Diffusion recording in photorefractive sillenite crystals: an analytical approach for engineering purposes

Simple formulae for the two-wave mixing (TWM) gain and diffraction efficiency obtained in the approximation of weak coupling and strong optical activity allow us to tune the experimental setup for interferometric applications. We prove that two invariant parameters, trace and determinant of the coupling tensor, are sufficient to optimize the experimental setup. Both practically important crystal cuts, (110) and (111), can be treated in a unified manner. Fundamental TWM properties (90°-jumps of the optimum polarization, apparent doubling of the local maxima of the diffraction efficiency in comparison with the gain, drastic changes between regimes of small and large polarization rotation, the crucial role of elastooptic properties) are systematized. The guidelines for the design of an optimum experimental setup for interferometric applications including anisotropic self-diffraction using sillenite crystals are presented. Quantitative agreement with previous experimental data is demonstrated.