Photorefractive polymer in reflection geometry with large efficiency

摘要

We have investigated photorefractive (PR) properties of a polymer composite with low glass-transition temperature (T_g) in a symmetric reflection geometry. A diffraction efficiency of more than 30% is observed in 105μm thick devices. In low T_g photorefractive polymers, poling of the nonlinear optical chromophores at room temperature leads to birefringence in the material. The birefringence will alter the Bragg condition, as the propagation vectors for object and reference beams as well as the readout angle are influenced. We observed the Bragg-mismatch effect that caused a reduction in diffraction efficiency as the external field is increased. We have varied the angle of readout beam slightly at each bias field to get the highest efficiency.