Synthesis and characterization of novel photorefractive low molecular weight glasses

Seven novel photorefractive glasses have been prepared in an effective four-step synthesis. The low molar mass glasses consist of a triphenylamine-core substituted with two carbazole moieties and a NLO-chromophore (NLO-DCTAs). In a second series of compounds (NLO-DATAs) the carbazole groups are replaced by diphenylamine. The compounds form stable glasses with T(g)s of about 120 degrees C (NLO-DCTAs) and 85 degrees C (NLO-DATAs). The photorefractive properties such as the diffraction efficiency eta, the modulation amplitude of the refractive index Delta n, and the gain coefficient Gamma were determined by means of degenerate four-wave mixing and two-beam coupling experiments. We observed diffraction efficiencies of eta=27% for only 40 mu m thick samples (corresponding to Delta n = 3.5.10(-3)) with a response time of 150 ms. The systems exhibit maximum two-beam coupling gain coefficients up to Gamma = 90 cm(-1). The samples have excellent properties with respect to optical quality and shelf-lifetime.