Interaction of screening solitons in cubic optically active photorefractive crystals

The coherent interaction of Gaussian light beams polarised parallel to the $[1\bar10]$ direction in a cubic optically active photorefractive crystal with the $(\bar1\bar10)$ cut is studied in an electric field applied to the crystal in the $[00\bar1]$ direction. The effect of optical activity on the interaction of the light beams with the phase difference $\Delta=0, \pi/2$, and $\pi$ is theoretically studied. It is shown that, while a change in the intensity of a combined light beam at $\Delta=0$ caused by the influence of optical activity in a 9-mm thick $Bi_{12}TiO_{20}$ crystal is comparatively small (less than 8%), this change achieves 36% in the crystal of thickness 18 mm. The interaction of orthogonally polarised beams in this crystal is considered. It is found that, although the optical activity of the crystal results in the appearance of the 'breathing effect', a soliton-like nature of the combined beam is preserved. The results obtained can be used for the address positioning of soliton-like light beams.