Dynamics of orientationally enhanced polymeric photorefractive composites

Empirical fits to the rise and decay of real time written holograms in a photorefractive-crystallization-resistant polymer composite (1-(2′-ethyl-hexyloxyl)-2,5-dimethyl-4-(4″-nitrophenylazo)benzene:poly(N-vinylcarbazole):2,4,7-fluorenone) are presented. The speed of response of the composite material in time-resolved four-wave-mixing experiments decreases with increasing percentage azo dye in the composite, increases with increasing poling voltage and increasing temperatures. Mach-Zehnder data show that there is a gradual decrease in the extent to which the dye molecules can reorient under a modulated applied field as the modulation frequency is increased. Greater reorientational freedom and hence faster reorientation for a greater percentage of dye is observed at lower frequencies of modulation of the applied field. Lower bounds to the mobility and photosensitivity of the composites are calculated.