High Efficiency Photorefractive BaTiO_3 Plate for Optical Image Processing

45°-cut BaTiO3 crystals have been studied and used for their enhanced photorefractive performance. Theoretically, BaTiO3 crystal has its maximum two-wave mixing （TWM） gain when the grating wave vector Kg is about 45° tilted with respect to its C-axis. However, for thick samples, the effective gain is usually reduced because of the fanning problem. At steady states, the effective TWM gain of a 45°-cut BaTiO3 is normally