Propagation of Dark Stripe Beams in Nonlinear Media: Snake Instability and Creation of Optical Vortices

We analyze the evolution of $(1+1)$ 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.