STEADY-STATE VORTEX-SCREENING SOLITONS FORMED IN BIASED PHOTOREFRACTIVE MEDIA

We report the observation of steady-state photorefractive vortex-scree ning solitons. As a singly charged circular vortex nested on a broad b eam propagates through a biased strontium barium niobate crystal, it s elf-traps in both transverse dimensions despite the inherent anisotrop y of the photorefractive nonlinearity. When the vortex beam is a dough nut-shaped narrow beam, it breaks up into two elongated slices (with a self-defocusing nonlinearity) or into two focused filaments (with a s elf-focusing nonlinearity). We demonstrate the optical guidance of a p robe beam in a circular waveguide induced by the self-trapped vortex. (C) 1997 Optical Society of America.