Influence of modulation and fringe velocity on the photorefractive response with moving gratings in Bi12SiO20

Hologram recording by a moving interference pattern in a dc-electric field can provide large enhancements in the photorefractive effect in crystals with long drift lengths, such as semiconductors and the sillenites. The theory of Refregier et al.1 predicts the photorefractive response, but only in the limit of small modulation. In practice, most experimental conditions cannot be adequately described by the linearized theory. The correction function used by Refregier et al.1 describes the effect of modulation, but only for two-wave mixing at the optimum velocity. Au and Solymar2 have demonstrated numerically a complicated photorefractive response. In this paper we provide more detailed numerical analysis, and for the first time, experimental characterization of the photorefractive response, including both diffraction and energy transfer, in BSO as function of modulation index and fringe velocity.