Analytical and numerical study of photorefractive kinetics at high modulation depths

A general approach to photorefractive kinetics, based on the band-transportmodel, has been developed for nonphotovoltaic materials in the diffusion regime. For small grating periods (? » ?_d, where ?_d is the Debye screening length) analytical solutions for the space-charge field have been found and compared with accurate numerical solutions in Bi₁₂SiO₂₀. The quantitative agreement is excellent when the solution includes all harmonics and greatly improves on the linear approach, even if a few (two or three) harmonics are taken into account. The analytical solutions show the most relevant features of the reported experimental results. Moreover, they include as particular cases other previous theoretical results. © 1996 Optical Society of America.