Theory of degenerate four-wave mixing an anisotropic, opticallyactive photorefractive crystals

A theory is presented of degenerate four-wave mixing (DFWM) of arbitrary polarized waves in an anisotropic optically active photorefractive crystal. Using the method of coupled waves, a system of differential equations is deduced describing the coupling process. This system is specified to DFWM in crystals of the Bi₁₂GeO₂₀ -type and numerically solved based on the shooting method. Some peculiarities of phase conjugation in these crystal are discussed