Internal modes of localized optical vortex soliton in a cubic-quintic nonlinear medium

The internal oscillation of localized optical vortex solitons (LOVS) in a cubic-quintic nonlinear medium is investigated in its stability parameter region. Internal modes both with and without angular dependence are found. The dynamics of LOVS perturbed by internal modes are simulated. Numerical results show that internal oscillations induced by these modes are very robust. Some novel and interesting phenomena are discovered during the propagation process. Evolution of the perturbed state visually appears like the LOVS uniformly (unevenly) breathing or rotating around the propagation axis periodically.