Nonlinear Optics Laboratory - ETH Znlo.ethz.ch/dl/JB1998.pdf · Nonlinear Optical Properties of Molecular Crystals 12 ... Organic Crystals and Polymers 15 Fluorescence Phenomena in

Institute of Quantum Electronics

Annual Report 1998

Nonlinear Optics LaboratoryNonlinear Optics LaboratoryNonlinear Optics LaboratoryNonlinear Optics LaboratoryNonlinear Optics Laboratory

Ë EidgenössischeEidgenössischeEidgenössischeEidgenössischeEidgenössische Technische Hochschule Technische Hochschule Technische Hochschule Technische Hochschule Technische HochschuleZürichZürichZürichZürichZürich

Previous Page:Organic electroluminescent molecules can be used to build large-area organic light-emitting devices (organic LEDs).The figure shows some test-devices produced by organic molecularbeam deposition in ultra-high vacuum.Left, top: the organic LEDs glow in the vacuum chamber.Left, bottom: an enlargement of a pair of organic LEDs.Right: The structure of the devices.From bottom to top: A glass substrate, a patterned transparentelectrode, two organic layers as an interface and hole-transportlayer, an electron-transport layer with the luminescent molecules,and a metal electrode.The voltage applied to the devices photographed here was about 10Volts.See section 3.2 on page 26

Nonlinear OpticsLaboratory

Annual Report 1998

Prof. Dr. P. GünterNonlinear Optics LaboratoryInstitute of Quantum ElectronicsETH – Hönggerberg – HPFCH – 8093 Zürich

Phone: +41 1 633 2295Fax: +41 1 633 1056e-mail: [email protected]: http://nlo-serv.ethz.ch/

iii Institute of Quantum Electronics

CONTENTS

Nonlinear Optics Laboratory iv

CONTENTS

PERSONNEL 1

ACADEMIC AND CORPORATE VISITORS 2

SPONSORS 2

RESEARCH SUMMARY 3

Activities of members of the Nonlinear Optics Laboratory in Conference Committees and Editorial Boards 5

MOLECULAR CRYSTALS AND POLYMERS 7

Design, Synthesis, and Crystal Growth of Second-Order Nonlinear Optical Materials 7Second-Order Optical Nonlinearities of Conjugated Organic Molecules 8Cascading of Second-Order Nonlinearities 9Third-Order Susceptibilities of Conjugated Organic Molcules 10Non-Local Contributions to Degenerate Four Wave Mixing in Acentric Materials 11Nonlinear Optical Properties of Molecular Crystals 12Electro-Optic Properties of Molecular Crystals 13Electro-Optic Polymer Waveguide Modulators 14Photorefractive Effects and Charge Transport Properties in

Organic Crystals and Polymers 15Fluorescence Phenomena in Organic Single Crystals 16Tunable nanosecond and picosecond infrared laser source based on

optical parametric generation in KNbO

3

17

PHOTOREFRACTIVE EFFECTS AND PHOTONICS 19

Growth, preparation and characterization of photorefractive crystals 19Ultraviolet photorefraction and its applications 20Charge Transport Properties of Polar Dielectric Crystals 21Holographic optical processing and memories 22Manipulation of ferroelectric domains by scanning force microscopy 23

MOLECULAR BEAM EPITAXY 25

Design, Preparation, and Characterization of Novel Organic Nonlinear Optical Thin Films Grown by Molecular Beam Deposition 25

Interface Properties of Organic and Inorganic Films in Multilayer Light-Emitting Structures 26

Ultra-High Vacuum Atomic Force Microscopy of Surfaces Prepared by Molecular Beam Deposition 27

INTEGRATED OPTICS AND OPTICAL FREQUENCY CONVERSION 29

Fabrication of first-order Bragg gratings on KNbO

3

waveguides 29Blue-light second-harmonic generation in KNbO

3

30Liquid phase epitaxy of K

1-y

Na

y

Ta

1-x

NbxO

3

thin films on Ba-doped KTaO

3

substrates 31Photorefractive effect in ion-implanted iron-doped KNbO

3

crystals 32

CONTENTS

v Institute of Quantum Electronics

NUCLEAR MAGNETIC RESONANCE 33

Point Charge Model Calculations of

87

Rb Spin-Lattice Relaxation and 2-D-Exchange NMR Spectra 33

Line Shape Transitions of the Chemical Shift Perturbed

31

P NMR Spectra Reveal Symmetrizing Slow Motion Effects 34

Analysis of the Intra- and Inter-Line Spin-Diffusion of

87

Rb in Ferroelectric RDP at 85K 35Comparison of Ester-Methyl-Group Rotation in Syndiotactic and Isotactic PMMA 36

PUBLICATIONS 1998 37

ORAL PRESENTATIONS 1998 43

PhD THESES IN PHYSICS 1998 51

DIPLOMA THESES IN PHYSICS 1998 52

PERSONNEL

Nonlinear Optics Laboratory 1

PERSONNEL

Head

Prof. Dr. P. Günter

Academic Guests

Dr. Janez Dolinsek

Institute Jozef Stefan, Ljubljana, SLO

Prof. Dr. J. Fousek

Czech Academy of Sciences, Prague, CZ

Prof. Dr. D. Hagan

University of Central Florida, Orlando, USA

Team Leaders

Dr. Ivan Biaggio

since May

Prof. Dr. Raymond KindPD Dr. Christian Bosshard Dr. Germano MontemezzaniDr. Daniel Fluck Dr. Bert Müller

until April

Academic Staff

Markus Abplanalp Michael Kiy

since April

Dr. Pietro Bernasconi Armin Kündig

until July

Dr. Ivan Biaggio

until April

Ilias LiakatasMartin Bösch Sabine Manetta

since February

Karolina Brugger

since April

Dr. Carolina MedranoDr. Simon Brülisauer

until April

Urs MeierDr. Chengzhi Cai Harald PierhöferPaola Cereghetti Roland RyfPhilipp Dittrich

since

April

Dr.

Christophe Seuret

until May

Dr. Stéphane Follonier

until May

Rolf SpreiterUlrich Gubler Carmen Tacchella

since November

Dr. Matthias Jäger Dr. Ye Tao

until August

Christian Jeitziner Marc Wintermantel

since October

Technical Staff

Marcel Ehrensperger Edwin Hausammann

since April

Iris Gamboni Hermann WüestJaroslav Hajfler

Administrative Staff

Lotti Nötzli

50%

Brigitte Spaenhauer

50%

ACADEMIC AND CORPORATE VISITORS

2 Institute of Quantum Electronics

ACADEMIC AND CORPORATE VISITORS

Prof. Dr. J.-L. Brédas

University of Mons-Hainaut, Mons, B

Dr. M. Böhringer

EMPA, Dübendorf

Dr. C. Denz

Technische Hochschule, Darmstadt, D

Prof. Dr. C. Flytzanis

CNRS, Palaiseau, F

Dr. Y. Furukawa

NIRIM, Tsukuba, Japan

J.-P. Herriau

sfim ODS, Courtaboeuf, F

Prof. Dr. T. Kaino

Tohoku University, Sendai, Japan

Dr. T. Kamata

Nat. Inst. of Materials and ChemicalResearch, Tsukuba, Japan

Dr. M. Kauranen

University of Leuven, Heverlee, B

Dr. K. Kitamura

NIRIM, Tsukuba, Japan

Dr. Komatsu

Tohoku University, Sendai, Japan

Dr. K. Meerholz

Ludwig-Maximilian-Univ., München, D

Dr. F. Micheron

Thomson-TRT Optronics, Guyancourt, F

Dr. U. Niggemeier

Universität Paderborn, D

Dr. P.M. Petersen

Risoe National Laboratory, Roskilde, DK

Dr. M. Saffmann

Risoe National Laboratory, Roskilde, DK

Dr. Martin Schadt

Rolic Research Ltd., Allschwil

Prof. Dr. B. Sturman

Inst. for Nonlinear Studies, Novosibirsk

Prof. Dr. T. Volk

Russian Academy of Sciences, Moscow

Prof. Dr. von der Linde

Universität Essen, D

Dr. J. Wollschläger

Universität Hannover, D

SPONSORS

ETH ZürichSwiss National Science FoundationSwiss Priority Program Optique IINational Research Program NFP 36 “Nanowissenschaften”

RESEARCH SUMMARY


RESEARCH SUMMARY

This report summarizes the main research activities performed within the Nonlin-ear Optics Laboratory in 1998. The main activities were in the fields of

• Molecular Crystals, Molecules and Polymers• Photorefractive Effects and Applications in Optical Parallel Processing• Integrated Optics and Optical Frequency Conversion• Molecular Beam Epitaxy of Organic Thin Films• Investigation of Organic Molecules at Interfaces using Nonlinear Optics

and Atomic Force Microscopy• Magnetic Resonance Spectroscopy.

The research projects in these areas are described briefly in this report. In most ofthe topics considerable progress has been made. In this foreword we would like tomention only a few highlights of the results which appear most interesting for us.

In the field of organic nonlinear optical materials the investigations of DAST crys-tals (full name see 1.2) new low temperature phase transitions were discovered atT = 30 K and 170 K. In addition the configurations for highly efficient optical para-metric interactions in this crystal near the telecommunication wavelengths havebeen identified for the first time.

Another new optical nonlinearity crystal (M2-MDB, see 1.1) developed and syn-thesized in this laboratory showed an unique and interesting crystallographic result.Depending on the crystal growth parameters two different types of crystals can begrown which besides the position of two hydrogen atoms within two different(O-H--O) bonds have exactly the same crystallographic structure but completelydifferent physical properties. By infrared and Raman spectroscopic experiments wecould prove that this unusual property is caused by a different proton location of theshort hydrogen bond (O-H--O) in the aggregation between the merocyanine dyeand the second molecule forming the bicrystal, which influences the optical prop-erties of the molecules.

In the field of two-dimensional conjugated molecules for nonlinear optics with de-liberatly changed substitution pattern, we were able to explain the measured nonlin-earities by the different symmetries of the electronic wavefunctions.

In the field of photorefraction research the following results have been obtained:• The fundamental studies of interband photorefractive gratings in KNbO

3

have been completed with the thesis of P. Bernasconi. These studies lead to afull characterization of the double layered structure of such gratings and theirdynamics.

• By using these interband photorefractive gratings in KNbO

3

, the first dynam-ic light induced waveguides with reconfiguration time of few tens of micro-seconds could be demonstrated.

RESEARCH SUMMARY


• A fast read-out rate holographic image memory operated in a pulsed modewith a read-out rate exceeding 1000 frames/s has been put in operation dur-ing 1998.

• New experiments with Sn

2

P

2

S

6

and LiTaO

3

crystals have been started.These crystals appear to be very attractive for recording ultraviolet inducedgratings and for fast interband photorefraction at visible wavelengths, re-spectively.

• The investigation of nanosize, ferroelectric domains written at the surface offerroelectrics were successfully continued. The temporal stability of nan-odomains could be studied in detail using atomic force microscopy (AFM)techniques. In BaTiO

3 small domains which are in close neighborhood oflarger ones (< 1 µm distance) are seen to nucleate with them within aboutone hour.

In the field of degenerate four-wave mixing the contributions of the first ordernonlinearities to this second-order nonlinear optical effect have led to a full under-standing of all the effects. It has been shown, that these secondary effects can leadto misleading results if they are neglected. In addition these contributions have beencalculated for KNbO3 and the results have been used to interprete the experimentalresults.

In 1998 the following PhD students have successfully completed their theses:Dr. Pietro Bernasconi, Dr. Simon Brülisauer, Dr. Stéphane Follonier and Dr.

Christophe Seuret. They all have left the Nonlinear Optics Laboratory and have ac-cepted university or industrial positions in the USA and in Switzerland. In additionDr. Bert Müller, A. Kündig and Dr. Ye Tao have left our laboratory and have joinedresearch institutes and industrial laboratories in Canada or Switzerland. It is mypleasure to thank all these colleagues for their successful and pleasant collaboration.During 1998 we could welcome Karolina Brugger, Philipp Dittrich, Michael Kiy,Sabine Manetta, Carmen Tacchella, Marc Wintermantel and Edwin Hausammannas new PhD students, scientific or technical coworkers.

RESEARCH SUMMARY


Activities of member s of the Nonlinear Optics Laborator y in Conf erence Committees and Editorial Boar ds 5.1

Several members of the nonlinear optics laboratory continued to be active in a se-ries of international committees and as editorial board member of scientific journalsin the fields of optics, nonlinear optics, quantum electronics, solid state physics offerroelectric, organic and polymeric materials. Prof. P. Günter is a member of theeditorial board of the following scientific journals:

• "Ferroelectrics"• "Ferroelectrics Letters"• "Nonlinear Optics"• "Optica"• "Optics Communication"• "Photonics Science News"

and was/is a member of the advisory or program committees of the following in-ternational conferences:

• "Conference on Lasers and Electro-Optics" (CLEO Europe '98)• "Electrical and Related Properties of Organic Solids" (ERPOS-7)• "European Conference on Applications of Polar Dielectrics" (ECAPD)

(Chairman of the European Steering Committee)• IEEE Ferroelectrics Committee of the "Ultrasonics, Ferroelectrics and Fre-

quency Control Society"• "International Conference on Organic Nonlinear Optical Materials"

(ICONO-4)• "Photonics China ‘98" (SPIE Int. Symp. on Lasers and Optoelectronics)• "Nonlinear Optics ‘98"• OSA Topical Meeting on "Photorefractive Effects and Applications"• World Ceramics Congress on "Electronic, Magnetic and Optical Ceramics".

(CIMTEC’98: 9th International Conference on Modern Materials andTech-nologies).

Prof. R. Kind is the Secretary General of the Groupement AMPERE.

Dr. G. Montemezzani is a member of the program committee of the OSA TopicalMeeting on "Photorefractive Effects and Applications".


MOLECULAR CRYSTALS AND POLYMERS 1.1


MOLECULAR CRYSTALS AND POLYMERS

Design, Synthesis, and Cr ystal Gr owth of Second-Or der Nonlinear Optical Materials 1.1 C. Cai, S. Manetta, and M. Ehrensperger

The potential upper limits of macroscopic nonlinearities and long-term orienta-tional stability of molecular crystals are significantly superior to those of polymersand Langmuir-Blodgett thin films. Therefore, these crystals are of great interest foropto-electronic applications, such as ultra-fast (GHz) electro-optic applications, oroptical parametric generation. However, the probability of molecules to crystallizenoncentrosymmetrically as required for second-order nonlinear optics is very low.Moreover, the crystallinity and crystal properties of the rod-like, highly extendedπ-conjugation systems are usually poor which is detrimental for practical applications.

To solve the above problems several crystal engineering approaches can be ap-plied. In this past year work concentrated on a novel approach based on the shorthydrogen bond induced self-assembling of molecular aggregates: We used the O-H--O bond as steering force to co-crystallize many novel nonlinear optical organicmaterials. The experimental work was based on systems made of a merocyaninedye (M1 or M2) and one of 30 phenolic and aniline derivatives. Co-crystals wereanalysed by melting point measurement, second-harmonic generation using theKurtz and Perry powder test, and by X-ray structural analysis. More than 60 % ofthe systems did co-crystallize, mainly when the phenol derivatives was used.

The strong and flexible hydrogen bond (O-H--O) plays a key role in the co-crys-tallization process. We have obtained two examples of two phases of a co-crystalwith the same X-ray structure but different linear and nonlinear optical properties.This unusual property in the co-crystals may be caused by a different proton loca-tion of the short hydrogen bond (O-H--O) in the aggregation between the merocy-anine dye and the guest molecules influencing the optical properties of themolecules.

Merocyanine dye and phe-nolic or aniline derivatives

Reference: Man Shing Wong, Feng Pan, Martin Bösch, Rolf Spreiter, Christian Bosshard, Peter Günter, and Volker Gramlich, J. Opt. Soc. Am. B 15, 426 (1998)

Sponsor: Swiss National Science Foundation

NO

Rx

Acceptor

5R = CH3

2

R = CH2CH2OH

3

+M1:

M2:

14

M

6

1.2 MOLECULAR CRYSTALS AND POLYMERS


Second-Or der Optical Nonlinearities of Conjugated Or ganic Mole-cules 1.2I. Liakatas, R. Spreiter, C. Cai, and Ch. Bosshard

Organic molecules with large second-order nonlinearities are a prerequisite for highlyefficient electro-optic and nonlinear optic crystals and polymers. Our group is contin-uously working on the development of conjugated, donor-acceptor organic moleculeswith large second-order nonlinearities. We investigate them using electric field in-duced second harmonic generation (EFISH) and hyper-Rayleigh scattering (HRS).

In poled polymer applications, such as electro-optic modulators (see Section 1.8),molecules need to exhibit a large product (µβ) of ground-state dipole moment µ andthe molecular nonlinearity β as this is the figure of merit for a high degree of orien-tational order in electric field poled polymeric thin films. We have now developedmolecules with nonlinearities of µβ up to 11 x the value of the current standard ma-terial Disperse Red 1. The incorporation of these molecules in guest-host and side-chain polymers promises a large improvement of the electro-optic properties ofpoled polymers (see Section 1.8).

Work on molecules for organic crystals concentrated on the two materials 4-N,N--dimethylamino-4'-N'-methyl stilbazolium tosylate (DAST) and 4-2-[1-(2-hy-droxyethyl)-4-pyridylidene]-ethylidene-cyclo-hexa-2,5-dien-1-one•methyl 2,4-dihydroxybenzoate (M2-MDB), both of which are very interesting for electro-opticmodulation applications. Due to the ionic nature of DAST the molecular nonlinearoptical properties were not measured up to now. We now determined β in the sol-vent dimethylsulfoxide (DMSO) at an elevated temperature of 50°C to increase thesolubility using the HRS technique (λ=1.5µm). We could separate the second-har-monic signal from the three-photon luminescence signal by the different depen-dence on the fundamental beam power and measured a value β of 1.3 x the one ofDisperse Red 1. Furthermore, we performed the first reliable EFISH measurementsof M2-MDB in the solvents methanol and DMSO. The strong influence of the en-vironment on the optical properties was proven by the strongly varying wavelengthof maximum absorption and the change in sign of β when exchanging the two sol-vents.

Sponsors: Swiss National Science Foundation, ETH Zürich



Cascading of Second-Or der Nonlinearities 1.3Ch. Bosshard and I. Biaggio

Cascading is a process where lower-order effects are combined to contribute to ahigher-order nonlinear process. Large nonlinear phase shifts due to cascading (sec-ond-harmonic generation and difference-frequency mixing as well optical rectifica-tion and the linear electro-optic effect) were observed in several materials.Cascading also occurs in third-harmonic generation through the combination of fre-quency-doubling and sum-frequency generation. Furthermore, cascading throughthe combination of optical rectification and the linear electro-optic effect canstrongly increase the diffraction efficency in degenerate four-wave mixing.

During this past year we have used degenerate four-wave mixing to determine themost important tensor elements of the nonlinear optical susceptibility χ(3) of thehighly nonlinear crystal 4-N,N--dimethylamino-4'-N'- methyl stilbazolium tosylate(DAST) and interpreted the results with an improved theory (see Section 1.5).

Third-order nonlinear optical properties of DAST were evaluated with degeneratefour-wave mixing using 100ps pulses at λ=1064nm yielding large values of the ef-fective third-order susceptibility of χ(3)=4300±500 x 10-22 m2/V2. We showedboth theoretically and experimentally that the combined processes of optical recti-fication and the linear electro-optic effect contribute to the large effective third-or-der susceptibilities (14 x χ(3)(CS2)) of DAST in degenerate four-wave mixingexperiments. Furthermore, the knowledge of the cascaded contributions was usedto determine absolute values of the third-order susceptibilities as well as their sign.

Schematic of cascading in degenerate four-wave mixing. The beams 1 and 3 (or 2 and 3) writea polarization grating with grating vector kG from which beam 2 (or 1) can be diffractedthrough the linear electro-optic effect.

Our experiments confirmed that degenerate four-wave mixing is a very useful andreliable tool for the determination of tensor elements of the third-order susceptibil-ity χ(3).

Sponsor: ETH Zürich

1

2

4

3

23

kG1

3 kG



Thir d-Order Susceptibilities of Conjugated Or ganic Molcules 1.4U.Gubler, Ch. Bosshard, and M. Jäger, in collaboration with R. Martin, R. Tykwinskiand F. Diederich, Laboratory of Organic Chemistry, ETH Zurich

For electronic and photonic applications, organic molecules with extended conjuga-tion of the π-orbitals and electron-donating or accepting substitution of the endgroupsare of particular interest. To improve our knowledge about the influence of molecularstructure on the second-order hyperpolarizabilities γ, we focus mainly on two aspects:conjugation length expansion and the symmetry of the substitution pattern.

For our one-dimensionally conjugated molecular system polytriacetylene (PTA),we could extend our third-harmonic generation (THG) measurements to longer un-substituted PTA molecules of oligomeric length n=8, 12 and 16. The previouslyfound power law behaviour of the nonlinearity with saturation for longer oligomerscould be confirmed.

Besides the THG method, we now established degenerate four wave mixing (DF-WM) in solution using a 10 ps laser with a wavelength of λ=1.047 µm as a furthertechnique.The DFWM measurements of γ(-ω,ω,-ω,ω) yield further informationabout the optical nonlinearity γ compared to THG, which measures γ(-3ω,ω,ω,ω).The DFWM on the different PTA samples yielded similar results as THG.

Molecular backbones under investigation: (a) two dimensionally conjugated tetraethy-nylethenes (TEE), (b) polytriacetylenes (PTA), and (c) asymmetrically substituted polyenes. Dand A denote electron donating and accepting molecular groups. The OTBDMS ((tert-bu-tyl)dimethylsilyloxyl) group enhances the solubility.

In the collaboration with M. Blanchard (ESN, Paris), we measured further polyenesamples by THG and the whole series also with DFWM. The far red shifted absorp-tion spectra of some polyenes prevented us from using THG so far. Due to thewavelength of λ=1.047 µm in DFWM, we are now able to also investigate thesemolecules.

Reference: U. Gubler, R.Spreiter, Ch. Bosshard, P. Günter, R. R. Tykwinski, and F. Diederich, Appl. Phys. Lett. 73, 17, 2396 (1998).

Sponsor: ETH Zurich

A/DD/A

A/DD/A

OTBDMS

TBDMSO

A/DD/A

DA

n

n

(a)

(c)

(b)



Non-Local Contrib utions to Deg enerate Four Wave Mixing in Acen-tric Materials 1.5I. Biaggio

Pulsed Degenerate Four Wave Mixing (DFWM) is a wide-spread tool for charac-terizing third order susceptibilities of candidate materials for nonlinear optical ap-plications such as all-optical switching and optical limiting. Because third ordernonlinear optical effects can be found in centrosymmetric materials such as amor-phous polymers and liquids, much of the research has focused on these materials,and their third order susceptibilities have been determined by DFWM. However,materials with an acentric crystalline structure can also show interesting third ordernonlinearities that make them very interesting for applications.

However, acentric materials can also exhibit strong second order effects which cancombine in a two-step process to give a nonlinear optical response that has the samecharacteristics of a third order response. These effects have a strong influence on themeasurements, and must be taken into account in order to determine uniquely the di-rect third order response. In DFWM, the important second order effects contributingto the signal are optical rectification, the linear electro-optic effect, and piezoelectricelastic relaxation. The effective third order susceptibility measured in degeneratefour-wave mixing becomes strongly dependent on experimental parameters that donot normally influence the third order response in centrosymmetric materials, suchas the angle between the interacting beams, the pulse length, the orientation of thesample, and the type of DFWM setup. This introduces new important requirementsfor a reliable reporting of experimental results. If neglected, the “cascaded” secondorder effects can lead to misleading DFWM results in acentric materials.

In this work we developed a complete analysis of the second order effects inDFWM and calculated complete expressions to calculate their contribution to thesignal. The contribution of the combination of electro-optic effect and optical recti-fication has been calculated both in the case where piezoelectric elastic relaxationcan take place during the length of the laser pulses, and in the case where the pulsesare so short that the crystal is effectively clamped. We showed that there are DFWMconfigurations where this piezoelectric contribution is important down to pulselengths of about 100 ps, and showed that it can introduce an additional dependenceon the angle between the interacting beams when using nanosecond pulses.

Moreover, we developed a new technique that allows to experimentally relate thethird order susceptibility to the high-frequency electro-optic and dielectric proper-ties and demonstrated it in BaTiO3 and KNbO3. In this way absolute third order sus-ceptibilities can be obtained by comparing to independently determined linearelectro-optic coefficients, without using a reference material.

References:I. Biaggio, Phys. Rev. Lett. 82(1), 193-196 (1999).



Nonlinear Optical Pr oper ties of Molecular Cr ystals 1.6U. Meier, R. Spreiter, S. Manetta, and Ch. Bosshard

In the scope of this project, promising organic nonlinear optical crystals are inves-tigated with special interest on highly extended π-conjugated systems (e.g. donor-acceptor di-substituted stilbene and hydrazone derivatives). Besides a large nonlin-earity the orientation of these molecules in the crystal lattice is also of great impor-tance to optimize the nonlinear optical and electro-optic effects.

The determination of (i) possible phase-matched parametric interaction as well asof (ii) the relevant figures of merits for nonlinear optical and electro-optic applica-tion are based on the values of the refractive indices and the nonlinear optical coef-ficients. By performing Michelson interferometric and standard Maker Fringemeasurements we are routinely investigating these optical constants of our crystals.

We compared the molecular first-order hyperpolarizability β of a chromophoremeasured in solution (see Section 1.2) to that of the same molecule in the solid state,which can be calculated from the measured nonlinear optical coefficient. In the ion-ic organic crystal DAST (4-N,N-dimethylamino-4'-N'- methyl stilbazolium tosy-late), we obtained βsolution = 5 βsolid and for M2-MDB (4-2-[1-(2-hydroxyethyl)-4-pyridylidene]-ethylidene-cyclo-hexa-2,5-dien-1-one)•(methyl 2,4-dihydroxy-benzoate) we obtained βsolution = 9 βsolid. For both materials the strong intermolec-ular interactions in the solid state result in a decrease of the molecular nonlinearity.It remains to be seen whether our observation is a general trend if one continues todevelop new molecules with even larger nonlinearities.

Its huge nonlinear optical coefficients dijk (for frequency doubling at 1318nm:d11=1010±110pm/V, d12=96±9pm/V, and d26=53±12pm/V) make DAST very in-teresting for frequency conversion with optical parametric oscillators. Using mea-sured refractive index values and the two level model to describe the dispersion ofthe measured nonlinear optical coefficients we calculated the possible phase match-ing configurations and the corresponding effective coefficients for frequency con-version. By angle tuning of the crystal, optical parametric oscillation can beachieved for pump wavelengths between 0.7µm and 1.2µm with high effective co-efficients (above 30pm/V). For the range of a Ti:Sapphire laser, 700-950nm, phasematching is possible with a calculated figure of merit which is up to 30 timeshigher than the one of the best inorganic crystal KNbO3.

Reference: U. Meier, M. Bösch, C. Bosshard, F. Pan, P. Günter, J. Appl. Phys., 83, 3486, (1998).


deff2 n3⁄



Electr o-Optic Pr oper ties of Molecular Cr ystals 1.7R. Spreiter and Ch. Bosshard

In certain materials the index of refraction changes when an electric field is ap-plied (electro-optic effect). This effect allows to control a light beam by an electricfield and can therefore be used as an interface between electronics and optics. Im-portant applications of such materials are phase or intensity light modulators, elec-tro-optic switches, electric field sensors and generation of THz radiation by opticalrectification of femtosecond light pulses.

Crystals composed of organic chromophores are promising materials for electro-optic applications, since they show a flat response over a broad frequency band ofthe applied electric field. The electro-optic effect contains three different contribu-tions with very different resonance frequencies. The electronic contribution (in thevisible spectrum), the infrared contribution (molecular vibrations) and the acousticcontribution (MHz range). Up to now it was assumed that the electro-optic effect inorganic materials is of almost pure electronic origin. We now could show that alsothe molecular infrared vibrations considerably contribute to the electro-optic effect.

As an example we discussthe cases of 4-N,N-dime-thylamino-4'-N'-methylstilbazolium tosylate(DAST) and 4-2-[1-(2-hydroxyethyl)-4-pyridyli-dene]-ethylidene-cyclo-hexa-2,5-dien-1-one)•(methyl 2,4-dihydroxy-benzoate) (M2-MDB).We calculated the elec-tronic contribution fromexperimental frequencydoubling results using thetwo-level model and com-

pared it to the measured electro-optic coefficients and acoustic contributions. Theresults show that almost the whole effect stems from electronic and optic resonanc-es, making organic crystals especially suited for broad band applications from DCup to the lowest molecular vibrational frequencies which start at around 10 THz.

These materials are therefore very interesting and promising as THz generatorsand detectors using femtosecond lasers.


100 104 108 1012 1016

0.1 fs1 ps10 ns0.1 ms1 s

Response Time

Frequency [Hz]

rT rs

re

Aco

ustic

Res

onan

ces

Opt

ic M

odes

Ele

ctro

nic

Schematic dependence of the overall electro-optic coefficienton the frequency of the applied electric field. Acoustic reso-nances are extremely weak in organic crystals.



Electr o-Optic P olymer Waveguide Modulator s 1.8M. Bösch, I. Liakatas, M. Jäger, and Ch. Bosshard, in collaboration with S. Hösli,N. Tirelli, and U. W. Suter, Institute of Polymers, ETH Zurich

Organic polymers have become an important class of nonlinear optical materialsfor electro-optic modulation. They have been the subject of intense research sincethey combine the nonlinear optical properties of conjugated π-electron systemswith the feasibility of molecular engineering, i.e. creating new materials with appro-priate optical, structural, and mechanical properties.

The present project concentrates on the application of existing polymers to elec-tro-optic modulator devices as well as on the synthesis of new polymers. These newmaterials consist of novel chromophores with a higher optical nonlinearity (see sec-tion 1.2) and polymer backbones having higher glass transition temperatures. Theresulting increased electro-optic coefficient and the better thermal stability consti-tute a major improvement towards practical devices.

This year we built a prototype electro-optic phase modulator by structuring chan-nel waveguides in an active polymer film located between two passive polymer lay-ers. The structuring was done through a photochemical process under ultra-violetillumination (photobleaching). Electrode poling was used for orienting the chro-mophores in the direction of an applied electric field. A very good poling efficiencywas obtained and an electro-optic coefficient r33=16 pm/V was measured. For thispreliminary, only 3mm long prototype a half-wave voltage of Vπ=84 V atλ=1.34µm was determined. By optimizing the modulator’s geometry a decrease ofVπ by one order of magnitude can be expected.

Furthermore we have been able to increase the modulator bandwidth of our pre-viously reported polymeric inline fiber modulator which has now a demonstratedbandwidth of 600 MHz. The current traveling-wave electrode design of this verylow loss electro-optic modulator is suitable for modulation above 1 GHz.

Oscilloscope trace showing the applied electrical signal and the modulated optical signal of awaveguide phase modulator.

Sponsors: Swiss Priority Program Optique II, ETH Zurich

Electrical signal

Optical signal

10 V / div

20 mV / div

200 µs / div

Vπ = 42 V

2



Photorefractive Eff ects and Char ge Transpor t Proper ties in Or ganic Crystals and P olymer s 1.9S. Follonier, Ch. Bosshard, work on polymers in collaboration with M. Döbler andU. W. Suter, Institute of Polymers, ETH Zurich

Organic crystals and especially polymers are of prime interest for low cost devicesbased on light-induced changes of refractive indices. Much progress was achievedin terms of photorefractive sensitivity as well as in the design of new compoundsoptimized for specific needs, like infrared enhanced photorefractive response. Nev-ertheless, the limits of organic materials have not been reached yet.

In order to improve the photorefractive sensitivity of organic crystals, the know-ledge of charge carrier photogeneration and charge transport properties is of primeimportance.Therefore, intrinsic parameters such as mobility and lifetime of chargecarriers and the quantum efficiency of carrier generation were investigated by DCphotoconductivity, two-beam coupling as well as Time of Flight experiments in 4-N,N-dimethylamino-4'-N'- methyl stilbazolium tosylate (DAST) crystals.

During this year this work was successfully completed. We identified experimen-tally the low quantum efficiency of photogeneration as well as the electron-holecompetition as two of the limiting parameters for increased photorefractive sensi-tivity of the organic crystal DAST. We gained a physical understanding of themechanisms required for the photorefractive effect to occur: We identified the pho-togeneration of free charge carriers in DAST with an excitonic state of the crystal.We demonstrated the competition of electrons and holes in the crystal and identifiedthe transport process of the photoexcited charge carriers as a hopping from stilba-zolium chromophore to stilbazolium chromophore. We estimated the mobility ofcharge carriers, µ = 16.5 ± 10 cm 2 /Vs, and their lifetime τ = 4 ± 2 ns. We deter-mined the structure-property relationships of the photogeneration and the transportin DAST.

After the successful demonstration of the importance of the field-induced orien-tational contribution to the photorefractive effect in high glass transition, polya-mide based polymers, work in this field was not pursued further.




Fluorescence Phenomena in Or ganic Single Cr ystals 1.10U. Meier and Ch. Bosshard

Nonlinear optical properties of acentric organic materials originate in the molec-ular electronic response of the material to applied fields (electrical or optical), mod-ified by the influence of molecular surroundings (crystal structure, solvents).Theoretical descriptions of the optical properties are therefore based on the energyconfiguration of the electronic states of the material (molecules, crystals). Severalof our newly developed organic materials show strong fluorescence after excitationwith UV or IR light. In this project we attempt to determine the intra- or intermo-lecular physical processes leading to the observed excitation and emission phenom-ena of these organic materials.

Different absorption and luminescence experiments are performed to determinethe relevant underlying processes (intramolecular charge transfer, intermolecularexcitons (e- & hole), ...) which lead to the observed one and two photon excited flu-orescence phenomena. Absorption spectra are obtained across the strong absorptionresonance region by measuring the wavelength dependence of the crystal reflectiv-ity and the use of the Kramers-Kronig formalism for the determination of the linearoptical constants. We further investigate the dependence of luminescence and ab-sorption upon temperature, excitation intensity, polarization, and excitation wave-length of our organic crystals and molecules in solution.

This year we concentrated on the measurement of quantum efficiencies for theemission and the separation of molecular and vibrational contributions to the emis-sion of the organic crystals by performing low temperature luminescence measure-ments. The luminescence efficiency of the most interesting material 4-N,N-dimethylamino-4’-N’-methyl-stilbazolium tosylate (DAST) in solution was com-pared to Rhodamine 6G; the obtained molecular quantum efficiencies for DAST arein the range of 0.5%. Our measurement at different temperatures down to 5°K re-vealed interesting spectral properties of our DAST crystals. These luminescencefeatures, shifts of the peaks as well as changes in peak height with temperature,which can be related to the crystal packing of the active molecules and possiblequenching processes in the crystals, will be further investigated.




Tunab le nanosecond and picosecond infrared laser sour ce based on optical parametric g eneration in KNbO 3 1.11U. Meier, U.Gubler, and Ch. Bosshard

The availability of laser sources over a wide range of wavelengths is a prerequisitefor spectroscopic characterization of the optical and nonlinear optical properties ofmaterials. To provide laser radiation with a wide wavelength tunability, the use ofoptical parametric generation and amplification of light in a nonlinear optical crys-tal is most attractive.

In this project, we focus on two concepts. (i) An optical parametric oscillator(OPO) system, which is directly pumped by nanosecond (ns) pulses from aNd:YAG laser (7 ns) at 1064 nm, using a two-crystal walk off compensated geom-etry. (ii) An optical parametric generator / amplifier (OPG/OPA) system pumpedby picosecond (ps) pulses from an amplified Nd:YLF laser (10 ps) at 1047 nm. Thenonlinear optical material used is KNbO3, because of its wide phase matching pos-sibilities, large effective nonlinear optical coefficients, and a high optical damagethreshold. Wavelength selection for both system will be done by angle tuning of theKNbO3 crystals.

(i) By consistent reduction of losses in the system we were able to reduce the os-cillating threshold of the OPO below the damage thereshold of the material. Withour two 7.5 mm long KNbO3 crystals we obtained a total output of up to 450 µJ perpulse. Using two new 12 mm long anti-reflection coated crystals we expect to reacha total OPO output above 10 mJ with more than 10% total conversion efficiency.

(ii) Only small progress has been achieved with the OPG/OPA system this yeardue to the reduced nonlinear optical coefficient of KNbO3 in the infrared and thelower damage threshold for non main axis crystal cuts than expected in the initialdesign. A new evaluation with the corrected values for the nonlinear optical coeffi-cients and damage thresholds yielded a minimal crystal length of 15 mm for KNbO3which will be ready by the end of this year.

Tuning curves of thewalk off compensatednanosecond optical pa-rametric oscillator usingtwo 7.5 mm longKNbO3 crystals.

Sponsor: Swiss priority program Optique II

5.50 5.75 6.00 6.25 6.50 6.75 7.00

1.5

2.0

2.5

3.0

3.5

Crystal Tuning Angle [°]

λ Sig

nal &

λId

ler

[µm

]

CalculationSignalIdler


PHOTOREFRACTIVE EFFECTS AND PHOTONICS 2.1


PHOTOREFRACTIVE EFFECTS AND PHOTONICS

Growth, preparation and c haracterization of photorefractive cr ystals 2.1C. Medrano, R. Ryf, H. Wüest, J. Hajfler, G. Montemezzani; in collaboration withK. Kitamura and Y. Furukawa, NIRIM, Japan; and A. A. Grabar, Univ. Uzhgorod,Ukraine

Crystalline materials showing the photorefractive effect, i.e. an optically inducednon local change of the refractive index, attract considering attention due to theirapplications in dynamic holography, optical processing and storage and opticalphase conjugation. These phenomena depend strongly on both intrinsic and extrin-sic properties of the material. It is therefore very important to be able to modify,characterize and optimize these properties in view of a specific application.

For this material research project, crystalline sam-ples grown in our laboratory, as well as samples ob-tained thanks to external collaborations areinvestigated. Among the home grown crystals the in-vestigations have been concentrated this year on Cedoped KNbO3 as well as on KNbO3:Rh subjected to ahigh-tempearture gas-reduction treatment. In additionwe have studied crystals of LiNbO3 and LiTaO3 bothof congruent and stoichiometric composition thatwere grown in Japan, as well as Sn2P2S6 samplesgrown at the University of Uzhgorod in the Ukraine.The crystal quality is characterized photorefractivelyas well as with optical and electrical techniques and chemical analysis. Laser scat-tering tomography, a new technique for the determination of the smallest scatteringdefects, became available this year thanks to the collaboration with the National In-stitute for Research in Inorganic Materials in Japan (see Figure).

The large photorefractive sensitivity of Rh-doped KNbO3 in the near IR observedearlier was shown to be well reproducible in a new batch of reduced samples.KNbO3:Ce was found to show high sensitivity, a fast holographic response timeτw = 30 ms at the wavelength of 488 nm and a very long dark decay time ofτdark = 35 hours. Stoichiometric LiNbO3 and LiTaO3 were proved to be a much bet-ter choice than congruently grown crystals for dynamic holography. The reason isa reduced influence of bulk photogalvanic fields and less scattering defects givingan optical quality comparable to the one of KNbO3 samples. Finally, Sn2P2S6,which is interesting for interband photorefraction at visible wavelengths, wasshown to respond in a time of few tens of µs under pulsed illumination in the green.This material may be very useful for optical correlation purpouses.


Laser scattering tomographicpicture of a nearly defect freeMn doped KNbO3 crystal.

1 mm

2.2 PHOTOREFRACTIVE EFFECTS AND PHOTONICS


Ultra violet photorefraction and its applications 2.2Ph. Dittrich, P. Bernasconi, G. Montemezzani; in collaboration with K. Kitamura andY .Furukawa, NIRIM, Japan;

Photorefractive effects at ultraviolet (UV) wavelengths are interesting for highspeed and high resolution applications. For instance, the use of recording light withwavelength shorter than the material band-gap (interband photorefraction) allowsto record high resolution dynamic holograms with response times about three or-ders of magnitude shorter than with conventional photorefractive effects.

Our investigations have been focused on two materials, congruent and stoichio-metric LiTaO3 crystals which are transparent in the near UV, and nominally pureKNbO3 crystals which is ideally suited for interband photorefraction. Two andfour-wave mixing techniques as well as optical and electrical measurements wereused for the material characterization.

With respect to the one of congruentsamples the fundamental absorptionedge of stoichiometric LiTaO3 isshifted by ≈15 nm down to ≈ 270 nm,making them more attractive for UVapplications involving coherent lightamplification or phase conjugation. Inthis kind of crystals we observed sim-ilar electro-optic properties, but fasterand stronger holographic responses ascompared to congruent samples. ForUV intensities of 500 mWcm-2, thetime constant was reduced from~1 min down to 5 sec, while the two-beam coupling gain increased bymore than a factor of two to ~7 cm-1.

Doped stoichiometric samples should become available soon and are expected toallow the realization of self-pumped phase conjugation. In pure KNbO3 the basicstudies of the interband photorefractive gratings started earlier have been completedexperimentally through off-Bragg angle diffraction measurements and the resultshave been modeled theoretically. The grating parameters allow now to predict thefundamental diffraction properties of interband gratings and their optimum opera-tion conditions. We also demonstrated the possibility to produce UV inducedwaveguides in this material over which we will report more extensively next year.Reference: P. Bernasconi, G. Montemezzani, M. Wintermantel, I. Biaggio, and P. Günter,

Opt. Lett. 24(3), Feb. 1, 1999.


Tim

e (s

)

10 20 300-10-20-30

10-5

10-4

10-310-2

10-11

∆ϑB (mrad)

Dynamics of the diffraction efficiency of in-terband photorefractive gratings as a functionof the angular deviation from the exactBragg-angle.



Charge Transpor t Proper ties of P olar Dielectric Cr ystals 2.3M. Wintermantel, I. Biaggio

Charge transport and photoinduced charge transport are at the basis of manyseemingly unrelated technologies. Interesting examples of promising new develop-ments based on charge transport are optical memories, neural networks, dynamicholography, or optoelectronic devices like organic light emitting diodes or even la-sers. A well known example of an established technology are the photoconductorsused in all laser printers and copying machines. However, despite the high interestfor their applications, fundamental charge transport parameters like the mobility ofcharge carriers and the free carrier lifetime are still unknown in many materials.This is due to the fundamental difficulties in determining low mobilities with freecarrier lifetimes of the order of some nanoseconds or less by conventional methods.

We use high-time-resolution optical tools, such as the Holographic Time of Flight(HTOF) technique, to investigate intrinsic charge transport mechanism in polar ma-terials, where the charge carriers are typically small and large polarons. An impor-tant example of a photoconductive polar material is the sillenite crystal Bi12SiO20,where the conduction electrons form large polarons at room temperature, with aband mobility as low as 3.4 cm2/(Vs), a value which is more than two orders ofmagnitude smaller than in GaAs.

We now investigated the temperaturedependence of the electron band mobilityin Bi12SiO20 using the HTOF techniquein an optical cryostat. The new measure-ments are plotted in the figure togetherwith earlier high temperature results fromanother sample [1]. The data from twodifferent samples follow the theory wellat temperatures above 250 K. The mobil-ity increase with decreasing temperaturein this range is related to the decreasingphonon density and is well explained bylarge polaron theory adapted to Bi12SiO20[1]. At a temperature around 180 K weobserved a transition towards a mobilitythat decreases with decreasing tempera-ture, more typical of a thermally activatedprocess. We are currently investigatingthe origin of this transition by looking atdifferent samples and extending the temperature range towards lower temperatures.References:I. Biaggio, R. W. Hellwarth, J. P. Partanen, Phys. Rev. Lett. 78 , 891 (1997)

150200300500 120

2 3 4 5 6 7 8 91

2

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µ [c

m2

/Vs]

T [K]

Electron band mobility vs. temperaturein Bi12SiO20. The high temperature be-haviour is predicted by large polarontheory (solid line).



Holographic optical pr ocessing and memories 2.4R. Ryf, G. Montemezzani

Due to its intrinsic parallelism, optics brings about several potential advantagesover conventional signal processing techniques. If a suitable nonlinear element isavailable, fast processing of information is possible because an enormous numberof channels are processed at the same time. For instance, an interferometer contain-ing a dynamic holographic element can be used to visualize temporally changingphase structures of an object in real time. On the other hand, static holographic op-tical memories may result in a dramatic increase of storage capacity as compared totwo dimensional storage systems and in a very high read-out throughput. In thisproject we investigate real time holographic interferometers as well as a high frame-rate optical image memory, which will be used in a second step, to feed an opticalprocessor (for example a high speed correlator).

A holographic interferometer was built with theprocessing element based on two-wave mixing in-teraction in a KNbO3 crystal. The signal wave isdepleted as long as the phase structure of the inputobject is not changing. The first experiments showthat phase variations of a liquid object illuminatedby the input wave can be successfully visualized inreal time. During this year most efforts have beenconcentrated into the realization of a static holo-graphic memory used as image library for fast read-out. A high repetition rate 532 nm laser with pulselength of 70 ns was used as light source. The storeddata were modulated on the object beam by meansof a ferroelectric liquid crystal spatial light modula-tor (256x256) and the reference beams were angu-larly multiplexed by means of a galvano-mirror.Currently we have stored 100 pages (images) indifferent LiNbO3, LiTaO3 and KNbO3 crystals. InLiNbO3 and LiTaO3 the strong photogalvanic ef-fect inproves the dynamic range and allowed us toreach a higher storage density. As a drawback, thephotogalvanic effect is also producing a self-defo-cusing effect which affects partially the image

quality. In contrast, KNbO3 does not show image distortion. We have demonstrateda readout rate of 1200 images per second (80 Mpixel/s) which we expect to increaseover 10'000 images/s (0.65 Gpixel/s) soon.Sponsor: Swiss National Science Foundation

Some input and readout imagesof the pulsed holographic mem-ory.

Inputimages

Readoutimages

34

37

47

76



Manipulation of f erroelectric domains b y scanning f orce micr os-cop y 2.5M. Abplanalp

The features of ferroelectric materials are determined to a major extent by the stat-ic and dynamic properties of ferroelectric domains. In order to study the dynamicbehavior of ferroelectric domains at the surface of bulk crystals a non-destructivemethod sensitive only to the polarization at the surface is needed. The piezore-sponse scanning force microscopy we developed during the last years fulfills allthese requirements.

The polarization is measured via the inverse piezoelectric effect: an a.c. voltageapplied to the conductive scanning force microscope tip leads to a local distortionof the crystal. The tip will follow the movements and as a result the cantileverbends. By measuring the amplitudes of the cantilever vibration normal to the sur-face by a phase sensitive amplifier, a voltage that represents the normal componentof the polarization vector is generated.

Nanoscale ferroelectric domains of antiparallel polarization with respect to thesurrounding can be nucleated by applying an unipolar voltage pulse to the tip of thescanning force microscope while keeping the back-electrode on the opposite side ofthe crystal grounded. Figure (a) shows the polarization distribution after nucleatingtwo circular domains in the vicinity of a large domain in a ferroelectric bulk singlecrystal of barium-titanate. Figures (b) and (c) present the time evolution of the twodomains: After some minutes an additional domain has nucleated between the up-per written domain and the large domain on the left. This domain grows with timeand melts together with the large domain. After 90 minutes the written domainshave disappeared, while the large domain on the left has grown. The measurementshows first that the small domains are not stable in bulk crystals and second that thedomain evolution consists not only in domain wall movements but also in the nu-cleation of additional domains.

Sponsor: National Research Program NFP 36 “Nanowissenschaften”

Time evolution of two oppositely written domains (white) close to a larger natural domain ina 120 µm thick barium-titanate crystal. Note the nucleation of an additional domain after a fewminutes (b) and the disappearance of all written domains within 90 minutes (c).

5 min after writing 90 min after writingjust after writing

500nm

a) c)b)



MOLECULAR BEAM EPITAXY 3.1


MOLECULAR BEAM EPITAXY

Design, Preparation, and Characterization of No vel Or ganic Nonlin-ear Optical Thin Films Gr own b y Molecular Beam Deposition 3.1 C. Cai, M. Bösch, M. Jäger, Y. Tao, I. Biaggio, Ch. Bosshard, and A. Kündig.

Thin films of nonlinear optical organic moleucles are interesting for applicationsin high-speed optical information processing or for optical frequency conversionbecause they allow miniaturized, low power solid state laser systems. However, itis quite difficult to fabricate thin-film macroscopical molecular assemblies thatmantain a non-centrosymmetric structure suitable for nonlinear optics. Althoughlarge molecular crystals habe been grown successfully, appropriate techniques forthe preparation of acentric molecular films are still missing. It is therefore importantto find new methods to grow robust non-centrosymmetric layers of organic mole-cules at a reasonable growth rate.

We have demonstrated the growth of non-centrosymmetric thin films by ObliqueIncidence Organic Molecular Beam Deposition (OMBD) of a new type of material:head-to-tail supramolecular polymers, such as the ones produced with PVBA andPEBA[1]. In these films, the molecular ordering is determined by the direction ofincidence of the molecular beam onto the substrate, and is caused by the specialshapes and bonding features of the constituent molecules.

We designed a new molecule,PEPG, that presents the requiredbonding characteristics for buildingsupramolecular polymers, but alsohas a stronger donor-acceptor sys-tem that should lead to higher non-lienar optical susceptibilities. A concise synthesis of PEPG has been developed.Thin films (100–400 nm) of PEPG were grown on amorphous glass substrates byOblique Incidence OMBD at 30˚C substrate temperature and were found to possessthe required non-centrosymmetric structure in second harmonic generation experi-ments. The solid state 15N-NMR spectra of PEPG indicate very strong intermolec-ular hydrogen bonding between the carboxylic H-atom and the adjacent N-atom,which also agrees with its high melting point (250˚C). As we expected from its mo-lecular structure, after sublimation in low vacuum, PEPG displayed greatly im-proved nonlinearity in the powder test as compared to PVBA and PEBA. Theoptical quality of the PEPG films are also much better than those of PVBA andPEBA. Further experiments are necessary to optimize the deposition conditions inorder to improve the ordering of the PEPG films.Reference: C. Cai, M. M. Bösch, Ye Tao, B. Müller, Z. Gan, A. Kündig, Ch. Bosshard, I.

Liakatas, M. Jäger, P. Günter, J. Am. Chem Soc. 120 , 8653 (1998)

Sponsor: Swiss Priority Program Optique II

NH N

O

H O

NH N

O

H O

N-4- trans[2-(4-pyridyl)ethnyl]-phenylglycine(PEPG) molecules linked via a strong hydrogenbond network

3.2 MOLECULAR BEAM EPITAXY


Interface Pr oper ties of Or ganic and Inor ganic Films in Multila yer Light-Emitting Structures 3.2M. Kiy, Y. Tao, I. Gamboni, I. Biaggio

Organic light emitting devices have recently attracted much attention in relationto the application to flat panel displays. Such devices have a mulitylayer structureincluding electrodes for electric contacts. The interfaces between the contacts andtheorganic materials and between the organic multilayers play a major role in theperformance. However, there is little knowledge about the electronic states of thesenovel materials, and how they are influence by a neighbouring interface.

In order to understand the physical mechanisms influencing the device perfor-mance in a final application we grow organic layers and controlled interfaces byMolecular Beam Deposition in a Ultra-High-Vacuum system (pressure below10-9 mbar). The system is equipped with 2 deposition chambers and in-situ surfaceanalysis and characterisation facilities (UPS, XPS, RHEED, LEED). The thicknessof the growing layers can be well controlled in-situ with an ellipsometer. For a bet-ter investigation of the influence of interface types and environment on the charge-injection and transport mechanisms in we plan to extend the UHV system with anew chamber for meauring current-voltage and luminance-current characteristics.

For the electrical properties of anOLED it is important to know the posi-tion of the Highest Ooccupied Molec-ular Orbital (HOMO) and the positionof the Lowest Unoccupied MolecularOrbital (LUMO). The binding energyof the HOMO can be measured direct-ly by ultraviolet photoelectron spec-troscopy (UPS). As an example, thefigure shows an UPS measurent of anAlq3 layer (a commonly used elec-troluminescent molecule) on a goldsubstrate. The peaks correspond to themolecular electronic states in the mol-ecule. We have also fabricated

CuPc/NPB/Alq3 three-layer organic light emitting devices with improved stabilityas compared to NPB/Alq3 devices. The typical brightness of such OLEDs is2500 cd/m2 at an applied voltage of 15V (an example can be seen on the title page).We have found, for the first time, that Mg exhibits partial condensation on Alq3 sur-face and diffuses into organic layer during device fabrication process, and an ultra-thin silver layer can be used to block this kind of diffusion.Sponsor: ETH Zürich

0.05.010.0

Inte

nsity

[a.

u.]

binding energy [eV]

N

O

Al

3

Alq3

Ultravialot Photoelectron Spectroscopy (UPS)measurement giving the binding energy ofelectrons in Alq3 relative to the energy of theHighest Occupied Molecular Orbital..

MOLECULAR BEAM EPITAXY 3.3


Ultra-High Vacuum Atomic For ce Micr oscop y of Surfaces Prepared by Molecular Beam Deposition 3.3A. Kündig, I. Gamboni, M. Kiy

An Atomic Force Microscope (AFM) can deliver detailed information on the sur-face morphology of thin films grown by molecular beam deposition in Ultra-High-Vacuum (UHV). We developed a new AFM that is attached to an existing UHV-system for molecular beam epitaxy and surface analysis. This is essential to be ableto investigate the growth processes by in-situ measurements of the surface rough-ness, or of the density, shape, and size of “islands” formed by the initial growth ofthe thin-film material on the substrate.

Constucting an AFM system for a running UHV environment presents someunique challenges because manual access is limited, and because mechanical andelectronic noise from running pumps and machinery have to be controlled. As anexample, the position of the AFM-cantiliver must be tracked in a robust way thatdoes not require manual adjustements. In our device this is done by using a piezore-sistive deflection sensor as a completely integrated electronic detection system. TheAFM-head is mounted in a metallic cylinder hanging in a suspension stage witheddy current damping. This design leads to optimum vibrational damping, mechan-ical stability, and electronic shielding. The device can scan an extraordinary largerange of 8×8 µm2 at any place within a large 25×32 mm2 area on the surface ofthree inch wafers without any manual adjustement. Different types of cantileversare available by an exchange system for the tip holder as a whole.

The AFM can work in both contactmode, where the repulsive force be-tween tip and sample is measured, andin dynamic mode, where the cantile-ver is vibrated at its mechanical reso-nance and the change in resonancefrequency produced by the force-gra-dient between tip and surface is mea-sured. The capabilities of the devicewere demonstrated by atomic-resolu-tion imaging of MoS2 samples in con-tact mode, and by detection ofmonoatomic steps on WSe2 andgraphite in contact mode, intermittentcontact mode, and noncontact mode.Our new UHV-AFM is a very flexible, easy to use, and powerful tool for the char-acterization of solid surfaces down to the atomic level because it combines atomicresolution, large scanrange, large accessible range, and different measuring modes.Sponsor: Swiss National Science Foundation

UHV Atomic Force Microscope system.The magnets of the eddy-current-baseddamping system are visible around the as-sembly. The tip of the AFM (pointing up) isin the middle of the circular hole at the top.


INTEGRATED OPTICS AND OPTICAL FREQUENCY CONVERSION 4.1


INTEGRATED OPTICS AND OPTICAL FREQUENCY CONVERSION

Fabrication of fi rst-or der Bra gg gratings on KNbO 3 waveguides 4.1D. Fluck, H. Wyss

For efficient frequency doubling of laser diodes, it is necessary to fix the emmis-sion wavelength to better than 0.1 nm for enabling phase-matching in a KNbO3waveguide. Conventional Fabry-Perot laser diodes do not fullfill this requirementbecause even small changes in the ambient conditions as well as uncontrolled opti-cal feedback disturbe the emmission spectrum and lead to mode hoping betweenlongitudinal modes of the cavity. Therefore, wavelength stabilization has to beforced via optical feedback from an external wavelength selective element. One ofthe approaches is to use an optical Bargg grating. Direct integration of a Bragg grat-ing into the frequency doubling KNbO3 waveguide could provide the most compactdevice with unique mechanical stability. First order gratings with Bargg wave-lengths between 860 nm and 980 nm in KNbO3 require a periode of about 200 nm.Because standard optical UV lithography is limited to a feature size of ≥ 0.4 µm,such small lines can only be realized with electron lithography or with optical twobeam interference lithography.

We have developed the technique to fab-ricate first order Bragg gratings intoKNbO3 by using two beam interferencelithography on photo resist with the UVlight from an Argon-ion laser and subse-quent argon-ion sputtering to transformthe resist grating mask into the surface ofthe crystal. The patterned photoresiststructure was directly used as the shield-ing mask for argon-ion sputtering, a tech-nique which has already been developedto form ridge waveguide structures intoKNbO3. First order Bragg gratings with aperiode of 216.8 nm corresponding to aBragg wavelength of 980.0 nm were fab-ricated. The surface relief gratings havebeen visualized with an atomic force microscope (see Figure).

Sponsor: Optique II

Atomic force microscope picture of a firstorder Bragg grating on KNbO3.

4.2 INTEGRATED OPTICS AND OPTICAL FREQUENCY CONVERSION


Blue-light second-harmonic g eneration in KNbO 3 4.2K. Brugger, T. Pliska, D. Fluck

The aim of our project is to achieve frequency conversion with high efficiencyfrom the near-infrared to the blue wavelength region. We use Potassium Niobate(KNbO3) for frequency up-conversion because it offers high nonlinear coefficients,a wide transparency range from 390 nm to 4500 nm and the possibility of phase-matching wavelengths down to 850 nm without requiring periodic poling of the ma-terial. Optical waveguides confine the laser radiation with highest intensities alongthe whole length of the guide, therefore providing highest conversion efficiency. Inaddition, the use of channel waveguides eliminates the problem of walk-off for anyphase-matching direction. Thus very strong nonlinear optical effects can beachieved in waveguides even at the power level of commercially available single-mode laser diodes.

We have developed the technique to fabricate ridge waveguides in KNbO3 bycombining planar ion implantation and ion sputtering. The first step, irradiation ofKNbO3 with He+ ions, leads to the formation of a planar waveguide. Then, a posi-tive photoresist mask defining strips of a few micrometers width is formed on topof the planar waveguide. Subsequently, ion sputtering is used to etch the planarwaveguide from the top in the unshielded regions. By this process, ridgewaveguides were formed for phase-matched second-harmonic generation withridge heights of about 1 µm. With 260 mW of fundamental power coupled into thewaveguide a second-harmonic power at 438 nm of 10 mW was generated in a7.3 mm long waveguide. Theoretical modeling shows that an increase of the ridgeheight should result in a considerable increase of the conversion efficiency. There-fore we further developed the process to form waveguides, leading to ridge heightsof about 1.7 µm. These waveguides are under investigation now.

Reference: T. Pliska, D. Fluck, P. Günter, L. Beckers and Ch. Buchal, "Linear and Nonlinear Optical Properties of KNbO3 Ridge Waveguides", J. Appl. Phys. 84 (3), 1186-1195 (1998).

Sponsor: Optique II

INTEGRATED OPTICS AND OPTICAL FREQUENCY CONVERSION 4.3


Liquid phase epitaxy of K 1-yNayTa1-xNbxO3 thin fi lms on Ba-doped KTaO3 substrates 4.3H. Pierhöfer, H. Wüest

Growth of ferroelectric thin films on a conducting substrate offers many possibil-ities in investigation of the film and also in many applications. The film-substratesystem can be used as pyroelectric sensors or as waveguides with the possibility tomodulate the light by the electro-optical effect. Especially for KNTN electro-opticapplications are very promising, because the composition of the film (i.e. the ratioof Ta to Nb ions) can be chosen to get a phase transition temperature slighly aboveroom temperature, hence resulting in very high electro-optical coefficients. Suchthin films would provide the basis for low-voltage electro-optic modulators.

Thin films of KNTN aregrown by liquid phase epitaxy(LPE). If KTaO3 (KT) is usedas substrate, the presence of Naions in the KNTN film allowgood lattice matching betweensubstrate and film and thusgrowth of very high qualityKNTN films. The drawback ofpure KT is its very high electri-cal resistivity, which can beovercome by the addition of Bato the melt. Ba-doped KT couldbe grown by Czochralski’smethod and showed electricalresistivities as low as 25 Ωmcompared to 1011 Ωm mea-sured in pure KT. Hence, it isnow possible to use the dopedsubstrate as bottom electrodefor poling procedures, electrical measurements or electro-optical applications. Frequencyand temperature dependency of real and imaginary part of the dielectric constant havebeen investigated using a low frequency impedance analyser (HP4192A). The curves inthe figure clearly show the strong relaxor behaviour of the film (even at low frequenciesaround 100 Hz the dielectric constant is strongly frequency-dependent). In the Cole-Coleplot the experimental data fall onto semi-circles indicating the good quality of the films. Reference :H. Pierhöfer, Z. Sitar, F. Gitmans, H. Wüest, and P. Günter, “New Semiconduct-

ing Substrate for Heteroepitaxial Growth of K1-yNayTa1-xNbxO3”, Ferroelectrics 201, 269 (1997).

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4.4 INTEGRATED OPTICS AND OPTICAL FREQUENCY CONVERSION


Photorefractive eff ect in ion-implanted ir on-doped KNbO3 crystals 4.4S. Brülisauer, D. Fluck

Photorefractive crystals such as KNbO3, BaTiO3, and Sr1-xBaxNb2O6 (SBN) arekey materials for real-time holography and photorefractive optical signal process-ing applications. It is an important goal to speed up their response time and to ex-tend their photorefractive sensitivity to the near infrared regime by appropriatemodification of the crystals.

We demonstrated that the photorefractive properties such as gain and responsetime in Fe-doped KNbO3 crystals can be greatly improved and that it is possible toextend the photorefractive sensitivity of Fe-doped KNbO3 to the telecommunica-tion wavelengths of 1.3 µm and 1.55 µm by high energy proton irradiation. In fact,MeV proton implantation seems to be the appropriate modification scheme forwide-bandgap photorefractive oxide crystals. We observe a change of the majoritycarriers in the irradiated crystals from p-type to n-type. This is caused by a changein the ratio R of the concentration of donors and acceptors. An important contribu-tion stems from the creation of oxygen vacancies, created by the high energy pro-tons. We have been able to adjust the reduction ratio R precisely over three ordersof magnitude by simply changing the irradiation dose. By applying this technique,we were able to increase the photorefractive gain from 3 cm-1 up to 50 cm-1 and todecrease the grating build-up time from 2 ms to 30 µs in a 1000 ppm Fe-dopedKNbO3 crystal for an intensity of 200 W/cm2. No other treatment has demonstratedthat capability. In addition, MeV proton implantation has proven to be an absolutelyhomogeneous and reproducible process and we have also shown that the irradiationeffect is additive. Implanting the same sample in several steps gives a continuousincrease of the reduction ratio R.

Reference: S. Brülisauer, D. Fluck, P. Günter, L. Beckers, Ch. Buchal, "Controlled Reduc-tion of Fe-Doped KNbO3 by Proton-Irradiation", Optics Communications 153, 375-386 (1998)

Sponsor: ETH Zürich

NUCLEAR MAGNETIC RESONANCE 5.1


NUCLEAR MAGNETIC RESONANCE

Point Char ge Model Calculations of 87Rb Spin-Lattice Relaxation and 2-D-Exc hang e NMR Spectra 5.1Ch. Jeitziner and R. Kind

We report on an improved model simulating the measured 87Rb 2D-NMR ex-change difference spectra of the structural glass D-RADP-50 at low temperatures,where the single particle correlation time of the deuterons on the O-D...O bonds isstill faster than our observation time. We conclude from spin-lattice relaxation datathat already at these temperatures most of the bonds are completely polarized, thatmeans that the (short-)time averaged integral over the local polarizations is±1. Superimposed to the fast biased hopping there is a slow process, changing thesign of the bias energies and therefore also the sign of . Thus any change of leads to a change of the local resonance frequency observable in a 2D-NMR ex-change spectrum as off-diagonal intensity.

We assume in our point charge model, that we observe experimentally not the fastbiased hopping process but only the variation of the time-averaged local polariza-tion which are ascribed to motions of Takagi defects, i.e. a PO4 groups with 1 or 3deuterons close to the oxygen atoms, which can move through the crystal like quasi-particles. Our model consists of an O-D...O network with 1152 PO4 groups arounda given 87Rb atom using periodic boundary conditions. To calculate the second or-der quadrupolar frequency shift of the central 87Rb we took into account the 32nearest deuterons giving the major contribution.

Fig. 1a) Simulated 2D exchange spectrum for 16 steps of the Takagi group. b) Integrated off-diagonal intensity as function of distance from the diagonal for 16 and 4096 steps.

Fig. 1a shows a calculated 2D exchange spectrum assuming that the Takagi groupperforms always 16 steps to create a new deuteron configuration. From Figs. 1 a, bit is evident that most of the intensity is very close to the diagonal meaning that thereare only small frequency changes (≤ 2kHz) due to the motion of the Takagi groups,which is also observed experimentally. Sponsor: Swiss National Science Foundation

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5.2 NUCLEAR MAGNETIC RESONANCE


Line Shape Transitions of the Chemical Shift P erturbed 31P NMR Spectra Re veal Symmetrizing Slo w Motion Eff ects 5.2Ch. Jeitziner and R. Kind

We are interested in the nature of the deuteron dynamics in the structural glassRb0.5(ND4)0.5D2PO4 (D-RADP-50). From our measurements we conclude thatthere are two processes influencing the deuteron motion on the hydrogen bonds: thefirst is fast intrabond hopping between the two potential minima and the other is aslow fluctuation of the bias energy of the O-D...O bonds. The latter can be ascribedto the motion of Takagi defects in the network of O-D...O bonds. Takagi defects arePO4 groups where not only two (Slater groups) but one or three deuterons are closeto the oxygens. When a Takagi group moves through a Slater group lattice, simplyby shifting a deuteron from one minimum in the double-well potential to the other,we assume that the bias energies of the involved O-D..O bonds change their sign.For temperatures above 45 K, the hopping motion is faster than the observation timeof 1 ms thus we observe only the time averaged local polarization, which, however,is influenced by the bias fluctuations imposed by the Takagi group motion.

The chemical shift describes the degree of screening of the external magnetic fieldat the 31P site, leading to a frequency shift in the NMR spectrum which is of the or-der of ppm. The chemical shift not only changes when rotating the crystal with re-spect to the external magnetic field, but also depends on the different configurationsof the deuterons belonging to the PO4 groups under consideration.

Fig. 1: 31P a-rotation measurements for from left to right.

For T = 45 K, the bias fluctuations are too slow to be visible in the spectrum. Fig. 1shows that for T > 77 K the Takagi groups start to change the time-averaged polar-izations of the deuterons faster, so that the signal intensity shifts towards the centerof gravity of the lines and eventually merges into one narrow line for very fast mo-tions at T = 168 K. This shows clearly the thermally activated Takagi motion, sym-metrizing the O-D...O bonds in the long time scale.


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NUCLEAR MAGNETIC RESONANCE 5.3


Anal ysis of the Intra- and Inter -Line Spin-Diffusion of 87Rb in Ferr o-electric RDP at 85K 5.3P. M. Cereghetti and R. Kind

The investigation of spectralspin diffusion[1] in solids by means of two dimen-sional (2D) exchange nuclear magnetic resonance (NMR) is important because thismechanism often masks the effects of slow chemical exchange which is in fact thetrue aim of such a study. We are interested in the mixed crystal systemRb1-x(NH4)xD2PO4 (RADP-x). In D-RADP-x for 0.35<x<0.7, chemical exchangepersists down to very low temperatures because of the hydrogen motion on theO-H…O bonds. On the other hand, in RbH2PO4 (RDP,x=0) only spin diffusion isleft, since the proton motion is frozen-in for temperatures below Tc=147, where anorder-disorder phase transition from a paraelectric (PE) to a ferroelectric (FE) statetakes place. Because of the structural similarity of RDP and D-RADP-x one can de-termine 87Rb spin-diffusion in the RDP single crystal at low temperatures, andadapt the results to D-RADP-x.

In the FE state the inhomoge-neously broadened central line of the87Rb 1D NMR spectrum is splitted.Spin diffusion occurs between 87Rbnuclear spins belonging either bothto the same resonance line (intra linespin diffusion) or each to one distinctline (inter line spin diffusion). Start-ing from 87Rb 2D NMR measure-ments we have developed a veryprecise method [2] to determine theintra- and inter-line spin diffusiontimes TSD as a function of the fre-quency separation between two ex-changing spins (Figure, open and fullcircles).

The dependence of the intra- and inter-line 87Rb spin diffusion times on the fre-quency separation ∆ν in RDP can be very well fitted with an inverted Gaussianfunction (Figure, plain and dashed lines), which can be explained with the overlapintegral of two Gaussian line shapes separated by ∆ν.

Reference: [1] D.Suter, and R.R.Ernst, Phys.Rev. B25,6038-6041 (1982)

[2] P. M. Cereghetti, R. Kind, “87RB spin diffusion in ferroelectric RbH2PO4 studied by two dimensional NMR,” to be published in J. of Magnetic Resonance.


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5.4 NUCLEAR MAGNETIC RESONANCE


Comparison of Ester -Methyl-Gr oup Rotation in Syndiotactic and Isotactic PMMA 5.4P. M. Cereghetti and R. Kind

An interesting feature in polymer glasses is the heterogeneity of the relaxation inthese systems. The basic question concerns the probability distribution function of thesingle particle autocorrelation time which is believed to be characteristic for the cor-relation length of the local order. While T1-measurements yield information aboutfast fluctuations, the 2D-NMR measurements cover the low frequency spectrumdown to 1/T1. Our actual interest is on the rotation of the deuterons on the ester methylgroup in poly (methyl methacrylate) (PMMA). At high temperatures the deuteronsperform a fast rotation around the ester methyl group C3 axis. This yields a partiallytime averaged electric field gradient tensor the averaged principal components ofwhich (V'zz and η) completely define the motionally narrowed powder pattern. Thedeuteron motion is slowed down at low temperatures so that to the motionally nar-rowed powder pattern a broader one with Vzz = 3V'zz is superimposed. This lineshape transition is characterised by a distribution of phase transition temperatures.

To characterise the slow motion of the ester methyl group we have investigated asyndiotactic PMMA sample with 2H two dimensional (2D) nuclear magnetic reso-nance (NMR). Because of the insufficient signal to noise ratio we were not able todetect any unambiguous signal of this motion. In a second step we are now investi-gating an isotactic sample, where the ester groups are aligned on one side of thepolymer chain. From 2H 1D broadband spectra we observe that the line shape tran-sition to the slow motion regime takes place at temperatures T≤80K at least 20 Kabove the one of the syndiotactic sample.

From broadband 2H T1 relaxation measurements on the isotactic sample we havedetermined a large distribution of autocorrelation times for the methyl group reori-entation. This distribution is about one order of magnitude above the one of the syn-diotactic sample. The corresponding mean activation energies are 94 meV and64meV, respectively. This clearly demonstrates that the deuteron motion in the iso-tactic sample is more hindered by its neighbors. In a next step we will investigatethe methyl group reorientation in the isotactic sample by means of 2H 2D NMR.


PUBLICATIONS 1998 Journal Publications


PUBLICATIONS 1998

Journal PublicationsM. Abplanalp, L. Eng and P. Günter"Mapping the Domain Distribution at Ferroelectric Surfaces by Scanning Force Mi-croscopy"Appl. Phys. A 66, S231-S234 (1998)S.C. Abrahams, H.W. Schmalle, T. Williams, A. Reller, F. Lichtenberg, D. Widmer, J.G. Bednorz, R. Spreiter, Ch. Bosshard and P. Günter"Centrosymmetric or Noncentrosymmetric: Case Study, Generalization and Structural Redetermination of Sr5Nb5O17"Acta Crystallographica B54, 399-416 (1998)L. Beckers, Ch. Buchal, D. Fluck, T. Pliska and P. Günter"Potassium Niobate Waveguides: He+ Implantation in Bulk Single Crystals and Pulsed Laser Deposition of Thin Films"Materials Science & Engineering A 253, 292-295 (1998)S. Brülisauer, D. Fluck, P. Günter, L. Beckers and Ch. Buchal"Controlled Reduction of Fe-Doped KNbO3 by Proton-Irradiation"Optics Communications 153, 375-386 (1998)Ch. Cai, M. Bösch, Y. Tao, B. Müller, Zh. Gan, A. Kündig, Ch. Bosshard, I. Liakatas, M. Jäger and P. Günter"Self- Assembly in Ultrahigh Vacuum: Growth of Organic Thin Films with a Stable In-Plane Directional Order"J. Am. Chem. Soc. 120 (33), 8563-8564 (1998)Ch. Cai, M. Bösch, Y. Tao, B. Müller, A. Kündig, Ch. Bosshard and P. Günter"Growth of Organic Thin Films with an In-Plane Dipolar Order Under Ultra-High Vac-uum"Polymer, 39 (2), 1069-1070 (1998)Ch. Cai, I. Liakatas, M.S. Wong, Ch. Bosshard and P. Günter"Synthesis and Nonlinear Optical Studies of Highly Efficient Chromophores with Bithiophene Stilbene as the Conjugating Unit"Polymer, 39 (2), 1111 (1998)M. Döbler, Ch. Weder, P. Neuenschwander, U.W. Suter, St. Follonier, Ch. Bosshard and P. Günter"Synthesis and Characterization of New Photorefractive Polymers with High Glass Transition Temperatures"Macromolecules 31 (18) 6184-6189 (1998)J. Dolinsek, M. Koren and R. Kind"Kinetic Freezing Dynamics of the Supercooled Liquid State in 2-Cyclooctylamino-5-Nitropyridine (COANP)"Phys. Rev. B 57 (5), 2812-2820 (1998)L. Eng, M. Abplanalp and P. Günter"Ferroelectric Domain Switching in Tri-Glycine Sulphate and Barium-Titanate Bulk Single Crystals by Scanning Force Microscopy"Appl. Phys. A 66, S679-S683 (1998)D. Fluck and P. Günter"Efficient Second-Harmonic Generation by Lens Wave-Guiding in KNbO3 Crystals"Optics Communications 147, 305-308 (1998)

Journal Publications PUBLICATIONS 1998


U. Gubler, R. Spreiter, Ch. Bosshard, P. Günter, R.R. Tykwinski and F. Diederich"Two-Dimensionally Conjugated Molecules: The Importance of Low Molecular Sym-metry for large Third-Order Nonlinear Optical Effects"Appl. Phys. Lett. 73 (17), 2396-2398 (1998)P. Günter und M. Abplanalp"Ferroelektrische Speichermedien: Lassen sich Daten noch dichter packen?"Bulletin der ETH 269, 52-55 (1998)R. Kind, N. Korner, Th. König und Ch. Jeitziner"Finite Size Effects in Proton Glass"J. Korean Phys. Soc. 32, S799-S802 (1998)O. Leifeld, B. Müller, D.A. Grützmacher and K. Kern"A UHV STM for In Situ Characterization of MBE/CVD Growth on 4-Inch Wafers"Appl. Phys. A 66, S993-S997 (1998)I. Liakatas, M.S. Wong, V. Gramlich, Ch. Bosshard and P. Günter"Novel, Highly Nonlinear Optical Molecular Crystals Based on Multidonor-Substitut-ed 4-Nitrophenylhydrazones"Advanced Materials 10 (10), 777-782 (1998)U. Meier, M. Bösch, Ch. Bosshard, F. Pan and P. Günter"Parametric Interactions in the Organic Salt 4-N,N-Dimethylamino-4'-N'-Methyl-Stil-bazolium Tosylate at Telecommunication Wavelengths"J. Appl. Phys. 83 (7), 3486-3489 (1998)B. Müller, L. Nedelmann, B. Fischer, H. Brune, J. Barth and K. Kern"Island Shape Transition in Heteroepitaxial Metal Growth on Square Lattices"Phys. Rev. Lett. 80 (12), 2642-2645 (1998)B. Müller, L. Nedelmann, B. Fischer, H. Brune, J. Barth, K. Kern, D. Erdös and J. Wollschläger"Strain Relief Via Island Ramification in Submonolayer Heteroepitaxy"Surface Review and Letters 5 (3 & 4), 769-781 (1998)T. Pliska, D. Fluck, P. Günter, L. Beckers and Ch. Buchal"Mode Propagation Losses in He+ Ion-Implanted KNbO3 Waveguides"J. Opt. Soc. Am. B 15 (2), 628-639 (1998)T. Pliska, D. Fluck, P. Günter, E. Gini, H. Melchior, L. Beckers and Ch. Buchal"Birefringence Phase-Matched Blue Light Second-Harmonic Generation in a KNbO3 Ridge Waveguide"Appl. Phys. Lett. 72 (19), 2364-2366 (1998)T. Pliska, D. Fluck, P. Günter, L. Beckers and Ch. Buchal"Linear and Nonlinear Optical Properties of KNbO3 Ridge Waveguides"J. Appl. Phys. 84 (3), 1186-1195 (1998)Ph. Prêtre, U. Meier, U. Stalder, Ch. Bosshard, P. Günter, P. Kaatz, Ch. Weder, P. Neu-enschwander and U.W. Suter"Relaxation Processes in Nonlinear Optical Polymers: A Comparative Study"Macromolecules 31 (6), 1947-1957 (1998)R. Ryf, M. Zgonik and P. Günter"Photorefractive Characterisation of Crystals with High Trap Densities"Nonlinear Optics 19, 79-91 (1998)

PUBLICATIONS 1998 Conference Publications


R. Ryf, A. Lötscher, Ch. Bosshard, M. Zgonik and P. Günter"Z-Scan-Based Investigations of Photorefractive Self-Focusing in KNbO3 Crystals"J. Opt. Soc. Am. B 15 (3), 989-995 (1998)R. Spreiter, Ch. Bosshard, G. Knöpfle, P. Günter, R. Tykwinski, M. Schreiber and F. Diederich"One- and Two-Dimensionally Conjugated Tetraethynylethenes: Structures Versus Second-Order Optical Polarizabilities"J. Phys. Chem. B 102 (1), 29-32 (1998)F. Steybe, F. Effenberger, U. Gubler, Ch. Bosshard and P. Günter"Highly Polarizable Chromophores for Nonlinear Optics: Syntheses, Structures and Properties of Donor-Acceptor Substituted Thiophenes and Oligothiophenes"Tetrahedron 54, 8469-8480 (1998)N. Tirelli, A. Altomare, R. Solaro, F. Ciardelli, U. Meier, Ch. Bosshard and P. Günter"Structure-Activity Relationship of New Organic NLO Materials Based on Push-Pull Azodyes. 1 Synthesis and Molecular Properties of the Dyes"J. Prakt. Chem. 340, 122-128 (1998)N. Tirelli, U.W. Suter, A. Altomare, R. Solaro, F. Ciardelli, S. Follonier, Ch. Bosshard and P. Günter"Structure-Activity Relationship of New Nonlinear Optical Organic Materials Based on Push-Pull Azo Dyes. 3. Guest-Host Systems"Macromolecules 31 (7), 2152-2159 (1998)R.R. Tykwinski, U. Gubler, R. Martin, F. Diederich, Ch. Bosshard and P. Günter"Structure-Property Relationship in Third-Order Nonlinear Optical Chromophores"J. Phys. Chem. B 102 (23), 4451-4465 (1998)M.S. Wong, F. Pan, M. Bösch, R. Spreiter, Ch. Bosshard, P. Günter and V. Gramlich"Novel Electro-Optic Molecular Cocrystals with Ideal Chromophoric Orientation and Large Second-Order Optical Nonlinearities"J. Opt. Soc. Am. B 15 (1), 426-431 (1998)

Conference PublicationsP. Bernasconi, G. Montemezzani and P. Günter"Interband Photorefraction for High Resolution Incoherent to Coherent Optical Con-verters"Conference on Lasers and Electro-Optics-Europe (CLEO/Europe '98), Glasgow, UK, IEEE Eds., Technical Digest, 396 (1998)I. Biaggio, S. Fischer, Ch. Bosshard and P. Günter"Second Order Cascading Contributions in Degenerate Four-Wave Mixing"European Quantum Electronics Conference (EQEC/Europe '98), Glasgow, UK, IEEE Eds., Technical Digest, 96 (1998)Ch. Bosshard, I. Biaggio, S. Fischer, S. Follonier and P Günter"Large Cascaded Second-Order Nonlinearities in Degenerate Four-Wave Mixing of Organic Single Crystals"Conference on Lasers and Electro-Optics (CLEO '98), San Francisco, USA, Optical Society of America, Technical Digest 6, 30-31 (1998)

Conference Publications PUBLICATIONS 1998


Ch. Bosshard"Organic Nonlinear Optical Materials"Conference on Lasers and Electro-Optics-Europe (CLEO/Europe '98), Glasgow, UK, IEEE Eds., Technical Digest, 124 (1998)Ch. Bosshard, I. Biaggio, S. Follonier, S. Fischer and P. Günter"Importance of Cascaded Second-Order Nonlinearities in Degenerate Four-Wave Mixing of Organic Single Crystals"8th Iketani Conference, 4th International Conference on Organic Nonlinear Optics (ICONO '4), Chitose, Japan, Editor H. Sasabe, Extended Abstracts 243-244 (1998)P. Cereghetti and R. Kind"Analysis of Inhomogeneous Spin-Diffusion in Ferroelectric RbD2PO4"Proceedings of the Joint 29th AMPERE - 13th ISMAR International Conference , Ber-lin, D, "Magnetic Resonance and Related Phenomena", Volume I, (Eds: D. Ziessow, W. Lubitz and F. Lendzian), 318-319 (1998)S. Follonier, Ch. Bosshard, I. Biaggio and P. Günter"Photorefractive and Charge Transport Properties of the Organic Crystal 4-N,N-Dim-ethylamino-4'-N'-Methylstilbazolium Toluene-p-Sulfonate"Nonlinear Optics '98, Materials, Fundamentals and Applications, Optical Society of America, IEEE Eds., 406-408 (1998)S. Follonier, M. Döbler, Ch. Bosshard, C. Weder, U.W. Suter and P. Günter"Polyamide Based Polymers: Influence of the Glass Transition Temperature on the Photorefractive Effect"8th Iketani Conference, 4th International Conference on Organic Nonlinear Optics (ICONO '4), Chitose, Japan, Editor H. Sasabe, Extended Abstracts 245-246 (1998)U. Gubler, Ch. Bosshard, P. Günter, R. Martin, R.R. Tykwinski and F. Diederich"Functionalized One- and Two-Dimensionally Conjugated Molecules for Third -Order Nonlinear Optics"Polymer Preprints 39 (2), 1067-1068 (1998)U. Gubler, Ch. Bosshard, P. Günter, R. Martin, R. Tykwinski and F. Diederich"Functionalized One and Two-Dimensionally Conjugated Molecules for Third Order Nonlinear Optics"European Quantum Electronics Conference (EQEC/Europe '98), Glasgow, UK, IEEE Eds., Technical Digest, 217 (1998)U. Gubler, Ch. Bosshard, P. Günter, R. Martin, R. Tykwinski and F. Diederich"Functionalized One and Two-Dimensionally Conjugated Molecules for Third Order Nonlinear Optics"8th Iketani Conference, 4th International Conference on Organic Nonlinear Optics (ICONO '4), Chitose, Japan, Editor H. Sasabe, Extended Abstracts 104-105 (1998)Ch. Jeitziner , Th. König and R. Kind"Point-Charge Model Calculations of the Proton Glass Dynamics in Rb0.5(ND4)0.5D2PO4 (D-RADP-50)"Proceedings of the Joint 29th AMPERE - 13th ISMAR International Conference , Ber-lin, D, "Magnetic Resonance and Related Phenomena", Volume I, (Eds: D. Ziessow, W. Lubitz and F. Lendzian), 103-104 (1998)R. Kind and Ch. Jeitziner"What Does NMR Tell us About the Hydrogen Ordering and Motion in Proton Glass"Proceedings of the 9th Int. Conference on Solid State Protonic Conductors (SSPC-9), Bled, SLO, MT4-3, 83-86 (1998)

PUBLICATIONS 1998 Conference Publications


C. Medrano, I. Biaggio, G. Montemezzani, P. Günter and I. Poberaj"Phase Conjugation Based on a Brillouin Liquid at 1.06 µm and 2.09 µm"Conference on Lasers and Electro-Optics-Europe (CLEO/Europe '98), Glasgow, UK, IEEE Eds., Technical Digest, 223 (1998)C. Medrano, M. Ewart, I. Biaggio, R. Ryf and P. Günter"Near Infrared Photorefraction in Reduced Rh-Doped KNbO3"Conference on Lasers and Electro-Optics-Europe (CLEO/Europe '98), Glasgow, UK, IEEE Eds., Technical Digest, 373 (1998)U. Meier, M. Bösch, Ch. Bosshard and P. Günter"Parametric Interaction in the Organic Salt 4-N,N-Dimethylamino-4'-N'-Methyl-Stil-bazolium Tosylate at Telecommunication Wavelengths"Conference on Lasers and Electro-Optics-Europe (CLEO/Europe '98), Glasgow, UK, IEEE Eds., Technical Digest, 291 (1998)U. Meier, M. Bösch, Ch. Bosshard and P. Günter"Phase-Matched Parametric Interactions in DAST at Telecommunication Wave-lengths"8th Iketani Conference, 4th International Conference on Organic Nonlinear Optics (ICONO '4), Chitose, Japan, Editor H. Sasabe, Extended Abstracts 241-242 (1998)G. Montemezzani and P. Günter"Influence of Material Anisotropies on Photorefractive Gain and Speed"Conference on Lasers and Electro-Optics-Europe (CLEO/Europe '98), Glasgow, UK, IEEE Eds., Technical Digest, 372 (1998)R. Ryf, G. Montemezzani, P. Günter and A. Zozulya"Photorefractive Spatial Soliton Formation in KNbO3 Crystals"Proceedings of European Quantum Electronics Conference (EQEC/Europe '98), Glas-gow, UK, Technical Digest, IEEE Eds., 212 (1998)R. Spreiter, Ch. Bosshard, G. Knöpfle, P. Günter, R.R. Tykwinski, M. Schreiber and F. Diederich"One- and Two-Dimensionally Conjugated Tetrathynylethenes: Structure versus Sec-ond-Order Optical Polarizabilities"European Quantum Electronics Conference (EQEC/Europe '98), Glasgow, UK, IEEE Eds., Technical Digest, 201 (1998)

5.4


ORAL PRESENTATIONS 1998


ORAL PRESENTATIONS 1998* = invited talk

M. Abplanalp"Direct Writing of Ferroelectric Domains with a Scanning Force Microscope"SPG'98, Bern26./.27.2.98

* M. Abplanalp"Imaging and Writing of Ferroelectric Domains with a Scanning Force Microscope"Forschungszentrum Jülich, D5.6.98M. Abplanalp"Writing of Sub Micrometer Ferroelectric Domains with SFM"Int. Symposium on Applications of Ferroelectrics (ISAF XI '98), Montreux24.-27.8.98M. Abplanalp"Imaging of Ferroelectric Domains with Sub Micrometer Resolution by SFM"Int. Symposium on Applications of Ferroelectrics (ISAF XI '98), Montreux24.-27.8.98

* M. Abplanalp"Imaging and Writing of Ferroelectric Domains with a Scanning Force Microscope"Workshop über "Rastermikroskopie an Oberflächen von Ferroelektrika", Forschung-szentrum Jülich, D11.11.98

* P. Bernasconi"Interband Photorefractive Effects for Holographic Applications and Material Charac-terization"University of Colorado, Boulder CO, USA16.7.98

* P. Bernasconi"Ultraviolet Interband Photorefractive Holography"Lucent Technologies, Holmdel NJ, USA11.11.98

* P. Bernasconi"Physics and Applications of Ultraviolet Induced Photorefractive Gratings"Laser-Seminar, ETH Zürich7.12.98

* I. Biaggio"Measurements of Charge Transport Parameters with HTOF and Space-Charge Mod-ulation Photoerasure"Dept.of Computer and Systems Engineering, Faculty of Engineering, Kobe University, Kobe, Japan13.2.98



* I. Biaggio"Measurements of Charge Transport Parameters with HTOF and Space-Charge Mod-ulation Photoerasure"The 73th Grystal Growth Seminar, National Institute for Research in Inorganic Mate-rials (NIRIM), Tsukuba, Japan16.2.98

* I. Biaggio"Large Polarons and Their Observation in Bi12SiO20"The 73th Grystal Growth Seminar, National Institute for Research in Inorganic Mate-rials (NIRIM), Tsukuba, Japan23.2.98

* I. Biaggio"Influence of Shallow Traps on Steady State and Transient Photoconductivity Mea-surements"The 73th Grystal Growth Seminar, National Institute for Research in Inorganic Mate-rials (NIRIM), Tsukuba, Japan25.2.98I. Biaggio"Optical Characterization of Charge Transport in Polar Dielectrics"European Conference on Applications of Polar Dielectrics (ECAPD-4 '98), Montreux24.-27.8.98I. Biaggio"Second Order Cascading Contributions in Degenerate Four-Wave Mixing"European Quantum Electronics Conference (EQEC/Europe'98), Glasgow, UK14.-18.9.98

* I. Biaggio"Nonlocal Contributions to Degenerate Four Wave Mixing in Acentric Materials"Electrical Engineering-Electrophysics and Department of Physics & Astronomy Joint Seminar, University of Southern California, Los Angeles.14.10.98M. Bösch"Polymer Based Electro-Optic Inline Fiber Modulator"European Conference on Applications of Polar Dielectrics (ECAPD-4 '98), Montreux24.-27.8.98

* Ch. Bosshard"Third Order Nonlinear Optics in Polar Materials: Cascaded Second-Order Nonlinear-ities and the Influence of Molecular Asymmetry"Management Committee Meeting of COST P2 Action "Applications of Nonlinear Op-tical Phenomena", Bruxelles, B6.2.98Ch. Bosshard"Large Cascaded Second-Order Nonlinearities in Degenerate Four-Wave Mixing of Organic Single Crystals"CLEO/IQEC 1988, San Francisco, CA, USA4.-8.5.98



* Ch. Bosshard"Nichtlinear optische Effekte 3. Ordnung in polaren Materialien"Universität Wien, A3.6.98

* Ch. Bosshard"Organic Nonlinear Optical Materials"Conference on Lasers and Electrooptics (CLEO/Europe'98), Glasgow, UK14.-18.9.98Ch. Bosshard, U. Gubler, P. Günter, R. Martin, R. Tykwinski and F. Diederich"Functionalized One and Two-Dimensionally Conjugated Molecules for Third Order Nonlinear Optics"Conference on Lasers and Electrooptics (CLEO/Europe'98), Glasgow, UK14.-18.9.98

* Ch. Bosshard"Importance of Cascaded Second-Order Nonlinearities in Degenerate Four-Wave Mixing of Organic Single Crystals"4th International Conference on Organic Nonlinear Optical Materials (ICONO '4), Chitose, Japan12.-15.10.98C. Bosshard, U. Meier, M. Bösch and P. Günter"Phase-Matched Parametric Interactions in DAST at Telecommunication Wave-lengths"4th International Conference on Organic Nonlinear Optical Materials (ICONO '4), Chitose, Japan12.-15.10.98Ch. Bosshard, S. Follonier, M. Döbler, C. Weder, U.W. Suter and P. Günter"Polyamide Based Polymers: Influence of the Glass Transition Temperature on the Photorefractive Effect"4th International Conference on Organic Nonlinear Optical Materials (ICONO '4), Chitose, Japan12.-15.10.98Ch. Bosshard, U. Gubler, P. Günter, R. Martin, R. Tykwinski and F. Diederich"Functionalized One and Two-Dimensionally Conjugated Molecules for Third Order Nonlinear Optics"4th International Conference on Organic Nonlinear Optical Materials (ICONO '4), Chitose, Japan12.-15.10.98

* Ch. Bosshard"χ(2) and χ(2) : χ(2) Effects in Organic Single Crystals"Tohoku University, Japan16.10.98

* Ch. Bosshard"Organische Materialien für die Nichtlineare Optik: neue Entwicklungen und Effekte"Universität Bayreuth, D1.12.98



* Ch. Bosshard"Organische Materialien für die Photonik: Grundlagen und Anwendungen"Antrittsvorlesung, ETH Zürich9.12.98Ch. Cai"Growth of Organic Thin Films with an Inplane Dipolar Order Under Ultra-High Vac-uum"American Chemical Society (ACS) Meeting, Boston, USA23.-27.8.98Ch. Cai"Synthesis and Nonlinear Optical Studies of Highly Efficient Chromophores with Bithiophene Stilbene as the Conjugating Unit"American Chemical Society (ACS) Meeting, Boston, USA23.-27.8.98

* Ch. Cai"Deposition of Ordered Organic Thin Films"Worchester Polytechnic Institute, Massachusetts, USA23.11.98

* Ch. Cai"Deposition of Ordered Organic Thin Films"McGill University, Montreal, Canada26.11.98

* Ch. Cai"Self-Assembly Growth of Organic Thin Films under Ultra-High Vacuum"MRS Meeting, Boston, USA30.11.-4.12.98Ch. Cai"A New Type of Hole-Transport Material Based on Bithiophene Stilbene"MRS Meeting, Boston, USA30.11.-4.12.98

* Ch. Cai"Deposition of Ordered Organic Thin Films"University of Washington, Seattle, USA3.12.98

* Ch. Cai"Deposition of Ordered Organic Thin Films"University of Illinois at Urbana-Champion, USA7.12.98

* Ch. Cai"Deposition of Ordered Organic Thin Films"Bowling Green State University, USA9.12.98

* Ch. Cai"Deposition of Ordered Organic Thin Films"City University of New York, Brookling College, New York, USA14.12.98



P. Cereghetti"Analysis of Inhomogeneous Spin-Diffusion in Ferroelectric RbD2PO4"AMPERE/ISMAR 98, Berlin, D2.-7.8.98D. Fluck"Compact and Stable Blue Lasers Based on KNbO3"Conference on Lasers and Electro Optics (CLEO '98), San Francisco, USA3.-8.5.98

* D. Fluck"Compact and Stable Blue Lasers"Istituto Elettrotecnico Nazionale Galilei Ferraris, Torino, I29.5.98

* D. Fluck"Compact and Stable Blue Lasers"Institute for Molecular Science (IMS), Okazaki, Japan17.7.98D. Fluck"Improvement of the Photorefractive Response of KNbO3 Crystals by MeV Proton Ir-radiation"11th Int. Conference on Ion Beam Modification Materials (IBMM), Amsterdam, NL31.8.-4.9.98D. Fluck"Controlled Reduction of Fe-Doped KNbO3 by Proton-Irradiation"Conference on Lasers and Electrooptics (CLEO/Europe'98), Glasgow, UK14.-18.9.98H. Goldbach, D. Erdös, B. Fischer, L. Nedelmann, J. Barth, K. Kern, B. Müller und J. Wollschläger"Wachstumdynamik von Cu auf Ni(100) bei tiefen Temperaturen"62. Physikertagung 1998 der DPG, Regensburg, D23.-27.3.98U. Gubler"Nonlinear Optical Properties of Conjugated Organic Materials"Workshop zwischen den Gruppen von Prof. Brédas, Prof. Diederich, Prof. Gross und Prof. Günter, Strasbourg, F12.6.98U. Gubler"Functionalized One- and Two-Dimensionally Conjugated Molecules for Third-Order Nonlinear Optics"American Chemical Society (ACS) - Meeting, Boston, USA23.27.8.98

* P. Günter"Organische und anorganische nichtlineare optische Materialien"Frühjahrstagung der Deutschen Physikalischen Gesellschaft, Konstanz, D16.-19.3.98

* P. Günter"Ferroelectric Oxides and Thin Films for Nonlinear Optics"Seminar, IBM Research Center, Rüschlikon23.4.98



* P. Günter"Hochschulforschung und High Tech Industrie"Einweihungsfeier ROLIC Research Ltd., Allschwil6.6.98

* P. Günter"Novel High Nonlinearity Organic Crystals"Summer Course: "Molecular Opto-Electronics", Madrid, E3.-7.8.98

* P. Günter"Thermally Stable Electro-Optic Polymers"Summer Course: "Molecular Opto-Electronics", Madrid, E3.-7.8.98

* P. Günter"Novel Organic Crystals and Polymers for Nonlinear Optics"European Conference on Applications of Polar Dielectrics (ECAPD-4 '98), Montreux24.-27.8.98

* P. Günter"Self-Induced Optical Effects in Nonlinear Optical Materials"4th International Conference on Intelligent Materials (ICIM '98), Makuhari, Japan5.-7.10.98

* P. Günter"Novel High Nonlinearity Organic Nonlinear Crystals"Keynote Lecture?4th International Conference on Organic Nonlinear Optical Materi-als (ICONO '4), Chitose, Japan12.-15.10.98

* P. Günter"Nonlinear Optical Crystals - Their Applications and Future"The 73th Grystal Growth Seminar, National Institute for Research in Inorganic Mate-rials (NIRIM), Tsukuba, Japan16.10.98

* P. Günter"Nonlinear Optics in Inorganic and Organic Materials: Recent Investigations and Ap-plications"Thomson-CSF and Thomson Optronique, Paris-Orsay, F12.11.98

* P. Günter"Optical Frequency Conversion in Inorganic and Organic Materials"1998 International Photonics Conference (IPC '98), Taipei, Taiwan15.-18.12.98R. Kind"Analysis of 87Rb Spind-Diffusion in Mixed Crystals of Rb1-x(ND4)xD2PO4"EENC '98, Bled, Slovenia10.-15.5.98R. Kind"Point Charge Model Calculations of the Proton Glass Dynamics in Rb0.5(ND4)0.5D2PO4(D-RADP-50)"AMPERE/ISMAR 98, Berlin, D2.-7.8.98



R. Kind and Ch. Jeitziner"What Does NMR Tell us About the Hydrogen Ordering and Motion in Proton Glass?"9th International Conference on Solid State Protonic Conductors (SSPC-9), Bled, SLO17.-21.8.98O. Leifeld, D. Grützmacher, B. Müller und K. Kern"Massgeschneiderte Germanium-Quantenpunkte durch Nukleation auf C/Si(001)"62. Physikertagung 1998 der DPG, Regensburg, D23.-27.3.98I. Liakatas"Highly Polar Molecular Crystals for Electro-Optic Applications"European Conference on Applications of Polar Dielectrics (ECAPD-4 '98), Montreux24.-27.8.98C. Medrano"Near Infrared Photorefraction in Reduced Rh-Doped KNbO3"European Conference on Applications of Polar Dielectrics (ECAPD-4 '98), Montreux24.-27.8.98C. Medrano"Phase Conjugation Based on a Brillouin Liquid at 1.06 and 2.09 µm"Conference on Lasers and Electrooptics (CLEO/Europe'98), Glasgow, UK14.-18.9.98C. Medrano"Near Infrared Photorefraction in Reduced Rh-Doped KNbO3"Conference on Lasers and Electrooptics (CLEO/Europe'98), Glasgow, UK14.-18.9.98

* C. Medrano"Ion-Implanted KNbO3 Waveguides and Blue Lasers"The 73th Grystal Growth Seminar, National Institute for Research in Inorganic Mate-rials (NIRIM), Tsukuba, Japan16.10.98U. Meier, M. Bösch, Ch. Bosshard and P. Günter"Parametric Interactions in The Organic Salt 4-N,N-Dimethylamino-4'-N'-Methyl-Stilbazolium Tosiylate at Telecommunication Wavelengths"Conference on Lasers and Electrooptics (CLEO/Europe'98), Glasgow, UK14.-18.9.98G. Montemezzani"Stoichiometric LiTaO3 for Ultraviolet Photorefraction"European Conference on Applications of Polar Dielectrics (ECAPD-4 '98), Montreux24.-27.8.98G. Montemezzani"Influence of Material Anisotropies on Photorefractive Gain and Speed"Conference on Lasers and Electrooptics (CLEO/Europe'98), Glasgow, UK14.-18.9.98G. Montemezzani"Interband Photorefraction for High Resolution Incoherent to coherent Optical Con-verters"Conference on Lasers and Electrooptics (CLEO/Europe'98), Glasgow, UK14.-18.9.98


G. Montemezzani"Photorefractive Holographic Memory with Pulsed Read-Out"COST Meeting, Madrid, Spain27./28.11.98

* B. Müller"Recent Developments in High-Resolution Electron Diffraction: A Comparison of RHEED and LEED"Seminar über Festkörperphysik, ETH, Zürich2.4.98

* B. Müller"A Microscopic Insight into Epitaxial Growth Using Scanning Probe Techniques"Seminar in Anorganischer, Analytischer und Physikalischer Chemie, Departement für Chemie und Biochemie, Universität Bern23.4.98

* R. Ryf"Experiments and Simulations of Photorefractive Spatial Solitons in KNbO3 Crystals"Supélec, Université de Metz, Metz, F15.6.98R. Ryf"Photorefractive Ce Doped KNbO3 as Holographic Storage Material"European Conference on Applications of Polar Dielectrics (ECAPD-4 '98), Montreux24.-27.8.98R. Ryf"Photorefractive Spatial Soliton Formation in KNbO3 Crystals"Conference on Lasers and Electrooptics (CLEO/Europe'98), Glasgow, UK14.-18.9.98R. Spreiter"A Co-Crystal Containing a MerocyanineDye, Perfectly Aligned for Electro-Optics"Conference on Lasers and Electrooptics (CLEO/Europe'98), Glasgow, UK14.-18.9.98R. Spreiter, Ch. Bosshard, G. Knöpfle and P. Günter"One- and Two-Dimensionally Conjugated Tetrathynylethenes: Structure Versus Sec-ond-Order Optical Polarizabilities"Conference on Lasers and Electrooptics (CLEO/Europe'98), Glasgow, UK14.-18.9.98Y. Tao"Inter-Diffusion at the Mg/Alq3 Interfaces: an In Situ XPS Study"Materials Research Society (MRS) 1998 Spring Meeting, San Francisco, CA, USA13.-17.4.98

PhD THESES IN PHYSICS 1998


PhD THESES IN PHYSICS 1998

Brülisauer, Simon"Control of the Photorefractive Effect in KNbO3 by Ion-Implantation"ETH Zürich, Nr. 12625 (Prof. Dr. P. Günter & PD Dr. Ch. Buchal)

Follonier, Stéphane"Light-Induced Charge Transport and Refractive Index Changes in Organic Electro-OpticMaterials"ETH Zürich, Nr. 12681 (Prof. Dr. P. Günter & Prof. Dr. U.W. Suter)

Bernasconi, Pietro"Physics and Applications of Ultraviolet Light Induced Photorefractive Gratings"ETH Zürich, Nr. 12761 (Prof. Dr. P. Günter & Prof. Dr. H. Melchior)

Seuret, Christophe"Atomic Force Microscopy of Organic Nonlinear Optical Molecules at the Gas-Liquid andGas-Solid Interface"ETH Zürich, Nr. 12905 (Prof. Dr. P. Günter & Prof. Dr. R. Zenobi)

Koreferat:

Krähenbühl, Roger"Electro-Optic Space Switches in GaAsP / InP for Optical Communication"ETH Zürich, Nr. 12498 (Prof. Dr.H. Melchior & Prof. Dr. P. Günter)

Nadler, Christoph„Polarization Insensitive Arrayed Waveguide Grating Wavelength Multiplexers for Opti-cal CommunicationETH Zürich, Nr. 12957 (Prof. Dr. H. Melchior & Prof. Dr. P. Günter)

DIPLOMA THESES IN PHYSICS 1998


DIPLOMA THESES IN PHYSICS 1998

Achermann, M."Ultrafast Electron Dynamics in Silver Films and Nanoparticles"ETH Zürich, March 1998 (Prof. Dr. P. Günter)

Hübscher, Marcel"Numerische Simulation der Frequenzverdoppelung in KNbO3 Wellenleitern"ETH Zürich, Oktober 1998 (Prof. Dr. P. Günter)

Tacchella, Carmen"Photorefractive Holographic Storage System with High Read-Out Frame-Rate"ETH Zürich, Oktober 1998 (Prof. Dr. P. Günter)

Wintermantel, Marc"Characterization of Electron-Transport and Polaron-Models in Bi12SiO20"ETH Zürich, Oktober 1998 (Prof. Dr. P. Günter)

Wyss, Hans"Frequenzverdopplung von Laserdioden mit Wellenlängenstabilisierung durch externeBragg-Gitter"ETH Zürich, March 1998 (Prof. Dr. P. Günter)

Documents

Nonlinear Optics Laboratory - ETH Znlo.ethz.ch/dl/JB1998.pdf · Nonlinear Optical Properties of Molecular Crystals 12 ... Organic Crystals and Polymers 15 Fluorescence Phenomena in