Abstract

Spatial solitons in photorefractive materials have been largely investigated in the past [1] They are really attractive due to the ultra-low 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 [2-3] By using BPM numerical simulation we have isolated particular regimes of the applied static voltage for which a nonlinear optical activity is realised [4] 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 selfocusing for almost the whole beam can be reached and soliton- like propagation can be found, as shown in fig 1 where the diffracting beam (left-hand-side) and solitonic propagation (left-hand-side) are presented Experimental testing has been performed along 2 diffraction lengths, by using 8mm long BSO ciystal produced by Altechna Co Ltd in Vilnius (Lithuania)

© 2000 IEEE