Stress birefringence patterning in photopolymer induced by structured illumination

4 pagesInternational audienceWe report on the stress birefringence distribution induced by the photopatterning of a multifunctional crosslinkable acrylate monomer sensitized in the visible range. The patterning of this material, prepared in a glass cell of a few tens of microns thickness, is obtained through illumination in a two steps process. The first step is performed using an illumination pattern with a high contrast and a low spatial frequency. The second one is a uniform illumination. The discrepancies in the shrinkage experimented by the material leads to the apparition of patterned stress birefringence revealed through polarimetry and diffraction measurements

Near infrared two-photon self-confinement in photopolymers for light induced self-written waveguides fabrication

We present the fabrication of single mode light induced self-written waveguides using two-photon absorption in photopolymers. The measurements are compared to the finite element method simulation of the propagation and demonstrate that two-photon process leads to the confinement of light

Synthesis, photophysics and nonlinear optical properties of stilbenoid pyrimidine-based dyes bearing methylenepyran donor groups.

International audienceThe nonlinear properties and the photophysical behavior of two π-conjugated chromophores that incorporate an electron-deficient pyrimidine core (A) and γ-methylenepyrans as terminal donor (D) groups have been thoroughly investigated. Both dipolar and quadrupolar branching strategies are explored and rationalized on the basis of the Frenkel exciton model. Even though a cooperative effect is clearly observed if the dimensionality is increased, the nonlinear optical (NLO) response of this series is moderate if one considers the nature of the D/A couple and the size of the chromophores (as measured by the number of π electrons). This effect was attributed to a disruption in the electronic conjugation within the dyes' scaffold for which the geometry deviates from planarity owing to a noticeable twisting of the pyranylidene end-groups. This latter structural parameter also has a strong influence on the excited-state dynamics, which leads to a very efficient fluorescence quenching

Light induced self-written waveguides interactions in photopolymer media

We present experimental and theoretical study of the interaction of Light Induced Self-Written (LISW) waveguides in photopolymers. We show that the diffusion of the monomer controls the refractive index distribution. Consequently it influences the interaction between the LISW channels allowing the observation of anti-crossing behavior or the propagation of an array of non interacting LISW waveguides

Polarization state studies in second harmonic generation signals to trace atherosclerosis lesions

We have performed multi-photon image reconstructions as well as polarization state analyses inside an artery wall affected by atherosclerosis to investigate the changes in collagen structure. Mice, either healthy or affected by spontaneous atherosclerosis, have been used for this purpose. A two-photon imaging system has been used to investigate atherosclerotic lesions in the ascending aorta of mice. Second harmonic imaging has been performed alternatively on healthy samples and on affected region. The reconstructed images show that the spatial distribution of the collagen network seems disorganized by the disease. The polarization state studies reveal however that the apparent disorganization of the collagen is related to its spatially diffuse distribution and that the internal structure of the collagen fibers is not affected by the disease. In addition, a theoretical simulation of the second harmonic polarization states shows that they are consistent with the known 3D structure of the collagen network

Sum-frequency generation in sol-gel material doped with binaphthol

A sum-frequency imaging system is used to investigate optical activity in a sol-gel material doped with the chiral molecule binaphthol. We show that this material can be optically structured to embed information that can be retrieved by sum-frequency

Solvent-free fluidic organic dye lasers

We report on the demonstration of liquid organic dye lasers based on 9-(2-ethylhexyl)carbazole (EHCz), so-called liquid carbazole, doped with green-and red-emitting laser dyes. Both waveguide and Fabry-Perot type microcavity fluidic organic dye lasers were prepared by capillary action under solvent-free conditions. Cascade Forster-type energy transfer processes from liquid carbazole to laser dyes were employed to achieve color-variable amplified spontaneous emission and lasing. Overall, this study provides the first step towards the development of solvent-free fluidic organic semiconducting lasers and demonstrates a new kind of optoelectronic applications for liquid organic semiconductors

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Dynamique de couplage et formation de structures dans les lasers à absorbant saturable

Le couplage d'oscillateurs non lineaires et la formation de structures spatiales sont deux domaines particulierement importants de l'etude de la dynamique non lineaire des systemes optiques. C'est dans ce contexte que s'inscrit ce travail de these. La premiere partie est consacree a l'etude experimentale du couplage de deux lasers co 2 monomode partageant un meme absorbant saturable. La forte non linearite de l'absorbant et le caractere impulsionnel de certains regimes du systeme donnent naissance a une dynamique de couplage localise dans le temps. Les phenomenes de synchronisation des impulsions de chaque laser ainsi que la perturbation des regimes d'un laser par les impulsions de l'autre sont analyses. En ce qui concerne les regimes non impulsionnels, le couplage non localise intervient dans la synchronisation de regimes quasiperiodiques et chaotiques.L'extension au cas bimode transverse se traduit par l'apparition d'une dynamique d'antiphase. Les simulations numeriques effectuees reproduisent les regimes dynamiques observes et mettent en evidence de nouvelles bifurcations introduites par le couplage. La deuxieme partie presente une etude theorique et numerique du comportement spatio-temporel d'un laser a absorbant saturable. L'analyse de stabilite lineaire de la solution nulle montre que l'absorbant controle la longueur d'onde critique des modes qui se destabilisent au seuil. La creation ou l'inhibition des structures est analysee suivant l'ecart en frequence de l'absorbant. Une analyse faiblement non lineaire au seuil montre que le systeme est decrit par une equation de swift-hohenberg. Les simulations numeriques mettent en evidence des solutions a ondes progressives, a ondes stationnaires et en echiquier. Enfin, les simulations sur le systeme complet permettent de verifier la validite du modele de swift-hohenberg tout en donnant aussi des regimes plus fortement non lineaires, comme des impulsions 2d progressives.LILLE1-BU (590092102) / SudocSudocFranceF