Influence of nonlinearities on two-wave mixing in photorefractive InP:Fe crystals with a moving grating

Two-wave mixing in photorefractive InP:Fe crystals is revisited in terms of an externally applied dc field combined with the moving-grating technique. We show that the disagreement between theory and experiment that was previously observed in the literature can be reconciled by an examination of the influence of both the absorption along the propagation axis and the nonlinearities that occur at relatively large fringe modulations. A finite-difference method is used to demonstrate the dependence of these nonlinearities on the average incident intensity.