Wavelength dependence of 4-dimethylamino-4 \u27-nitrostilbene polymer thin film photodegradation

The polymeric electro-optical stilbene material, 4-dimethylamino-4 \u27-nitrostilbene (DANS), was illuminated at wavelengths ranging from the visible to near-infrared in order to quantify its photodegradation processes. Photodegradation due to one-photon and two-photon absorption was studied. The quantum efficiency of the chromophore degradation is found to be strongly wavelength and absorption mechanism dependent. This suggests that, in different regions of the spectrum, different excited states or different mechanisms are involved in the degradation process. In the near-infrared spectral region, operation lifetimes of electro-optic devices made from this chromophore are expected to be around only few hundreds hours, dramatically shorter than it was previously believed

Mechanisms of remanent optical alignment of dyes in a gel matrix

International audienceWe present the mechanisms of a remanent alignment of polarizable molecules dispersed in a solid silica gel matrix, when submitted to powerful, femtosecond, linearly polarized, optical pulses emitted from a dye laser. This alignment can be related to third-order nonlinearities of the dopants through an orientational optical Kerr effect. Its remanence results from the strong interactions the dopants share with their host matrix, particularly through hydrogen bonds. We expose here the detailed mechanism of this phenomenon, considering that such a rotation of large chromophores may not be compatible at first sight with subpicosecond pulse durations. Through several experiments, we show that this apparent contradiction is solved once analyzed, by the structure of the excitation pulses, which cannot be simply described as ''femtosecond pulses'', but consist of two temporal components--a femtosecond one and a nanosecond one--playing different but essential roles in the proces

Temperature dependence of second-order nonlinear relaxation of a poled chromophore doped sol-gel material

International audienceSecond-order optical nonlinearity relaxations of hybrid inorganic/organic sol-gel films doped with poled Disperse Red 1 chromophores were measured by second harmonic generation at several temperatures. The decay curves were fitted to biexponentials and Ko¨hlrausch, Williams, and Watts ~KWW! stretched exponentials. It can be concluded that the KWW model well describes chromophore thermal reorientation in hybrid sol-gel materials, as is known for all-organic polymers. Using the Arrhenius law, the activation energy of the reorientation process has been determined to be about 50 or 70 kcal mol21. A stability of roughly a decade has been extrapolated at room temperature. Another experiment at room temperature gave an estimation of the stability that was found to be in qualitative agreement. It is shown that poled chromophore-doped sol-gel materials have the potential to be stable enough for applications in telecommunication device

Two Photon Absorption in Chromophore Doped Solid Matrices

Over the past decades organic materials have shown an important potential for applications in the field of nonlinear optics. Two-photon absorbing materials can be optically addressed in three dimensions of space, which make them unique for many new applications, including 3D displays, optical memories, bio-sensors, etc. Fluorescent organic chromophores can be synthesized with structures especially optimized for this nonlinear optical property. Yet, for some applications, they have to be incorporated in solid state matrices. We especially investigate hybrid organic/inorganic doped matrices synthesized by solgel process. However , the linear transmission for such molecules is often significantly less than unity. Two-photon absorption (TPA) offers the advantage of very high transmission at low incident intensity, while being sensitive to high intensity laser pulses. Our aim is to record a 3D layered pattern of optical memory inside the sample by the use of the picosecond pulsed ND3+:YAG laser at 532nm, or 1064nm

Toward millions of laser pulses using pyrromethene and perylene doped xerogels

International audienceSignificant improvements have been obtained for solid-state dye lasers with doped xerogels. By using longitudinal pumping with a frequency-doubled Q-switched Nd: YAG laser, we obtained as much as 86% slope efficiency and 5 3 105 pulses lifetime. Furthermore, newly prepared deoxygenated samples exhibited even greater lifetime

Perylene and pyrromethene doped xerogels for solid state pulsed laser

International audienceHydrophobic photostable dye molecules such as perylenes or pyrromethenes were trapped in xerogel matrices. Using these new materials as solid-state dye lasers, we have demonstrated efficient laser operation. Slope efficiencies of up to 30% were obtained in the millijoule output-energy range. Tunabilities of up to 60 nm were observed, and more than 150,000 pulses were emitted by the same spot of a given sample when the laser was pumped at millijoule energy level

Reverse saturable absorption in solid xerogel matrices

International audienceAluminophthalocyanine (APC) and fullerene carbon 60 (C,) have been studied encaged in different silica matrices. The reverse saturable absorption properties of these doped xerogels have been compared to those of reference solutions of APC and C&,. We show that reverse saturable absorber molecules retain their properties even when they are enclosed in the pores of a solid xerogel matri

Stable photorefractive memory effect in sol-gel materials

International audienceWe report on the synthesis and the optical characterization of a photorefractive sol-gel material which contains nonlinear azo chromophore and carbazole charge transporting molecules. Both of these functional groups are covalently attached to the silica based backbone. Thin sol-gel films exhibit stable optically nonlinear properties: the electro-optic coefficient r13 measured at 633 nm is found to be 17 pm/V one day after corona poling and 15 pm/V after three weeks and over a period of several months. Photorefractivity is demonstrated by two beam coupling experiments without external applied electric field. Sol-gel films present a stable photorefractive memory effect with a net internal gain of 200 cm-

Local and external factors affecting the photodegradation of 4N,N \u27-dimethylamino-4 \u27 nitrostilbene polymer films

The photodegradation of the electro-optic chromophore 4N,N\u27-dimethylamino-4\u27nitrostilbene was investigated as a function of wavelength, temperature, local atmosphere, and local molecular environment, i.e., attached as a side chain to a polymer or dissolved as a guest in a host polymer

DR1 doped sol-gel planar waveguides for nonlinear devices operating at telecommunications wavelengths

International audienceWe report on linear and nonlinear optical properties of Disperse Red 1-doped solgel waveguides. The refractive-index and optical-propagation losses of the guiding layer were measured between 0.756 mm and 1.64 mm. The spectral broadening of the chromophore charge-transfer transition in the visible is modeled with a Voigt-profile function. In the telecommunications window the attenuation is dominated by the overtones of the O--H bonds vibration bands. The nonlinear optical coefficients were measured at different poling strengths with the Maker-fringe method. The nonlinear coefficient d33 was found to be 4.5 pm V21 at 1.58 mm for a poling field of 60 Vmm21