A NONLINEAR, TRANSIENT ANALYSIS OF 2-WAVE AND MULTIWAVE MIXING IN A PHOTOREFRACTIVE MATERIAL USING RIGOROUS COUPLED-WAVE DIFFRACTION THEORY

Rigorous coupled-wave diffraction theory is used to analyze two- and m ulti-wave mixing in a diffusion-controlled photorefractive material wh ich is modeled by the Kukhtarev equations. These equations are first d ecoupled to yield a nonlinear time dependent differential equation for the induced refractive index profile. The transmitted and reflected f ield coupling coefficients are studied for the cases when the incident optical fields are coherent and partially coherent, for materials wit h different gain constants, and for different values of the linear ref ractive index mismatch. In each case, the exact longitudinal inhomogen eity in the photorefractive medium is analyzed using rigorous coupled- wave diffraction theory. Our computations predict a possible temporal instability resulting in self-pulsation and anisotropic diffraction co ntributing to a significant generation of higher orders when two plane waves are incident on photorefractive materials. Six-wave coupling in index mismatched barium titanate is studied.