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Raman Scattering From a Single Molecule between Two Metal

Nanoparticles

T. Dadosh1,2, G. Haran3, J. Sperling2, A. Yacoby1, and I. Bar-Joseph1

Department of Condensed Matter Physics, The Weizmann Institute, Israel

Department of Organic Chemistry, The Weizmann Institute, Israel

Department of Chemical Physics, The Weizmann Institute, Israel

Single molecule spectroscopy is an emerging field that provides detailed information on

molecular response, which is inaccessible in ensemble averaged measurements. The

obvious problem, however, in implementing most spectroscopic techniques is the very

weak signal which is obtained from a single molecule. Inelastic light (Raman) scattering

is an example for that. The direct access to the vibration degrees of freedom of the

molecule provided by this technique makes it very attractive for studying the response of

a single molecule to external forces and its interactions with the environment.

Unfortunately, the typical cross sections per molecule are extremely weak, of the order

10-30 cm-2, yielding a practically undetectable signal. A way out of this was suggested by

using the enhancement of Raman scattering near metal surfaces. It is well known that a

dramatic signal increase may occur if the molecule is adsorbed to metal particles of sub-

wavelength dimensions. This technique, known as surface enhanced Raman scattering

(SERS), was recently was demonstrated to enhance the effective Raman cross section by

a staggering 14–15 orders of magnitude. This huge enhancement has proven enough for

successful single molecule spectroscopy.

In this work we shall report measurements of Raman scattering from a small aromatic

molecule in a novel dimer structure, consisting of two metal nanoparticles connected by a

single molecule. We have recent ly shown that this structure may serve as an efficient tool

for conducting electrical transport measurements of the molecule. In this work we show

that the Raman enhancement in this dimer structure is extremely large, yielding an easily

detectable signal.

SCANNINGLESS DEPTH RESOLVED MICROSCOPY BY TEMPORAL FOCUSING OF ULTRASHORT PULSES

Dan Oron, Eran Tal, Yaron Silberberg Dept. of Physics of Complex Systems

Weizmann Institute of Science Rehovot 76100, Israel

E-mail: yaron.silberberg@weizmann.ac.il

ABSTRACT: The ability to perform optical sectioning is one of the great advantages of laser-scanning microscopy, be it confocal or multiphoton microscopy. This comes however, at a cost of long image acquisition times, of an order of tens of milliseconds, due to the serial acquisition of data points. We show that by introducing spatiotemporal pulse shaping techniques it is possible to obtain full-frame depth resolved imaging without scanning, in a very simple setup. In multiphoton laser scanning microscopes, the depth resolution is achieved by spatially focusing an ultrashort pulse to achieve a high intensity at the focal plane [1]. Due to the nonlinear dependence of the signal on the intensity this results in superb rejection of the out-of-focus signal. In contrast, our method relies on temporal focusing of the illumination pulse. The pulsed excitation field is compressed as it propagates through the sample, reaching its shortest duration (and highest peak intensity) at the focal plane, before stretching again beyond it. This method is applied to obtain depth-resolved two-photon excitation fluorescence (TPEF) images of drosophila egg-chambers with nearly 100,000 effective pixels in a scanningless setup using a standard Ti:Sapphire laser oscillator. A single cross-section obtained by this method is compared to a full-frame multiphoton image obtained by plane-wave illumination in Fig. 1. This method can be particularly useful for multiphoton time-resolved studies such as full-frame depth resolved fluorescence lifetime imaging.

Figure 1: Scanningless images of a drosophila egg-chamber stained with DAPI. Image (a) was taken with a temporal lens in the microscope path. Image (b) shows, for comparison, a

non-depth resolved image, illuminating with a plane wave. The area of each image is 140x140�m. The excellent rejection of the out-of-focus fluorescence in (a) is apparent.

1. W. Denk, J. H. Strickler, W. W. Webb, "Two-photon laser scanning fluorescence microscopy", Science 248, 73-76 (1990).

Incoherent matter-wave solitons: Mutual self-trapping of

a Bose-Einstein condensate and its surrounding thermal cloud

H. Buljan,1,2 M. Segev,1∗ and A. Vardi31Physics Department, Technion - Israel Institute of Technology, Haifa 32000, Israel

2Department of Physics, University of Zagreb, PP 332, Zagreb, Croatia and3Department of Chemistry, Ben Gurion University of Negev, Beer Sheva, Israel

(Dated: December 1, 2004)

The physics of quantum-degenerate, interacting bosegases closely resembles the behavior of light in non-linear media. The dynamics of Bose-Einstein conden-sate (BEC) at zero-temperature is within the Gross-Pitaevskii (GP) mean-field theory described by the non-linear Schrodinger equation (NLSE) for the condensateorder parameter. The same equation describes the evo-lution of coherent light in nonlinear Kerr medium. Thisanalogy has opened the way for the field of nonlinearatom optics [1, 2] with striking demonstrations of famil-iar nonlinear optics phenomena carried out with matter-waves. One such nonlinear phenomenon is the forma-tion of matter-wave solitons, which were studied experi-mentally [3, 4] and theoretically [5, 6] in various systems.To the best of our knowledge, all previous theoreticalefforts on matter-wave solitons have utilized the zero-temperature GP mean-field theory. However, in a realis-tic system, elementary excitations arising from thermaland/or quantum fluctuations are always present, and theBEC dynamics may be considerably affected by the mo-tion of excited atoms around it (thermal cloud), givingrise to new nonlinear matter-wave phenomena.

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FIG. 1: The evolution of the system (a) with interactionspresent, and (b) without interactions. In both cases, initialconditions were identical, while external potential was turnedoff during evolution. When interactions are present, the sys-tem self-trapps and exhibits incoherent matter wave soliton-like propagation, while in the other case the matter wavesquickly disperse.

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FIG. 2: (color online) The complex degree of coherence|µ(ξ, ξ′, t)| of a partially-coherent, self-trapped matter-waveat times t = 0 (black dashed line), t = 0.4∆t (red solid line),t = 0.8∆t (green dot-dashed line), and t = 1.2∆t (blue dottedline); ∆t = 2π/ωx, where ωx is the frequency of the trappingpotential. For comparison, the complex degree of coherenceof zero-temperature GPE solitons is exactly one.

We present an example of such novel phenomena,and show that a BEC and a portion of its surroundingthermal cloud can exhibit mutually self-trapped motion.This motion is achieved via attractive interactionsbetween particles, and not by the external confinement.We emphasize that the finite-temperature self-trappingproduces a truly novel type of matter-wave solitons,where localization is attained not only in spatial density(see Fig. 1) but also in spatial correlations (see Fig.2). These self-trapped incoherent matter-waves areanalogous to composite random-phase (incoherent)optical solitons [7]; one component is the BEC while theother is a part of its thermal cloud. An important resultof this work is that the established analogy betweenzero-temperature BECs and coherent nonlinear opticscan be elevated to the analogy of incoherent light behav-ior in nonlinear media and BECs at finite-temperatures.

[1] G. Lens, P. Meystre, and E.M. Wright, Phys. Rev.Lett. 71, 3271 (1993).[2] S. L. Rolston and W. D. Phillips, Nature 416, 219 (2002).[3] L. Khaykovich et al., Science 296, 1290 (2002).[4] K.E. Strecker, et al., Nature 417, 150 (2002).[5] P.A. Ruprecht et al., Phys. Rev. A 51, 4704 (1995).[6] Th. Busch, and J.R. Anglin, Phys. Rev. Lett. 84, 2298(2000).[7] M. Mitchell et al., Phys. Rev. Lett. 77, 490 (1996); M.Mitchell and M. Segev, Nature (London) 387, 880 (1997).

∗corresponding author: msegev@tx.technion.ac.il

Spontaneous pattern formation with incoherent “white” light

Tal Schwartz, Tal Carmon, Hrvoje Buljan and Mordechai Segev Physics Department, Solid State Institute, Technion, Haifa 32000, Israel

schtal@sspower.technion.ac.il

Spontaneous pattern formation in optical systems has been extensively studied for the past few

decades. In this process, modulational instability (MI) causes a broad uniform-intensity beam to

break up into an array of light filaments with a regular periodicity. Traditionally, pattern formation

in nonlinear optical systems was studied with fully coherent light, relying on the intuition that spatial

correlations are necessary for wave amplification. However, in the past few years our group has

shown theoretically1 and experimentally2 that a spatially incoherent beam, in which many

stochastically-populated modes interact through the nonlinearity, can also undergo MI breakup. This

phenomenon shows the characteristics of super-critical transition, having a distinct threshold for the

instability to occur. We have later shown that the long-term evolution of this "incoherent MI" results

in clustering of the incoherent light-filaments3. Motivated by the observation of white-light optical

spatial solitons4, our group has started to investigate MI of white light: light which is both spatially

and temporally incoherent, thus making nonlinear interactions among a broad continuum of

temporal frequencies an important ingredient of the underlying nonlinear dynamics. In a recent

theoretical paper5 our group has predicted that white-light MI is a collective effect, in the sense that

the whole temporal spectrum is becoming unstable at a common threshold and all temporal

frequencies lock up to a single spatial periodicity. Here we report the first observation of

modulational instability and spontaneous pattern formation with incoherent “white” light emitted

from an incandescent light bulb6. Typical results are shown in Fig. 1(a), showing a real-color image

of the pattern at the output face of our nonlinear material (photorefractive SBN:60 crystal), when the

nonlinearity strength exceeds the instability threshold. We

measured the visibility (contrast) of the emerging pattern at

specific wavelengths isolated from the rest of the spectrum, as the

nonlinearity is increased. The results are presented in Fig. 1(b),

which clearly demonstrates that (1) white light MI is indeed a

collective effect where all frequencies become unstable at common

threshold, and (2) the temporal spectrum of the emerging pattern

self-adjusts so that shorter wavelengths (higher frequencies)

contribute more to the collective white-light pattern.

1. M. Soljacic et al., Phys. Rev. Lett. 84, 467 (2000. 2. D. Kip et al., Science 290, 495 (2000). 3. Z. Chen et al., PNAS 99, pp. 5223-5227. 4. M. Mitchell, M. Segev, Nature 387, 880 (1997). 5. H. Buljan et al., Phys. Rev. E. 66, 035601 (2002). 6. T. Schwartz et al., Phys. Rev. Lett. 93, 223901 (2004).

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Microscopic model of the susceptibility of semiconductor quantum dots as a Kerr-like medium for optical self organization

S. Barbaya, I. Perrinib, T. Maggipintob, M. Brambillab and R. Kuszelewicza(*) (*) robert.kuszelewicz@lpn.cnrs.fr

a Laboratoire de Photonique et Nanostructures/CNRS-UPR20, Route de Nozay, 91460 Marcoussis, France b INFM, Istituto Politecnico di Bari, via Orabona, Bari, Apulia 70126, Italia

We present a model for the calculation of the optical response of an extended semiconductor

quantum dot (QD) medium. This model goes beyond the two-level system approach considered

in [1]. In particular it allows for larger excitation intensities and is not restricted to one electron-

hole pair per dot. We build a microscopic model with Bloch equations and assume a spatially

continuous, inhomogeneously broadened distribution of QD coupled with a common 2D Wetting

layer (WL). This way, we incorporate carrier exchange between the WL and the QD such as

thermoemission-capture and Auger processes. We ignore band-gap renormalization effects as

long as the WL population is low enough.

Fig1. Comparison of the real part of the susceptibility between the present model and the one e-h pair model

Fig.2 : Compared hysteresis cycles obtained with the two

models

We consider systems in which the energy separation between the QD levels is larger than the

homogeneous linewidth of each level. We also consider the inhomogeneous linewidth as smaller

than the energy difference to the closest allowed optical transition. Hence, the electromagnetic

field couples the same electron and hole states of the QD ensemble. The susceptibility derived

from this model shows a strong focusing optical Kerr non linearity. It compares (fig.1) to that of

the one electron model and yields significant changes for the threshold of modulational

instabilities in QD vertical microresonators (Fig.2).

1 S. Barbay et al., IEEE Journal of Quantum Electronics, Vol. 39, No. 2, pp. 245 – 254, February 2003.

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POLYMER BASED NON CIRCULAR MICRO-BILLIARD LASERS: A BENCHMARK FOR NONL INEAR DYNAMICS AND CHAOS

Mélanie Lebental, Tahar ben Messaoud, Angela Vella and Joseph Zyss(*), Laboratoire de Photonique Quantique et Moléculaire (UMR 8537)

Institut d’Alembert (IFR 121) Ecole Normale Supérieure de Cachan (*) joseph.zyss@lpqm.ens-cachan.fr

Visible and near IR emitting micro-lasers are an important class of devices that are in demand to complement the existing passive and electro-optic waveguide technology on the way to a full fledged all-polymer based integrated optical circuitry with a wide range of applications from information technologies to biotechnologies. Whereas electrical pumping of polymer based micro-lasers still remains an elusive challenge, a simplified technology as compared to semiconductor based multiple layer cavities remains a major asset of polymers with the enticing perspective opened up by the low cost and large scale replication potential of soft material technologies [1]. We have developed in our laboratory, from technological fabrication all the way to optical investigations, three kinds of basic configurations for micro-lasers: polymer micro-rings around silica fibres [2], distributed feedba ck structures (DFB’s) [3] and planar micro-cavities such as sustaining whispering gallery modes (WGM). In this communication, we concentrate on lower index polymer based planar micro-cavities [4-8]. The current driving force followed in these studies is both conceptual (in conjunction with basic issues pertaining to the electromagnetic billiard as a benchmark for nonlinear dynamics and chaotic phenomena) and practical primarily in view of steering the out -coupled refracted emission of microcavities of give n shapes in well defined direction towards further optical processing. Moreover, we have concentrated on a variety of non-circular shapes (sometimes referred to as ARC’s for Asymmetric Resonant Cavities) which are designed, contrary to circular microdisks whereby emission is isotropic and purely evanescent at the interface, so as to favour emission along well defined directions from specific out-coupling spots on the boundary. A current lack of both theoretical understanding underlying the angular, spectral, polarization and gain features of various types of ARC’s as well as of systematic experimental data, particularly for low index materials, is motivating this work. From a fundamental perspective, a major asset of polymers as low index materials is to unveil a wealth of interesting phenomena embedded in domains of the Poincaré-Husimi surface of section representation that would be otherwise “hidden” by the higher index total internal reflection condition for semiconductor materials. Microcavities are fabricated according to traditional polymer based integrated optics techniques based on microlithography and plasma etching. A variety of boundary shapes has been studied, in particular circles (micro-cylinders), squares, polygons, quadrupoles, hexadecapoles and spirals of various overall sizes ranging from 10 to a few 100’s of µm and thicknesses of the order of 1 to 2 µm [4-7]. Among the results to be presented (see Fig.1), we show that a pump geometry whereby coupling to relevant WGM modes is favoured significantly improves the outgoing directionality [8] as compared to non discriminate flooding of the whole micro-cavity area. The emission pattern is shown to dramatically depend on the external cavity geometry and we are lead, based on a Poincaré surface of section analysis, to propose that unstable manifolds originating from periodic orbits guide the flow in this representation, thus playing a crucial role in determining the out -coupling angular features [6].

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Figure 1: Emission properties of a 318 µm sp iral microcavity pumped by a matching transversely micro-ring shaped pump so as to maximize the overlap of the gain region with the outer gallery modes. The two far-field angular patterns above correspond to different shapes (smaller and larger radii of respectively (a) diameter 320 µm, width w = 35 µm and (b) diameter 350 µm, width 50 µm). The lower pictures evidence typical and well behaved laser emitted intensity versus pump intensity plots [8]. Current ongoing work concentrates on the Bunimovitch stadium shaped cavities which are by nature unable to sustain stable periodic orbits. We have recently experimentally demonstrated that the refractive out-coupling properties of such structures evidence well defined angular directions and emitting zones [9] and are currently concentrating on development of electromagnetic models as well as numerical simulations to account for this interesting and somewhat surprising behaviour. The implicit and all pervading assumption that “well behaved” modes made-up of stable orbits (preferably of lower order) are to be privileged whereas other types of behaviour, such as chaotic, are hence to be eliminated, is thus being challenged by this work. Not only do chaotic modes exist but they are moreover potentially exploitable and likely to open up new perspectives of both conceptual and practical relevance. Acknowledgement: collaborations with Richard Chang and co-workers, J.P.Wolf and F.Courvoisier at Lyon I University (LASIM), E.Bogomolny and C.Schmit at Orsay University (LPTMS) are gratefully acknowledged.

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References: [1] Bottom-up soft-lithographic fabrication of three-dimensional multilayer polymer integrated optical microdevices Yanyi Huang, George T. Paloczi, Joyce K. S. Poon, and Amnon Yariv Appl. Phys. Lett. 85(15), 3005,2004 [2] Polymer microring lasers with longitudinal optical pumping S.X.Dou, E.Toussaere, T.Ben Messaoud,A.Potter, D.Josse, G.Kranzelbinder and J.Zyss Appl.Phys.Lett. 80(2),165(2002) See also News and Views report on this article in Nature (April 4th 2002, vol. 416, p.489) "A boost for optics fiber" by V.Vardeny [3] Dye doped organic distributed feedback lasers with index and surface gratings: the role of pump polarization and molecular orientation, D.Wright, E.Brasselet, J.Zyss, G.Langer, W.Kern, J.Opt.Soc.Am.B. 21(5), 944(2004) [4] Tahar Ben Messaoud (Ph.D. thesis, Dec. 2003, ENS Cachan) [5] Direct evidence of open ray orbits in a square two-dimensional resonator of dye-doped polymers G.D.Chern, A.W.Poon, R.K.Chang, T.Ben Messaoud, O.Alloschery, E.Toussaere, J.Zyss and, S.Y.Kuo, Opt. Lett. (29), 1674 (2004) [6] Dramatic shape sensitivity of directional emission patterns from similarly deformed cylindrical polymer lasers H.G.Schwefel N.B.Rex, H.E.Tureci, R.K.Chang, A.D.Stone, T.Ben Messaoud, J.Zyss, J.Opt.Soc.Am.B 21(5), 923 (2004) [7] Diffractive coupling in spiral microcavities with femtosecond light bullets F.Courvoisier, V.Boutou, R.K.Chang, J.Zyss, J.P.Wolf to appear in Optics Letters [8] Unidirectional laser emission from polymer based spiral microdisks: T. Ben Messaoud and J.Zyss, submitted to Appl.Phys.Lett. (December 2004) [9] M.Lebental, A.Vella and J.Zyss, to be published

Third-harmonic generation gap solitons

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

Deptartments of Chemistry and Electro-Optics, Ben-Gurion University, Beer-Sheva, Israel

Boris A. Malomed <malomed@eng.tau.ac.il>,Department of Interdisciplinary Studies, Faculty of Engineering, Tel Aviv University

Abstract

We find novel solitons in a pair of gap soliton systems, mutually coupled by third-harmonic generation (THG) and thecorresponding parametric down-conversion term (required for a system with THG to be Hamiltonian). The physicalrealization requires a waveguide that is non-absorbent at a fundamental frequency (FF) and its third-harmonic (TH)with a Bragg grating in resonance with waves at those frequencies. The THG-gap soliton system exhibits a richvariety of behaviors.

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One solution discovered, the “THG-gap soliton” [e.g., above left, showing absolute value, and real and imaginaryparts of the amplitudes] has most of its energy at the FF and a lesser part in the TH band. A second solution is theusual (“simple”) gap soliton, sitting entirely in the TH band. More complex solutions [e.g., above right] are found

in the form of bound states of THG-gap solitons and simple gap solitons,with a finite binding energy.

In the THG-gap soliton, the FFpart is always single-humped; theTH part may be single- or double-humped. When quiescent, theTHG-gap soliton is stable over thegreater part of its existence region;as the velocity increases, the stabil-ity region shrinks, and then the ex-istence region shrinks. Instabilitiesare oscillatory. The ultimate resultof a linear instability [e.g., bottomright] is usually emission of radia-tion, and formation of a new local-ized structure, either with internalenergy (i.e., a breather) or without.In the stable region, the THG-gapsolitons generally support an excitedstate (a localized eigenmode of thesystem linearized about the soliton).

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Brillouin-zone spectroscopy of nonlinear photonic lattices Guy Bartal,1 Oren Cohen,1 Hrvoje Buljan,1,2 Jason W. Fleischer,1,3 Ofer Manela,1 Mordechai Segev1

bartal@tx.technion.ac.il

1Physics Department, Technion - Israel Institute of Technology, Haifa 32000, Israel

2Department of Physics, University of Zagreb, PP 322, 10000 Zagreb, Croatia

3Electrical Engineering Department, Princeton University, New Jersey 08544

We present a novel, real-time, experimental technique for linear and nonlinear Brillouin zone

spectroscopy of photonic lattices. The method relies on excitation with random-phase (partially-

incoherent) waves and far-field visualization of the spatial spectrum of the light exiting the

lattice. Our method allows the characterization of the underlying lattice structure, while mapping

out the borders of the extended Brillouin zones through linear energy transfer between Fourier

modes (Fig. 1d,j), and marking the areas of normal and anomalous dispersion through nonlinear

energy transfer between Bloch waves (Fig. 1e,f). Specifically, for photonic lattices with defects

(e.g., photonic crystal fibers [1]), our technique enables far-field visualization of the defect mode

overlaid on the extended Brillouin zone structure of the lattice (Fig. 1k,l). The technique is

general and can be used for photonic crystal fibers as well as for periodic structures in areas

beyond optics.

Figure 1: Experimental mapping of the edges of Brillouin zones of square and hexagonal lattices. (a) Interference pattern of the array waves forming the square lattice at the crystal input face. (b) Fourier spectrum of the probe (broad circle) and lattice forming beams (four sharp peaks) at the input face. (c) Calculated extended BZ scheme of a square lattice [2]. (d) True experimental picture depicting the Fourier spectrum of the probe beam at the output face of the crystal with induced 2D square lattice. (g)-(j) Same as a-d with a hexagonal lattice; Experimental Fourier spectrum of the probe beam at the output face of the crystal with the induced 2D square lattice under (e) self-focusing nonlinearity and (f) self-defocusing nonlinearity; Defect modes in a hexagonal lattice: Experimental Fourier spectrum of the probe beam at the output face of the crystal with induced 2D hexagonal lattice. (k) with a positive defect, and (l) with a negative defect. References

1. P. St. J. Russell, Science 299, 358 (2003). 2. N.W. Ashcroft, N.D. Mermin, Solid State Physics (Saunders College, Philadelphia, Pa.1976)

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Optical Quasi Crystals – Properties and Dynamics

Barak Freedman1, Guy Bartal1, Mordechai Segev1, Demetrios N. Christodoulides2 and Jason W. Fleischer3 freedman@tx.technion.ac.il

(1) Physics Dept. and Solid State Institute, Technion, Haifa 32000, Israel (2) School of optics – CREOL, University of Central Florida, Orlando, Florida 32816-2700 (3) Department of Electrical Engineering, Princeton University, Princeton, NJ 08544

The discovery of quasi-crystals by Dan Shechtman et al. in 1984 [1] revolutionized the field

of crystallography. Here we present the first experiments in 2D Penrose-Tile quasi-periodic optical

lattices (waveguide arrays). We observe “discrete diffraction” from various non-equivalent lattice

sites, study nonlinear localization, and experiment with nonlinearly interacting quasi-periodic

lattices. These interacting lattices are needed for the study of transport dynamics (defects, phasons,

etc.). Also planned, is mapping the band-structure of a quasi-crystal using the recently developed

Brillouin Zone spectroscopy method [4].

We produce the 2D quasi-periodic waveguide array using an optical induction technique [2].

This array pattern (Fig. 1a,b) resembles a five-fold Penrose-tile like structure. A similar technique

was used in the past to produce such patterns with cold atoms [3].

The standard bench-mark experiments to study wave dynamics in lattices is via “discrete

diffraction”. In quasi-crystals, there are many different lattice sites, contributing to the lack of

translational and rotational symmetries. Thus, the transport behavior in a quasi-crystal varies from

one site to another. Figure 1 shows numerical and experimental results of discrete diffraction from

two different lattice sites in an optical quasi-periodic 2D lattice. The two points chosen differ from

one another by their nearest-neighbor symmetry. Figure 1c denotes a high-symmetry point while

Fig.1b denotes a low-symmetry point.

Figure 1: (a) Simulated, and (d) experimental pictures of a 2D quasi

lattice. (b,c,e,f) Linear discrete diffraction in an optical quasi-crystal: (b),

(c) are siimulated discrete diffraction patterns from two separate lattice

sites [marked by yellow arrows in (a)]; (e), (f) are the

corresponding preliminary experimental results.

(g) is a self-focusing effect (under positive voltage) of the diffraction in (f).

References [1]. D. Shechtman, I. Blech, D. Gratias and J. W. Cahn, "Metallic Phase with Long-Range Orientational Order and No

Translational Symmetry", Phys. Rev. Lett. 53, 1951 (1984). [2]. N. K. Efremidis, S. Sears, D. N. Christodoulides, J. W. Fleischer, and M. Segev, "Discrete solitons in photorefractive

optically induced photonic lattices", Phys. Rev. E 66, 046602 (2002). [3]. L. Guidoni, C. Triché, P. Verkerk, and G. Grynberg, "Quasiperiodic Optical Lattices ", Phys. Rev. Lett. 79, 3363 (1997). [4]. G. Bartal, O. Cohen, H. Buljan, J. W. Fleischer and M. Segev, "Fourier-space imaging in nonlinear photonic lattices",

Frontiers in optics 2004 88th annual OSA meeting, Rochester, NY, October 2004.

Physico-chemical studies of ITO-coated fiber-optics biosensor

Tania Konry a and Robert S. Marks a, b *

The Institute for Applied Biosciences b and the Department of Biotechnology

Engineering a, Ben Gurion University of the Negev, P.O. Box 653, Beer Sheva, 84105,

Israel

ABSTRACT

Our recent studies have shown that thin films of Indium Tin Oxide (ITO) could be

deposited onto non-conductive optical fiber tips, which were then used as working

electrodes for the electrochemical deposition of polymers with reactive groups

(biotin), so as to create a biosensor. Physico-chemical properties of ITO thin films

(260 nm) deposited by r.f. sputtering onto fiber-optic have been studied and compared

to the existing literature on flat glass surface. The properties vary particularly for

different oxygen pressure used during deposition. The microstructure of these thin

films is determined using X-ray diffraction, TEM, SEM and AFM.

Keywords: ITO, Sheet resistance, oxygen pressure, grain size, transparency,

biosensor, immunosensor.

Convective structures in 2nd order nonlinear media with walk-off

Preben Buchhave and Mikael Lassen Dept. of Physics, Technical University of Denmark, DK-2800 Lyngby, Denmark

Phone: (45) 45 25 25 25, email: pbu@fysik.dtu.dk

Abstract

Dynamic convective patterns have been predicted for certain pumping levels of multi-mode

parametric oscillators (OPOs) with transverse walk-off. Such dynamic structures have not so far

been recorded experimentally except as a certain asymmetry of the mean far field beam pattern.

The transverse convective patterns in an OPO are predicted to occur in two pumping regimes: A

noise sustained instability regime, where domain patterns are formed by amplified spontaneous

noise and grow while convecting out of the pump region and an absolutely unstable regime, where

the noise sustained structures are overwhelmed by a stripe pattern oriented normal to the walk-off

direction. The time scales for the noise sustained patterns are very fast making them difficult to

observe with ordinary image recording equipment. Instead, spectral analysis of selected parts of the

near field image has been suggested as a means to identify these structures as the power spectrum

of the intensity fluctuations is predicted to be much broader than that of the ordinary OPO intensity

pattern. In this note we present measurements of convective space-charge structures in

photorefractive BSO excited by a running light intensity grating and subjected to a transverse

electric field. The generation of these patterns have previously been described in detail. In the

present publication we compare the photorefractive space-charge patterns to the multi-mode

intensity patterns predicted in an OPO with walk-off. We show the equivalence of the governing

differential equations for the pattern formation in the two physically very different phenomena and

from this point of view predict a similarity in the patterns generated in the two cases. Such

similarities between patterns generated in widely different physical systems have been pointed out

previously. However, the photorefractive space-charge field and the intensity patterns in a

multimode OPO also differ in some respects, primarily by the very different dispersion relations

between wave vector and group velocity in the two cases.

We also present experimental results showing in detail the growth and convection of the

photorefractive subharmonic domains including microscopic pictures of the onset of instability and

of domain wall structures.

Tu-12

CONFORMATION ANALYSIS OF SYMMETRIC DIMER SYSTEMS BY COMPARATIVE STUDY OF THEORETICAL ABSORPTION AND 2D PHOTON

ECHO ELECTRONIC SPECTRA

V. SZÖCS Institute of Chemistry, Faculty of Natural Sciences, Comenius University, Mlynská dolina CH2, 842 15, Bratislava,

Slovakia szocs@fns.uniba.sk

T. PÁLSZEGI Department of Chemical Physics, Faculty of Chemical Technology, Slovak Technical University, Radlinského 9, 812 37

Bratislava, Slovakia

V.LUKEŠ Department of Chemical Physics, Faculty of Chemical Technology, Slovak Technical University, Radlinského 9, 812 37

Bratislava, Slovakia

J.SPERLING

Institute of Physical Chemistry, University Vienna, Währingerstrasse 42, A-1090 Wien, Austria

We study the information content of two-dimensional electronic two-pulse photon-echo (2D-2PE) spectra, with special emphasis on their potential to distinguish between different conformations of electronically coupled symmetric dimers (SDs). The analysis has been done on the basis of an analytically derived formula for the 2D frequency-domain 2PE signal of symmetric dimers [1,2]. The spectra of conformationally weighted ensembles, composed of either two or four dimers are compared with their one-dimensional (1D) linear absorption counterparts. In order to approach a realistic situation in the case of the four SD ensemble, excitonic couplings have been estimated on the basis of optimized geometries and site-transition dipole moments calculated by standard semiempirical methods for the bridged bithiophene structure 1,2-bithiophene-2-yl-ethane-1,2-dion (T2[CO]2). We demonstrate that at least in such simple cases, the highly readable 2D-2PE spectra unambiguously decipher related spectral doublets, whereas an assignment on the sole basis of linear absorption becomes rather ambiguous, in particular in the presence of strong homogeneous broadening. We further show, that in the special case of two energetically and spectrally identical but conformationally different SDs, the range of possible orientation angles and dimer conformation probabilities can be conspicuously scaled down by comparing the ratios of special sums that are derived from the 1D and 2D peak heights. [1] V.Szöcs, T.Pálszegi, A.Tortschanoff and H.F.Kauffmann, J.Chem.Phys. 116, 8218 (2002) [2] V.Szöcs, T.Pálszegi, J.Sperling, V.Lukeš, and H. F. Kauffmann, in preparation

Tu-13

Surface Enhanced Raman Scattering of Ultra-thin Rhodamine 6G Layers on Ag Nanocrystals

A. Ofir, Yu. Kaganovskii, and M. Rosenbluh

The Jack and Pearl Resnick Institute for Advanced technology, Department of Physics, Bar-Ilan University, Ramat-Gan 52900, Israel;

Abstract.

Surface-enhanced Raman scattering (SERS) has emerged as a powerful tool for the

investigation and structural characterization of interfaces and thin-film solid materials.

The high sensitivity and selectivity of SERS allows for the determination of chemical

information from single monolayers on planar surfaces and extends the possibilities of

surface vibrational spectroscopy to solve a wide array of physical problems. To explore

the large SERS enhancement that enables the observation of single molecule Raman

spectra, we measured Raman spectra of ultra-thin rhodamine 6G (R6G) layers located on

glass and Si3N surfaces covered by Ag nanoparticles (50 – 200 nm in radius).

Nanoparticles were prepared by vacuum deposition of thin (5 – 10 nm) Ag layers onto

appropriate substrates and subsequent annealing in air or in a hydrogen atmosphere at

230oC during 20 min. The spectra, obtained in a Raman microscope, allowed us to probe

very small local surface areas (about 1 µm) as well as to get Raman intensity distribution

over a larger surface area, which was scanned at a given Raman shift. To measure the

enhancement factor caused by Ag particles, we prepared spin coated R6G layers using

various solution concentrations of rhodamine in methanol ranging from 10-3 to 10-6

mg/ml. For excitation we used a wavelength of 514.5 nm. We have detected large SERS

effect on glass substrates covered by relatively large Ag particles (200 nm) and extremely

heterogeneous enhancement factor, as well as its variation with time due to photo

bleaching of the R6G. Maximal enhancement factor (108) was obtained on Si3N surfaces

after annealing of 5 nm Ag films in air. We discuss a model in which huge SERS

intensities result from single chemisorbed molecules interacting with ballistic electrons in

optically excited large Ag particles.

Fermion Superchemistry: Boson-Like Quantum Dynamics of Fermion Association

I. Tikhonenkov and A. Vardi

Department of Chemistry, Ben-Gurion University of the Negev, Beer-Sheva 84105, Israel

e-mail: avardi@bgu.ac.il

We study the collective association dynamics of a cold Fermi gas of 2N atoms in M atomic

modes into a single molecular bosonic mode. The many-body fermionic problem for 2M

amplitudes is effectively reduced to a dynamical system of min{N,M}+1 amplitudes, making

the solution no more complex than the solution of a two-mode Bose-Einstein condensate and

allowing realistic calculations with up to 104 particles. The many-body dynamics is shown to

be formally similar to the dynamics of the bosonic system under the mapping of boson

particles to fermion holes, producing collective enhancement effects due to many-particle

constructive interference.

0 2 4 6 8 10−1

−0.5

0

0.5

1

τ

w

0 2 4 6 8 10−1

−0.5

0

0.5

1

τ

w

(a)

(b)

0 5 10 15 20−1

−0.5

0

0.5

1

τ

w

0 5 10 15 20−1

−0.5

0

0.5

1

τ

w

(a)

(b)

Figure 1: Comparison of quantum dynamics of Boson atoms (left) and Fermion atoms (right)

association into a molecular Bose-Einstein condensate. The population imbalance w=[nmol

-(1/2)natoms]/N is plotted as a function of the rescaled time τ, for N=5 (dashed), N=50 (dotted) , and

N=500 (dash-dotted) pairs. At the limit of large N=M, Fermion association (right, (a)) maps precisely

to Boson dissociation (left, (b)), including its dynamical instability. This instability which for bosons

originates in the Bose-stimulation of spontaneously dissociating pairs, is reproduced for fermions by

Pauli-blocking effects enhancing spontaneous association. Similarly, Fermion dissociation (right, (b))

is mapped onto Boson association (left, (a)).

Tu-15

Loading Bose condensed atoms into the ground state of an optical lattice Marek Trippenbach Email: matri@fuw.edu.pl Institute of Experimental Physics, Optics Division, Warsaw University, ul. Hoza 69, Warsaw 00-681, Poland P S. Julienne , C. J.Williams Atomic Physics Division, A267 Physics, National Institute of Standards and Technology, Gaithersburg, MD 20899 Y. B. Band Department of Chemistry, Ben-Gurion University of the Negev, Beer-Sheva, Israel 84105 We optimize the turning on of a one-dimensional optical potential, VL(x, t) = S(t)V0 cos2(kx) to obtain the optimal turn-on function S(t) so as to load a Bose-Einstein condensate into the ground state of the optical lattice of depth V0. Specifically, we minimize interband excitations at the end of the turn-on of the optical potential at the final ramp time tr, where S(tr) = 1, given that S(0) = 0. Detailed numerical calculations confirm that a simple unit cell model is an excellent approximation when the turn-on time tr is long compared with the inverse of the optical trap frequency and short in comparison with nonlinear time h/µ where µ is the chemical potential of the condensate. We demonstrate using the Gross-Pitaevskii (GP) equation that the ground state of the optical lattice can be loaded with very little excitation even for times tr short compared with the inverse trap frequency upon applying an optimal turn-on function S(t).

Tu-16

Forming molecular Bose-Einstein condensates by Feshbach

resonance under optimizing conditions V. A. Yurovsky and A. Ben-Reuven

School of Chemistry, Tel Aviv University, 69978 Tel Aviv, Israel

abram@post.tau.ac.il

The formation of ultracold molecules from atomic Bose-Einstein condensates, using time-

dependent Feshbach resonance, has been achieved recently [1-6]. A theoretical analysis shows

how the processes of molecular association and dissociation are affected by controlling the

various relevant experimental parameters. The analysis was carried out using a non-mean-

field parametric approximation [7] that takes into account the formation of non-condensate

atoms due to molecular dissociation, as well as the effects of atom-molecule and molecule-

molecule inelastic collisions. The incorporation of all these processes allows one to determine

optimal conditions for the formation of molecular BEC in a backward sweep (in which the

molecular state crosses the two-atom energy state downwards). This analysis shows the

existence of an optimal magnetic ramp speed, depending on the resonance strength and on the

initial gas density. The parametric approximation produces also the energy spectrum of

entangled non-condensate atom pairs by molecular dissociation using a forward sweep, as in

the experiments [5,6]. The simpler mean-field approach [8], neglecting the formation of non-

condensate atoms, is applicable at high densities and in weak resonance. It can be extended to

inhomogeneous gases [9], as in the expanding Bose-Einstein condensate studied in

experiments [4].

1. J. Herbig et al., Science 301, 1510 (2003).

2. M. Mark et al., preprint cond-mat/0409737 (2004).

3. K. Xu et al., Phys. Rev. Lett. 91 , 210402 (2003).

4. S. Dürr, T. Volz, A. Marte, and G. Rempe, Phys. Rev. Lett. 92, 020406 (2004).

5. S. Dürr, T. Volz, A. Marte, and G. Rempe, preprint cond-mat/0405606 (2004).

6. T. Mukaiyama et al., Phys. Rev. Lett. 92, 180402 (2004).

7. V. A. Yurovsky and A. Ben-Reuven, Phys. Rev. A 67 , 043611 (2003).

8. V. A. Yurovsky, A. Ben-Reuven, P. S. Julienne and C. J. Williams, Phys. Rev. A 60, R765

(1999); Phys. Rev. A 62 , 043605 (2000).

9. V. A. Yurovsky and A. Ben-Reuven, Phys. Rev. A 70 , 013613 (2004).

Luminescence of a Semiconductor 2DEG in a Squeezed Vacuum

Eran Ginossar and Shimon Levit

Department of Condensed Matter, Weizmann Institute of Science, Rehovot 76100, Israel∗

We consider a semiconductor quantum-well interacting with broadband squeezed vac-

uum radiation, inside a waveguide microcavity. The radiation is squeezed around central

frequency ω0, which is tuned above the electron-hole gap Eg. The waveguide modifies the

spontaneous emission from the quantum well, such that the emission is only allowed into the

squeezed vacuum. The luminescence exhibits a peak around ω0, which is a result of both

the squeezed radiation and the particle-hole continuum. The dependence of the squeezing

spectrum on the occupation and squeezing of the incoming field is qualitatively different

from the atomic case. It is realistic to observe the above phenomena even in the presence

of additional non-radiative (e-e, phonon) dephasing.

FIG. 1: Left: Power spectrum around ω0. Right: Squeezing spectrum for the in-phase quadrature

(dashed) and out-of-phase quadrature (solid).

∗ Electronic address: eran.ginossar@weizmann.ac.il

[1] C. W. Gardiner, Phys. Rev. Lett. 56 (18), 1917 (1986).

[2] D. Kleppner, Phys. Rev. Lett. 47, 233 (1981).

[3] G. Khitrova, H. M. Gibbs, F. Jahnke, M. Kira and S. W. Koch, Rev. Mod. Phys. 71, 1591 (1999).

Optical Frequency Division by Polarization Mixing in a

Non-Resonating Optical Parametric Oscillator

Gal Kalmani (1), Pinhas Blau (2) and Ady Arie(1) (1)Dept. of Physical Electronics, Tel-Aviv University, Tel-Aviv, Israel, ady@eng.tau.ac.il

(2) Electro-Optics Div., Soreq NRC, Yavne, Israel, pinhas@soreq.gov.il A new device for degenerate parametric down-conversion of a Nd:YAG laser to the mid-IR

spectral range was investigated. This device is a type of a Non-Resonating Oscillator

(NRO)[1] for which, in every full round trip, the signal or the idler are alternately coupled out

of the oscillator. Nevertheless, thanks to the nonlinear coupling and mixing of these two

fields, oscillation at a very specific frequency is obtained.

The experimental setup is shown in Fig. 1. When the signal and idler fields go through the

wave plate, their polarizations alternately change by 90° and the polarizer is causing the Z

polarization to be coupled out of the cavity. The nonlinear mixing of the waves is performed

in the 36 mm long PPKTP crystal, having a period of 60 µm, which is suitable for Type II

quasi-phase-matching of the 1064 nm Y-polarized pump with the Z and Y polarized signal

and idler at 2128 nm. The threshold was obtained at pump intensity of 67 MW/cm2.

Conversion efficiency of 2.3% was reached by pumping at 1.9 times the threshold.

A very interesting feature is that the polarization mixing NRO produces exactly half the

frequency of the pump wave, in a very stable manner. As shown in Fig.2, changing the

crystal temperature from 68.4 to 75.8 degrees does not change at all the output frequency of

the device. The frequency division capability can be highly useful for precise optical

frequency measurements.

TFP@2128nm

Output Mirror r=∞ R>99%@1064, 2128nm

Spectrum - PMNRO

0

1

2

3

4

5

2123 2128 2133Wavelength (nm)

Inte

nsity

(A.U

.)

T=70 deg. c T=68.4 deg. cT=75.8 deg. c T=73 deg. c

@1064nm2/λ @2128nm4/λ

PPKTP

Nd:YAG

Filter

Input Mirror r1=r2=100mm R<1%@1064nm AR@1064nm R>99%@2128nm

2/λ

Figure 1: Polarization Mixing NRO Setup Figure 2 : Polarization Mixing NRO Spectrum

[1] Guyer, R. D. and Lowenthal, D. D. “Novel cavity for a high efficiency, high energy near infrared β-BaB2O4

parametric generator”, Proc. SPIE Vol. 1220 Nonlinear Optics pp. 41-44, (1990).

Tu-19

Nonlinear optics with intensity waves

David Kviat, Tal Arditi, Shmuel Sternklar and Er'el Granot Dept. of Electrical and Electronic Engineering, College of Judea and Samaria

Ariel, Israel,

Moshe Tur Dept. of Interdisciplinary Studies, Tel-Aviv Universit y, Ramat Aviv, Israel

email: shmuel@yosh.ac.il

Modulated light beams are ubiquitous in both linear and nonlinear optics.

Investigations of nonlinear effects, however, have for the most part focused on the

interaction of the lights beams' electromagnetic field waves, with little formal

attention given to the modulated light envelope, which is essentially a wave of light

intensity. This is not the case , for example, in the study of light scattering in diffuse

media, where the formal treatment of this intensity wave , known as "photon density

waves", has lead to the development of a new paradigm for characterizing these

media [1].

We present a theoretical and experimental study of the behavior of intensity waves

in nonlinear media, which has lead to a new understanding of the interaction between

counter-propagating intensity waves in third-order stimulated scattering. Various new

effects are predicted, which are reminiscent of interactions among light field waves in

second-order parametric wave-mixing. This is exemplified by a new type of phase

mismatch between the intensity waves, which causes suppression of the intensity

wave’s amplitude [2] , and is characterized by an unusually sharp singularity. In

addition, an oscillatory dependence of the intensity waves’ amplitude and phase on

this phase-mismatch is predicted. Our initial experimental investigations show good

agreement with theory, and point to new applications in sensing and optical

processing.

[1] A. Yodh and B. Chance , “Spectroscopy and Imaging with Diffusing Light”,

Physics Today, 48 , 34-40(1995); Y. Chen et al, "Metabolism-enhanced tumor

localization by fluorescence imaging: in vivo animal studies ", Optics Letters, 8, 2070

(2003)

[2] S. Sternklar and E. Granot, “Narrow spectral response of a Brillouin

amplifier” Opt. Lett., 28 ,977 (2003)

The three-body Coulomb Problem: from 1D to 3D

Javier Madronero

Max-Planck-Institut fur Physik komplexer Systeme, Dresden

e-mail: jma@mpipks-dresden.mpg.de

Andreas Buchleitner

Max-Planck-Institut fur Physik komplexer Systeme, Dresden

(Dated: December 1, 2004)

Abstract

Quantum S and P states associated with two characteristic configurations of the three body

Coulomb problem are identified in ab initio quantum calculations on helium confined to a one, two

and three dimensional configuration space. We compare the autoionization rates of these states

and find that the two dimensional restriction leads to results that are in quantitative agreement

with those of the real physical system, whilst confinement of the nucleus and the two electrons to

one single dimension can lead to a dramatic underestimation of the actual decay rates (by orders

of magnitude). With the help of an additional electromagnetic field, non-dispersive two-electron

wave packets can be induced in the planar problem, which propagate along classical periodic orbits,

exhibit rather small ionization rates, and thus open novel perspectives for coherent control.

1

Gap solitons in a model of a hollow optical fiber

I. M. Merhasin ∗ and Boris A. MalomedDepartment of Interdisciplinary Studies, School of Electrical Engineering, Tel Aviv University, Tel Aviv 69978, Israel

We introduce a model for two coupled waves propagating in a hollow-core fiber: a linear dis-persionless core mode, and a dispersive nonlinear surface one. The linear coupling between themmay open a bandgap, through the mechanism of avoidance of crossing between dispersion curves.The third-order dispersion of the surface mode is necessary for the existence of the gap. Numericalinvestigation reveals that the entire bandgap is filled with solitons, and they are stable in direct sim-ulations. The gap-soliton (GS) family includes stable pulses moving relative to the given referenceframe, up to limit values of the corresponding boost δ, beyond which they do not exist. The limitvalues are asymmetric for δ ≷ 0. Recently observed solitons in hollow-core photonic-crystal fibersmay belong to this GS family.

[1] W. Chen and D. L. Mills,Phys. Rev. Lett. 58, 160(1987).[2] A. B. Aceves and S. Wabnitz, Phys. Lett. A 141, 37 (1989);[3] D. N. Christodoulides and R. I. Joseph, Phys. Rev. Lett. 62, 1746 (1989).[4] B. J. Eggleton R. E. Slusher, C. M. de Sterke, P. A. Krug, and J. E. Sipe, Phys. Rev. Lett. 76, 1627 (1996).[5] C. M. de Sterke and J. E. Sipe, Progr. Opt. 33, 203 (1994);[6] C. Conti, G. Assanto, and S. Trillo, J. Nonlin. Opt. Phys. Mat. 11, 239 (2002).[7] J. Feng, Opt. Lett. 18, 1302 (1993).[8] R. F. Nabiev, P. Yeh, and D. Botez, Opt. Lett. 18, 1612 (1993).[9] Yu. S. Kivshar, Phys. Rev. E 51, 1613 (1995).

[10] W. C. K. Mak, B.A. Malomed, and P. L. Chu, Phys. Rev. E 58, 6708 (1998).[11] D. Mandelik, H. S. Eisenberg, Y. Silberberg, R. Morandotti and J. S. Aitchison, Phys. Rev. Lett. 90, 053902 (2003).[12] R. F. Gregan B. J. Mangan, J. C. Knight, T. A. Birks, P. St. J. Russell, P. J. Roberts, and D. C. Allan, Science 285, 1537

(1999).[13] D. G. Ouzounov, F. R. Ahmad, D. Muller, N. Venkataraman, M. T. Gallagher, M. G. Thomas,J. Silcox, K. W. Koch, and

A. L. Gaeta, Science 301 1702(2003).[14] F. Luan, F. R. Ahmad, D. Muller, N. Venkataraman, M. T. Gallagher, M. G. Thomas, J. Silcox, K. W. Koch, and A. L.

Gaeta, Opt. Express 12, 835(2004).[15] W. Gobel, A. Nimmerjahn, and F. Helmchen, Opt. Lett. 29, 1285(2004).[16] D. V. Skryabin, F. Biancalana, D. M. Bird, and F. Benabid, Phys. Rev. Lett. 93, 143907 (2004)[17] H. Lim and F. W. Wise, Opt. Express 12, 2231(2004).[18] C. M. Smith, N. Venkataraman, M. T. Gallagher, D. Muller, J. A. West, N. F. Borrelli, D. C. Allan, and K. W. Koch,

Nature 424, 657(2003).[19] K. Saitoh, N. A. Mortensen, and M. Koshiba, Opt. Express 12 394(2004).[20] E. Lidorikis, M. Soljacic, Mi. Ibanescu, Y. Fink, and J. D. Joannopoulos, Opt. Lett. 29 851(2004).[21] M. G. Vakhitov and A. A. Kolokolov, Radiophys. Quantum Electron. 16, 783 (1973).

∗ corresponding author e-mail address: merkhasi@post.tau.ac.il

Emission spectrum of chaotic lasers with overlapping resonances

Carlos Viviescas

carlos@mpipks-dresden.mpg.de

Max-Plank-Institut fur Physik komplexer Systeme,

Nothnitzer Strasse 38,

D-01187 Dresden, Germany

We present a quantum theory for lasers in open chaotic resonators with spectrally

overlapping resonances. Our theory accurately accounts for both the quantum excess

noise present in weakly confining resonators and the chaotic nature of the field modes

in chaotic cavities. We study analytically and numerically the complex emission

spectrum of such lasers close and far above the laser threshold. We demonstrate that

due to the strong correlation between the different overlapping modes the spectral

linewidth collapses, but no sharp emission peaks appear.

Our work may serve as a starting point for a microscopic theory of random lasers

with incoherent feedback. In these lasers, made of disordered optical media, the

multiple scattering events provide only a weak confinement mechanism. Thus, light

propagation is subject to large losses, and a laser theory for overlapping laser modes

is necessary to describe them.

Tu-23

Lattice solitons in Kronig-Penney waveguide array with cubic-quintic

(CQ) nonlinearity

Boris V.Gisin, Ilya Merhasin, Rodislav Driben and Boris A. Malomed We introduce a model combining a periodic array of rectangular potential wells [the Kronig-Penney KP) potential] and the cubic-quintic (CQ) nonlinearity. A plethora of soliton states is found in the system: fundamental single-humped solitons, symmetric and antisymmetric double-humped ones, three-peak solitons with and without the phase shift ¼ between the peaks, etc. If the potential profile is shallow, the solitons belong to the semi- infinite gap beneath the band structure of the linear KP model, while finite gaps between the Bloch bands remain empty. However, in contrast with the situation known in the model combining a periodic potential and the self- focusing Kerr nonlinearity the solitons fill only a finite zone near the top of the semi- infinite gap, which is a consequence of the saturable character of the CQ nonlinearity. If the potential structure is much deeper, fundamental and double (both symmetric and antisymmetric) solitons with a flat-top shape are found in the finite gaps. Computation of stability eigenvalues for small perturbations and direct simulations show that all the solitons are stable. In the shallow KP potential, the soliton characteristics, in the form of the integral power Q (or width w) vs. the propagation constant k, reveal strong bistability, with two and, sometimes, four different solutions found for given k (the bistability disappears with the increase of the depth of the potential). Disobeying the Vakhitov-Kolokolov criterion, the solution branches with both dQ=dk > 0 and dQ=dk < 0 are stable. The curve Q(k) corresponding to each particular type of the solution (with a given number of local peaks and definite symmetry) ends at a finite maximum value of Q (breathers are found past the end points). The increase of the integral power gives rise to additional peaks in the soliton's shape, each corresponding to a sub pulse trapped in an a local channel of the KP structure (a beam-splitting property). It is plausible that these features are shared by other models combining a saturable nonlinearity and a periodic substrate Basic results will appear in Phys.Review E.

Tu-24

Intramolecular Dynamics from Frequency Domain Spectroscopy in the Gas Phase

Alexander Portnova, Evgeny Bespachianskya, Yuval Ganota, Salman Rosenwaks a and

Ilana Bar a,b

aDepartment of Physics

Ben Gurion University of the Negev, Beer Sheva 84105, Israel bThe Institutes for Applied Research

Ben Gurion University of the Negev, Beer Sheva 84105, Israel

Abstract

The characterization of intramolecular interactions is of fundamental

importance in determining the mechanisms that underlie chemical transformations.

Vibrationally mediated photodissociation is emerging as a useful tool for studies of

intramolecular dynamics in polyatomic molecules due to its sensitivity to both

vibrational and electronic dynamics. The method involves laser techniques depositing

energy in skeletal motions of molecules , their subsequent interaction with photons and

consequent promot ion to the excited electronic states and the ir dissociation. Jet–

cooled action and Doppler spectroscopies, reflecting the yield of the ensuing atomic

fragments are compared to simultaneous measured room temperature photoacoustic

spectra and to simulated spectra. The narrowed action spectra expose in favorable

cases resonance splitting and estimates for the homogeneous broadening, allowing

evaluation of time scales for intramolecular vibrational energy redistribution to close

resonating states and to bath states, respectively . Experimental studies on the

acetylenic and alkylic C-H stretches of the acetylene homologues, propyne and 1-

butyne, demonstrate how the nature of rovibrationally excited states and the

dissociation encounter are highlighted by photolysis of pre-excited molecules.

Tu-25

Tubular dye-polymer waveguides embedded in silicon

S. Stepanov(1), S. Ruschin(1), J. Zyss(2), and I. Ledoux(2)

1. Faculty of Engineering, Tel-Aviv University, Tel-Aviv 69978, ISRAEL,

E-mail: ruschin@post.tau.ac.il

2. MQOL, Ecole Normale Supérieure de Cachan, 61, du President Wilson Av., 94235 ,

Cachan, FRANCE, E -mail: zyss@lpqm.ens-cachan.fr

We present new technology process for fabrication of embedded polymer-based waveguides

in silicon substrate (Fig.1) . The cross-section shape of the waveguides can be varying from

ellipse to circle. Moreover the technology allows manufacturing three-dimensional tapered

waveguides. The technology can be useful for fabrication of polymer- based amplifier and

other nonlinear integrated optics devices.

Specifically we report here, an observation of luminescence and optical amplification in

buried dye-polymer waveguides. Norland optical adhesive with Rhodamine 6G was chosen as

active material. Cross-section of the waveguides had circle shape and radius of ones ranged

from 5µm to 15µm (Fig.2) . Second harmonic of a CW Nd: YAG laser (λ =532 nm) was used

as pumping light source. The power and spectral characteristics of the luminescence will be

presented at conference.

Fig.2 Embedded tubular hole in silicon with silicon dioxide buffer layer

Air

Si Si

Si

Polymer

Fig. 2 Tubular dye-polymer waveguide

embedded in silicon

Tu-26

Ordinary solitons and gap solitons in a system with separated

nonlinearity and dispersion.

Arik Zafrany, Boris A. Malomed, and Ilya M. Merhasin

Department of Interdisciplinary Studies, Faculty of Engineering

Tel Aviv University, Tel Aviv 69978, Israel

Abstract:

In order to clarify the roles of nonlinearity and dispersion in the creation of optical

solitons in the temporal domain, we introduce a model with two parallel-coupled cores,

one nonlinear (with the cubic nonlinearity) and one dispersive. The model may

be given an interpretation in the spatial domain too (a solid linear waveguide coupled to a

parallel array of nonlinear discrete waveguides). The linear spectrum of the system

contains a Semi- infinite band gap and a finite one. If the dispersion of the second core is

anomalous, the model supports a family of stable solitons in the semi- infinite gap, while

the finite one is empty. In the case of the normal dispersion, the situation is opposite,

The finite band gap being filled with a family of stable solitons. In the spatial-domain

version of the model, the two cases correspond to the interplay of the transverse

diffraction in the solid waveguide and, respectively, self- focusing or self-defocusing

cubic nonlinearity in the discrete array. We have checked that the solitons are structurally

and dynamically stable against addition of weak dispersion to the nonlinear core.

Attendee at the symposium: Arik Zafrany

Contacts: E-mail: ericz@netvision.net.il

Cellular: 050-6792963

Home: 03-9307637

Tu-27

THEORETICAL STUDY OF PUMP-PROBE AND FLUORESCENCE SIGNALS OF TWO SPECIAL PHENYLENE-VINYLENE DENDRIMERS

T. PÁLSZEGI

Department of Chemical Physics, Faculty of Chemical Technology, Slovak Technical University, Radlinského 9, 812 37 Bratislava, Slovakia palszegi@ap.univie.ac.at

V. SZÖCS

Institute of Chemistry, Faculty of Natural Sciences, Comenius University, Mlynská dolina CH2, 842 15, Bratislava, Slovakia

V.LUKEŠ Department of Chemical Physics, Faculty of Chemical Technology, Slovak Technical University, Radlinského 9, 812 37

Bratislava, Slovakia

A.TORTSCHANOFF Ecole polytechnique fédérale de Lausanne, Institut des sciences et ingénierie chimiques, CH-1015 Lausanne,

Switzerland

The light-harvesting properties of benzene centered, distyrilbenzene cored, one and two stilbene generation containing dendrons formed phenylene-vinylene (G1, G2) dendrimers have been studied theoretically on the basis of time-frequency and frequency-frequency frame 2D pump-probe and fluorescence signals. For that goal we used the doorway-window solution of the NEE (non- linear excitonic equations) formulation of the non- linear optical processes in excitonic systems for the snapshot limit (Mukamel et al. [1, 2]). The excitonic eigenstates, linear optical spectra and electronic excitation transport related quantities of the dendrimers were analyzed and provided relations between the energy of excitons, their spatial and coherence lengths, excitonic density of states, structure functions and absorption spectra. These quantities together with electronic coherence correlation functions, electronic energy relaxation and transfer factors have been compared for our G1 and G2 dendrimers. On the basis of our results the conditions for the effectiveness of the dendrimeric light absorption and energy funneling processes can be formulated, which allow the explanation of the oscillatory behavior of the excitonic entropy, superposed with their rising and consecutive lowering period. The entropy was projected into nonstationary excitonic eigenstates, identifying the reasons for the ordering-reordering oscillations and of monotonic entropy evolution periods. We compare different contributions to intra- and inter-generational pump-probe and fluorescence signals and formulate conditions for regulating the intra- and inter-generational influences on the signals. [1] M. Dahlbom, T. Minami,V. Chernyak, T. Pullerits, V. Sundström and S. Mukamel, J. Phys. Chem. B 104, 3976 (2000). [2] A.Tortschanoff and S. Mukamel, J. Phys. Chem. A 106, 7521-7529 (2002).

Local Control theory for Unitary transformations:

Application to quantum computing without leakage

Shlomo Sklarz and David Tannor

Abstract

We devise a local optimal control method for achieving target unitary transformations on a quantum register, while avoiding intermediate leakage into mediating states coupled to the quantum register. The technique exploits a phase locking of the field to the system such as to eliminate the undesirable excitation. This method is then applied to produce a Fourier transform on the vibrational levels of the ground electronic state of the Na2 molecule. The emerging mechanism uses two-photon resonances to create a transformation on the quantum register while blocking one-photon resonances to excited states.

Tu-29

Excited State Proton Transfer in the Green Fluorescent Protein and its Mutants.

Dan Huppert,1 Pavel Leiderman,1 Liat Genosar1 and Lior Cohen2

1Raymond and Beverly Sackler Faculty of Exact Sciences, School of Chemistry, 2G. Wise

Faculty of life science, Tel Aviv University, Tel Aviv 69978, Israel

Proton transfer reactions are among the most common and important chemical and

biological processes in aqueous solutions. The green fluorescent protein (GFP) of the jellyfish

Aequorea Victoria has attracted great interest as a biological fluorescence marker and one of the

few examples of excited-state proton transfer in nature. We used the accumulated knowledge of

ESPT processes in solution to study, by time-resolved spectroscopy several, aspects of the

excited state proton transfer of wild type GFP (wt- GFP), GFP mutants and synthetic analogs of

the GFP chromophore.

The main topics we shall discuss in my talk :

a. The temperature dependence of the time-resolved emission of wt-GFP shows that the

proton transfer rate slows down as the temperatures decreases. At very low temperatures, T <

80K, the proton transfer rate is almost independent of temperature. We explain the temperature

dependence of the proton transfer rate by a model that includes an intermolecular vibration

assisted tunneling.

b. GFP mutants S65T/H148D and G. The prototype, S65T/H148D, has anomalous pH

dependent fluorescence and proton transfer characteristics suggestive of ultrafast ESPT. The low

pH crystal structure shows the existence of a low -barrier hydrogen bond (LBHB) between the

chromophore and Asp148. We have found that the isotope effect is small in one mutant and

fluorescence quenching is taking place.

c. We have used short wavelength pulses at 270 – 320 nm to excite wt-GFP. We have found

that the ESPT rates slow by a factor of 10 and 3 for H 2O and D2O samples, respectively.

d. We have found that at relatively low hydrostatic pressures (P< 0.8GPa), the time-resolved

emission of the protonated form, ROH of wt-GFP, is only slightly modified as the pressure

increases.

e. We studied the radiationless decay and the ESPT process of synthetic compounds, which

have a similar structure to that of the GFP chromophore. The main finding is the very fast

radiationless decay that depends on both viscosity and temperature. The fluorescence decay of

the chromophore analog is nonexponential.

Electromagnetically induced waveguiding in double Λ systems

A. D. Wilson-Gordon, H. Shpaisman, and H. Friedmann, Department of Chemistry, Bar-Ilan University, Ramat Gan 52900, Israel

e-mail: gordon@mail.biu.ac.il

Near the threshold for electromagnetically-induced transparency (EIT) or coherent

population trapping (CPT), two-photon-resonance -enhanced self-focusing of a Λ system

can be exploited to induce spatial confinement in a second, diffracting Λ system. The

diffracting Λ system is characterized by parameters below the EIT or CPT threshold, and

the two Λ systems must be coupled to form a closed-loop double Λ system.

The waveguiding effect is shown to be strongly phase dependent, indicating that it derives

from the phase-dependent effective third-order susceptibility rather than the phase-

independent effective first -order susceptibility, as is the case in previously studied

systems.

We also show that when the second Λ system initially involves only a single laser

beam, the loop is completed by the efficient generation of radiation at the four-wave

mixing frequency, within a propagation distance much shorter than the diffraction length.

As shown in the following figure, both the applied (V'31, V'32, V'42) and generated (V'41)

fields exhibit electromagnetically-induced waveguiding.

Near-stoichiometric lithium tantalate and near-stoichiometric lithium niobate by Vapor-transport equilibration for frequency conversion applications

Mordechai Katz

Electro-Optics Div., Soreq NRC, Israel

E-mail: moti@soreq.gov.il

David S. Hum, Roger K. Route , and Martin M. Fejer E. L. Ginzton Laboratory, Stanford University, Stanford, CA, 94305

Abstract:

Frequency conversion of light via periodically-poled lithium niobate (PPLN) and

periodically-poled lithium tantalite (PPLT) has widely been demonstrated during the last

decade. Two material issues limit the performance of congruent PPLN and PPLT crystals for

frequency conversion at room temperature with high intensities and visible light:

photorefractive damage (PRD) and green-induced infrared absorption (GRIIRA). Recent

publications [1] on as-grown near-stoichiometric MgO:LiNbO3 crystals and as-grown near-

stoichiometric LiTaO3 and MgO:LiTaO3, show a remarkable decrease in photorefraction and

GRIIRA in these crystals. However, it is much more difficult to grow stoichiometric or near-

stoichiometric LiNbO 3 and LiTaO3 crystals than congruent crystals.

Vapor transport equilibration (VTE) method [2] has been used to fabricate near-

stoichiometric, 1% Mg-doped LiNbO 3 and near-stoichiometric LiTaO3 from congruent

crystals. Photogalvanic current, photoconductivity, photorefractive damage, GRIRA and the

coercive field of those crystals have been investigated. According to these measurements, the

VTE’d crystals show high PRD resistance at room temperature and low GRIIRA [3].

The VTE'd SLT (VSLT) samples were periodically poled with an 8-µm-period grating,

enabling first-order quasi-phase-matched second-harmonic generation of 532 nm radiation at

43°C. The coercive field of the VSLT samples found to be as low as 80 V/mm. A 17-mm-

long sample generated 1.6 W of continuous wave output power at 532 nm for 50 hours. With

150 ns pulses at a 100 kHz repetition rate in the same sample, 5-W-average-power, 532-nm

radiation was generated for 1000 hours. No damage to the crystal and no aging effects were

observed during these experiments

References: 1. Takaaki Hatanaka et. al. “Quasi-phasematched optical parametric oscillation with periodically poled

stoichiometric LiTaO 3” Opt. Lett., 25, 651-653 (2000). 2. D.H. Jundt, M. M. Fejer, and R. L. Byer, “Optical properties of lithium-rich lithium niobate fabrication by

vapor transport equilibartion” IEEE J. Quant. Electron. 26, 135-138 (1990). 3. M.Katz, R.K.Route, D.S.Hum, K.R.Parameswaran, G.D.Miller,and M.M.Fejer "Vapor-transport equilibrated

near-stoichiometric lithium tantalate for frequency -conversion applications" Opt. Lett., 29, 1775-1777 (2004).

Tu-32

Measurement of Light Scattering by CaO from 10 to 900 C Steve Wiesner Physics Dept., Tel Aviv University, Ramat Aviv, Israel wiesner@netvision.net.il Sid in Hebrew, quick lime, or CaO, has been produced in Israel since pre-historic times and is mentioned in numerous places in the bible and talmud. CaO appears white at room temperature. The scattering of light from a xenon flash lamp by CaO placed in an electric furnace has been measured with a silicon detector from 10 to 900 C and found to be constant to within 10%. This lends weight to the idea that the intense “lime light” produced by CaO in a limekiln can not be black body radiation but must be due to catalysis of flame gasses. CaO, TiO2, CeO2 and ThO2 are similar materials, large bandgap semiconductors with low lying empty inner shells that appear to act as photo-catalysts and also as spin -catalysts. TiO2 is under intensive investigation because it brakes down water into H2 and O2 under near UV light ( the Honda-Fujishima effect.) Systems are suggested that might produce hydrogen from water at the center of the solar spectrum. A. Fujishima, K. Honda, Nature 238:37 1972

High density self-assembled InAlAs/GaAlAs quantum dots as active material for cavity solitons applications

J.M. Benoit*, A. Lemaître, G. Patriarche, L. Largeau, O. Mauguin, S. Barbay and R. Kuszelewicz * jean-michel.benoit@lpn.cnrs.fr

Laboratoire de Photonique et Nanostructures/CNRS-UPR20, Route de Nozay, 91460 Marcoussis, France

InAlAs/GaAlAs quantum dots (QD) appear as a very promising material for laser1 and non-

linear optical applications in the visible/near infrared range due to the higher confinement of

quantum states and the better spectral compatibility with the GaAlAs system. In particular,

this family gives very promising perspectives as a focusing Kerr-like medium for pattern

forming and cavity solitons sustaining systems2.

MBE self-assembled InAlAs/GaAlAs quantum dots (QD) were prepared using Stranski-

Krastanov growth mode. The TEM pictures (fig. 1) highlight the high density of the grown

QD as well as the dislocations in the wetting layer (WL). Both TEM and XRD confirm the

expected barrier thickness and stoechiometry. At ambiant temperature, 2 luminescence bands

are observed : one at 1.42 eV corresponding to the GaAs substrate, and the second one at

1.49 eV attributed to the QD (fig. 1). At 80 K, these 2 bands are still observed at 1.51 eV and

1.64 eV. One can note that no bands related to the GaAlAs barriers are observed, probably

because of the large density of dislocations. Moreover, experiments show the decrease of the

QD luminescence intensity when increasing the temperature.

a.

b.

50 nm

100 nm

a.

b.

a.

b.

50 nm

100 nm

1,3 1,4 1,5 1,6 1,7 1,8 1,9

Inte

nsity

(A

.U.)

Energy (eV)

1,42 1,49

QuantumDots

GaAsSubstrate

1,508

1,644

Ambiant Temperature

80 K

To understand this behavior; we have developped a simple model which takes into account a

thermal activation of the carriers from the QD to the WL and that accurately describes the

experimental PL collapse. This gives precious indications on how to fine tune the growth

conditions so as to reduce the density of dislocations. 1 K. Hinzer & al., J. Appl. Phys., 87, 1496 (2000) 2 S. Barbay & al., IEEE J. of Quantum Electronics, 39, 245 (2003)

Fig. 1: TEM pictures of the sample. a.) cross-section view, b.) plan-view of the InAlAs QD

Fig. 2: Ambiant and low temperature photoluminescence of the device