Anisotropic scattering in photorefractive crystals

Abstract

A well-defined ring of anisotropically scattered light is observed when a linearly polarized laser beam is incident upon a birefringent photorefractive crystal such as BaTiO3, LiNbO3, and LiTaO3. An analysis is presented that accurately predicts the cone angle, polarization, and the location of the discontinuities in these rings. Unlike the photovoltaic model proposed recently by others, the analysis presented herein is based on the standard photorefractive theory and is independent of the photovoltaic activity of the crystal. The analysis also illustrates the strict phase matching and electro-optic tensor symmetry constraints that must be satisfied in order to observe beam coupling and normal and anisotropic self-diffraction. Preliminary experimental results are presented for BaTiO3 and LiNbO3 and are found to be in excellent agreement with standard photorefractive theory.