(2D+1) spatial optical solitons in dye doped liquid crystals

We report on the observation of (2D + 1) optical spatial solitons in dye doped liquid crystal. The presence of the dye in the liquid crystal enhances the thermal non-linearity of the medium and yields the orientational one to occur for beam powers in the range of mW. As the power of the input beam is increased, two specific modes of propagation which are similar to spatial optical solitons are observed. However, it is experimentally observed different behaviors for the low and high power modes: energy profiles, interaction of two similar modes (collisions). This suggests that the non-linear processes involved are different for the low and high power soliton modes. Experimental results obtained in cylindrical and planar cells are presented to discriminate the roles of the thermal and orientational non-linearities. In planar cells, a quasi-static field is applied to stiffen the director. It turns out that the low power mode looks originated by the thermal effect alone. (C) 2001 Elsevier Science B.V. All rights reserved.