Vortex evolution and bound pair formation in anisotropic nonlinear optical media

We present a theoretical and experimental study of the propagation, decay, and interaction of optical vortices in media with an anisotropic nonlocal nonlinearity. The initial stage of decay of a circular vortex is characterized by charge dependent rotation, and stretching of the vortex. Our results suggest that a compact vortex of unit topological charge cannot exist in such media, but that a counterrotating vortex pair can form a bound state. Some analogies and differences between optical vortices and the classical dynamics of vortices in an ideal fluid are described.