Summary

Recently there has been increased interest in the study of self-guided optical beams (also known as spatial optical solitons) that propagate in nonlinear optical media under conditions where the nonlinearity exactly compensates for diffraction (see, e.g., the recent overview of Segev and Stegeman (1998) and the pioneering paper by Chiao et al. (1964)). The intensity distribution of the resulting beam is, to first approximation, invariant in the propagation direction—a property similar to that of a beam confined within an optical waveguide—and this gives rise to the notion of self-guidance. These self-guided beams can be created in slab waveguides where guidance normal to the film is produced by the refractive index structure of the slab, whilst in the plane of the film it results from the optical nonlinearity. Self-guided beams can also exist in bulk nonlinear optical media without any supporting wave-guiding structures.