Abstract
Two-beam coupling in photorefractive (PR) materials has been extensively studied in the literature [1]. Theoretical analyses are based on linearized time dependent models [1], empirical predictions and nonlinear steady state albeit approximate theories. The difficulty in providing an analytical nonlinear time dependent theory is due to the inability to exactly decouple the Kukhtarev equations [1], and the fact that in a typical two-beam coupling setup, the PR crystal is finite and has a large linear refractive index mismatch with the surrounding medium if no matching liquid is used, prompting reflections from boundaries.