Abstract

In a linear medium the simplest physically realizable spatial wave-packet is the gaussian beam, which spreads during propagation. Surprisingly enough, in nonlinear media it is replaced by an even simpler entity: the spatial soliton. The latter is the basic concept for understanding the interplay between diffraction and nonlinearity, and its universality is confirmed by the several and diversified media where it has been theoretically predicted and experimentally observed. [1] We propose a novel model describing spatial solitons in nematic liquid crystals, and supporting the recent experimental investigations carried out on 3D solitons due to a re-orientational nonlinearity. Our approach immediately sets this new family of nonlinear waves in the framework of the recent results obtained for quadratic solitary waves, as well as for nonlocal media, and it permits to understand the basic mechanism of energy trapping and stabilization in the phenomena observed in undoped nematics. The model described hereby catches the underlying physics and generalizes in a substantial way previous approaches, limited to an equivalent Kerr response [2], or neglecting the effects of an external bias [3].

© 2002 Optical Society of America