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Polarization evolution of spatial solitons in photorefractive crystals with large optical activity

We found out analytical solutions of the propagation equations in photorefractive crystals with nonlinear birefringence, large optical activity and absorption, which show the occurrence of spatial solitons, in the usual orientations with respect to the external electric field. Here, we calculate the Stokes parameters of these solitons and we show their polarization evolutions on the Poincare sphere, in function of the crystal orientation, propagation distance, the soliton-background-intensity-ratio and the external electric field. The experimental polarization states correspond well to our analytical results and numerical simulations. These results are useful for selection of optimum parameters in spatial soliton generation and for future applications in optical switching, routing and storage.