Stable multicharged localized optical vortices in cubic-quintic nonlinear media

We investigate analytically and numerically the stability of multiply-charged two-dimensional bright vortex solitons in media with focusing cubic and defocusing quintic nonlinearities. A vortex soliton becomes robust with respect to symmetry-breaking azimuthal perturbations in the self-defocusing regime above some critical beam power when its radial profile flattens. A stable high-power vortex has nearly homogeneous energy distribution across the beam with a rather sharp boundary. The dynamics of a slightly perturbed stable vortex soliton is found to be similar to oscillations of a liquid stream having a surface tension. We propose an explanation of stabilization of vortex solitons in media with competing nonlinearities based on the idea of sustaining effective surface tension.