Two-dimensional spatial, solitons in nematic liquid crystals

We have observed, for the first to the best of our knowledge, time 2+1 dimensional spatial solitons with an Argon-ion beam in planar cells containing an undoped nematic liquid crystal, The cells provided planar anchoring for the liquid crystal molecules, with transparent electrodes for applying an external voltage across the 75 mum-thick crystal. The voltage allowed to pre-orientate the director field in the principal plane containing the linearly polarized optical field vector, thereby eliminating the Fredericks threshold. In this regime, powers low enough to prevent thermal effects could be employed to obtain transverse localization through a local light-induced index increase, trapping the beam into a spatial soliton. Self-trapping, as-well-as guidance of a copolarized probe at 633nm, were demonstrated at biases of 1V with 3.9 mW-powers in the green at 514nm. A beam orthogonally polarized with respect to the director tilt-plane failed to produce self-localization, thereby confirming the reorientational nature of the phenomenon.