Higher-order analysis of the photorefractive effect for large modulation depths

Abstract

In an extension of earlier work by Moharam et al. [ J. Appl. Phys.50, 5642 ( 1979)], we use a perturbation scheme to obtain a higher-order expression for the steady-state photorefractive effect at large modulation depths and moderate applied electric fields. The expression is applicable for paraelectric crystals for which there is no photovoltaic effect and under conditions of weak coupling. The dependence of the size of the correction term on modulation depth, concentration of donor–trap sites, and applied field is discussed. Comparison of both the first-order and the second-order theories to the Kukhtarev model, valid for small modulation depths, allows the range of validity to be quantified for certain regimes.