Geminate recombination in photorefractive crystals

Even though the Kukhtarev model [Sov. Tech. Phys. Lett. 2, 438 (1976); Sov. Phys. Solid State 16, 2414 (1975); Ferroelectrics 22, 949 (1979); Sov. J. Quantum Electron. 8, 231 (1978); Opt. Commun. 23, 338 (1977)] successfully describes many aspects of the photorefractive effect, the physics of photocarrier generation has not been explicitly accounted for in discussions of this model. In this paper, Onsager’s model [Phys. Rev. 54, 554 (1938)] for initial recombination of charge pairs is used to describe the photogeneration process and a quantum yield which is a function of both electric field and temperature is introduced into the Kukhtarev model. While the steady-state value of grating strength is only weakly affected by these considerations, the rate of grating formation and decay may show a much greater sensitivity to the physics of photocarrier production in low dielectric materials.