Spatial Photorefractive Solitons

Abstract

The photorefractive nonlinearity is described in Chap. 3 beginning with the origins of the space charge field arising in these materials from their interaction with light. The band transport model equations are used to formulate the basic equations for the photorefractive nonlinearity. The complexity is gradually increased, starting with one beam interacting with the nonlinear material and then taking a second beam into account to show the beamcoupling properties of photorefractive crystals. An important feature of a diffusion-dominated photorefractive material is the possibility of performing an energy exchange between interacting beams in a wave-mixing process. The two-beam coupling properties are thoroughly discussed for the special case of a counterpropagating geometry, which is the configuration of choice for the investigations of pattern formation effects described in Chaps. 8 to 10. Special care has been taken to introduce the main variables and equations that represent the starting point for subsequent considerations.