) as a function of time. (The 2nd pulse is applied at time 0 in the figure).

Focused Field Symmetries for Background-Free Coherent Anti-Stokes Raman Spectroscopy

D. Gachet1, F. Billard2 and H. Rigneault* Institut Fresnel, Mosaic group, CNRS UMR 6133, Université Paul Cézanne, Aix-Marseille III,

Domaine universitaire St Jérôme, 13397 Marseille cedex 20, France

(β) Corresponding author: herve.rigneault@fresnel.fr Gaussian focused beams exhibit specific properties that drive the emitted fields in nonlinear optical microscopy. Specifically the Gouy phase shift is a π-phase shift anomaly of the electric field when crossing the focal plane of a focused beam. Because the Gouy shift affects the electric field components, it has a strong influence on the induced nonlinear polarization in second and third-order parametric processes. Following the pioneer work of Richards and Wolf1 on focused beams, it is interesting to note that the Gouy phase shift reduces to the simple mathematical expression

E(-r)= -E*I, where r is the spatial coordinate. This basic symmetry property can be favorably used to obtain background-free spectra in third-order nonlinear optical processes. As a demonstration, we concentrate on coherent anti-Stokes Raman scattering (CARS) spectra. In CARS microscopy, the vibrational related (resonant) signal is often overwhelmed by a nonresonant background. Various strategies have been implemented to circumvent the undesirable effects of this nonresonant background in CARS microscopy: picosecond pulse excitation, time resolved, polarization sensitive and epi detections, signal processing, interferometry or spectral phase control. More recently, spatial phase shaping of focus beams was numerically investigated to cancel the coherent addition of the nonresonant signal from a bulk medium in CARS microscopy2. Nevertheless, such implementation requires complex phase mask or interferences. We suggest here a new simple method to obtain pure Raman spectrum in CARS spectroscopy in a collinear configuration when the resonant medium is forming a planar transverse interface with a nonresonant medium. This is done by the subtraction of two consecutively obtained CARS spectra at interfaces where the roles of the resonant and nonresonant media are inverted. This simple operation cancels the nonresonant background detected in the forward direction and uses the nonresonant medium as a local oscillator with which the Raman spectrum is measured in heterodyne detection. Such a scheme is useful when the sample nonresonant background is stronger than the resonant signal as usually found in CARS microscopy and spectroscopy. High resolution Raman spectroscopy is thus enabled using the enhancement inherent to the stimulated CARS process. An experimental demonstration of these predictions is carried on N,N-dimethylformamide (DMF) squeezed between two glass substrates3. This scheme is also applicable to a thin layer of a resonant medium embedded between two nonresonant media and can find application in micro-fluidic devices4. References [1] B. Richards and E. Wolf, Proc. R. Soc. London A 253, 358 (1959). [2] V. V. Krishnamachari and E. O. Potma, Chem. Phys. 341, 81 (2007). [3] D. Gachet, F. Billard and H. Rigneault, Phys. Rev. A 77, 061802I (2008). [4] D. Gachet, F. Billard and H. Rigneault, J. Opt. Soc. Am. B 25, 1655 (2008).

We-9

We-10

Observation and Coherent Control of Transient Two-Photon Absorption: The Bright Side of Dark Pulses

Andrey Gandman, Lev Chuntonov, Leonid Rybak, Zohar Amitay Schulich Faculty of

Chemistry, Technion, Haifa, Israel (gandman@tx.technion.ac.il)

We present experimental observation and coherent control of transient state population excited via nonresonant two-photon transition by shaped femtosecond pulses. By proper pulse shaping, utilizing the invariance of the two-photon absorption to specific phase transformations of the pulse, different time evolutions of the transient population are photoinduced for a given (fixed) final state population. The work is conducted in the weak-field regime for which the transient two-photon excitation is described by second-order perturbation theory. The model system is the Na atom. Figure 1 shows the corresponding Na excitation and detection scheme, together with a schematic of the phase patterns used in our experiments. Each phase pattern results from the addition of two patterns: (i) a simple π phase step that sets the final population level, and (ii) a pattern that is anti-symmetric around one-half of the two-photon transition frequency that tunes the transient population without affecting the finite population. One most attractive case is the extended family of two-photon dark pulses, where different temporal evolutions are photo-induced for a zero final population. Corersponding results are shown in Figure 2.

Laser Induced Alignment of Water Spin Isomers Erez Gershnabel, and Ilya Sh. Averbukh

Department of Chemical Physics, Weizmann Institute of Science Rehovot, 76100, Israel erez.gershnabel@weizmann.ac.il

According to quantum mechanics, a molecule that contains two identical atoms whose nuclei have

nonzero spins exists in the form of spin isomers. In particular, a water molecule has two spin isomers,

ortho or para, with parallel or antiparallel proton spins, respectively. We analyze feasibility of

selective alignment of ortho and para spin isomers of water molecules by using strong and short off-

resonance laser pulses [vii]. By alignment we mean angular localization of one of the principal axes of

the molecule, while antialignment refers to the confinement of the molecular axis in a plane

perpendicular to the laser pulse polarization. Recently, this approach was experimentally

demonstrated for linear Nitrogen molecules [viii], but here we perform the first theoretical analysis for

bent triatomics, like water. Following the application of a laser pulse, the molecular highest

polarizability axis tends to be aligned along the laser field polarization axis (we denote the angle

between the axes as θ ). We show that a single linearly polarized laser pulse ( 133 10⋅ W/cm2, 20fs) is

able to induce distinct transient alignment and antialignment dynamics of the isomeric species (Figure

1a). This dynamics can be further selectively controlled by applying a second laser pulse (of the same

intensity and duration) at t=1.9ps, when the ortho and para molecules are on the way of becoming

antialigned and aligned, respectively. The results are shown in Figure 1b.

(a)

(b)

Figure 1. (a) Alignment factor, 2cos θ< > vs time after the first laser pulse. (b) Alignment factor vs time after the second pulse. In both cases the temperature is 20K.

It can be seen that the second pulse enhanced a bit the alignment of the para molecules, but

suppressed almost completely the alignment of the ortho molecules, leaving them isotropically

oriented. This confirms the ability to control selectively the alignment of different spin isomers of

water, which opens new ways for further manipulation of these species, including actual spatial

separation with the help of external fields. 1 E. Gershnabel and I. Sh. Averbukh, Phys. Rev. A, (2009) in press. 2S. Fleischer, I. Sh. Averbukh and Y. Prior, Phys. Rev. Lett., 99, 093002 (2007)

We-11

Suppression of photo-ionization by a static field *

Ido Gilary Schulich Faculty of Chemistry, Technion-Israel Institute of Technology, Haifa, 32000, Israel

Nimrod Moiseyev

Schulich Faculty of Chemistry and Department of Physics, Technion-Israel Institute of Technology, Haifa, 32000, Israel

The dc-field Stark effect is studied theoretically for atoms in high intensity laser fields. We prove that the first order perturbation corrections for the energy and photo-ionization rate vanish when the dc-field strength serves as a perturbational strength parameter. Our calculations show that by applying a dc-field in the same direction as the polarization direction of the ac-field, the photo-induced ionization rate is almost entirely suppressed. This suppression is attributed to changes in the phase shift of the continuum atomic wavefunctions which can be controlled by the dc-field. *I. Gilary, Y. Sajeev, M. F. Ciappina, A. Croy, C. M. Goletz, S. Klaiman, M. ·Sindelka, M. Winter, W. Wustmann and N. Moiseyev., Phys. Rev. Lett, 101, 163002 (2008).

We-12

Walks on the Bloch sphere: Coherent manipulations of an atomic two-state system Menachem Givon, Amir Waxman, David Groswasser, Ron Folman Atom Chip Group, Ben Gurion University, Israel www.bgu.ac.il/atomchip The time evolution of a quantum two-state system can be represented by the Bloch sphere. The

87Rb ground-state hyperfine levels are chosen as the |0> and |1> states. To manipulate those states we use two coherent phase-locked laser beams that induce a two-photon Raman transition from one state to the other. Direct transitions between these levels can be realized using microwave (MW) radiation, but use of optical Raman beams makes possible addressing even a single atom with a tight focus and control over the polarization of the Raman beams, as well as driving a ΔmF=2 transition (not possible with one MW photon). Moreover, the Δυ/υ ratio that determines the accuracy of our pulses is smaller in the optical regime, reducing uncertainty in the position of the Bloch vector. We built a combined system that is capable of producing a pair of coherent laser fields (Raman beams) as well as a pair of coherent microwave (MW) and RF fields. We monitored population oscillations of 87Rb room temperature vapor, produced by MW radiation alone (one-photon transition) or by MW and RF radiation (two-photon transitions). We are now integrating a Magneto-Optical Trap (MOT) of 87Rb atoms to the system, so that we will be able to manipulate ultracold atomic clouds with the Raman laser beams, and realize the optical ΔmF=2 Raman transition.

We-13

0 500 1000 1500 2000-0.01

0.00

0.01

0.02

0.03

0.04

0.05

Data: Data1_DModel: rabifit Chi 2 = 7.2327E-6R^2 = 0.93606 A -0.02715 ±0.0009B 0.01921 ±0.00019W 0.01214 ±0.00004to 1410.24841 ±78.61067phi 6.41279 ±0.02902

rabi oscillations 3 dbm

popu

latio

n F=

2

Time [microsec.]

The experimental system MW-induced population oscillation

Quantum Information studies with trapped ions and flying photons Yinnon Glickman, Nitzan Akerman, Shlomi Kotler, Yoni Dallal, Ana

Weksler and Roee Ozeri Weizmann Institute of Science, Rehovot 76100, Israel

The internal states of trapped ions are a promising candidate system for quantum information

processing and storage. The polarization states of photons are good carriers for quantum information

transfer over long distances. Here we describe an experimental setup in which quantum information

studies will be performed using both the 5s2S1/2 Zeeman states of trapped Sr+ ions and the polarization

states of spontaneously scattered photons as quantum bits (qubits). Ions are trapped in an ultra high

vacuum environment (~10-11 Torr) by a linear RF Paul trap. With an ion-electrode distance of 275 μm,

20 MHz RF frequency and various RF amplitudes and end-cap voltages the trap axial (radial)

frequency varies between 0.2-1.2 (0.5-3) MHz. Laser cooling and Resonance fluorescence on the

5s2S1/2-5p2P1/2 transition (422 nm) are observed. Ions are imaged with a resolution of 0.8 μm on either

a CCD camera or two PMTs detecting photons of different polarization states. Magnetic field noise in

the ions vicinity is actively stabilized to a few μGauss level, in order to achieve a relatively long

coherence time (T2). A 405 nm external cavity diode laser is used to coherently manipulate the ion-

qubit via stimulated Raman transitions. Work is done to lock and narrow the frequency of a 674 nm

laser down to a bandwidth below ~1 kHz in order to shelve one of the 5s2S1/2 Zeeman states on the

5d2S1/2-4d2D5/2 quadruple transition, thus enabling fluorescence selective state detection. With this set-

up we will study ion-photon entanglement both as a source of decoherence as well as an information

resource.

We-14

Visualization of Branch Points in PT -Symmetric Waveguides* Shachar Klaiman and Nimrod Moiseyev

Since the introduction of parity and time-reversal symmetric Hamiltonians, briefly referred to as PT symmetric Hamiltonians, by Bender and Boettcher (Phys. Rev. Lett., 80, 5243, (1998)), a new class of non-hermitian Hamiltonians have been drawing a great deal of attention. Under certain conditions PT - symmetric Hamiltonians can have a completely real spectrum and thus can serve, under the appropriate inner products, as the Hamiltonians for unitary quantum systems. The equivalence of the Maxwell and Schr¨odinger equations in certain regimes provides a physical system in which the properties of PT - symmetric operators can be studied and exemplified. Moreover, such realizations can be very useful in connecting general mathematical concepts with observable physical measurements. An extremely interesting property of PT - symmetric operators is the transition from a completely real spectrum into a non strictly real spectrum. This property has come to be known as exact/spontaneously-broken PT - symmetry. In most cases the transition between exact and broken PT symmetry is governed by some parameter serving as a measure of the non-hermiticity. At the transition point two (or more) of the real eigenvalues of the Hamiltonian coalesce. However, this is no ordinary degeneracy as the corresponding eigenfunctions coalesce as well forming a self-orthogonal state. Such points in the spectrum are often referred to an exceptional point. Beyond this point the eigenvalues separate into a pair of complex conjugate solutions. In this work, the visualization of an exceptional point in a PT symmetric directional coupler (DC) is demonstrated; see Fig. 1(a). The imaginary part of the refractive index serves here as the non-hermiticity parameter. By varying the non-hermiticity parameter the beat length of the DC can be controlled, see Fig. 1(b). This allows a unique perspective on exceptional points. Usually, in order to detect an exceptional points one has to go around it in some parameter space. Such a circulation around an exceptional point produces a geometrical phase that can then be measured. In our case, however, we are able to go directly through the exceptional point by varying only a single parameter. This is not merely a more direct method of detecting the exceptional point but also opens the door to previously unobservable quantities. One such quantity is the visualization of the self-orthogonal state that in our suggested experiment can be observed directly. Using the Rayleigh-Schr¨odinger perturbation theory we prove that the spectrum of a PT symmetric Hamiltonian is real as long as the radius of convergence has not been reached. We also show how one can use a PT symmetric DC to measure the radius of convergence for non PT symmetric structures. While the visualization is done on a PT symmetric waveguide, the measured radius of convergence corresponds to the maximum value of an added antisymmetric index profile which can still be treated within perturbation theory. For such systems the physical meaning of the rather mathematical term: radius of convergence is exemplified. *S. Klaiman, U. G¨unther, and N. Moiseyev, Phys. Rev. Lett., 101, 080402, (2008).

We-15

Dynamics of elementary excitations in para-hydrogen crystals: long living, coherent phonons, rotons and stimulated rotational Raman beats

1, Nikolaus Schwentner2Anderson. , David T1, Nina Owschimikow1nigsmannöFalk K

1Freie Universität Berlin, Institut für Experimentalphysik, Arnimallee 14, D-14195 Berlin;

2Department of Chemistry, University of Wyoming, Laramie, WY 82071, USA;

One of the most distinct spectroscopic features of cryogenic para-hydrogen are the sharp linewidths. The thus expected very long coherence times in the dynamics did however not show up in previous ultrashort pulsed excitations. Our approach is ultrashort, spectrally resolved Optical Kerr Effect (OKE) spectroscopy, sensitive to induced anisotropies. We grow 3 cm long, transparent para-hydrogen crystals in an enclosed cell at 10 K, which are then cooled down to 4 K. The crystals are pumped with 150 fs pulses at 780 nm of a Ti:Sa amplified laser system and the induced birefringence is detected with the second harmonic in a colinear way. We observe long lasting (>20 ps) sinusodial birefringence modulation with a period of 907 fs (Fig. 1a) [1]. While the phonon density of states would cover a broad range from 0-180 cm-1, the observed coherent phonon has a sharp frequency centered at 36,8 cm-1. It coincides with the transverse, optical phonon at the center of the Brillouin-zone, which is observed exclusively in Raman scattering [2]. The phonon wave packet is anisotropic and the amplitude lies perpendicular to the c axis. Para-hydrogen also shows long lasting, higher frequency birefringence modulations with a period of 94 fs in the wings of the detected second harmonic, matching the J=2←0 roton excitation of approximately 355 cm-1 [3]. Here we detected the molecular alignment caused by the impulsive formation of a k=0 roton wavepacket consisting of the J=0 and J=2 states of para-hydrogen by the pump pulse. Additionally, pump-induced, stimulated Stokes- and Anti-Stokes Raman bands of the probe pulse were detected. They carry a 17 ps beating structure, which corresponds to the 2.0 cm-1 splitting in the roton triplet (Fig. 1b) also known from cw Raman-spectroscopy. The beat pattern varies with the polarization direction due to different amplitudes of the triplet components.

Fig. 1. (a) Long lived phonon dynamic with a period of 907 fs. (b) The Fouriertransformation of the Raman-sidebands resolves the crystal field splitting of the J=2←0 roton.

[1] F. Königsmann, M. Fushitani, N. Owschimikow, D.T. Anderson, N. Schwentner, Chem. Phys. Lett., 458, 303 (2008). [2] I.F. Silvera, W.N. Hardy and J.P. McTague, Phys. Rev. B, 5, 1578 (1972). [3] E. Goovaerts, X.Y. Chen, A. Bouwen and D. Schoemaker, Phys. Rev. Lett., 57, 479 (1986).

We-16

Hydrogen clusters that remain liquid at low temperature

Kirill Kuyanov-Prozument1) and Andrey F. Vilesov Department of Chemistry, University of Southern California, Los Angeles, CA 90089 1) Present address: Department of Chemistry, Massachusetts Institute of Technology,

Cambridge, MA 02139 Accepted to Phys. Rev. Lett.: October 8, 2008

Abstract Superfluidity of hydrogen, predicted three decades ago, continues to elude experimental observation,

due to the high freezing temperature of H2 at T = 13.8 K. Here, large para- H2 clusters are obtained in

a cryogenic pulsed free jet expansion and are studied via nonlinear Raman spectroscopy. Clusters

formed from neat pH2 are solid, as evidenced by the characteristic splitting of the rotational S0(0) line.

However, clusters formed of highly diluted pH2 (≤ 1%) in He have a single S0(0) line and remain

liquid at the estimated superfluid transition temperature of T = 1 – 2 K.

We-17

Direct Observation of a Localization Transition in Quasi-periodic Photonic Lattices

Y. Lahini1, R. Pugatch1, F. Pozzi2, M. Sorel2, R. Morandotti3, N. Davidson1 and Y. Silberberg1 1Department of Physics of Complex Systems, the Weizmann Institute of Science, Rehovot, Israel

2Department of Electrical and Electronic Engineering, University of Glasgow, Glasgow, Scotland 3Institute National de la Recherche Scientifique, Varennes, Québec, Canada

yoav.lahini@weizmann.ac.il

Abstract: We observe the signature of a localization phase transition in one-dimensional quasi-periodic photonic lattices. In addition we compare experimentally the effect of nonlinearity before and after the transition.

Anderson localization [1] - the localization of classical and quantum mechanical waves in disordered media - is a universal phenomenon studied in a variety of different physical systems. A localization crossover was recently observed in disordered one- and two-dimensional systems [2, 3]. However, for disordered systems a true localization phase transition is expected only in three-dimensions, making the transition very hard to observe. Aubry and André [4] have predicted that a true localization phase transition can occur in one-dimensional systems, in which a periodic lattice is modulated at a maximally incommensurate frequency. The Aubry -Andre model is given by:

[ ] )()2cos( 110 −− +++=∂

∂nnn

n Cnt

i ψψψχπλβψ (1)

where ψn is the wavefunction at site n, β0 is the single-site energy of the periodic lattice, C is the tunneling rate between sites and 2/)15( +=χ (the golden mean). A localization phase transition was predicted to take place at a critical modulation strength λc=2*C. Here we report an experiment that realizes the Aubry-André model in a photonic quasi-crystal, where we observe the signature of this localization transition. Below the transition, all the modes of the system are extended and therefore an initially narrow wave packet eventually spreads across the whole system. Above the critical point all modes are localized and expansion is suppressed. Experimental results are presented in Fig.1.

−10 −5 0 5 100

0.01

0.02

Nor

mal

ied

Inte

nsity

−10 −5 0 5 100

0.01

0.02

Distance from input site (lattice sites)

−10 −5 0 5 100

0.02

0.04

6 mm

21 mm

−2 −1 0 1 20

1

2

3

ln(C*z)

ln(P

R)

λ/C=0

λ/C=1.6

λ/C=3.1

λ/C=4.6

λ/C=7

(a) λ/C=0 (b) λ/C=1.6 (c) λ/C=3.1 (d)

Fig. 1. Experimental measurements of a localization transition in incommensurate photonic lattices. (a) The expansion of a single site initial wave packet in a periodic lattice (λ=0) after 5 mm of propagation (blue) and 21 mm (red), corresponding to different evolution times. (b) The same for an incommensurate lattice with λ=1.5. The wavepacket still exhibits expansion, but at a reduced speed. (c) The same for an incommensurate lattice with λ=3, the wavepacket remains tightly localized about the input position throughout the propagation, signifying localization. (d) Logarithmic Plots of the measured width of the wavepackets (given by the participation ratio P) at different lengths, for different λ values. This shows the transition from expansion to localization as a function of the incommensurate modulation strength, signifying the localization transition. (e) Plots of the wavepacket width after 22mm of propagation at increasing nonlinearity. In addition, we have measured the effect of nonlinearity on the dynamics, and found that in the localized regime the localization length increases as the non-linear interactions increase. [1] Anderson, P. W. , Phys. Rev. 109, 1492-1505 (1958). [2] T. Schwartz et. al., Nature 446, 52 (2007). [3] Y. Lahini et. al. Phys. Rev. Lett. 100, 013906 (2008). [4] Aubry, S. & André, G., Ann. Israel. Phys. Soc. 3, 133 (1980).

We-18

A photonic cluster state machine gun

Netanel H. Lindner1*, and Terry Rudolph2,3

1Department of Physics, Technion—Israel Institute of Technology, Haifa 32000, Israel 2Optics Section, Blackett Laboratory, Imperial CollegeLondon, London SW7 2BZ, United Kingdom

3 Institute for Mathematical Sciences, Imperial College London, London SW7 2BW, United Kingdom

We show§ that with current technology it is possible to manipulate certain single photon sources, in

particular quantum dots, so as to generate a continuous stream of photons, each of which is entangled

with the photons which both precede and follow it. Specifically, it is possible to use the source to emit

long strings of (various varieties of) 1-dimensional cluster states in a controlled and pulsed “on

demand'' manner.

Such a source greatly alleviates the resources required to achieve linear optical quantum computation.

Using these strings, it is possible to efficiently fuse cluster states capable of running arbitrary quantum

algorithms via the simple procedure of making individual single-qubit measurements on the photons

involved. Standard spin errors, such as dephasing, are shown to affect only 1 or 2 of the emitted

photons at a time. We analyze all error mechanisms and show that the error rates can be very low -

close to fault tolerant thresholds for quantum computing - even if the source is operated for timescales

much longer than the typical decoherence times. Using realistic parameters for current quantum dot

sources, we conclude high entangled-photon emission rates are achievable, with Pauli-error rates less

than 0.2%. Our analysis of the emitted wavepackets allows us to design filtering techniques which can

push these error rates even lower.

§ Netanel H. Lindner and Terry Rudolph, arXiv:0810.2587 * email: lindner@tx.technion.ac.il

We-19

AFM TIP ASSISTED LASER INDUCED SURFACE MODIFICATION

Alexander A Milner and Yehiam Prior Department of Chemical Physics, Weizmann Institute of Science, Rehovot, Israel 76100

Yehiam.prior@weizmann.ac.il

The ability to modify surfaces on a length scales comparable with the apex of the Atomic Force Microscopes (AFM) tip became attractive almost simultaneously with the appearance of the AFM. The development of different techniques for active nano-scaled tip-surface controlled interaction continues to be a subject of constant interest. Here we report a recently developed approach to nano-lithography based on the effect of strong laser beam focused onto a tip hovering a few nanometers above a surface. Two different mechanisms have been discussed in the literature as contributing to surface modification: hot tip lithography [1] and tip assisted laser material ablation [2]. We devised an approach to separate these two effects, and demonstrate each one individually. The work is done in a specially designed “true” non-contact mode of AFM operation, when the tip scans the sample surface keeping the predetermined tip-sample gap of a few nano-meters [3]. The effect of the two physical mechanisms are very clear: i) heat diffusion from the laser heated AFM tip to the sample surface, strongly concentrated in the area comparable to tip apex; ii) electro-magnetic field enhancement in the vicinity of the sharp tip (“lightning-rod” effect) causing the material ablation. In both processes bare silicon tips were used. They didn’t touch the sample surface, and the lines drawn had accurate profile, ~20 nm width and a few nano-meters depth. In the first case (“hot tip”) the materials under processing were polymers (Fig.1), and in the second case it was thin gold film (Fig.2). Fig.1. “Hot tip” nano-lithography Fig.2. Field-enhanced gold Fig.3. Si Raman line at different

on the polymer.

film ablation.

laser powers focused

on the AFM

tip.

For the tip temperature control, we involved the micro-Raman technique and monitored the silicon Raman line shift vs laser power (Fig.3). We tuned the system such that the tip temperature was high enough (350 - 500°C) for melting the polymer, and yet too low to affect the gold metal film. The details of the method as well as the potential for further surface modification will be discussed. [1] Kirsanov, A., Kiselev, A., Stepanov, A., Polushkin, N. Femtosecond laser-induced nanofabrication in the near-field of atomic force microscope tip. J.Appl.Phys., 94 6822 (2003).

[2] Chimmalgi, A., Choi, T. Y., Grigoropoulos, C. P. & Komvopoulos, K. Femtosecond laser aperturless near- field nanomachining of metals assisted by scanning probe microscopy. Appl. Phys. Lett., 82 1146 (2003).

[3] A.A. Milner, K. Zhang, Y Prior. Floating Tip Nanolithography. Nano Letters, 8 2017-2022 (2008).

We-20

Nonlinear polarimetric analysis of DNA in liquid crystalline phases Halina MOJZISOVA,1,2 Joanna OLESIAK,3 Marcin ZIELINSKI,1 Katarzyna MATCZYSZYN,3

Dominique CHAUVAT,1 and Joseph ZYSS1

1Laboratoire de Photonique Quantique et Moléculaire,d’Alembert Institute,ENS Cachan,

61 avenue du Président Wilson, 94235 Cachan, Cedex, France 2Laboratoire de Biotechnologies et de Pharmacologie génetique appliquée,d’ Alembert Institute ENS Cachan,

61 avenue du Président Wilson, 94235 Cachan, Cedex, France 3Laboratory of the Materials Research, Institute of Physical and Theoretical Chemistry,

Wroclaw University of Technology, Wyb. Wyspianskiego 27, 50-370 Wroclaw, Poland

In eukaryotic cells 1 to 10 cm long DNA molecules are tightly packed into few micrometer-sized

volume of the cell nucleus. In these highly condensed states, DNA exhibits self-ordering properties

such as self organized liquid crystalline phases. Besides their potential implication in physiological

processes, these partially organized structures provide interesting models for developing new

experimental techniques for the study of molecular orientation in biological material. In this work we

present a nonlinear polarimetric analysis of dye-doped DNA liquid crystals. The binding parameters of

two different DNA specific markers, i.e., Propidium Iodide and Hoechst, are determined. The

orientation of DNA is then inferred from by the polarization analysis of two-photon fluorescence

emitted by these molecules. In this approach, nonlinear microscopy presents several advantages. In

particular, due to two-photon excitation, this technique enables to realize an “intrinsic” axial

sectioning and thus a 3D mapping of the local DNA orientation in different liquid crystalline phases.

Our results show that polarization sensitive two-photon microscopy is a promising tool for analysing

organization of higher-ordered structures in the biological field.

Figure: Two-photon fluorescence intensity scan of Propidium Iodide (PI) doped DNA. The experimental and theoretical

polar graphs of the fluorescence intensity vs. angle of incident polarization reveal the orientation of PI emission dipoles.

We-21

Plasmon-enhanced third harmonic generation in gold nanorods Osip Schwartz and Dan Oron

Department of Physics of Complex Systems,Weizman Institute of Science, Rehovot

Metallic nanoparticles exhibiting surface plasmon polaritons are a subject of extensive research, motivated by their possible applications to photovoltaics, sensor technology and bioimaging. Their attractiveness as contrast labels for bioimaging is provided by the enhancement of the electric field in the vicinity of the nanoparticles caused by the plasmon resonance. This effect boosts the nonlinear optical processes in the particles, allowing one to image them by detecting nonlinear optical signal, such as two-photon luminescence1 or third harmonic generation (THG)2. In this work we study THG in gold nanorods, whose longitudinal plasmon mode resonance can be controlled by choosing the aspect ratio of the particles. This allowed us to tune this mode in resonance with the fundamental frequency of the Ti:Sapphire laser we used. We detected THG in a quartz cell containing water suspension of gold nanorods. The resonant enhancement of the nonlinear cross section allowed us to observe the signal at peak intensity as low as 108 W/cm2. The observed THG signal demonstrates unusual polarization properties. If the illuminating beam is circularly polarized, the THG process is prohibited in spherically-symmetric particles. However, due to their anisotropic shape, gold nanorods produce THG even when the illuminating light is circularly polarized. This feature can be used to discriminate the signal from the background.

60 40 20 20 40 60

2010

1020

1510 5 5 10 15

5

10

15

Fig. 1. Polarization diagrams obtained with linearly (a) and circularly (b) polarized illuminating light. The plot (b) describes the polarization of signal after passing through a λ/4 waveplate. The plots in Fig.1 show the polarization diagrams of the signal measured with linear (a) and circular (b) polarization of incoming light. In the last case, the signal passed through a λ/4 waveplate before entering the analyzer. The anisotropy of the plot in Fig.1 (b) indicates the presence of a circularly polarized component in the THG signal. The polarization properties of the signal are in good agreement with our numeric simulations.

1. M. Lippitz, M.A. van Dijk, and M. Orrit. Nano Letters, 5(4):799-802, 2005. 2. H. Wang et al, PNAS, 102:1575

We-22

Fields in Atomic Vapor-dimensional Light-e of ThreeCoherent Storag

Ron . , AFirstenberg. O ,Shuker. M Physics Department, Technion

il.ac.technion.shuker@physics

R. Pugatch, N. Davidson Department of Physics of Complex Systems, Weizmann Institute

The information carried by a light field (‘probe’) may be encoded in the ground-state coherence of

atomic ensembles, and recovered at a later time, using a second light field (‘pump’) [1]. Here, we

study the possibility to store arbitrary three-dimensional light fields using EIT in room-temperature

vapor [2]. While the pump beam was a plane wave, an arbitrary transverse image was imprinted on the

“probe” beam (see left side of the figure). We find that the main limitation on the storage fidelity is the

diffusive motion of the atoms during the storage duration (see right side of figure). A quantitative

measure of the possible storage resolution was obtained by storing an image of three resolution lines.

We suggest and implement a technique to mitigate the effect of diffusion on the storage fidelity, by

phase-manipulations of the input image. This is an extension of a previous work showing the storage

stability of helical modes light [3]. Finally, we study the storage of various transverse modes of the

light field [4], and show that all the modes are self-similar under diffusion.

Left – artist view of storing the digit ‘2’, Right – experimental results

[1] D.F. Phillips et al., Phys. Rev. Lett. 86, 783 (2001). [2] M. Shuker, et al., Phys. Rev. Lett. 100, 223601 (2008). [3] R Pugatch et al., Phys. Rev, Lett. 98, 203601 (2007). [4] O. Firstenberg et al., in preparation.

We-23

Controlling Material Transformation and Plasma Emission with Trains of Ultrafast Laser Pulses

Sima Singha, Zhan Hu, Yaoming Liu, and Robert J. Gordon Department of Chemistry, University of Illinois at Chicago

Laser transformation of materials is a highly complex process involving multiple time and length scales. One way of separating and possibly controlling such processes is to excite the material with trains of sub-ps pulses separated by the characteristic times of the processes of interest. Here we describe experiments performed on two such time scales. In the first experiment, we irradiated a crystal in air with a pair of 50fs, 800nm pulses having delays of up to 100ps. A typical result is shown in Fig. 1 for Si(111), where the ratio of the plasma fluorescence produced by the pulse pair to that produced by a single pulse of the same total energy is plotted as a function of delay and fluence. At constant fluence, the enhancement ratio grows to a plateau with a time constant of 30-40ps, whereas at a fixed delay the ratio passes through a maximum and falls off at high fluence. We interpret this as an incoherent effect in which the first pulse melts the surface and the second pulse interacts more strongly with the liquid phase, as the melt front propagates into the bulk.3,4

Figure 1. Fluorescence enhancement at 505.6nm produced by double pulse ablation of Si(111). Left panel: enhancement ratio vs. pulse delay at a fixed fluence of 10.4J/cm2. Right panel: 3D plot showing both time and fluence dependence of the

enhancement ratio.

In a second set of experiments, trains of three or more pulse were generated with a spatial light modulator, with separations on the order of 1 ps. Figure 2 shows the enhancement ratio for GaAs. The peak spacing corresponds approximately to the LO phonon period of the crystal and is highly suggestive of a coherent effect.

Figure 2. Fluorescence enhancement of GaAs produced by a 3-pulse train. Left: Enhancement ratio at a fluence of 15.3 J/cm2. The arrows indicate multiples of the phonon period. Right: 3D plot of enhancement vs. pulse delay and total fluence.

3 Z. Hu, S. Singha, Y. Liu, and R. J. Gordon, Appl. Phys. Lett. 90, 131910 (2007). 4 S. Singha, Z. Hu, and R. J. Gordon, J. Appl. Phys. (in press).

We-24

Attractive Phenomena in Attractive BECs: Fragmentation and Collapse

A.I. Streltsov, O.E. Alon and L.S. Cederbaum

Theoretische Chemie, Physikalisch-Chemisches Institut, Universität Heidelberg,

Im Neuenheimer Feld 229, D-69120 Heidelberg, Germany

To study the relevance of fragmentation channels (macroscopic occupation of several orbitals) for the many-body dynamics of attractive bosonic clouds in 1D we apply the recently developed MCTDHB [1] theory. We show that within this theory an initially coherent wave-packet can dynamically dissociate into two parts when its energy exceeds a threshold value. In contrast, the time-dependent Gross-Pitaevskii theory applied to the same initial state does not show up the splitting. We call the split object fragmenton (see Fig.1 and [2]), because it possesses remarkable properties: (1) it is two-fold fragmented, i.e., not coherent; (2) it is dynamically stable, i.e., it propagates almost without dispersion; (3) it is delocalized, i.e., the two dissociated parts still communicate with one another. The importance of fragmentation for 3D studies on attractive BECs is also shown. It is well known that attractive condensates in 3D do not have a stable ground state. The Gross-Pitaevskii theory predicts the existence of metastable states up to some critical number NGPcr of atoms. It is demonstrated (see Fig.2 and [3]) that fragmented metastable states exist for atom numbers well above NGPcr. The fragments are strongly overlapping in space.

Fig 1

Fig 2

[1] A. I. Streltsov, O. E. Alon, and L. S. Cederbaum, Phys. Rev. Lett. 99, 030402 (2007); O. E. Alon, A. I. Streltsov, and L. S. Cederbaum, Phys. Rev. A 77, 033613 (2008).

[2] A. I. Streltsov, O. E. Alon, and L. S. Cederbaum, Phys. Rev. Lett. 100, 130401 (2008).

[3] L. S. Cederbaum, A. I. Streltsov, and O. E. Alon, Phys. Rev. Lett. 100, 040402 (2008).

We-25

Bloch Sphere Representation of SFG and Efficient Adiabatic Conversion

H. Suchowski1, D. Oron1, A. Arie2, Y. Silberberg1 1Weizmann Institute of Science, Physics of Complex Systems, Rehovot, 76100, Israel

2Tel Aviv University, School of Electrical Engineering, Tel Aviv, 62000, Israel

We present a geometrical representation for sum frequency generation (SFG) process in the undepleted pump approximation, in analogy with the known optical Bloch equations [1]. This analogy could be used to produce efficient wavelength converters. In particular, we show that the mechanism of rapid adiabatic passage (RAP) [2-3], where a strong chirped excitation pulse scans slowly through the resonance to achieve robust full inversion, can be adapted for frequency conversion. By varying adiabatically the phase mismatch parameter along the propagation axis, we introduce a novel technique for achieving a robust, highly efficient ultra-broadband frequency conversion device (see Fig. 1).

Fig 1. Adiabatic conversion scheme for SFG in the undepleted pump approximation. a) Continuous adiabatic variation of the phase-mismatch parameter is required. This can be achieved by slowly changing the poling periodicity along the propagation direction. b) The adiabatic following trajectory, where the torque vector initially points at the south pole, and ends up at the vicinity of the north pole. c) The projection of the trajectory onto the W axis yields the conversion efficiency.

This adiabatic frequency conversion scheme was experimentally demonstrated by using an aperiodically poled KTP device, design to achieve high efficiency signal-to-idler conversion over a bandwidth of 140nm, and for 100ºC crystal's temperature variation as shown in Fig. 2. This scheme can be utilized also for efficient broadband fluorescence upconversion, as well as for ultrashort pulses.

Fig 2. Conversion efficiency as a function of (a) input wavelength and (b) crystal temperature, using the adiabatic APPKTP design at a pump intensity of 15 MW/cm2.

References [1] H.. Suchowski, D. Oron, A. Arie, Y. Silberberg, accepted to PRA (2008). [2] N. V. Vitanov et al., Ann. Rev. of Phys.Chem. 52, 763 (2001). [3] L. D. Allen and J. H. Eberly “Optical Resonance and Two Level Systems” (1975).

We-26

FEEDBACK-CONTROLLED RADIATION PRESSURE COOLING

Mark Y. Vilensky, Yehiam Prior, and Ilya Sh. Averbukh

Department of Chemical Physics, Weizmann Institute of Science, Israel

: mail-Eil.ac.vilensky@weizmann.marik

We propose a new approach to laser cooling of micromechanical devices such as micro-mirrors and cantilevers5. The technique is based on the phenomenon of optical bistability. As a model, we consider a Fabry-Perot resonator with one fixed and one oscillating mirror. The bistability may be induced by an external nonlinear optical feedback loop controlling the phase between the incident and

intracavity field. When excited by an external laser, the cavity field has two co-existing stable steady-states depending on the position of the mirror. If the latter moves slow enough, the field in the cavity adjusts itself adiabatically to the mirror's instantaneous position. The mirror experiences radiation pressure depending on the intensity of the intra-cavity field. A sharp transition between two values of the radiation pressure happens twice per every period of the mirror oscillation, at two different positions (hysteresis effect, see Figure 1). This leads to a net energy loss in every oscillation cycle. The cooling mechanism resembles Sisyphus cooling in which the cavity mode performs sudden transitions

between two stable states. We provide a dynamical stability analysis of the coupled moving mirror – cavity field system, and find the parameters for

efficient cooling. Direct numerical simulations show that a bistable cavity provides much more efficient cooling

compared to the regular one (see Figure 2).

5 Mark Y. Vilensky, Yehiam Prior, and Ilya Sh. Averbukh, Feedback-Controlled Non-Resonant Laser Cooling, Laser Physics, 2009 (in press).

We-27

-5 -4 -3 -2 -1 0 1 2 3 4 50

0.2

0.4

0.6

0.8

1

Total detuning, Δ

Inte

nsit

y, |

A|2

1

2

Figure 1. Intracavity intensity vs. total detuning depending on the mirror position. Black circles mark the points where the intensity switches up and down.

Figure 2. The evolution of the mirror oscillation: solid blue line shows behavior in the bistable cavity,

dashed black line – in the regular cavity.

0 1 2 3 4 5 6

x 104

-100

-50

0

50

100

Time, κ-1

Mirr

or p

ositi

on, p

m

(b)

-15 -10 -5 0 5 10 150.01

0.02

0.03

0.04

0.05

0.06

0.07

Inte

nsity

[Vol

ts]

Frequency detuning [GHz]

3.4 GHz

3

2

-1

-3

-2

1

0

6.8 GHz

Modulation Enhancement of a Laser Diode in an External Cavity

A. Waxman, M. Givon, G. Aviv, D. Grosswasser and R. Folman

Atom Chip Group, Ben Gurion University, Israel atomchip/il.ac.bgu.www

High-frequency modulation of laser beams is important for various fields including atomic physics, metrology and optical communications. In particular, it is useful in generating two coherent phase-locked laser beams with a frequency difference of several GHz, corresponding to the hyperfine splitting of the ground state of alkali atoms, which are commonly used in cold atoms experiments. We present experimental results demonstrating enhanced current modulation of an AR-coated edge-emitting laser diode placed in an external cavity. By eliminating the internal cavity of the laser diode and matching the external cavity FSR to the modulation frequency, we have increased the modulation response by 3 orders of magnitude up to nearly complete carrier suppression. We intend to use this tool to manipulate the internal (hyperfine) state of isolated single atoms on atom chips including, for example, to prepare a superposition state and measure its coupling to the macroscopic environment via the dephasing observable.

We-28

Figure 2. The emission spectrum of the modulated AR coated laser diode. The carrier (detuning zero) is completely

suppressed.

Figure 1. The moveable “stage laser”. The design enables the matching of the cavity’s FSR to the modulation frequency.

Thursday February 12, 2009

POSTER SESSION 2

Th-1 - Th-29

A Large Blue Shift of the Biexciton State in Tellurium Doped CdSe Colloidal

Quantum Dots

Assaf Avidan and Dan Oron Department of Complex Systems the Weizmann Institute of Science Rehovot

Colloidal semiconductor quantum dots (QDs) have received a great amount of scientific attention in the past ten years, due to their tunable band edge emission which covers all of the visible spectrum up to the near IR. In particular, the potential of QDs as optical gain media has stimulated an extensive study of the relaxation dynamics of QDs. Here we experimentally study tellurium doped CdSe QDs, and show that doping leads to favorable physical properties for optical gain. As a result of the spin degeneracy of the QD's electronic levels, population inversion requires part of the dots to be doubly excited. A single electron hole pair (exciton) decays radiatively with a lifetime of tens of nanoseconds. However, a biexciton state (two excitons occupying the dot), can also decay into a single exciton state via a fast (subnanoseconds) non radiative process called Auger recombination. This significantly raises the QDs' gain threshold, and limits the gain lifetime to tens of ps2,3. Here we show that the spin degeneracy of the exciton state can be removed by doping regular CdSe QDs with a few atoms of tellurium which create a hole trap located slightly above the valence edge (Fig 1a), inside the energy gap of the host. The tellurium atoms create a large Stokes shift1 between the absorption and emission spectra of the QD (Fig1a), which is much larger than that observed in undoped QDs. This is the result of a conduction electron and a trapped hole (rather than valence hole) recombination.

Fig1. (a) Energy diagram of a QD. Absorption is at the band edge wavelength, emission is from the tellurium defect. (b) The Biexciton blue shift of doped/undoped (green/blue) as a function of the dot diameter. For large doped dots the defect is shallower, hence the decrease in both the Stokes and blue shifts. The tellurium hole trap has, however, a much more dramatic effect on the biexciton spectrum of the QD. As can be seen in Fig.1b, the biexciton is blue shifted with respect to the exciton emission line, with exciton-exciton repulsion as large as 285 mev. This is in stark contrast with the weak exciton-exciton binding observed in undoped QDs . The huge biexciton blue shift we observe is the result of a large Coulomb repulsion between the two holes spatially located on the tellurium trap. For very small traps, we show that it roughly scales with the Stokes shift. Thus, we believe that population inversion in tellurium doped QDs will be limited to the single exciton regime, with a much lower gain threshold, as compared with undoped CdSe.

3. T. Franzl et. Al. Phys. Chem. C, 111, 2974, (2007). 4. V. Klimov et. Al. Science 290, 314, (2000). 5. V. Klimov et. Al. Nature 447,441, (2007).

Th-1

Two-photon Rabi oscillations in 87Rb atom

Bloch Q-bit: Multiphoton Coherent Manipulations of an Atomic Two-

State System , Menachem Giveon, Amir Waxman, David Grosswasser, Ron FolmanGal Aviv

(Atom Chip Group, Ben Gurion University atomchip/il.ac.bgu.www)

The fast experimental progress made with atoms in quantum optics in the last several years underlines the great potential of QIP (Quantum Information Processing) devices. In some realizations of a quantum computer, it will be required to perform manipulations on neutral atoms [Calarco 00, Reichel 06]

In this connection, we investigate the differences among several magnetic transitions in the 87Rb hyperfine ground-state manifold, comparing properties of single-photon transitions with two-photon transitions. We focus on the following transitions:

Single-photon, ΔmF=0: o |F=1,mF=0>→ |F=2,mF=0>

Two-photon, ΔmF=0: o |F=1,mF=0> → |F=2,mF=0>

Two-photon, ΔmF=2 : o |F=1,mF=-1> → |F=2,mF=+1>

The first transition, known as the “clock transition”, is used as the common atomic frequency standard; the second is known as a (magnetic) “qubit” transition. The qubit states are magnetically trapped states. Their differential first-order Zeeman shift is zero at the magnetic field value of 3.23 G; furthermore, both states experience nearly identical trapping potentials in magnetic traps. As a result, undesired coupling between internal and external degrees of freedom of the atoms is avoided. In this poster we present experimental results and discuss the design of future studies.

[Calarco 00] T. Calarco et al., Phys. Rev. A61, 022304 (2000).

[Reichel 06] P. Treutlein et al., Phys. Rev. A74, 022312 (2006).

Th-2

Molecular Symmetries of Non-adiabatic Couplings and Quantum Dynamical Simulations for Intramolecular Torsion Switched by Laser Pulses

M. Baer[1], O. Deeb[2], S. Jabour[2], M. Leibscher[3], J. Manz[3], S. Zilberg[4]

[1]Fritz Haber Center for Molecular Dynamics, The Hebrew University of Jerusalem, Israel, [2]Faculty of Pharmacy, Al-Quds University, Palestine, [3]Institut für Chemie und Biochemie, Freie Universität

Berlin, Germany, [4]Department of Physical Chemistry and the Farkas Center for Light Induced Processes, The Hebrew University of Jerusalem, Israel

An important step towards the design of laser pulses for the control of torsional switches is the evaluation of the relevant non-adiabatic coupling terms (NACTs) which may induce the transition from the photo-excited reactant to the product. Prominent effects are expected near conical intersections or crossing seams. We predict that these should have symmetry properties according to the molecular symmetry group [1]. The general rules for the symmetry properties of the NACTs may be used in order to assign their signs and nodal properties, which in turn may serve to test quantum chemistry calculations of the NACTs. Those symmetry results are demonstrated for the model system C5H4NH which has the molecular symmetry C2v(M). As an example, the potential energy curves are shown in Fig. 1 along a circular path of the hydrogen atom of the NH-group around the CN bond, revealing two and four symmetric conical intersection, respectively. For the NACTs, one readily recognizes the alternating signs, corresponding either to A2 or B1 symmetry.

Figure 1: Intramolecular torsion of C5H4NH: Circular path of the H-atom around the CN-bond (left), adiabatic potential energy curves (top) and the corresponding non-adiabatic coupling terms (bottom) Moreover, we show that the NACTs of C5H4NH obey the quantization rules for non-adiabatic couplings [2]. We also present the results of quantum dynamical simulations of laser induced molecular torsion on the three coupled electronic states and show how the torsional dynamics depends on the strength and symmetry of the NACTs. Referenzes: [1] P. R. Bunker, P. Jensen, Molecular Symmetry and Spectroscopy, NRC RP (1998). [2] A. M. Mebel, G.J. Halász, Á. Vibók, A. Alijha, M. Baer, J. Chem. Phys. 117, 991 (2002). Financial support of our trilateral cooperation by Deutsche Forschungsgemeinschaft (project Ma 515/22-2) is gratefully acknowledged.

Th-3

Zero Backscattering in Honeycomb Photonic Lattice

Omri Bahat-Treidel, Or Peleg, Mark Grobman and Mordechai Segev Department of Physics , Technion--Israel Institute of Technology, Haifa 32000

Scattering of relativistic fermions is fundamentally different from that of non-relativistic

ones, because relativistic fermions are described by a first order (Dirac) equation rather than the Schrodinger equation. The massless Dirac equation yields linear dispersion curves, which results in unique scattering properties, e.g., such a wavepacket incident upon a potential barrier exhibits non-resonant unity transmission. When the relativistic particles are not massless, such a wavepacket undergoes total reflection [1]. This behavior is in sharp contrast to wavepackets described by the Schrodinger (or Klein-Gordon) equation, for which unity transmission can occur only as a resonance effect. Unfortunately, to this day it is impossible to carry out such experiments with true relativistic fermions. However, lately it has been demonstrated that charge carriers in graphene behave approximately like massless fermions, thus providing an opportunity to study massless Dirac fermions in the lab [2]. Nevertheless, our group has shown that honeycomb photonic lattices have a band structure very similar to graphene [4]. Here, we study the scattering of 1D wavepackets from a variety of defects in deformed honeycomb photonic lattice (Fig.1a). We show that a deformed honeycomb lattice exhibits linear diffraction curve in one direction, and hyperbolic in the perpendicular direction [5], and that the optical excitations corresponding to these directions exhibit non-resonant unity transmission and total reflection, respectively.

Wave propagation in honeycomb photonic lattices is described by the paraxial wave equation, identical to the Schrodinger equation with time replaced by z coordinate, and the z-invariant refractive index modulation ),( yxnΔ analogues to the potential. The honeycomb lattice is strained in a single direction [Fig. 1a], which yields two intersecting bands [Fig. 1b]. The diffraction curve is linear in one direction [Fig. 1c] and hyperbolic in the other [Fig. 1d]. As such, we have the opportunity to study both massless and massive fermions, respectively in the same lattice. We set a 1D defect in the lattice, and simulate scattering from it at normal incidence. Wavepackets from the linear curve exhibit non-resonant zero backscattering (as massless fermions; Fig.1e-h), while wavepackets from the hyperbolic curve undergo total reflection (as massive fermions; Fig.1i-l), in contrast to Schrodinger particles whose reflection is always non-zero. These results are independent of the width and shape of the defect.

In conclusion, the deformed honeycomb photonic lattice is an optical system with reflectionless and totally-reflecting potentials, manifesting fermionic behavior of light.

Figure 1: (a) Deformed honeycomb lattice. (b) Vicinity of the intersection of the fist two bands. (c),(d) Cross sections along the major axes. (e,i) Initial and finial intensities of wavepackets (e) passing through and (i) reflected off the negative 1D defect (potential barrier) V(y). (f,j) mean propagation constant as a function of z, (g,k) mean position of the beam, and (h,l) are the correlation of the scattered field with the initial field. References: 1. M. I. Katsnelson, The European Physical Journal B 51, 157 (2006). 2. K. S. Novoselov at el., Nature pp. 197200 (2005). 3. R. G. Winter, American Journal of Physics 27, 355 (1959). 4. O. Peleg at el., Physical Review Letters 98, 103901 (2007). 5. O. Bahat-Treidel, O. Peleg, and M. Segev, Opt. Lett. 33, 2251 (2008)

Th-4

Autoresonant Optics and Many-Body Random-Phase Autoresonance Assaf Barak1, Mordechai Segev1, Lazar Friedland2

1. Physics Department, Technion, Haifa 32000, Israel

2. Racah Institute of Physics, Hebrew University of Jerusalem, Jerusalem 91904, Israel

We study nonlinear phase-locking of weakly-coupled light waves passing adiabatically through a linear resonance. We show that, under certain conditions, the passage trough resonance yields nonlinearity-assisted phase-locking, such that the amplitudes of the waves self-adjust to stay in a continuous resonance despite variation of system parameters. This autoresonance process was studied in many areas, from plasmas to planetary dynamics [1], but was never discussed in optics. We suggest a system for experimental studies of autoresonant optics. Furthermore, combining the concept of autoresonance with effects arising from incoherent nonlinear waves, we unravel a new phenomenon that was never proposed in other areas: many-body random-phase autoresonance. This is a system of multiple driven waves, with randomly-fluctuating phases. When the waves exceed a sharp common threshold, the many-body system displays nonlinear autoresonant phase-locking, such that each of the multiple coupled waves locks to its pump, yielding amplification to predetermined values.

We study the effect in a chirped directional coupler [Fig. 1a], with Kerr nonlinearity. We launch a pump wave into the right waveguide, and examine the dynamics of cR and cL (the complex amplitudes in the right and left waveguides). The solid-blue line in Fig. 1b shows the evolution of |cL| and of the phase mismatch, Φ, between cL and cR. The green-dotted line marks the linear resonance. As the system approaches resonance, Φ slowly approaches zero, and |cL| grows to maintain the nonlinear phase-locking, until the pump is exhausted [Fig. 1c]. Unlike an ordinary directional coupler, this autoresonant device is unidirectional, and has a sharp threshold. The threshold is realized by controlling the initial value of |cR|. The red–dotted line in Fig. 1b shows the evolution of |cL| and Φ below the threshold. Below threshold, the phases do not lock, the process is inefficient, and most of the power remains in the right waveguide (Fig. 1d).

Next, consider the dynamics of a beam made of many mutually-uncorrelated waves, launched into the right waveguide. We find that the phase-mismatch of each of the waves locks, and that the system maintains the resonance by increasing the total intensity of all the waves. Figure 2a shows the evolution of |cL

m|, Φm, for 5 beams. The phase of each driven wave passes the linear resonance, hence it is amplified. However, in the many-body system the threshold is a collective phenomenon, that is, all phases lock simultaneously. For example, by slightly decreasing the initial value of cR for only one of the waves, none of the waves is captured into resonance, yielding inefficient amplification as none of the phases lock [Fig. 2b]. [1] J. Fajans, and L. Friedland, Am. J. Phys. 69, 1096-1102 (2001).

Th-5

Fig. 1. (a) Chirped refractive index at several propagation planes. (b) Evolution of |cL| and Φ. Blue-solid (red-dashed) shows the dynamics above (below) the threshold. (c,d) Beam propagation above (below) threshold, yielding full (almost no) flux conversion, respectively.

Fig. 2. Autoresonante evolution of |cLm|, Φm for 5 mutually-incoherent

waves. (a) Above-threshold evolution. (b) For a slightly smaller initial amplitude of just one of the waves, autoresonance is destroyed (phases do not lock, final values of |cL

m| are much lower than in (a). Black-dashed lines represent the square root of the sum of the |cL

m|2.

m=1→5

(a) (b)

m=1

m=2→5

(a)

(d)(c)

(b)

Cavity solitons in a Vertical Cavity Semiconductor Optical Amplifier: from single to cluster states

S. Barbay, T. Elsass, X. Hachair, I. Sagnes and R. Kuszelewicz Laboratoire de Photonique et de Nanostructures, CNRS-UPR20,

Rte de Nozay, 91460 Marcoussis, France. email : sylvain.barbay@lpn.cnrs.fr

Cavity solitons (CSs) are localized states arising in extended nonlinear cavities [1,2]. They generally appear as bright spots, sitting on a dark background, that are controllable: they can be excited (written) and destroyed (erased) at any transverse location of the cavity. CSs are interesting from the practical point of view since they open new perspectives for all-optical processing of information, all the more that they form in materials with fast timescales such as semiconductor materials. When cavity solitons are far away from each other, they are independent objects while at short distances they can form “bound-states”. The understanding and control of these cluster states are of crucial importance for applications, and shed some light on the relation between localized states and patterns on a more fundamental viewpoint. We present experimental results on the formation of single localized states and clusters of localized states in a Vertical Cavity Semiconductor Optical Amplifier [3]. A titled snaking instability is evidenced showing multistability among the different structures. We discuss the possible reasons why all the cluster states do not perfectly coexist within a given parameter range but rather appear on “tilted” hysteresis loops. Our results agree qualitatively well with what is expected from theory in 1D and show the passage from single localized states to larger states that can be considered as “localized pattern” states. At last, a parameter range where cluster states are inhibited is evidenced, showing the possibility to excite only singlepeaked CSs. This reveals very interesting when thinking of CSs as bits of information in an all-optical information processing context.

Fig. 1: Tilted snake obtained by ramping the optical pump and monitoring the total reflected intensity. Each branch of higher-order structures

corresponds to a different state. Multistability is observed between the different branches.

Acknowledgments This research has been carried out in the framework of the FunFACS IST-STREP European program. We also acknowledge support from the Rיgion ־le-de-France. References [1] S. Barland, J. R. Tredicce, M. Brambilla, L. A. Lugiato, S. Balle, M. Giudici, T. Maggipinto, L. Spinelli, G. Tissoni, T. Knodl, M. Miller, and R. Jager, Nature 445, 699 (2002). [2] S. Barbay, Y. Mיnesguen, X. Hachair, L. Leroy, I. Sagnes, and R. Kuszelewicz, Opt. Lett. 31, 1504 (2006). [3] S. Barbay, T. Elsass, I. Sagnes and R. Kuszelewicz, to appear in Phys. Rev. Lett. (2008).

Th-6

Many-Body Excitations and their Decay in a BEC

Nir Bar-Gill, Eitan Rowen, Gershon Kurizki and Nir Davidson Weizmann Institute of Science, Rehovot 76100, Israel

In this work we study, both theoretically and experimentally, many-body excitations in a Bose-Einstein Condensate (BEC), and their decay into the reservoir of available modes in the condensate itself. Our experimental setup consists of a BEC, which we excite using Bragg spectroscopy. In this technique, we use two far-detuned laser beams to excite the condensate with a well defined momentum and energy. The state of the system is probed using Time Of Flight (TOF) absorption imaging. In this way we obtain the momentum-space distribution of the atoms. First, we study low-momentum excitations, for which the decay is negligible. Here we find that due to quantum constructive interference between excitation pathways, a ladder of excitations is created (Fig. 1a), with high order excitation having comparable population with first order excitations [1].

Fig. 1: (a) Excitation ladder for a strong Bragg excitation with low momentum k=0.35kL (where kL=2π/λ, λ=780nm), indicating constructive interference for the high excitation modes. (b) Forward and backward superradiant excitation modes obtained by a two-frequency pump (frequency difference of 15 kHz). (c) The remaining fraction of coherent atoms in the excitation following 400 μsec of decay, as a function of optical lattice depth.

Second, we examine the coherence of superradiance in a BEC, by stimulating Bragg excitations between a pump beam and spontaneously excited beams along the long axis of the condensate (Fig. 1b). By using a two-frequency pump we are able to study the time dynamics of this process, and show coherent oscillations of the superradiant modes, indicating the existence of coherence in this spontaneous process [2]. Finally, we study the decay of these quasi-particle excitations due to interaction with the available modes of the condensate through the process of Beliaev damping. We control this decay by loading the condensate into a 1D optical lattice, the depth of which is well-controlled. For deep lattices the standard Golden Rule theory of decay predicts strictly no decay. However, here we measure significant decay, indicating that our system is in the non-exponential regime. These results are in agreement with the universal decay theory (Fig. 1c) [3]. References:

1. E. E. Rowen, N. Bar-Gill and N. Davidson, Phys. Rev. Lett. 101, 010404 (2008). 2. N. Bar-Gill, E. E. Rowen and N. Davidson, Phys. Rev. A 76, 043603 (2007). 3. N. Bar-Gill, E. E. Rowen, G. Kurizki and N. Davidson, submitted to Phys. Rev. Lett.

Th-7

Towards selective heat transfer between a hot surface and an atom

T. Passerat de Silans1, I. Maurin1, Ph. Ballin1, A. Laliotis1, P. Chaves de Souza Segundo1, S. Saltiel1 *, M.-P. Gorza1, D. Bloch1, M. Ducloy1, D. de Sousa Meneses2, P. Echegut2

1 Laboratoire de Physique des Lasers, UMR 7538 du CNRS et de l’Université Paris13,

F 93430 Villetaneuse, France 2 Centre de recherche sur les Matériaux à Haute Température, UPR 3079 du CNRS,

F-45071 Orléans Cedex2

We report on the progress of an experiment aiming to observe a change in the long-range van der Waals–type atom-surface interaction that would be governed by surface temperature, as a result of a virtual selective exchange of energy. This led us to detail the analysis of surface resonances of fluoride crystals, whose spectrum falls in the thermal infrared.

The van der Waals (vW) long-range atom-surface interaction is often described as a dipole–dipole interaction, originating in the coupling between the quantum dipole fluctuations of an atom and the instantaneously induced fluctuations in the electrostatic image. Due to the finite light velocity, this atom-surface interaction is better understood in the more general frame of the Casimir-Polder theory. Recently, it was demonstrated that the Casimir-Polder interaction undergoes an observable dependence on the vacuum temperature [1]. In a shorter distance range, it is expected that thermally excited surface modes could resonantly modify the vW interaction, when it coincides with a virtual atomic transition [2,3].

This motivates our experimental set-up, where we analyze through selective reflection spectroscopy on Cs vapour at 388 nm (6S-8P transition) [4] the vW interaction exerted onto the Cs (8P) level at a typical distance below 100 nm. With fluoride windows, such as CaF2 or BaF2 [5], near coincidences of the surface resonances with the strong dipole (absorptive) couplings to Cs(7D) are expected (atomic couplings fall at 29, 36, 39 µm). Experiments are conducted for different temperatures of the window, while all efforts are made to keep the vapour conditions identical.

Presently, our measurements of the vW interaction yield stronger values than expected at a

CaF2 window, and the construction of a cell with BaF2 windws remains challenging. To secure quantitative predictions, we have studied in detail the temperature dependence of the optical constants of fluoride materials, notably around the resonances, in a range spanning from room temperature to 500°C. For CaF2, and Cs(8P), the major predicted dependence of the vW interaction appears to be solely related to quantum effects of the thermal excitation [3], while for BaF2, the resonance being closer, the evolution of the crystal resonances with temperature could be of large influence.

[1] J. Obrecht et al, Phys. Rev. Lett., 98, 0632201 (2007) [2] G. Dutier et al., in "Laser Spectroscopy-Proceedings of the XVI International Conference" (P. Hannaford et al. eds.), pp 277-284, World Scientific, Singapore (2004) [3] M.-P. Gorza and M. Ducloy, Eur. Phys. J. D 40, 343 (2006) [4] P. Chaves de Souza Segundo et al., Laser Phys. 17, 983 (2007) [5] A. Laliotis et al, Appl. Phys. B 90, 415 (2008)

Th-8

A photon turnstile with single atoms coupled to chip-based microcavities

Barak Dayana, Takao Aokib, A. S. Parkinsc, D. J. Alton, C. A. Regal, S. Kelber and H. J. Kimble

Norman Bridge Laboratory of Physics 12-33, California Institute of Technology, Pasadena, California 91125, USA

E. P. Ostby and K. J. Vahala

T. J. Watson Laboratory of Applied Physics, California Institute of Technology, Pasadena, California 91125, USA

Abstract: We demonstrate a robust and efficient mechanism for routing single photons via the

mediation of a single atom coupled to a chip-based toroidal microcavity.

Photons from a coherent input are coupled through a tapered fiber to a toroidal microcavity [1], which interacts with single Cesium atoms that fall through the evanescent wave of its optical mode [2], as depicted in Fig. 1 below. As a result of the interaction with the atom, single photons are directed to one output of the fiber, whereas excess photons are directed to the opposite direction, as is confirmed by the observation of non-classical anti-bunching photon statistics at one output of the fiber, and bunching at the second [3,4].

a Permanent address: Department of Chemical Physics, Weizmann Institute of Science, Israel b Permanent address: PRESTO, Japan Science and Technology Agency, Saitama, Japan c Permanent address: Department of Physics, University of Auckland, Auckland, New Zealand

References: 1. D. K. Armani et al., “Ultra-high-Q toroid microcavity on a chip”, Nature 421, 925 (2003). 2. Takao Aoki et al., “Observation of strong coupling between one atom and a monolithic

microresonator”, Nature 443, 671 (2006). 3. Barak Dayan et al., “A Photon Turnstile Dynamically Regulated by One Atom”, Science 319, 1062

(2008). 4. T. Aoki et al., submitted.

Th-9

Figure 1: A simple schematic of the setup, showing the falling Cs atoms interacting with the evanescent wave of the optical mode of the microtoroid, and the input and output fields that couple to the microtoroid through a tapered fiber.

Enhancement in microwave modulation efficiency of vertical cavity surface-emitting laser by optical feedback

N. Gavra, V. Ruseva, and M. Rosenbluh

Resnick Institute for Advanced Technology and Department of Physics, Bar-Ilan University, Ramat-Gan, Israel, 52900 E-mail: gavran@mail.biu.ac.il

Abstract

The CPT based atomic clocks have the advantage of all-optical interrogation that does not require a

resonant rf cavity surrounding the alkali atoms. The implementation of CPT requires, however, the

simultaneous phase coherent illumination of the atoms by two resonant optical frequencies with a

frequency difference between them corresponding to the energy difference between two atomic

hyperfine states.

In this work[1] we report on a method that enables rf modulation of a VCSEL`s current, used as

the source of a CPT based atomic clock, with greatly enhanced efficiency at the rf frequency of

interest. The method is based on a relatively weak feedback from an external feedback cavity for the

VCSEL, with the external cavity mode spacing corresponding to the desired modulation frequency.

In Fig. 1 we show the impressive 10dBm improvement of the modulation efficiency at 3.417 GHz for the external cavity enhanced VCSEL. Shown is the modulation amplitude as a function of rf frequency with −15dBm rf power (31µW) added to the VCSEL injection current. This efficiency improvement allows for the production of a CPT resonance even at −30dbm! Using the external cavity enhanced VCSEL we measured the quality figure Q of the CPT resonance, defined by Q=C/Δν. The contrast C is the CPT signal level divided by the background dc detector level and Δν is the linewidth of the CPT resonance. Fig. 2 shows that for the same atomic cell and experimental parameters, at modulation power of −16dBm the Q value is higher in the presence of an external cavity than in its absence and with a high modulation power of +1.25dBm.

1. N. Gavra, V. Ruseva, and M. Rosenbluh, "Enhancement in microwave modulation efficiency of vertical cavity

surface-emitting laser by optical feedback," Appl. Phys. Lett. 92, 221113- (2008).

Th-10

FIG. 1. The modulation efficiency vs modulation frequency measured on the laser light by a fast detector and a rf spectrum analyzer for a free running VCSEL (empty squares) and the same VCSEL with a low finesse external cavity (filled squares).

FIG. 2. Quality figure of the CPT resonance as a function of rf modulation.Free running VCSEL (empty squares) and VCSEL with an external cavity (filled squares).

Exploiting Symmetry Selection Rules for Strong Evanescent Fields in

Resonant Photonic Crystal Slabs Eran Grinvald, Gidi Lasovski, Shimon Levit and Asher A. Friesem

Department of Physics of Complex Systems, Weizmann Institute of Science, Rehovot 76100, Israel

Tel: +972-8-9342051 Fax: +972-8-9344105 e-mail: Eran.Grinvald@weizmann.ac.il

Abstract: Subwavelength photonic crystal slabs (PCS) of one or two dimensions exhibit a resonance

type anomaly of abrupt variations in the amplitude and phase of the reflected and transmitted light.

The anomaly is due to the resonant excitation of a discrete mode in the structure, such as surface

plasmons in metallic slabs and guided modes in dielectric slabs. We concentrate on guided mode

resonance and discuss how symmetry selection rules are responsible for the resonance dependence on

polarization and unique disappearance of resonance in one of the resonant bands at normal incidence

shown in the bottom band of Fig.1. Slight breaking of the symmetry in lossless subwavelength PCS

results in a strong resonant response with an ultra

narrow bandwidth and high field

enhancement. We discuss breaking the

symmetry by either altering the crystals' unit cell

geometry or alternatively by varying the

angular orientation of the incident light near the

point of disappearance of the resonance. Thus the

field enhancement of a specific PCS can be

actively tuned by varying the angular

orientation. The coupling between the modes and selection rules are analyzed using the photonic

crystal approach which treats Maxwell equations as a linear hermitian operator on the magnetic

fields[1]. We treat the periodicity of the PCS as a perturbation of the homogeneous slab. Numerical and

Experimental results of the resonance near the symmetry point will be presented, the influence of

losses on the resonance field will be discussed and practical solutions to decrease losses will be

suggested. Resonant PCS are of interest to the non-linear optics community since they serve as a field

enhancement platform for local non-linear processes[2] as well as a method to manipulate ultra short

pulses by acting resonantly on the phase of the pulses' different spectral components[3].

REFERENCES [1] J. D. Joannopoulos, R. D. Meade and J. N. Winn, "Photonic Crystals", Princeton University Press, NJ (1995). [2] A. Thayil et al. Opt. Exp. 16, 13315-13322 (2008). [3] D. Pietroy et al. Opt Exp. 16 17119-17130 (2008).

Th-11

0 2.5-2.5 5-5

1

0.5

0

1.504

1.510

1.516

Wav

elen

gth

[μm

]

deg][NCθFigure 1. Photonic band gap of TM guided modes under classical incidence for a 50% duty cycle grating.

Ref

lect

ion

effic

ienc

y

Control of Molecular Torsion by Intense Laser Pulses: Two-Dimensional Model Studies

T. Grohmann, J. Floß, M. Leibscher

Institut für Chemie und Biochemie, Freie Universität Berlin, Germany

Molecular rotation can be effectively controlled by intense laser pulses. The resulting alignment of rigid molecules has been studied intensively during the last years. Recently, it has been demonstrated that internal degrees of freedom of non-rigid molecules with low torsional barrier can also be controlled with intense laser pulses, leading to alignment of molecular torsion [1, 2].

Figure 1: Alignment of molecular torsion after interaction with a short, intense laser pulse for different intramolecular potentials.

Here, we investigate in detail the dynamics of hindered torsion induced by short, intense laser pulses. We employ a two-dimensional model system, assuming that the molecules have already been aligned along one axis (see Figure 1). The prospects of effective torsional alignment, depending on the molecular potential and the interaction strength are explored. We find that the maximal alignment depends in a non-monotonic way on the interaction strength. For molecules with identical nuclei at symmetric positions, the dynamics of molecular rotation and torsion depends strongly on the nuclear spin of the molecules [3, 4]. Therefore, we also investigate the nuclear spin selective dynamics and its effect on molecular alignment for combined rotational and torsional motion.

References: [1] S. Ramakrishna, T. Seideman, Phys. Rev. Lett. 99, 103001 (2007). [2] C. B. Madsen et al., arXiv:0809.2935 [physics.atom-ph] (2008). [3] S. Fleischer, I. S. Averbukh, Y. Prior, Phys. Rev. Lett. 99, 093002 (2007). [4] O. Deeb, M. Leibscher, J. Manz, W. von Muellern, T. Seideman, ChemPhysChem 8, 322 (2007).

Th-12

φ

Magnetic Casimir-Polder force near superconductors and metals H.Haakh, F. Intravaia and C. Henkel, Universtitaet Potsdam, Germany

S. Spagnolo and R. Passante, Università di Palermo, Italy B.Power and F. Sols, Universidad Complutense de Madrid, Spain.

We study the Casimir-Polder interaction between the magnetic dipole moment of an atom and metallic and superconducting surfaces. This interaction can become relevant for precision spectroscopy in miniaturized traps, e.g. on atom chips [1, 2]. In these situations, the relevance of magnetic dipole coupling has been demonstrated by spin flip transitions [3]; also, conducting surfaces generate predominantly magnetic (not electric) fields at low frequencies [4]. The atom-surface inter-action is characterized here by a free energy and an entropy per atom. We use the thermal response theory of Ref.[5] and characterize the superconductor by the two-fluid model [6]. Our results (see Figures) can be summarized as follows. The atom-surface free energy shows a rapid change through the superconducting temperature Tc in some range of distances. The entropy jumps, illustrating the "participation" of the atom in the phase transition. As T goes to 0, the entropy vanishes, and the free energy approaches the value for a perfect reflector at large distances. For a metallic surface, we recover at T = 0 the atom-surface potential of Ref.[7] and observe for T > 0 a strong suppression of the free energy at large distances. The main features of this behavior are similar to the Casimir interaction between two metallic plates, whose calculation at nonzero temperature is a currently quite controversial [8]. Measurements of the atom-surface interaction could thus provide an alternative scenario to settle this issue.

(left) Atom-surface free energy for a Drude metal (similar to Al) and normalized to a 1/z3 power law. The frequency Ωm of the magnetic transition is set to 3 GHz (~ hyperfine splitting in Rb). δ is the skin depth at frequency Ωm, λT the thermal wavelength. (right) Atom-surface entropy as a function of temperature, normalized to the transition frequency Ωm, arbitrary scale. The superconductor is described by a two-fluid model, based on the Gorter-Casimir rule. The "plasma" entropy (lossless dielectric function) has been multiplied by 1000 to be visible on this scale. The "perfect crystal" has a electron scattering rate γ(T) ~ T2. [1] D. M. Harber, J. M. Obrecht, J. M. McGuirk, and E. A. Cornell, Phys. Rev. A 72 (2005) 033610 [2] T. Nirrengarten et al., Phys. Rev. Lett. 97 (2006) 200405 [3] C. Henkel, S. Pötting, and M. Wilkens, Appl. Phys. B 69 (1999) 379 [4] K. Joulain, R. Carminati, J.-P. Mulet, and J.-J. Greffet, Phys. Rev. B 68 (2003) 245405 [5] J. M. Wylie and J. E. Sipe, Phys. Rev. A 32 (1985) 2030 [6] J. R. Schrieffer, "Theory of superconductivity" (Perseus Books, Reading MA 1999) [7] C. Henkel, B. J. Power, and F. Sols, J. Phys.: Conf. Ser. 19 (2005) 34 [8] K. A. Milton, J. Phys. A: Math. Gen. 37 (2004) R209; G. L. Klimchitskaya and B. Geyer, J. Phys. A: Math. Gen. 41 (2008) 164032

Th-13

Figure 1: A plot of the Leggett-Garg inequality as a function of τ for fixed values of γ and s. The inequality is violated when it exceeds 2. The range of τ values for which a violation is possible is evident.

Figure 2: The behavior of the inequality for 4 selected values of s and γ (for each s the value of γ that gives maximal violation is chosen). It is evident that for s=0.981 no violation is possible (for any γ and τ)

Breakdown of Macroscopic Realism in the Dynamics of a Harmonic Oscillator Amir Leshem and Omri Gat

Racah Institute of Physics, The Hebrew University, Jerusalem, Israel Abstract

In this work, we investigate the conditions that lead to the breakdown of macroscopic realism in a quantum dynamical system. Our model consists of a harmonic oscillator undergoing temporal consecutive measurements during its time evolution. The operator that is being measured and the time evolution operator do not commute and are both Hamiltonians of harmonic oscillators that are squeezed relative to each other. Violation of the Leggett-Garg inequality[1] indicates the breakdown of macroscopic realism: this inequality imposes a bound on the temporal correlation functions of a macro realistic theory, similar to the one imposed by the Bell-type inequalities[2,3] on local realistic theories. We construct temporal correlation functions of an operator , where is a parameter , is the action operator of and h is Planck's constant. In addition to , our model consists of two more dimensionless parameters: and , which are the (dimensionless) time interval between adjacent measurements and the squeezing parameter, respectively. Using phase-space representation of quantum mechanics[4], we derive an analytic expression for the Leggett-Garg inequality which is a function of these three parameters and, in addition, the model is analyzed semi-classically. Our main results are the following: (i) in this model, a violation of the inequality is possible when the parameters are restricted to some ranges in their values:

and (ii) the violation becomes stronger as , and , with a limiting value of (iii) the semi-classical analysis also admits a violation due to quantum corrections to the classical evolution.

Th-14

Figure 3: A plot of the inequality as a function of s and γ. For each (s,γ) configuration, the value of τ chosen, is the one that gives maximal violation. The violation is approaching the limiting value as s →1 and γ→∞.

References [1] A. J. Leggett and Anupam Garg. Quantum mechanics versus macroscopic realism: Is the flux there when nobody looks? Phys. Rev. Lett., 54(9):857–860, Mar 1985. [2] J. S. Bell. Speakable and Unspeakable in Quantum Mechanics: Collected Papers on Quantum Philosophy. Cambridge University Press, June 2004. [3] John F. Clauser, Michael A. Horne, Abner Shimony, and Richard A. Holt. Proposed experiment to test local hidden-variable theories. Phys. Rev. Lett., 23(15):880–884, Oct 1969. [4] M. Hillery, R. F. O’Connell,M. O. Scully, and E. P.Wigner. Distribution functions in physics: Fundamentals. , 106:121–167, April 1984.

Effect of linear chirp on strong field photodissociation of H2+.

U. Leva, V. S. Prabhudesaib, A. Natanb, A. Dinera, O. Hebera, B. Brunerb, D. Strassera, Y. Silberbergb, D. Zajfmana

a Dept. of Particle Physics, Weizmann Institute of Science, Rehovot, Israel 76100 bDept. of Physics of Complex, Weizmann Institute of Science, Rehovot, Israel 76100

Controlling molecular dynamics for achieving chemical control has been long cherished dream for Physicists and Chemists. Towards this, coherent control using ultrashort laser pulses has been demonstrated by many experiments in the weak field regime. Molecular photodissocaiation in the strong field regime has also received a lot of attention in recent past with the chemical control as the ultimate goal. The well established learning loop algorithms are successfully implemented for optimizing a specific output of molecular interaction with photon field1. Although the optimization of the output is demonstrated, the role of specific shape of the laser pulse in the actual mechanism of control is yet unknown.

As an initial step to address this issue we carried out a simple photodissociation experiment with H2+

ion beam using linearly chirped 35fs laser pulses (stretched to 120 fs) centred at 795nm in wavelength. We see a distinct effect on the kinetic energy released (KER) spectra due to the chirped pulses in comparison with that from the transform limited pulse with similar peak intensity as well as that from the relatively weaker pulses. The significant difference in the KER spectra from positively and negatively chirped pulses indicates the possible role of pulse front (in the time domain) in the dissociation. Interestingly, for all the corresponding vibrational levels the dissociation mechanism is known to be either bond hardening or bond softening2.

1. R. J. Levis, G. M. Menkir, H. Rabitz Science 292, 709 (2001) 2. J. H. Posthumus, Rep. Prog. Phys. 67, 623 (2004).

Th-15

Breakdown of Anderson Localization due to Dynamic Disorder Liad Levi, Tal Schwartz, Mordechai Segev, and Shmuel Fishman Physics Department and Solid State Institute, Technion, Haifa 32000, Israel

We investigate the transport of wave-packets in photonic lattices containing disorder, and demonstrate experimentally and numerically that Anderson localization breaks down and diffusion is restored when the disorder is allowed to evolve at a rate exceeding a particular value. The equivalence between optics to solid-state physics stems from the equivalence between the Schrödinger equation and the paraxial wave equation of monochromatic light. In the latter case, the propagation coordinate z plays the role of time, and ∆ , the spatial change in the refractive index, plays the role of the potential. In 2007, our group used the transverse localization scheme [1] for the first experimental demonstration [2] of Anderson localization in any periodic system containing disorder, which is the original context in which it was proposed [3]. Other groups have followed – in optics [4] and with matter-waves [5]. For Anderson localization to occur, the underlying potential (lattice + fluctuations) must be constant in the “evolving coordinate”. Otherwise, localization breaks down and diffusive transport prevails. Figure 1 shows the experimental scheme in which the optical induction technique is used [1] to transform an optical intensity pattern into a refractive index change ∆ , , , including both the photonic lattice and the disorder.

In optics, the propagation distance (time) is always finite, hence transport must be studied through ensemble-averaging over many realizations of the disorder (under the same parameters), as appropriate for an expectation-value problem. Figure 2(a) shows the average (over 100 realizations) of such an ensemble, manifesting that the probe beam has exponentially decaying tails - direct evidence for Anderson localization. We now examine how z-variations of the disorder affect localization. Inducing and tuning z-variations is accomplished by placing different diffusers, with decreasing scatterer size, in the Fourier plane of the 4-F system described in Fig 1. Fig 2 shows experimental and numeric results of four experimental settings, differing only in the strength of the diffusers. When the scatterer size is made comparable to the width of the light ring, the disorder varies weakly with propagation, but Anderson localization still occurs (Fig. 2b,c). However, when the scatterer size is made significantly smaller than the thickness of the light ring, the disorder varies considerably with z, Anderson localization breaks down, and diffusion is restored. This is highlighted by the ensemble-average of the intensity structure (on Log scale), shown by the experimental and numerical results presented in Fig. 2d.

2.

[1] A. Lagendijk, Phys. Lett. A 136, 81 (1989). [2] T. Schwartz, et al.,, Nature 446, 52 (2007) [3] P.W Anderson, Phys. Rev 109, 1492 (1958) [4] Y.Lahini, et al., Phys. Rev. Lett. 100, 013906 (2008) [5] J. Billy, et al., Nature 453, 891 (2008)

Fig. Experimental results confirmed by numerical simulations showing the breakdown of Anderson Localization. In (a) (b) and (c), diffusers of 0.5 ,1 and 5 are used, and localization survives. In (d), a diffuser of 10 is used, which causes the breakdown of Anderson localization due to strong z-variations of the disorder. The diffusive nature is restored, up to the point where the underlying hexagonal symmetry of the lattice reappears. In all experiments, the maximum disorder strength is 40% of the lattice depth.

~400um

(b) (c) (d)

~400um ~400um ~400um

- Diffuser - Diffuser - Diffuser . - Diffuser

mm mm mm mm

l

(a) lo

Fig.1. Three plane waves create a hexagonal lattice (on the left). The disorder (in the middle) is created by passing a wide Gaussian beamthrough a conical lens, and then placing a diffuser at the Fourier plane which is located in the middle of the 4-F system. The disorder and the lattice are then both coherently added and imaged to the input facet of the media, where a weak probe is injected (on the right) and monitored the output facet. The underlying highly-anisotropic nonlinearity used to write the potential is the photorefractive screening nonlinearity in SBN.

at

Multiexcitons in colloidal semiconductor nanocrystals

Prof. Efrat Lifshitz, Schulich Faculty of Chemistry, Russell Barrie Nanotechnology Institute and Solid State Institute, Technion.

Aims: The study of multiexcitons in colloidal quantum dots (CQDs) is a timely topic, as these multiexcitons have practical applications in gain devices, photovoltaic cells and as single photon light sources. However, these excitons decay primarily via nonradiative Auger relaxation at a time scale of 10-100 ps, due to the enhancement of many-body interactions inside dots with a typical diameter of 3-4 nm surrounded by low dielectric medium. Despite the predicted limitations, the present study unambiguously showed an emission of neutral biexciton (BX), triexciton (TX) and quandraexciton (QX) in a time-integrated micro-photoluminescence (μ-PL) spectrum of quasi-type II CdTe/CdSe CQDs. These CQDs offer the option of Auger relaxation suppression and an extension of multiexcitons’ lifetime. This upturn should permit charge extraction in photovoltaic cells and inversion of population in a gain device.

Methods: CdTe/CdSe CQDs were synthesized by a unique colloidal procedure, allowing the existence of Cd0 Cd+2 equilibrium during the reaction process, regulating precursors supply and the growth of spherical structures with the highest emission quantum efficiency (90%) [1]. The μ-PL

spectra of a CdTe/CdSe CQDs were recorded by the use of a cryogenic fibre-based confocal microscope (NA = 0.45), pumped by a 2.41 eV cw-Ar+ laser [2].

Results: The attached figure represents μ-PL spectra of CdTe/CdSe CQDs. Possible multiexciton recombination processes are drawn schematically in the insets, while the variation of the μ-PL bands’ intensity versus the laser intensity is given by the contour plot. The energetic shift of the 2X, 3X and 4X, with respect to the emission energy of X, was evaluated by a second order perturbation theory including Coulomb many-body interactions in quasi-type II CQDs, with a partial separation of the radial distribution of the electron and hole wave-functions. The theoretical evaluations showed close agreement to the experimental results.

References:

[1] Kloper V.; Osovsky R.; Kolny-Olesiak J.; Sashchiuk A.; Lifshitz E. “The Growth of Colloidal Cadmium Telluride Nanocrystal Quantum Dots in the Presence of Cd0 Nanoparticles” J. Phys. Chem. C (2007), 111(28), 10336-10341.

[2] Osovsky R.; Cheskis D.; Kloper V.; Sashchiuk A.; Kroner M.; Lifshitz E. “Multiexciton photoluminescence in a single colloidal quantum dot pumped by a continuous-wave source “ PRL, submitted.

Th-17

Visualization of coherent population trapping

L. Margalit, T. Zigdon, A. D. Wilson-Gordon, Department of Chemistry, Bar-Ilan University, Ramat Gan 52900, Israel

S. Rochester and D. Budker, Department of Physics, University of California, Berkeley, California 94720-7300

A simple example of coherent population trapping (CPT) occurs when the

1 1g eF F= → = transition in the D1 line of 87Rb interacts with σ+ .and σ− polarized

lasers [1]. When the σ+ field is resonant with the transition, the absorption spectrum

of the σ− field, plotted as a function of its detuning from resonance, displays a

transparency window centered at two-photon resonance. The system is then

characterized by a linear combination of the 1gm = and 1gm = − Zeeman sublevels,

called the dark state. Here, we present an alternative way of describing CPT in terms

of the angular-momentum probability surfaces (AMPS) of the ground-state

polarization [2]. This method contains complete information about the ground-state

density matrix. We can distinguish three regions in the CPT spectrum: (1) when the

σ− polarized laser is very far from resonance, the population is optically pumped into

the 1gm = state. Thus the AMPS preferentially points along the quantization axis z

[Fig. 1(a)]. (2) When the probe is tuned closer to resonance, but the lasers are still

incoherent to each other, the population is increasingly pumped into 0gm = and this

causes the AMPS to look like a hot-air balloon [Fig. 1(b)]. (3) When both the pump

and probe are in resonance and coherent to each other, the population is shared

equally between the 1gm = − and 1gm = Zeeman sublevels and the two-photon

coherence takes its maximum value. The AMPS now takes on a "doughnut" shape

with the principal axis of rotation along the x-axis [Fig. 1(c)].

Figure 1. Visualization of CPT by AMPS of the ground-state polarization.

[1] C. Goren et al., Phys. Rev. A 68, 043818 (2003).

[2] S. M. Rochester and D. Budker, Am. J. Phys. 69, 450 (2001).

a b c

Quantum tunneling of hydrogen atoms in dissociation of photoexcited

methylamine and methylamine-d3

Ran Marom,1 Chen Levi,1 Tal Weis,1 Salman Rosenwaks,1 Yehuda Zeiri,2 Ronnie Kosloff3 and

Ilana Bar1

1Department of Physics, Ben-Gurion University, Beer Sheva 84105, Israel 2 Department of Biomedical Engineering, Ben-Gurion University, Beer Sheva 84105, Israel

and Department of Chemistry, NRCN, Beer-Sheva 84190, Israel 3Department of Physical Chemistry and the Fritz Haber Center for Molecular Dynamics, The

Hebrew University of Jerusalem, Jerusalem 91904, Israel

The dissociation probability of hydrogen atoms from methylamine, CH3NH2, and

methylamine-d3, CD3NH2, molecules is found to increase extensively by promoting them to

excited vibrational states on the first bound electronic state. The (1 + 1) resonantly enhanced

multiphoton ionization and action spectra together with their comparison to an analytical

model and to direct dynamics calculations indicate that H atom release in N-H bond fission of

both molecules is dominated by resonance enhanced quantum tunneling.

Th-19

Two-dimensional spatial solitons and vortices in photonic crystals

Thawatchai Mayteevarunyoo1 and Boris A. Malomed2 1Department of Telecommunication Engineering, Mahanakorn University of Technology, Bangkok 10530,

Thailand 2Department of Physical Electronics, School of Electrical Engineering, Faculty of Engineering, Tel-Aviv

University, Tel-Aviv 69978, Israel

We introduce several species of fundamental and topologically structured spatial solitons in the natural model of a two-dimensional (2D) photonic crystal with the square-shaped intrinsic structure and Kerr self-focusing (SF) or self-defocusing (SDF) nonlinearity:

( )2( , ) 1 | | 0,z xx yyi W x y σΨ + Ψ + Ψ + + Ψ Ψ = where z is the propagation distance, modulation function W(x,y) is taken as per the 2D Kronig-Penney model, see the figure, and 1 or 1σ σ= + = + correspond, respectively, to the SF or SDF nonlinearities. In the former case, the linear confinement of light in local guiding channels competes with the trend to the collapse; in the latter case, the linear trapping in the channels is in competition with the nonlinear self-repulsion. Recently, families of spatial solitons and their bound states were investigated in the 1D version of the model [1]. In this work, we identify families of fundamental solitons, their bound states, and two species of vortices – "squares" and "rhombuses", see examples in the figure. Stability of all these species of 2D solitons is investigated, and evolution scenarios for unstable solitons are identified. In the SF model, the solitons and vortices are found in the semi-infinite gap (alias total-internal-reflection gap), while in the model with the SDF nonlinearity they are constructed in the two lowest finite bandgaps (Bragg-reflection gaps). In the latter case, fundamental solitons are stable in the first finite bandgap, while there is an intrinsic instability border in the second gap. Exactly at the border, the solitons feature a flat-top shape. In the same case (SDF), families of vortex solitons are stable in the first bandgap, and unstable in the second. In the SF model, families of the fundamental solitons and vortices are completely stable in the semi-infinite gap.

Left: the structure of the 2D photonic crystal. Right: power and phase distributions in stable square- and rhombus-shaped

vortices in the second finite bandgap, in the case of the self-defocusing nonlinearity. [1] T. Mayteevarunyoo and B.A. Malomed, Solitons in one-dimensional photonic crystals, J. Opt. Soc. Am. B 25, 1854-1863 (2008).

Th-20

Universal Electromagnetically Induced Transparency Spectra of Random Coherent Recurrence

R. Pugatch1, O. Firstenberg2, M. Shuker2, and N. Davidson1 1Department of Complex Systems, Weizmann Institute of Science, Rehovot 76100, Israel

2Department of Physics, Technion-Israel Institute of Technology, Haifa 32000, Israel

The probability of a random walker to return to its starting point in dimensions one and two is unity, a

theorem first proven by Polya [1]. The recurrence probability P(0, t) to be found at the origin at a time

t is a power law with a critical exponent −d/2 in dimensions d = 1, 2. We report an experiment that

directly measures the Laplace transform of the recurrence probability in one dimension using

Electromagnetically Induced Transparency (EIT) spectroscopy of coherent rubidium atoms diffusing

in a vapor-cell filled with buffer gas. We find a regime where the limiting form of the complex

spectrum is universal and depends only on the effective dimensionality of space. In an effective one-

dimensional diffusion setting the measured spectrum exhibits power law dependence over two and a

half decades in the frequency domain with a critical exponent of −0.53 ± 0.03. Our findings can be

readily extended to other systems e.g. quantum billiards or quantum dots.

Figure: Measured EIT spectra for the 1d beam configuration (triangles) and for the wide area beam (circles). The straight lines are the prediction of our universal theory |s|-β with a single fit parameter - the critical exponent β. We found β = 0.53 ± 0.03 in the 1d case and β' =1.00± 0.03 in good agreement with the predicted values of 0.5 and 1 respectively. Where s=iΔ+Г0/2, Δ is the two-photon detuning, and 1/Г0 is the lifetime of the dark state 2-1/2(|5S1/2,F=1,m=0>+|5S1/2,F=2,m=0>). Inset (b) shows the EIT beams that were used to realize effectively one-dimensional diffusion.

[1] G. Polya, Mat. Ann. 84, 149 (1921).

Th-21

(b)

(a) (a)

Slow and Fast Light through nonlinear Wave Mixing in Liquid Crystals

S. Residori1, U. Bortolozzo1, J.P. Huignard2 1 INLN, Université de Nice Sophia-Antipolis, CNRS, 1361 route des Lucioles,

06560 Valbonne, France 2 Thales Research & Technology, RD 128 91767, Palaiseau Cedex, France

e-mail: stefania.residori@inln.cnrs.fr The ability to control the velocity of light pulses has recently received a large interest both for the development of all-optical communication networks and to enhance the spectral sensitivity of certain type of interferometers [1]. Early achievements on slow light were obtained using electromagnetically induced transparency in ultracold atomic gas [2]. More recently, a considerable deceleration of light pulses was obtained at room temperature by creating spectral holes in the absorption spectrum of a ruby crystal [3] or by using photorefractive crystals close to Bragg resonance [4]. Recently, we have demonstrated that slow and fast light phenomena can be obtained by performing nonlinear wave mixing experiments in liquid crystals [5]. Liquid crystals are particularly attractive for their unique features of large electro-optic response over a small interaction length, visible and neafr IR transparency and imaging capabilities.

a) Schematic setup for fast and slow-light operation of the liquid crystal light-valve. Experimental time dependencies of the output pulse taken b) on the m=0 (red), c) m=-2 (blue) diffraction order of the input pulse (black); b) fast, c) slow-light behavior. In this paper, we show how we can obtain slow and fast light phenomena by

performing non-degenerate two-wave mixing experiments in a liquid crystal light-valve, a device combining a liquid crystal layer with a Bi12SiO20 photorefractive crystal cut in the form of a cell wall, and how we can control the group delay of the light pulses by exploiting the dispersion properties associated with the nonlinear mixing process. The two-wave mixing occurs in the Raman-Nath regime of diffraction, thus multiple order beams are observed at the output. Depending on the order considered and on the initial frequency detuning between the pump and probe, different group delays are obtained in a single experiment, with the output pulse either anticipated or delayed. Finally, we will present an example experimental application of slow light to enhance the sensitivity of a Mach-Zender interferometer and for enhanced sensitivity vibrometric measurements. [1] Z. Shi, R.W. Boyd, D.J. Gauthier, and C.C. Dudley, Opt. Lett. 32, 915 (2007). [2] L. V. Hau, S. E. Harris, Z. Dutton, and C. H. Behroozi, Nature 397, 594 (1999). [3] M. S. Bigelow, N. N. Lepeshkin, and R.W. Boyd, Phys. Rev. Lett. 90, 113903 (2003). [4] A. Shumelyuk, K. Shcherbin, S. Odoulov, B. Sturman, E. Podivilov, and K. Buse, Phys. Rev. Lett. 93, 243604 (2004). [5] S. Residori, U. Bortolozzo, and J.P. Huignard, Phys. Rev. Lett. 100, 203603 (2008).

Probing the spatio-temporal properties of a re-collision process D. Shafir*, Y. Mairesse†, B. Fabre†, J. Higuet†, E. Mével†, E. Constant†, D. M. Villeneuve**, P. B. Corkum** and N. Dudovich* ** *Department of Physics of Complex Systems, Weizmann Institute of Science, Rehovot 76100, Israel † CELIA, Universit'e Bordeaux I, UMR5107, 351 Cours de la Lib'eration, 33405 Talence, France ** National Research Council of Canada, 100 Sussex Drive, Ottawa, Ontario K1A 0R6, Canada Recently it has been demonstrated that electron-ion recollision events produced in the process of high harmonic generation (HHG) can be utilized to resolve the spatial properties of the wavefunctions involved in the process. In this scheme an electron is removed by tunnel ionization from the neutral molecule (or atom) and then manipulated by the laser field. In the final step the electron recollides with its parent ion emitting high energy photons. Such an approach has been applied to perform a tomographic reconstruction of N2 molecules [1]. The basic model which describes the HHG process is based on the strong field approximation (SFA) assuming that the free electron’s dynamics are dictated by the strong laser field, neglecting the Coulomb force exerted by the parent ion. In this work we perform a systematic study resolving the spatial properties of both the ground state and the free electron in a recollision process. Manipulating the fundamental parameters of the interaction - the laser intensity and wavelength, we investigate its basic properties. Following an earlier study on atomic systems [2], we use an elliptically polarized light to control both the ionization and recollision angles of the electron. Such manipulation controls the quantization axis of the ionized electronic state, decoupling it from the recollision angle. By adding ellipticity, we rotate the recollision angle rapidly within the optical cycle. Such rapid rotation is imprinted in the polarization of the emitted harmonics.

Measuring the HHG polarization, we can characterize the 2D sub-cycle dynamics of the free electron as well as the spatial properties of the ground state. In the present experiment we measured the polarization of high order harmonics produced from Argon and Xenon atoms as a function of the fundamental field's ellipticity. The measured polarization is applied to extract the spatial properties of the atomic ground state and the free electron. It is apparent that in the high laser intensity regime (2-3*1014 W/cm2), the measured polarization does in fact follow the polarization calculated by SFA. In the low intensity regime (0.7-1*1014 W/cm2), the measured results differ from the model calculations suggesting a breakdown of the SFA. Assuming that the ground state in the atomic wave function is well known, this deviation is related to the Coulomb interactions. By changing the laser wavelength from 800 nm to 1800 nm we obtain results that agree with SFA even at low intensities. In summary, we present a new approach which relies on the high spatial resolution provided in a recollision process, to probe spatial properties of the process. In the present experiment the atomic wavefunction serves as an accurate spatial probe which measures the free electron 2D dynamics. References: [1] J. Itatani et al., Nature 432, 867 (2004). [2] D. Shafir et al., submited (2008)

Th-23

Sawtooth grating-assisted-phase-matching Pavel Sidorenko,1,2 Alon Bahabad,2 Tenio Popmintchev,2 Margaret Murnane,2

Henry Kapteyn,2 and Oren Cohen1,2

1Solid state institute and physics department, Technion – Israel Institute of Technology, Haifa, Israel 2JILA and Department of Physics, University of Colorado at Boulder Boulder, CO 80309, USA

Quasi-phase matching (QPM) is a widely used technique in nonlinear optics for enhancing the efficiencies of processes that suffer from a phase-mismatch between the nonlinear polarization and the signal waves [1]. However, all QPM schemes only partially correct for the phase-mismatch, resulting in reduced conversion efficiency compared with perfect phase matching interaction. For example, the QPM efficiency factor, which is the conversion efficiency (for intensity) normalized by the efficiency at perfect phase matching, of 1st order QPM is (2/π)2~0.4 Here, we propose a new QPM scheme – sawtooth grating-assisted-phase-matching - that leads to QPM efficiency factor that approaches 1. We propose various schemes where sawtooth grating assisted phase matching can be implemented in low-order as well as in high-order harmonic generation.

In grating-assisted-phase-matching (GAPM), the phase-mismatch is corrected by a periodic modulation of the difference between the refractive indices of the pump and harmonic beams. In previous works, sinusoidal and square periodic modulations were investigated.1-3 Figure 1 shows that (sharp or rounded) sawtooth profiles are more efficient for GAPM.

Sawtooth GAPM can be implemented in various nonlinear processes and schemes. In second harmonic generation, we propose using a waveguide with a sawtooth surface corrugation. In a second scheme, the process is drivien by counterpropagating beams at a wavelength that corresponds to four coherence lengths. Sawtooth GAPM can also be implemented in high-order harmonic generation (HHG).4 In HHG, the phase of the high-order polarization is proportional to the intensity of the fundamental laser. Thus, a rounded sawtooth modulation in the laser intensity along the propagation direction, which can be induced by interfering the strong driving laser pulse with weak quasi-CW waves, can be used for sawtooth GAPM of high harmonic generation.

Figure 1: Sawtooth grating assisted phase matching. (a) Under phase-mismatch condition, the shift between the phases of the driving and harmonic fields (ΔФ0) grows linearly, leading to oscillations in the harmonic signal (b) a sawtooth phase-shift (ΔФGAPM) for correcting the phase mismatch of the nonlinear process. The sharp sawtooth (solid line) wave consists of an infinite number of Fourier components. Also plotted is a rounded sawtooth wave that consists of the first three Fourier components (dashed line). (c) The combination of the medium phase-mismatch and the sharp sawtooth (K=∞) phase-shift ΔФ0+ΔФ results in a step-function phase that leads to a linear growth of the HHG signal – corresponding to perfect phase matching. (d) The QPM efficiency factor (conversion efficiency normalized by the conversion efficiency at perfect phase-matching) of rounded sawtooth that consists of K Fourier components. The conversion efficiency with K=2 is higher than the QPM efficiency factor of 1st order QPM where the polarization direction is flipped every coherence length (e.g., as in PPLN).

References 1 M. M. Fejer, G. A. Magel, D. H. Jundt, and R. L. Byer, “Quasi-phase-matched second harmonic generation-Tuning and tolerances,” IEEE J. Quantum Electron 28, 2631–2654 (1992). 2 S. Somekh and A. Yariv, “Phase-matchable nonlinear optical interactions in periodic thin films,” Appl. Phys. Lett., 21, 140-141 (1972). 3 O. Cohen et al., “Grating-Assisted Phase Matching in Extreme Nonlinear Optics,” Phys. Rev. Lett. 99, 053902 (2007).

Matter-Laser Interaction: Derivation of coupled Maxwell-Schr¨odinger equations from the first principles

of quantum electrodynamics

Milan Sindelka1 Department of Physics and Minerva Center for Non-Linear Physics of Complex Systems,

Technion – Israel Institute of Technology, Haifa 32000, Israel Abstract We study general problem of matter-laser interaction within the framework of nonrelativistic quantum

electrodynamics, with particular emphasis on strong laser field effects. Consequently, we formulate a

well defined approximation leading in a straightforward manner towards the conventional

semiclassical mode of description. Namely, we arrive naturally to two coupled equations of motion: i)

the Schr¨odinger equation which governs the quantum dynamics of an atomic system driven by

classically described radiation field (composed of an incoming laser pulse plus radiation emitted from

the atom), and ii) the classical Maxwell wave equation which describes emission of radiation from the

mentioned atomic source. Employing the formalism of adiabatic Floquet theory, we derive a simple

criterion of validity of the just described semiclassica pproach. It shows that the semiclassical

treatment is justified in most situations. On the other hand, it turns out that the semiclassical

approximation breaks down completely in certain special but realistic cases, regardless to the fact that

the incoming laser pulse contains a huge number of photons. Under such special circumstances, we

anticipate new effects arising due to quantized nature of the radiation field, to be observable e.g. in

harmonic generation spectra.

1Electronic mail: chmilan@tx.technion.ac.il

Th-25

PHOTOLUMINESCENCE RING FORMATION IN COUPLED QUANTUM WELLS:

A MANIFESTATION OF THE MOTT TRANSITION

M. Stern, V. Garmider, E. Segre, M. Rappaport, V. Umansky, Y.Levinson and I. Bar-Joseph

Department of Condensed Matter Physics,

The Weizmann Institute of Science,

Rehovot, Israel

The lateral diffusion of indirect excitons in coupled quantum wells has been a subject of intensive interest

lately in the context of creating a cold and dense interacting exciton gas. The long life time of these excitons

allows them to diffuse for relatively long distances while cooling down to the lattice temperature.

Furthermore, the electrons and holes in this structure are typically separated by ~ 10 nm, giving rise to strong

dipole moments, which are all aligned in the same direction. The interaction between the dipoles generates a

strong force, which drives the excitons away from each other. These properties have been used in a series of

recent experiments, which attempted to reach the critical density and temperature for Bose Einstein

condensation. An interesting observation in these experiments is the appearance of two photoluminescence

rings around the excitation spot. The external ring, which was originally considered as a manifestation of a

degenerate exciton gas, was later shown to be due to recombination of excess free carriers in the quantum

well [1]. The inner ring was attributed to enhanced luminescence of excitons as they cool down while

diffusing away from the hot excitation spot. A detailed hydrodynamic model was proposed to describe this

diffusion, and concluded that a high degeneracy of the exciton gas has been achieved. This was perceived as a

step towards BEC, and an optical trap which is based on this effect was demonstrated [2].

In this work we study the formation of the inner photoluminescence ring and show that the excited system is

not a degenerate exciton gas but rather consists of unbound electrons and holes. We find that e-h diffusion is

ambipolar, and is characterized by a large diffusion coefficient, similar to that found in p-i-n junctions, while

correlation effects in the excitonic phase significantly suppress the carriers’ diffusion. Hence, there is a drastic

change in the diffusion properties of the system at the Mott transition [3], and we show that it gives rise to the

appearance of the ring pattern. The appearance of the ring can therefore be viewed as a manifestation of the

exciton Mott transition in this system.

[1] R. Rapaport et al., Phys. Rev. Lett., 92, 117405 (2004).

[2] A.T. Hammack et al., Phys. Rev. Lett., 96, 227402 (2006).

[3] M. Stern et al., Phys. Rev. Lett., 100, 256402 (2008).

Th-26

Observable effects of non-integrability on three-body one-dimensional collisions

Vladimir A. Yurovsky and Abraham Ben-Reuven

School of Chemistry, Tel Aviv University

Ultracold atoms under tight cylindrical confinement can reach the ‘‘single-mode,’’ or quasi-one-dimensional regime, where only the ground state of the transverse motion is significantly populated (see [1] and references therein). Atom waveguides that tightly confine a particle’s motion in two transverse directions have been realized recently in elongated atomic traps, two-dimensional optical lattices, and atomic chips. Quasi-one-dimensional Bose gases can be approximately described by the Lieb-Liniger-McGuire model with energy-independent zero-range atom-atom interactions. This model has an exact Bethe-ansatz solution, expressed as the superposition of plane waves with all possible permutations of the asymptotic momenta, one per each atom. Therefore, this model is characterized by non-diffractive scattering, where the atoms can exchange their momenta, but the asymptotic momentum set remains unchanged. One-dimensional molecules are described by this model in the case of attractive interaction. The Lieb-Liniger-McGuire model is a rare example of integrable many-body systems. Integrability means the conservation of integrals of motion, which are as numerous as the degrees of freedom. The integrability of a many-body system can lead to some experimentally observable consequences and, vise-versa, the presence of certain effects can be a proof of the absence of integrability. Reflection and dissociation in atom-diatom collisions and three-atom association [2] are possible observable effects of non-integrability. The asymptotic momentum set is changed in such processes, while they are forbidden in the Lieb-Liniger-McGuire model. If a Feshbach resonance appears in two-body scattering, an elimination of the closed channel leads to zero-range interaction with energy-dependent strength. This energy dependence removes the integrability of the Lieb-Liniger-McGuire model, although the two-body problem remains non-diffractive due to energy and momentum conservation. The closed channel was eliminated in the three-body case, and the case of energy-dependent interactions was analyzed by a numerical solution of the Faddeev-Lovelace equations [2]. The results demonstrate that the reflection becomes the dominant output channel of atom-molecule low-energy collisions, while dissociation appears above a threshold. Another property of the Lieb-Liniger model is a suppression of atom-atom correlations at low collision energies, leading to suppression of possible inelastic processes. It is demonstrated [3], however, that atom-molecule correlations are not suppressed within this integrable model, but become suppressed when the integrability is lifted due to a Feshbach resonance. Thus the stabilization of broad Feshbach di-bosonic molecules in atom waveguides can be another possible observable effect of non-integrability. 1. V. A. Yurovsky, M. Olshanii, and D. S. Weiss, Adv. At. Mol. Opt. Phys., 55, 61, (2007). 2. V. A. Yurovsky, A. Ben-Reuven, and M. Olshanii, Phys. Rev. Lett, 96, 163201, (2006). 3. V. A. Yurovsky, Phys. Rev. A 77, 012716 (2008).

Th-27

Polarization Dragging Phenomena in Stimulated Brillouin Amplification/Attenuation in Standard Single-Mode Fibers

Avi Zadok1, 2, Elad Zilka1, Avishay Eyal1, Luc Thévenaz3, and Moshe Tur1 1School of Electrical Engineering, Faculty of Engineering, Tel-Aviv University, Tel-Aviv 69978, Israel

2Currently with the Department of Applied Physics, MC 128-95, California Institute of Technology, Pasadena, CA 91125, USA 3Ecole Polytechnique Fédérale de Lausanne, Institute of Electrical Engineering, STI-GR-SCI Station 11, 1015 Lausanne, Switzerland

avizadok@caltech.edu; avishay@eng.tau.ac.il; luc.thevenaz@epfl.ch; tur@eng.tau.ac.il;

ABSTRACT Stimulated Brillouin Scattering (SBS) depends on optical interference between the pump and signal waves [1]. Specifically, the local SBS interaction, at a given point along an optical fiber, is maximized when the electric fields of the pump and signal are aligned, i.e., their vectors trace parallel ellipses and in the same sense of rotation. Conversely, if the two ellipses are again similar, but traced in opposite senses of rotation, with their long axes being orthogonal to each other, then the SBS interaction at that point averages to zero over an optical period. Consequently, in the presence of birefringence, the overall signal gain (or loss) depends on the birefringent properties of the fiber, as well as on the input states of polarization (SOPs) of both pump and signal. Following initial work by Horiguchi et al. [2], van Deventer and Boot [3] have studied the cases of maximum and minimum gain for a few scenarios of fiber birefringence. However, the SBS amplification of an arbitrarily polarized input signal SOP was not discussed, nor was the role played by the Brillouin effect itself in the evolution of the signal SOP considered. In this paper we study the SBS amplification/attenuation of an arbitrarily polarized input signal, as well as the role of SBS in the evolution of the signal SOP. A new set of equations is derived for the Stokes parameters of the propagating waves and the analysis includes both SBS amplification and attenuation. In particular, we find that the output SOP of an SBS amplified Stokes wave in a standard, single mode fiber is drawn towards the complex conjugate of the input pump SOP. On the other hand, the output SOP of the residual, attenuated anti-Stokes signal is repelled from the conjugate of the pump [4]. These findings are supported by simulations and experiments. Results: The figure shows the experimentally obtained SOP of a Stokes signal, as a function of pump power, at the output of a 2250m long standard fiber. Three cases are studies. (i) Maximum gain (blue solid circles): the signal is launched into the fiber with an SOP, for which the gain is maximum; (ii) Minimum gain (green open diamonds): the signal is launched into the fiber with an SOP for which the gain is minimum; (iii) The intermediate case (red squares): the signal is launched into the fiber with an SOP close to the SOP of the minimum gain case, but rotated from it by 400 around the RL axis. Open symbols denote SOPs in the back of the sphere. The size of the red square is a measure of the signal power, increasing with pump power for Stokes signals. The black ‘+’ is the SOP of the spontaneous SBS. The straight line through the center of the sphere connects this SOP to its orthogonal counterpart. The figure clearly demonstrates the dragging effect of the SBS: from the vicinity of the 'diamonds' cloud, the SOP approaches that of blue circles area.

The significance of these findings and some of their applications will be discussed in detail. 1. R. W. Boyd, Nonlinear optics, (San Diego, CA: Academic Press, 2003) chapter 9, 409-427. 2. T. Horiguchi, T. Kurashima, and M. Tateda, IEEE Photon. Technol. Lett. 2, 352-354, (1990). 3. M. O. van Deventer, and A. J. Boot, J. Lightwave Technol. 12, 585-590, (1994). 4. A. Zadok, E. Zilka, A. Eyal, L. Thévenaz, and M. Tur, “Vector analysis of stimulated Brillouin scattering

amplification in standard single-mode fibers,” submitted for publication in Opt. Express 16, (2008).

Pump-probe spectroscopy in degenerate two-level atoms with arbitrarily strong

fields T. Zigdon, A. D. Wilson-Gordon, and H. Friedmann,

Department of Chemistry, Bar-Ilan University, Ramat Gan 52900, Israel

We report calculations of the pump and probe absorption spectra for the cycling 2 3g eF F= → =

transition in the 2D line of 87Rb, interacting with a resonant σ + polarized pump and either π or σ −

polarized probe, for the case where the probe intensity is high enough to affect the pump absorption

[1]. We have constructed a computer program that can calculate the spectra without requiring one to

write out the Bloch equations explicitly for any g eF F→ alkali metal transition interacting with an

arbitrarily intense pump and probe which are perpendicularly polarized to each other with either σ ± or

π polarizations. We show that when the pump is σ ± polarized and the probe π polarized, or vice-

versa, the pump and probe absorptions depend on the Zeeman coherences between the nearest-

neighboring ground or excited Zeeman sublevels, whereas when the pump is σ + polarized and the

probe σ − polarized, or vice-versa, the Zeeman coherences that directly determine the absorption are

between next-nearest neighbors. We show that the pump and probe absorption spectra have the same

behavior at line center and complementary behavior in the wings, when 1 2Ω ≥Ω <Γ [Fig.1 (a) and (b)]

and are mirror images of each other when 1 2Ω ≥Ω >Γ [Fig.1 (c) and (d)], where Γ is the rate of

spontaneous decay from eF to gF .

Fig.1. Probe and pump absorption spectra as a function of pump-probe detuning δ /Γ.

[1] T. Zigdon, A. D. Wilson-Gordon, and H. Friedmann, Phys. Rev. A 77, 033836 (2008).

Th-29