Diffraction efficiency and phase stability of poly(N-vinylcarbazole)-based photorefractive polymer composites as a function of azo-dye concentration

Abstract

Diffraction efficiency and phase stability of photorefractive polymer composites doped with alkylether-substituted azobenzene dyes are studied as a function of dye concentration. Composites doped with 2,5-dimethyl-4-(4′-nitrophenylazo)phenyl benzyl ether (DMNPAPBE) are phase stable at all concentrations studied while composites doped with 2,5-dimethyl-4-(4′-nitrophenylazo)phenyl octyl ether (DMNPAPOE) exhibit a critical concentration of 47% above which the composite rapidly degrades due to dye crystallization. The glass transition temperatures Tg of DMNPAPBE- and DMNPAPOE-doped composites are approximately 67 and 57 °C, respectively. Diffraction efficiency measurements of DMNPAPOE-doped composites show a threefold increase at 100 V/μm over DMNPAPBE-doped composites at the same dye concentration and applied field.