Internal oscillations of spatial optical solitons in a cubic-quintic nonlinear medium

The internal oscillation of spatial optical solitons in a Cubic-quintic nonlinear medium is investigated systemically in their stability parameter region. Both internal oscillations of fundamental soliton and localized optical vortex soliton are determined. Internal modes with and without angular dependence are found. Our results show that internal oscillations exist only when the power of the soliton exceeds a threshold value. We also simulate the dynamics of soliton perturbed by internal modes. 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 that the spatial soliton is uniformly (unevenly) breathing or rotating around the propagating axis periodically, the periods approximately equal to that of the internal oscillations.