Multi-vortex beams in nonlinear media with harmonic potential wells.

As is well known, the vortex beams have significant potential applications in both quantum and classical communication systems. In this paper, we study the existence and robustness to propagation of families of multi-vortex waveforms, namely multi-vortex optical beams in nonlinear self-focusing cubic (Kerr) media with harmonic potential wells. The intensity patterns, phase structures, transverse energy flow, and gradient forces (upon micro-particles) of those multi-vortex beams are presented and we found that they are all different from those of the ordinary vortex beams. The evolution during propagation of the intensities and widths of the multi-vortex beams is investigated in detail. The obtained results show that the one-vortex beams have asymmetric patterns and spiral propagation trajectories, depending on the off-axis parameter of the vortices. The two-vortex beams and the higher than two-vortex waveforms have symmetric patterns, which rotate during propagation, and the rotation direction can be controlled by the sign of the topological charge. [ABSTRACT FROM AUTHOR]