Soliton propagation in BSO crystals with strong optical activity

Abstract

Spatial solitons in photorefractive materials have been largely investigated in the past. They are really attractive due to the ultralow intensity regimes at which they occur. Many different kinds of solitons can be found, as for example screening ones, or photovoltaic, according to the nonlinearity mechanism that compensates the light diffraction. Screening solitons have been demonstrated in materials without optical activity, since the rotation of light polarisation limits the achievable diffraction compensation. By using BPM numerical simulation we have isolated particular regimes of the applied static voltage for which a nonlinear optical activity is realised. The power transfer between polarisation components strongly depends on the transverse position inside the beam giving rise to effective optical activity that can compensate the diffraction. In this case, according to the signal vs background intensity ratio, efficient self-focusing for almost the whole beam can be reached and soliton-like propagation can be found. Experimental testing has been performed along 2 diffraction lengths, by using 8 mm long BSO crystal.