Abstract

Under no external electric field, GaAs crystal of the $\overline{4}3m$ symmetry is optically isotropic. Thus the cross-polarization phenomenon in the beam coupling and four-wave mixing in photorefractive GaAs can be easily observed and implemented in image processing, as recently demonstrated. However, when an external electric field is applied, the situation is different. Experimental results of an investigation on the effect of the dc electric field on properties of phase conjugate beam of four-wave mixing in photorefractive GaAs crystals are presented. The GaAs crystals used were in the rectangular form of three surfaces normal to (001), (110), and $\left(1\overline{1}0\right)$ crystal orientations. It was observed that, in the samples with electrical contacts on (110) surfaces, an applied field of 13 kV/cm not only enhanced the diffraction efficiency by 2–3 orders of magnitude, depending on the experimental condition and sample properties, but also induced a polarization rotation of the phase conjugate beam by ~80° with respect to that of no electric field. In the samples with electrical contacts on (001) surfaces, only the enhancement in diffraction efficiency was observed.

© 1988 Optical Society of America