Until recently, optical solitons with two transverse degrees of freedom were not known to exist, and thus, nonlinear optical engineering often required the use of waveguides to constrain diffraction. Catastrophic beam collapse can occur once this constraint is relaxed in a self-focusing system. In a self-defocusing system, on the other hand, a new class of soliton phenomena, including dark soliton stripes and grids,1 and optical vortex solitons,2 have been observed. Because these effects occur in a bulk medium, without the constraints of a waveguide, new techniques may be possible, especially in the areas of planar spatial light modulation, image processing, optical switching, and optical interconnection.
by G. A. Swartzlander Jr., and C.T. Law