COVALENT GRAFTING OF OPTICALLY-ACTIVE MOLECULES ON SILICA-GELS

Active organic molecules are grafted on the xerogel silica matrix by u sing functionalized alkoxides f-R' -Si(OEt)(3), where f is a chemical function and R' is ara alkyl spacer to limit the degrees of freedom of the molecules. Organic-inorganic hybrid films are prepared in which o ptically nonlinear DR1 chromophores are covalently bound to the Silica network. These films exhibit a large and stable second-order nonlinea r coefficient from second harmonic generation experiments. Protoporphy rin molecules are attached double covalently to the xerogel matrix via flexible organic spacers. Persistent spectral holes are still burnt w ith moderate fluency at 120 K.