Perturbative analysis of higher-order photorefractive gratings

Abstract

Analytic expressions are derived for second- and third-order space-charge fields for a moving intensity pattern and arbitrary field strengths. The dependence on the spatial frequency, the applied field strength, and the velocity of the moving grating is examined. The magnitude of the term of correction to the fundamental harmonic is strongly dependent on experimental conditions and the relative strengths of characteristic fields. For diffusion-dominated charge transport and optimum fringe spacing the cubic correction term is only 5% of the fundamental amplitude, even for a large modulation depth of unity. Limiting cases yield the same results as previous studies.