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Pierre-Alexandre Blanche, Ph.D. Contact
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Photoinduced Birefringence Abstract There are several ways to record optical information into media, surface relief and complex index change (refractive index or absorption) are among the best known. But light polarization also carries information and can be used for data storage. There exist materials that are sensitive to light polarization like azo molecules. Tanks to their double chemical bond between two nitrogen atoms, those organic molecules have cis or trans conformational isomers. The more stable trans form can be converted into cis when absorbing a photon. Multiple trans to cis photoinduced isomerization followed by cis to trans thermal relaxation orient the molecules perpendicular to the light polarization vector. Since those molecule are also anisotropic, the bulk material becomes birefringent. Studying such a material is important to understand the chemical bonds between molecules (free volume, cooperative and conformational stiffness) in polymer but also as a technological point of view since this can lead to a new class of self developing and reversible holographic recording media. As an example, polarization holography can be done in those materials making interfere orthogonally polarized wave fronts (linear or circular). Publications
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