Annular light beams induced by coupling a dissipative spatial soliton on the top of a sharp external potential

We numerically reveal the rich dynamics of a two-dimensional fundamental soliton coupled on the top of a sharp external potential in dissipative nonlinear media based on the cubic-quintic complex Ginzburg-Landau model. Here, we consider two kinds of radially symmetric potentials, namely, a tapered potential (TP) and a raised-cosine potential (RCP). It is found that if the sharpness and depth of the potential are large enough, the soliton can emit either one annular beam or a cluster of ring-like beams, all of which gradually expand upon propagation. By using the TP, one can get a nonstationary annular beam, while a single stationary annular beam can be achieved by using the RCP. The radius of the stationary annular beam is controllable by the modulation period of the potential. Other soliton dynamics, including soliton localization, soliton oscillation, lateral drift, soliton collapse, and soliton decay, are also revealed. The reported results provide what we believe to be a new method to generate annular beams in dissipative systems.