Publications 1991 : Third-order materials. Processes and characterization F. Kajzar, J. Messier, J-M. Nunzi, P. Raimond Livre : Polymers for lightwave and integrated optics - Technology and applications", édité par L.A. Hornak Conjugated polymers for third-order nonlinear optics P. Raimond Rapport interne Nonlinear optical properties of poled polymers Gadret-G; Kajzar-F; Raimond-P Proceedings-of-the-SPIE --The-International-Society-for-Optical-Engineering. vol.1560; 1991; p.226-37 Second order nonlinear optical properties of doped polymer thin films are studied by optical second harmonic generation and electrooptic coefficient measurements. The studied thin films are guest-host systems and crosslinked polymers with charge transfer noncentrosymmetric amines as curing agents. The in situ second harmonic generation (SHG) measurements during poling allow one to optimise the poling process and corresponding components of chi /sup (2)/(-2 omega ; omega , omega ) tensor, depending on the fundamental harmonic electric field polarization configurations. At the same time they allow one to follow the stability of induced dipolar orientation by poling. The electrooptic measurements in thin films are used to measure r/sub 33/ coefficient even in the doped polymer absorption band and to give its real and imaginary parts. 1992 : Films organiques minces polarisés pour les applications en optique non linéaire guidée P.A. Chollet, G. Gadret, F. Kajzar, P. Raimond OPTO 92 Picosecond light-induced noncentrosymmetry in a dye solution Charra-F; Devaux-F; Nunzi-J-M; Raimond-P Physical-Review-Letters vol.68, no.16; 20 April 1992; p.2440-3 By means of a phase-conjugation experiment by nondegenerate six-wave mixing, the authors demonstrate a transient chi /sup (2)/ grating induced by a nonzero E/sup 3/ time average in a solution of noncentrosymmetric dye molecules. The origin of the induced phase-matched second-harmonic generation is found in an orientational hole-burning effect. Its lifetime, limited by molecule rotation, is 210+or-10 psec and the chi /sup (2)/ magnitude reaches 2.5*10/sup -3/ pm/V for 1 GW cm/sup -2/ pumps at 1064 nm. Spectre d'absorption à deux photons d'un polythiophène soluble N. Pfeffer, P. Raimond, J.M. Nunzi, F. Charra IQEC' 92 (Vienne, Autriche) Picosecond light-induced X(2) in a dye solution F. Charra, J.M. Nunzi, P. Raimond IQEC' 92 (Vienne, Autriche) 1993 : Electrooptic organic thin films for applications in waveguided devices Chollet-P-A; Gadret-G; Kajsar-F; Raimond-P; Zagorska-M Proceedings-of-the-SPIE--The-International-Society-for-Optical-Engineering. vol.1775; 1993; p.121-32 Different types of poled polymer thin films (guest-host, grafted and crosslinked) are studied. The optical birefringence is related to electrooptical coefficients. Those coefficients are measured in the absorption range. Their value off resonance is equal to 10 pm/V. Loss and time relaxation experiments are also presented. Light-induced second-harmonic generation in azo-dye polymers Charra-F; Kajzar-F; Nunzi-JM; Raimond-P; Idiart-E Optics-Letters vol.18, no.12; 15 June 1993; p.941-3 The permanent all-optical poling of an azo-aromatic acrylic copolymer is experimentally demonstrated by seeding preparation in a backward phase-conjugation geometry. The microscopic mechanism involves an orientational hole burning followed by orientational redistribution caused by trans-to-cis isomerization of the azo-dye chromophores. The characteristic kinetics of growth and decay of the noncentrosymmetry grating is monitored by second-harmonic generation. Determination of the two-photon absorption spectrum of a soluble polythiophene Pfeffer-N; Raimond-P; Charra-F; Nunci-J-M Chemical-Physics-Letters vol.201, no.1-4; 1 Jan. 1993; p.357-63 The two-photon absorption spectrum of the soluble conjugated polymer poly(3-octylthiophene) is measured in the visible range using the picosecond Kerr ellipsometry technique. The largest two-photon absorption feature peaks at 3.5 eV, which is 0.6 eV above the one-photon absorption peak. It has 0.27 eV half-width at half-maximum and 0.27 cm/GW magnitude in a 25 g/l solution. The average value of the associated transition dipole moment is 18 D. A weaker two-photon feature with 7 D average dipole moment which parallels the linear absorption spectrum is observed, it may be associated with some disorder-induced local non-centrosymmetry. Orientation tout optique de molécules organiques C. Fiorini, F. Charra, J.M. Nunzi, P. Raimond Lumières 93 Jussieu Effet d'isomérisation et de mémoire induits par absorption à deux photons dans les polymères fonctionnalisés F. Charra, E. Idiart, F. Kajzar, JM. Nunzi, N. Pfeffer, P. Raimond Rapport interne 1994 : Interférences bifréquences dans les matériaux organiques C. Fiorini, F. Charra; JM. Nunzi, P. Raimond EQEC' 94 New electrolytic capacitors with a polypyrrole counterelectrode Geffroy-B; Raimond-P L'Onde-Electrique vol.74, no.4; July-Aug. 1994; p.25-8 Determination of the dispersion of linear and quadratic electro-optic coefficient in thin films by electric field-induced modulated ellipsometry Chollet-P-A; Gadret-G; Kajzar-F; Raimond-P Proceedings-of-the-SPIE--The-International-Society-for-Optical-Engineering. vol.2143; 1994; p.54-67 An experimental method enabling a simultaneous determination of the linear and quadratic electroptic coefficients in thin film is described. The technique is based on the interference between electric field induced modulation of transverse electric (TE) and transfer magnetic (TM) fields propagating through a stratified medium consisting on a substrate, semitransparent electrode and the measured thin film. It allows to determine both the real and the imaginary parts of corresponding electrooptic coefficients as well as their dispersion. The use of thin film enables both electrooptic coefficients measurements in the thin film absorption band allowing nonlinear spectroscopy studies. The technique is applied to a poled functionalized polymer thin film and the results are interpreted in terms of a two level model. This allows a determination of microscopic parameters such as: excited and fundamental state permanent dipole moment difference and transition moment between fundamental and first excited state. A presence of an excited state in the bottom of absorption band is revealed Two-photon induced isomerization and memory effect in functionalized polymers Charra-F; Idiart-E; Kajzar-F; Nunzi-JM; Pfeffer-N; Raimond-P Proceedings-of-the-SPIE--The-International-Society-for-Optical-Engineering. vol.2042; 1994; p.333-46 Functionalized polymers with non-centrosymmetric groups of the diazo-dye type are good candidates as three-dimensional optical memory materials. The two-photon absorption features relevant to molecular non-centrosymmetry are discussed. A four-wave mixing experiment performed in functionalized polymers reveals the possibility of inducing a permanent grating via two-photon absorption. The effect is used for the storage of a permanent non-centrosymmetry grating. Electro-optic coefficient determination in stratified organized molecular thin films: application to poled polymers Chollet-P-A; Gadret-G; Kajzar-F; Raimond-P Thin-Solid-Films vol.242, no.1-2; 15 April 1994; p.132-8 We describe a method which enables us to determine the linear and quadratic electro-optic coefficients (real and imaginary parts) of thin stratified films even inside the absorption range. The principle is based on the interferences between the electric-field-induced modulation of the transverse electric and transverse magnetic reflected waves. Experiments performed on a poled polymer yield microscopic parameters such as the excited and fundamental state permanent moments and the difference and transition moments which are in a very good agreement with other determinations. The presence of an excited state not detected by linear spectroscopy was revealed. Optical preparation of polymers for phase-matched frequency doubling Nunzi-J-M; Charra-F; Fiorini-C; Raimond-P Molecular-Crystals-and-Liquid-Crystals vol.255; 1994; p.85-93 The nonlinear optical process which permits the optical preparation of centrosymmetric materials for frequency doubling is described in terms of an orientational hole-burning effect induced through non-zero E/sup 3/ resonant six-wave mixing. A permanent all-optical poling is achieved by seeding preparation under backward and forward geometries in an azoaromatic acrylic copolymer. The frequency doubling second order susceptibility reaches 90 pm/V, as large as using the more classical corona poling technique. This offers a new molecular engineering route to the control and optimization of phase-matched oriented microstructures for frequency conversion and also for electro-optic organic devices. 1995 : The synthesis of [U-14C phenyl] LS 840606, an agricultural fungicide G. Madegard, P. Mestre, P. Raimond, J-P. Noël Journal of Labelled Compounds and Radiopharmaceuticals XXXVI, 12 (1995), 1123-1132 Recent progress in nonlinear spectroscopy of conjugated polymers Chollet-P-A; Gadret-G; Raimond-P; Kajzar-F Nonlinear-Optics,-Principles,-Materials,-Phenomena,-and-Devices vol.14, no.1-4; 1995; p.47-60 An ellipsometric method enabling nonlinear spectroscopy studies in thin films through wave dispersed quadratic electrooptic coefficient measurements is described. The technique is based on the interference between electric field induced modulation of transverse electric (TE) and transfer magnetic (TM) fields propagating through a stratified medium consisting of a substrate, semitransparent electrode and the measured thin film. It allows to determine both the real and the imaginary parts of quadratic electrooptic coefficient as well as its dispersion. The use of thin film enables the electrooptic coefficient measurements even in its absorption band. The technique is applied to a functionalized polymer thin film and the results are interpreted within a two level model. This allows a determination of microscopic parameters such as: excited and fundamental state permanent dipole moment difference and transition moment between fundamental and first excited state. The influence of poling on quadratic electrooptic coefficient is also studied and discussed. Experimental investigation of second harmonic generation from organic waveguides deposited on diffraction gratings Coutaz-J-L; Blau-G; Roux-J-F; Reinisch-R; Kajzar-F; Raimond-P; Robin-P; Chastaing-E; Le-Barny-P Nonlinear-Optics,-Principles,-Materials,-Phenomena-and-Devices vol.10, no.1-4; 1995; p.347-56 We study second harmonic generation from organic waveguides deposited on metallic diffraction gratings. Depending on the experimental conditions, we observe maxima or minima in the second harmonic reflectivity curve when guided modes at pump frequency are excited. These results show the importance of the diffraction process and of the absorption at the second harmonic frequency. We detect also two-photon absorption induced luminescence, which is coupled into the waveguide and diffracted by the grating. Photoinduced non centrosymmetry in azo-dye polymers Fiorini-C; Charra-F; Nunzi-J-M; Raimond-P Nonlinear-Optics,-Principles,-Materials,-Phenomena-and-Devices vol.9, no.1-4; 1995; p.339-47 Quasi-permanent light-induced second-order susceptibility chi /sup (2)/ in PMMA polymer matrix (guest/host or side-chain system) doped with the azo-dye molecule DR1 is demonstrated. The method of all optical poling consists in a seeding-type process. In a first step two beams at fundamental and second harmonic frequencies are simultaneously incident on the sample. Their coherent superposition results in a selective polar excitation of the molecules: orientational hole burning. The permanent orientation is described in terms of a trans/cis photoisomerization process. Growth of the induced chi /sup (2)/ is monitored in real time using frequency-doubling of the fundamental beam inside the sample. Maximum efficiency is achieved within one hour preparation time. Free orientational losses of the induced non centrosymmetry are of the order of 10% within 15 hours. It is shown that the induced susceptibility is 90 pm/V, as high as that obtained by the more standard method of corona poling, and that a periodic poling of the sample, with the period necessary to have phase matching, is achieved. Grating-assisted phase-matched second-harmonic generation from a polymer waveguide G. Blau, E. Popov, F. Kajzar, P. Raimond, J.F. Roux, J.L. Coutaz Optics Letters 1995, 20(10), 1101-1103 1996 : All optical poling of polymers Charra-F; Fiorini-C; Kajzar-F; Nunzi-JM; Raimond-P; Chalupczak-W Photoactive Organic Materials. Science and Applications. Proceedings of the NATO Advanced Research Workshop. Kluwer Academic Publishers, Dordrecht, Netherlands; 1996; x+572 pp. p.513-26 An alternative and original technique of molecule orientation in polymeric thin films, using only laser beams (all optical poling), is described and discussed. The technique has been demonstrated first with side chain polymers PMMA-disperse red chromophores in the four wave mixing geometry, and later in the seeding geometry, using two collinear beams at omega and 2 omega frequencies. The mechanism of all optical orientation, its efficiency as well as some possible improvements are also discussed. chi /sup (2/)-holography in organic materials Fiorini-C; Charra-F; Nunzi-J-M; Kajzar-F; Raimond-P Nonlinear-Optics,-Principles,-Materials,-Phenomena,-and-Devices. vol.15, no.1-4; 1996; p.421-4 We present an original poling technique, using purely optical means and based on nonclassical holographic processes with coherent dual-frequency fields. The microscopic processes involved with azo-dye polymers are discussed and the relevant parameters leading to an efficient polarization are identified. The efficiency of photomodulation and spectral concentration of conjugated oligomers Pfeffer-N; Nunzi-J-M; Charra-F; Raimond-P; Fichou-D; Garcia-P; Taliani-C Nonlinear-Optics,-Principles,-Materials,-Phenomena,-and-Devices. vol.15, no.1-4; 1996; p.89-92 Spectral concentration describes the phenomenon of sharp transient absorption spectra first observed in alpha -conjugated oligomers of thiophene in solution. Its importance for the efficiency of photomodulation by excited state absorption is discussed. Structural conditions for achieving narrow line shapes in conjugated oligomers are identified and confirmed experimentally in several triaryl oligomers. The model of a free electron in a potential well simply accounts for the outlined characteristics of these linear conjugated molecules. A comparative table of third order pump-and-probe susceptibilities is given and discussed with respect to a relevant figure of merit. Efficient all-optical poling of an azo-dye copolymer using a low power laser Chalupczak-W; Fiorini-C; Charra-F; Nunzi-J-M; Raimond-P Optics-Communications vol.126, no.1-3; 1 May 1996; p.103-7 Efficient all-optical poling of an azo-dye copolymer (consisting of a PMMA backbone to which DR1 molecules were grafted as pendant side groups) using a low power microsecond laser is demonstrated. Conversion efficiencies are as large as those usually achieved using more standard methods such as Electric Field poling. Periodic poling of the sample is evidenced. Influence of the preparation conditions on the second-harmonic generated signal is presented. Blue light-emitting diodes with doped polymers Gautier-E; Nunzi-J-M; Sentein-C; Lorin-A; Raimond-P Synthetic-Metals vol.81, no.2-3; 15 Aug. 1996; p.197-200 Light-emitting diodes made of a single spin-coated layer of poly(9-vinylcarbazole) doped with Coumarin-515 dye have been prepared. The influence of layer thickness and dye doping ratio on blue emission and current-injection characteristics has been studied. Optical patterning of 3-dimensional spatio-tensorial micro-structures in polymers C. Fiorini, J.M. Nunzi, F. Charra, P. Raimond Optics and Photonics News "Optics in 1996" Photoinduced second harmonic generation in molecular media : from fundamentals to applications C. Fiorini, J.M. Nunzi, F. Charra, W. Chalupczak, P. Raimond ICONO'3 1997 : All-optical patterning of 3-dimensional micro-structures in azo-polymers: towards a full control of the molecular order Fiorini-C; Nunzi-J-M; Charra-F; Raimond-P Proceedings-of-the-SPIE--The-International-Society-for-Optical-Engineering. vol.2998; 1997; p.286-94 One challenging requirement for the design of devices for photonic applications is to achieve complete manipulation of molecular order. The great latitude and flexibility of optical means offers interesting prospects for material engineering using light-matter interactions. Efficient spatial modulation of polymer macroscopic properties is usually achieved using holographic recording of an interference pattern between intense light-waves. However, patterning with polarized monochromatic beams results only in axial order (e.g. vertical or horizontal alignment). For second-order optical nonlinear processes, a polar organization is mandatory (e.g. upwards or downwards orientation). We report here on a new, purely optical technique based on a non-classical holographic process with coherent mixing of dual-frequency fields. It enables an efficient and complete 3-dimensional spatio-tensorial control of polymer micro-structures. Two-photon absorption in non-centrosymmetric dyes Delysse-S; Raimond-P; Nunzi-J-M Chemical-Physics vol.219, no.2-3; 1 July 1997; p.341-51 The two-photon absorption spectra of two non-centrosymmetric dyes are studied using picosecond Kerr ellipsometry. Physico-chemical similarities of the two dyes permit comparison. A two-level model is well adapted for spectral dispersion in the Disperse Red 1 dye. A three level model accounts for the red shifted spectral dispersion observed in the dialkylamino nitrostilbene dye. Quasi-permanent all-optical encoding of noncentrosymmetry in azo-dye polymers Fiorini-C; Charra-F; Nunzi-J-M; Raimond-P Journal-of-the-Optical-Society-of-America-B-(Optical-Physics) vol.14, no.8; Aug. 1997; p.1984-2003 We present an original poling technique that uses a purely optical excitation process. The experiment consists of a seeding-type process. Writing and probing periods are alternated. Writing periods correspond to simultaneous irradiation of the sample by the coherent superposition of the 1064-nm fundamental and the 532-nm second-harmonic light of a picosecond-pulsed Nd:YAG laser. The sample is a spin-coated film of a poly(methyl methacrylate) copolymer onto which the azo-dye molecule Disperse Red 1 is grafted. We demonstrate efficient and quasi-permanent poling of the molecules with a spatial period that satisfies the phase-matching condition for second-harmonic generation. The influence of seeding parameters such as the relative phase and the relative intensities between the writing beams is studied both theoretically and experimentally. Tensorial properties and the spatial profile of the photoinduced chi /sup (2)/ are analyzed from a microscopic point of view. Dark and photostimulated relaxation processes are investigated from a chemical-physics point of view. The physical origin of the photoinduced molecular orientation process is discussed. A minimal model involving the relevant experimental parameters is developed. Numerical simulations are in agreement with the experiment. Coumarin concentration effect on PVK-based blue light-emitting diodes Gautier-Thianche-E; Sentein-C; Nunzi-J-M; Lorin-A; Denis-C; Raimond-P Synthetic-Metals vol.91, no.1-3; Dec. 1997; p.323-4 We study the influence of the doping ratio on current-voltage characteristics and electroluminescence quantum efficiency of single-layer poly(9-vinylcarbazole) (PVK)-polymer blue light-emitting diodes. Driving voltage increases monotonically with coumarin doping ratio, up to 10/sup -1/% photons/electron for a 30 wt.% doping ratio. Time-of-flight experiments give evidence of a hole-trapping effect of the coumarin. It improves the balance for injection of holes and electrons. Holes which drift through the film are expected to have a higher probability of recombination with electrons on the coumarin luminescent centers. All-optical induction of noncentrosymmetry in a transparent nonlinear polymer rod Fiorini-C; Charra-F; Raimond-P; Lorin-A; Nunzi-J-M Optics-Letters vol.22, no.24; 15 Dec. 1997; p.1846-8 What is believed to be the first evidence of an all-optical orientation of a highly transparent polymer is presented. The samples are bulk rods of poly(methyl methacrylate) grafted with paranitroaniline (PNA) obtained by use of copolymerization of methyl methacrylate (MMA) monomers mixed with grafted MMA-PNA monomers. Bulk samples were obtained after molding and polishing of the copolymer with standard techniques. Experiments show that the photoinduced second-order susceptibility chi /sup (2)/ may occur through molecular reorientation following selective polar excitation of the nonlinear chromophores by simultaneous two- and three-photon absorption on the same electronic level. Seeding and all-optical patterning of polymers Nunzi-J-M; Fiorini-C; Etile-A-C; Raimond-P; Charra-F Bragg Grating, Photosensitivity, and Poling in Glass Fibers and Waveguides: Applications and Fundamentals. Technical Digest. Postconference Edition. Opt. Soc. America, Washington, DC, USA; 1997; xv+350 pp. p.319-21 All-optical poling is based on the excitation of nonlinear molecules using dual-frequency beams. In polymers, the process permits the optical patterning of 3-dimensional spatio-tensorial micro-structures. We propose a simplified model which, based on 3 significant parameters, accounts for the essential physics relevant to the all-optical poling process and permits optimization of its efficiency. Predictions of the model are compared with the experiment. Finally, we give an insight into the all-optical tailoring of the 3-dimensional spatio-tensorial micro-optical properties of polymers. Functionalized polymers for electro-optic modulation through grating-induced resonant excitation of guided modes Blau-G; Vitrant-LG; Chollet-P-A; Raimond-P; Kajzar-F Applications of Photonic Technology 2. Communications, Sensing, Materials, and Signal Processing. Plenum Press, New York, NY, USA; 1997; xvii+927 pp. p.15-21 We were able to demonstrate an electro-optic modulator based on polymer materials using a diffraction grating. We measured a light modulation of 40% with a change in the applied voltage of 60 V and an electro-optic coefficient of 4.3 pm/V. This modulator was based on paranitroaniline grafted on a PMMA matrix as the nonlinear waveguiding material. 1998 : Effect of coumarin on blue light-emitting diodes based on carbazol polymers Gautier-Thianche-E; Sentein-C; Lorin-A; Denis-C; Raimond-P; Nunzi-J-M Journal-of-Applied-Physics vol.83, no.8; 15 April 1998; p.4236-41 Light-emitting diodes made of a single spin-coated layer of poly(9-vinylcarbazole) have been doped with coumarin-515 dye and the effect of the dye concentration on emission and electrical characteristics has been studied. Two different regimes have been identified. For low concentrations, the apparent hole injection barrier rises, holes are trapped, and mobility decreases. External quantum efficiency increases with concentration. At concentrations larger than 10 wt% coumarin aggregates, photoluminescence yield drops and electroluminescence yield increases up to 0.1% photons per electron. As a conclusion, using coumarin dye in a single-layer diode improves electron-hole injection and recombination balance more than using an additional hole-blocking layer. Optical manipulation of molecules for non-centrosymmetric optical device fabrication Fiorini-C; Prudhomme-N; Etile-A-C; Lefin-P; Raimond-P; Nunzi-J-M Proceedings-of-the-SPIE--The-International-Society-for-Optical-Engineering. vol.3474; 1998; p.96-102 A challenging issue to design devices for photonic applications is to achieve a complete manipulation of the molecular order. Azo-dye aromatic polymers have been shown to offer interesting prospects for material engineering using light matter interactions. Dual-frequency irradiation using appropriate combinations of circular beams polarizations are demonstrated to enable full control of the molecular polar rotation. More recent results on photoinduced surface-relief gratings have also opened the way of molecular translation control using optical fields. Understanding of the relevant parameters of molecular translation processes is a key issue for optimization of such optomechanical effect: a simple model accounting qualitatively for the essential features of photoinduced surface-relief gratings is presented. It illustrates the application of optically powered molecular motors. Concentration effects on charge transport in dye doped polymer light emitting diodes Nunzi-J-M; Gautier-Thianche-A; Lorin-A; Denis-C; Raimond-P; Sentein-C Proceedings-of-the-SPIE--The-International-Society-for-Optical-Engineering. vol.3281; 1998; p.302-9 Light emitting diodes made of a single spin-coated layer of poly(9-vinylcarbazole) doped with coumarin-515 dye have been studied. The influence of dye concentration on emission and electrical characteristics is evidenced. Two different regimes are identified. At low concentrations, apparent hole injection barrier raises, holes are trapped and mobility decreases. External quantum efficiency increases with concentration. At concentrations larger than 10%wt, coumarin aggregates, photoluminescence yield drops and electroluminescence yield increases up to 0.1%-photons per electron. We show that using coumarin dye in a single-layer diode improves electron-hole injection and recombination balance more than using an additional hole-blocking layer. Modulation of second harmonic generation in photochromic materials by the application of electric fields and low intensity light Large-MCJ; Kajzar-F; Raimond-P Applied-Physics-Letters vol.73, no.25; 21 Dec. 1998; p.3635-7 The simultaneous application of low intensity optical and static electric fields to photoisomerizable electro-optic materials is shown to allow manipulation of the refractive index. A dc electric field was applied to the sample by means of a corona poling mechanism, which was illuminated within the absorption band using a low power laser. The application of the optical field caused a reduction in polar order in the material, with a corresponding change in the refractive index. The change of polar order was monitored by optical second harmonic generation. For typical experimental values, the variation in refractive index was calculated to be about 1%, which is sufficient to change waveguiding conditions. Electroded samples also showed the effect. Dye Concentration study in PVK based light emitting diodes E. Gautier-Thianche, C. Sentein, J.M. Nunzi, A. Lorin, C. Denis, P. Raimond J. Chim. Phys 1998, 95, 1343-1346 All-optical manipulation of azo-dye molecules C. Fiorini, A.C. Etilé, P. Lefin, N. Prudhomme, P. Raimond, J.M. Nunzi Meeting ACS Boston, août 1998 1999 : Dye sensitized polythiophene solar cells Sicot-L; Fiorini-C; Lorin-A; Nunzi-J-M; Raimond-P; Sentein-C Synthetic-Metals vol.102, no.1-3; June 1999; p.991-2 The photovoltaic characteristics of spin-coated thin films of polythiophene sensitized with two different dyes have been measured. We reported on the influence of the affinity between the polymer and the dye. By changing the dye, the power conversion efficiency is multiplied by 20 to reach 0.01% under a white light of 50 mW cm/sup -2/. Poling induced improvement of organic polymer device efficiency Sentein-C; Fiorini-C; Lorin-A; Nunzi-JM; Raimond-P; Sicot-L Synthetic-Metals vol.102, no.1-3; June 1999; p.989-90 In order to build single polymer film photovoltaic cells, we realize an equivalent distributed PN junction in a polymeric monolayer. Orientation is performed through DC-field ordering of the polar molecules contained in the polymer. We describe experimentally an increase by one order of magnitude for the efficiency of our photovoltaic cell by polar ordering of the molecules. Near-field electroluminescence probe of polymer light-emitting diodes Charra-F; Bouchel-S; Plessis-O; Nunzi-J-M; Raimond-P; Denis-C; Gautier-Thianche-E Optical-Materials vol.12, no.2-3; June 1999; p.249-53 We used the luminescence induced in a polymer light-emitting diode (LED) by the biased tip of a scanning tunneling microscope (STM) to study under air the local factors affecting polymer electroluminescence. We have observed the light emission induced by the scanned platinum:iridium tip of an STM in 100 nm thick PVK films doped with a Coumarin dye, spin-coated on a transparent ITO electrode. The light is detected through indium tin oxide (ITO) electrode by photon-counting and photon-maps are acquired simultaneously with STM images, in the Z (i.e. constant-current) mode. Two emission regimes are evidenced: the first emission was observed when increasing tip bias, it occurs through discharges appearing as emission segments along the scan direction in photon maps. At higher voltages a more regular emission regime is observed. These two regimes appear at different locations, that can be correlated to the characteristics of the surface profile measured simultaneously by STM. Light control of molecular order and applications Combellas-C; Kajzar-F; Large-MC; Matheya-G; Petit-MA; Raimond-P; Thiebault-A Proceedings-of-the-SPIE--The-International-Society-for-Optical-Engineering. vol.3796; 1999; p.288-98 For a large class of practical applications, based on second order nonlinear optical effects, one needs not only noncentrosymmetric molecules, like charge transfer molecules, but also their assemblage to macroscopically noncentrosymmetric materials. The targeted applications include: frequency conversion through its doubling or parametric interaction, electro-optic modulation, photorefractive effect, generation of ultra short electrical pulses through the linear rectification effect, otherwise nonachievable with electronic circuitry. Composite polymeric materials have emerged to be interesting materials for these kind of applications. They are inexpensive and can be easily processed into good optical quality thin films. The active chromophore orientation is obtained by static field or all optical poling techniques. The authors have studied the photoassisted poling of isotropic polymers doped or grafted with biaryl chromophores for which no double bond with possible cis-trans isomerization could be advocated. Orientation induced molecular rectification in polymer films: improving organic-semiconductor device efficiency Sentein-C; Fiorini-C; Lorin-A; Raimond-P; Sicot-L; Nunzi-J-M Proceedings-of-the-SPIE--The-International-Society-for-Optical-Engineering. vol.3623; 1999; p.80-9 In the field of organic semiconductor devices, such as electroluminescent diodes or photovoltaic cells, a rectifying junction is mandatory to improve their efficiency. In order to build single polymer film photovoltaic cells, we realize an equivalent distributed p-n junction in a polymeric monolayer. For this purpose, we propose an inter-disciplinary principle derived from the application of nonlinear optical techniques to the technology of polymer semiconductors. We give experimental evidence that molecular rectification induced in an oriented amorphous polymer bearing polar chromophores improves efficiency of polymeric semiconductor device such as photovoltaic cells. Orientation is performed through DC-field ordering of the polar molecules contained in the polymer. Second harmonic generation is used as a probe of the molecular order and permits optimization of the sample orientation parameters, i.e., orientation-field, sample temperature, poling duration and cooling conditions to achieve the largest stable orientation. Additionally, to establish a model which describes charge injection and transport through such device, we propose to use Solid Electric Field Induced Second Harmonic Generation (SEFISHG) as an in situ internal field measurement technique. In this way, before orientation of the molecules, SEFISHG provides the electron work function difference between the two electrode materials, and after orientation, SEFISHG permits the measure of the internal field stored in the structure. Modal dispersion phase-matched frequency doubling in composite planar waveguide using ion-exchanged glass and optically nonlinear poled polymer Khalil-MA; Vitrant-G; Raimond-P; Chollet-PA; Kajzar-F Optics-Communications vol.170, no.4-6; 1 Nov. 1999; p.281-4 We report on the fabrication and characterization of composite planar waveguides for frequency doubling. Modal dispersion phase matching is obtained for TM/sub 0/ fundamental and (TM/sub 1/, TM/sub 2/) harmonic wavelength. The experimental conversion efficiency was eta =0.45% with an SH wavelength of 0.516 mu m for TM/sub 0//sup omega /-TM/sub 2//sup 2 omega / mode conversion. The phase-matching condition can be fulfilled by adjusting the diffusion time of ion-exchange and the thickness of the polymer layer. Polythiophenes functionalized with Disperse Red 1 chromophore M. Zagorska, I. Kulszewicz-Bajer, A. Pron, P. Raimond, F. Kajzar, A-J. Attias Synthetic Metals 102 (1999), 1141-1142 2000 : Azo chromophore functionalized polythiophenes. Synthesis and nonlinear optical properties Zagorska-M; Gase-T; Kajzar-F; Raimond-P; Kulszewicz-Bajer-I; Prona-A Molecular-Crystals-and-Liquid-Crystals vol.354; 2000; p.1081-9 New polythiophene derivatives containing an azo dye side group were prepared via copolymerization of 3-alkylthiophenes and disperse red 1 substituted thiophenes. The presence of chromophore groups in the polymers was confirmed by NMR and FTIR spectroscopies as well as by elemental analysis. The obtained soluble polymers were processed into thin films by the spin coating technique and their nonlinear optical properties were studied by the optical second harmonic generation technique and by the quadratic electro-optic Kerr effect. The second order nonlinear optical coefficients are: d/sub sp/=6.8 pm/V and d/sub pp/=28.3 pm/V at 1064 nm fundamental wavelength. The quadratic electro-optic Kerr coefficient is about three times larger for the functionalized polymer than for the unfunctionalized one. Molecular migration mechanism for laser induced surface relief grating formation Fiorini-C; Prudhomme-N; de-Veyrac-G; Maurin-I; Raimond-P; Nunzi-J-M Synthetic-Metals vol.115, no.1-3; 1 Nov. 2000; p.121-5 Direct and reversible holographic recording of surface-relief gratings in azo-dye polymers was recently evidenced using atomic force microscopy. Irradiation with an interference pattern of polarized laser beams was observed to lead to substantial mass-transport. In typical experiments, the wavelength of the laser was chosen to be near the absorption of the chromophores. The surface gratings have a negative amplitude which can be as large as twice the polymer film thickness. The origin of such photo-driven mass transport is still unclear. We provide here experimental evidence of a migration of the chromophores from high to low intensity regions. It indicates that, in such doped or grafted guest-host systems, polymer chain migration is a result of the guest chromophores photoinduced movements. This is in good agreement with our recently developed model of azo-dye photoinduced translation diffusion. Optical parametric amplification in composite polymer/ion exchanged planar waveguide Khalil-MA; Vitrant-G; Raimond-P; Chollet-PA; Kajzar-F Applied-Physics-Letters vol.77, no.23; 4 Dec. 2000; p.3713-15 A simple hybrid polymer/ion exchanged planar optical waveguiding structure has been fabricated which allows us to realize phase matching between different guided modes without any corrugation or modulation of the structure. A nonlinear polymer is deposited on top of glass substrate with a waveguide realized by the ion-exchange technique. Efficient optical parametric amplification is demonstrated for a pump at 532 nm and a signal at 814 nm. A 1 dB internal optical gain is achieved after propagation on 5 mm, with a pump power of 15 kW/mm. Comparative study of nonlinear-optical polymers for guided-wave second-harmonic generation at telecommunication wavelengths Pliska-T; Wook-Rae-Cho; Meier-J; Le-Duff-A-C; Ricci-V; Otomo-A; Canva-M; Stegeman-GL; Raimond-P; Kujzar-F Journal-of-the-Optical-Society-of-America-B-(Optical-Physics) vol.17, no.9; Sept. 2000; p.1554-64 We report on the linear and nonlinear-optical properties of 4-dimethylamino-4'-nitrostilbene (DANS), 4-diethylamino-1-nitrobenzyl (DANB), and 4-[N-ethyl-N-(2-hydroxyethyl)]amino-4'-nitroazobenzene) (Disperse Red 1;DR1) side chain polymers whose second-harmonic generation at the telecommunication wavelength of 1.55 mu m was investigated. Measured ultraviolet-visible-near-infrared spectra were analyzed with an inhomogeneously broadened line-shape model, in particular, in the long-wavelength tail of the electronic transitions, which determines the absorption loss at the second-harmonic wavelength. The nonlinear-optical coefficients were measured at different poling temperatures and poling fields by the Maker fringe technique. On the basis of the measured material parameters we calculated the normalized conversion efficiencies for guided-wave second-harmonic generation at 1.55 mu m. The DR1 polymer exhibited the best nonlinearity-absorption trade-off, with a calculated normalized conversion efficiency of several hundred percent per watt, whereas the figures of merit for DANS and DANB are lower and comparable with each other. Symmetry of the all-optical orientation dynamics of an octupolar azo-dye salt Fiorini-C; Nunzi-J-M; Raimond-P; Branger-C; Lequan-M; Lequan-R-M Synthetic-Metals vol.115, no.1-3; 1 Nov. 2000; p.127-31 Optical patterning of the molecular order in dye doped polymers offers interesting and quite rich prospects. The generalization of the principles of holography to the recording of an interference pattern between mutually coherent fields of different frequencies, such as fundamental and second harmonic has been demonstrated to enable a full 3D polar control of the molecules. Together with exhibiting fairly large second order nonlinearities, donor-acceptor substituted azobenzene type materials were demonstrated to be very efficiently ordered materials under all-optical poling conditions. Photoinduced cis/trans isomerization results indeed in a free rotation of the molecule leading to an efficient molecular redistribution following the molecules selective polar excitation. In order to investigate the possible influence of the poling process on the resulting symmetry of the optically induced macroscopic susceptibility, a tetrahedral organotin azobenzene derivative was synthetized. All-optical orientation dynamics and symmetry of the second-order susceptibility chi /sup (2)/ induced in PMMA rods doped with such a T/sub d/ space-group molecule are reported and discussed. The molecular relaxation dynamics is shown to have a determining influence on the symmetry resulting from the all-optical poling process. Improvement of the photovoltaic properties of polythiophene-based cells Sicot-L; Fiorini-C; Lorin-A; Raimond-P; Sentein-C; Nunzi-J-M Solar-Energy-Materials-and-Solar-Cells. vol.63, no.1; 15 June 2000; p.49-60 The photovoltaic properties of organic cells based on a polythiophene film have been studied. An external power efficiency of 10/sup -4/% has been obtained in the pristine polymer diode. In order to improve this result, three complementary routes have been investigated. Optical sensitization of the polythiophene with a dye of the indane group leads to a 75 increase in power efficiency. A hybrid molecular/polymeric p-n type junction instead of the original Schottky type provides a 0.15% efficiency. Molecular rectification in oriented polymers incorporating diode-like chromophores increases the PV efficiency by a factor of 40. Evidence for photoinduced molecular migration mediated surface-relief grating formation in azo-dye polymers Nunzi-J-M; Fiorini-C; De-Veyrac-G; Raimond-P; Maurin-I Molecular-Crystals-and-Liquid-Crystals vol.353; 2000; p.427-34 Direct and reversible holographic recording of surface-relief gratings in azo-dye polymers was recently evidenced using atomic force microscopy. Irradiation with an interference pattern between polarized laser beams was observed to lead to quantitative mass-transport. The surface gratings have a negative amplitude that can be twice as large as the polymer film thickness. The origin of such photo-driven mass transport is still controversial. We provide here experimental evidence that the chromophores migrate from the high to low the intensity regions. Chain migration in such doped or grafted guest-host polymer systems results from the photoinduced migration of the guest chromophores. Periodically structured polymers for tunable laser applications Rocha-L; Dumrcher-V; Fiorini-C; Denis-C; Raimond-P; Nunzi-J-M Conference Digest. 2000 Conference on Lasers and Electro-Optics Europe (Cat. No.00TH8505). IEEE, Piscataway, NJ, USA; 2000; xii+394 pp. 1 pp. Summary form only. Controlling the light emission properties of materials is a challenging issue. By analogy with semiconductor in which a potential periodicity allows modifications of electron propagation, periodic modulations of a material dielectric constant enables control of light propagation. We report here the development of a compact organic laser based on a distributed feedback scheme (DFB) achieved by permanent modulation of the polymer refractive index. 2001 : Laser emission in periodically modulated polymer films Rocha-L; Dumarcher-V; Denis-C; Raimond-P; Fiorini-C; Nunzi-J-M Journal-of-Applied-Physics vol.89, no.5; 1 March 2001; p.3067-9 We report on the realization of a compact distributed feedback laser using luminescent polymer films where the optical feedback is provided by Bragg diffraction on an index grating. Permanent modulation of the polymer refractive index is achieved using an original technique for photoinduced patterning of surface relief grating, using laser-controlled mass-transport in azoaromatic polymers. We describe the fabrication of such surface gratings and show the laser emission properties resulting from a transversal one-photon pumping of the sinusoidally modulated polymer films upcovered with a luminescent-dye-doped film. Control of the laser wavelength by the grating pitch is evidenced. Photovoltaic properties of Schottky and p-n type solar cells based on polythiophene Sicot-L; Geffroy-B; Lorin-A; Raimond-P; Sentein-C; Nunzi-JM Journal-of-Applied-Physics vol.90, no.2; 15 July 2001; p.1047-54 The electrical and photovoltaic properties of organic Schottky and p-n type cells have been studied. Schottky devices are based on a spin-coated film of poly(3-butylthiophene) blend with the dye 1,3-bis-(dicyanomethylidene)-2- (4-dibutylaminobenzylidene)in dane which is sandwiched between indium tin oxide (ITO) and gold electrodes. A depletion zone of 9.5 nm thick has been determined on a 220-nm-thick film. The conversion efficiency is equal to 0.01% under 100 mW cm/sup -2/ white light illumination. Effects of dye loading, film thickness, and light intensity are described. A model based on simple assumptions is used to fit the photoaction spectra. By evaporation under vacuum of a layer of N,N'-dimethyl-3,4,9,10-perylenetetracarboxylic diimide between the ITO and the polymer film, we have fabricated hybrid polymer-molecular p-n type photovoltaic cells. The role of this molecule in the photogeneration has been studied. A constant power conversion efficiency of 0.15% has been measured under white light illumination between 0.2 and 200 mW cm/sup-2/. 2002 : Photo-induced microstructured polymers for the optimisation and control of organic devices emission properties ROCHA Licinio, DUMARCHER Vincent, MALCOR Eymeric, FIORINI Céline, DENIS Christine, RAIMOND Paul, GEFFROY Bernard, NUNZI Jean-Michel Synthetic Metals Volume 127, Issues 1-3, 26 March 2002, Pages 75-79 Congrès Novel Organic Material and Technological Advances for Photonics. E-MRS Symposium R, Strasbourg , FRANCE (05/06/2001) Patterning and microstructuring of functional polymers is a key process in order to control the emission properties of polymer thin films towards the design and realisation of devices such as electroluminescent diodes (OLEDs) or organic lasers. We present an original method for the realisation of periodic structures in the visible wavelength region using laser controlled molecular motion. The optical pumping of an azo-dye aromatic polymer film was indeed shown to allow efficient mass-transport in conjunction with the interference pattern. We have implemented a compact organic laser using transversal one photon pumping of a sinusoidaly modulated surface of such periodically structured films upcovered with a luminescent dye. Efficient laser emission was observed over the whole emission spectrum of the luminescent dye following control of the surface relief grating periodicity. Patterning of gratings with periodicities going down to 200 nm has been recently achieved. Interestingly, surface relief gratings also appear to be a good way to optimise OLED emission properties. 2007 : Spontaneous photoinduced patterning of azo-dye polymer films : the factsChristophe Hubert, Céline Fiorini-Debuisschert, Licinio Rocha, Paul Raimond, Jean-Michel Nunzi J. Opt. Soc. Am. B Vol. 24, No. 8/August 2007/1839 We describe the spontaneous photoinduced patterning of azo-dye polymer films. We have observed that the illumination of an azo-dye polymer film by a uniform single laser beam with normal incidence leads to a selfstructurization process that results in the formation of well-ordered submicrometer-sized structures whose organization depends on the light polarization direction. A modulation depth as high as 100 nm can be achieved. The influence of several experimental parameters on the structure formation is studied. Results are discussed and confronted to different models and phenomena already investigated in the literature. A physical origin to this peculiar photopatterning process is proposed. Evidence of the improvement of photovoltaic efficiency by polar molecule orientation in a new semiconducting polymer Carole Sentein, Licinio Rocha, Aleksandra Apostoluk, Paul Raimond, Iris Duyssens, Ineke Van Severen, Thomas Cleij, Laurence Lutsen, Dirk Vanderzande, Vaidotas Kazukauskas, Mindaugas Pranaitis, Valius Cyras Solar Energy Materials and Solar Cells, Volume 91, Issue 19, 23 November 2007, Pages 1816-1824 2008 : Investigation of the patterning efficiency in a new azo-dye copolymer under UV irradiation towards photonic applications ROCHA Licinio, FIORINI Céline, MATCZYSZYN Katarzyna, RAIMOND Paul, NUNZI Jean-Michel Congrès Nanophotonics II (7-9 April 2008, Strasbourg, France) Proceedings of SPIE, the International Society for Optical Engineering ISSN 0277-786X CODEN PSISDG 2009 : Growth of thin polymer films containing side-chain azo-dye analyzed by atomic force microscopy Hubert Gojzewski, Asta Richter, Danuta Wróbel, Aleksandra Apostoluk, Przemyslaw Siejaka, Paul Raimond Surface Science Volume 603, Issue 1, 1 January 2009, Pages 237-246

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