Polarization and energy transfer dependencies on crystal depth in self-diffraction in BSO

The stationary coupled wave equations for two-wave mixing experiments in an optically active, linearly birefringent BSO (Bi₁₂SiO₂₀) crystal are presented. It is shown that there are some fundamental problems with the coupled amplitude equations in general form with three components of the incident field polarization. However, using the small angle approximation, a reasonable set of equations is obtained. These equations are solved numerically including the effect of self-diffraction. The polarization and the energy coupling of the two beams are described as functions of crystal depth. It is shown that the angle of ellipticity and the coupling efficiency are oscillating throughout the medium because of the optical activity. Finally, the theoretical results are compared with experiments.