The exact solution of the degenerate four–wave mixing in transmission geometry in photore-fractive media for a zero phase shift between the refractive index grating and interference pattern of the optical beams is presented. Our solution gives both the intensities and the phases of various beams.
We develop a numerical method to solve the coupled-wave equations for four-wave mixing phase conjugation in a photorefractive crystal with unequal complex coupling constants; by this method we can obtain both the intensities and the phases of various beams. We discuss the intensities and the phases of the interacting beams in a photorefractive crystal for the cases in which the phase shifts between the refractive-index gratings and the interference pattern are all π/2 and in which they are not all π/2.