A NEW CLASS OF ORGANIC-INORGANIC SOL-GEL MATERIALS FOR 2ND-ORDER NONLINEAR OPTICS

A new class of organic/inorganic sol-gel second-order nonlinear optica l (NLO) materials based on the prepolymer of hexakis(methoxymethyl)mel amine (HMM) and an alkoxysilane dye (ASD) has been investigated. The N LO-active alkoxysilane dye containing nitroazobenzene was incorporated into the melamine matrixes with a weight ratio of 1:1. This organic-i norganic composite (HMM/ASD) was formed via sol-gel reaction of the re spective components. The optically clear (HMM/ASD) sample exhibits lar ge second-order optical nonlinearity (d(33) = 40 pm/V) after poling an d curing at 220 degrees C for 30 min. The poled/cured HMM/ASD sample h as better temporal stability at 100 degrees C compared to that of the poled/cured ASD, due to its higher cross-linking density. This is conf irmed by dielectric relaxation results indicating that the molecular m obility associated with the glass transition was suppressed remarkably for the cured HMM/ASD sample. Furthermore, the second harmonic genera tion (SHG) relaxations of these NLO-active sol-gel materials were stud ied via biexponential function curve-fitting.