Intensity redistribution in a thin photorefractive crystal caused by strong fanning effect and internal reflections

Propagation of the light beam in a thin photorefractive crystal with the diffusion-type mechanism of nonlinearity has been studied both experimentally and theoretically. Total internal reflections of fanned beams from the crystal’s side surfaces and their coupling with the pump beam result in the light-intensity redistribution and in the generation of the photorefractive surface wave. We propose a theoretical model of the intensity redistribution that considers the light-energy flow from the pump beam to the fanning beam and backward after the fanning beam reflection. A numerical simulation shows that the total internal reflection off the surface, toward which the flow of the light energy is directed, is responsible for the light-energy self-concentration.