Abstract

Self-diffraction in bismuth silicon oxide (Bi₁₂-SiO₂₀ or BSO) crystals exhibits pronounced optical polarization effects due to concomitant natural optical activity and electric field-induced linear birefringence. Foote and Hall have recently studied the case wherein BSO is used in the diffusion limit (i.e., with small linear birefringence) and with a fixed grating.¹ The model described herein extends these results to the case of an optically active material in which either fixed or running gratings can be present, in both the diffusion and/or drift limits. Detailed computer studies of this polarization behavior have clarified the optimum configurations for maximizing energy transfer in two-wave mixing experiments, both with and without running gratings. Experimental parameters that can be manipulated for such an optimization include the crystallographic orientation, the polarization state of the incident beams, and the externally applied electric field. When both optical activity and absorption are included in the analysis, the effective electrooptic coefficient of BSO is closer to the value measured by electrooptic techniques² compared to previously reported photorefractive measurements.³ In addition, the large enhancement of the space–charge field by the moving grating technique gives rise to peculiar polarization properties that are commonly used to increase the signal-to-noise ratio in photorefractive devices utilizing BSO crystals.

© 1986 Optical Society of America