Photorefractive properties of a 0.05-wt. % -doped crystal are investigated at visible wavelengths. Compared with the performance of the undoped crystal, sensitivities as high as 3 cm/J represent an increase of almost two orders of magnitude, and a photorefractive gain of 25 cm-1 for extraordinary polarization exhibits a fourfold increase. The saturated diffraction efficiency varies with the intensity ratio of the incident beams owing to strong beam coupling. Photoconductivity at 514.5 nm and dark conductivity are also measured. The intensity dependence of these light-induced parameters suggests a nonsingle-photon behavior. We use a two-center model that involves both a shallow level and a deep level to explain the measured results.
© 2000 Optical Society of America