Competition between forward- and backward-stimulated photorefractive scattering in BaTiO_3

The gain–length product for two-wave mixing in photorefractive BaTiO3 is calculated as a function of the angles between a pump beam and a scattered beam and the crystal c axis. The gain–length product at times shortly after the pump is turned on often shows a maximum for backscattering, whereas the steady-state gain–length product is usually maximized for near-forward scattering (an angle of about 10° between the pump and scattered beams). The calculations suggest that backscattering will be optimized in a hole-dominated crystal with a large trap density.