Even though the Kukhtarev model lsqb;Sov. Tech. Phys. Lett.2, 438 (1976); Sov. Phys. Solid State16, 2414 (1975); Ferroelectrics22, 949 (1979); Sov. J. Quantum Electron.8, 231 (1978); Opt. Commun.23, 338 (1977)rsqb; 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, Onsagerrsquo;s model lsqb;Phys. Rev.54, 554 (1938)rsqb; 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 steadyhyphen;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.
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