We analyze the evolution of ͑111͒ dimensional dark stripe beams in bulk media with a photorefractive nonlinear response. These beams, including solitary wave solutions, are shown to be unstable with respect to symmetry breaking and formation of structure along the initially homogeneous coordinate. Experimental results show the complete sequence of events starting from self-focusing of the stripe, its bending due to the snake instability, and subsequent decay into a set of optical vortices.

We investigate theoretically and experimentally breakup and subsequent spatial dynamics of ͑1ϩ1͒and ͑2ϩ1͒-dimensional beams in bulk media with an anisotropic photorefractive nonlinear response. ͓S1050-2947͑96͒02207-X͔

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We present a detailed theoretical analysis of the properties and formation of single solitons and higher-order bound dipole pairs in media with anisotropic nonlocal photorefractive material response. The single solitons are elliptical beams, whereas the dipole pairs are formed by a pair of displaced elliptical beams with a phase shift between their fields. The theory predicts convergence of Gaussian beams to the solitary states within a certain basin of attraction. Experimental observation of these solitons has been presented elsewhere. The experimental portion of the present paper concentrates on the region further away in parameter space, where complex spatial oscillations, including asymmetric filamentation into several beamlets, occurs. ͓S1050-2947͑97͒03011-4͔

We investigate self-focusing in bulk media with anisotropic nonlocal photorefractive response. Analytical results demonstrate the possibility of the existence of anisotropic soliton solutions. Self-focusing of Gaussian beams and their convergence to elliptically shaped soliton solutions is investigated theoretically and demonstrated experimentally.