Abstract

Dark spatial solitons in nonlinear planar waveguides are observed as nondiffracting intensity dips on a broad background beam [1]. These stationary nonlinearity-supported structures can be used as self-induced optical waveguides to guide or steer another (probe) beam, thus manipulating light by light (see eg, [2]). To achieve the dark soliton propagation at relatively low power, highly nonlinear materials should be employed. However, such materials often exhibit saturation, ie the n₂(I) dependence is nonlinear [3]. Soliton propagation is such materials is described by the generalised nonlinear Schrodinger equation (GNLS), and its solutions may be unstable. The general criterium for linear instability of dark solitons has been found recently [4], it is based on analysis of the dependence Q(q), where Q is the renormalised soliton momentum and q is the soliton velocity. However, the linear stability analysis does not allow to describe the subsequent evolution of unstable solitons. Nevertheless, the evolution of unstable solitons seems to be very important for eg, nonlinear soliton switching which basically involves unstable rather than stable stationary solutions [2].

© 1996 Optical Society of America