It is shown that the propagation of steady-state spatial solitons in a bismuth titanium oxide (Bi<sub>12</sub>TiO<sub>20</sub>) photorefractive crystal is strongly affected by the presence of concomitant natural optical activity. We assume that the Bi<sub>12</sub>TiO<sub>20</sub> crystal is (110) cut and that the external bias field is along the [001̅] axis. Such orientation introduces self-focusing in one polarization of an optical wave front, whereas it has no effect whatsoever on the component orthogonal to it. Under these conditions, the equations that describe the coupled evolution of the two polarizations of an optical planar beam are derived. Our numerical study of the interaction dynamics shows that, even though the optical beam experiences periodic diffraction in one of the polarization components, it can still recover significantly at particular distances within the crystal. Moreover, it is initially capable of maintaining its solitonlike form over a certain distance of propagation. Relevant examples are provided.
© 1996 Optical Society of AmericaPDF Article