Optical vortex solitons observed in Kerr nonlinear media

Optical vortex-soliton filaments are observed in a bulk self-defocusing Kerr nonlinear refractive medium. The dark cylindrical core, located at the axis of a 2\ensuremath{\pi} helical phase ramp, is stationary and stable, with a size that depends inversely on the field strength. Wave guiding of a weak probe beam within the core is reported. A single optical vortex soliton was experimentally created using a quasihelical phase mask. Pairs having opposite topological charge were experimentally and numerically investigated using a convective Kelvin-Helmholtz instability of dark soliton stripes.