Switching with vortex beams in nonlinear concentric couplers.

We demonstrate that a concentric ring coupler can be employed for nonlinear switching of the angular momentum of light carried by an optical vortex. We find different types of stationary vortex states in the nonlinear coupler and study coupling of both power and momentum of an optical vortex launched into one of the rings, demonstrating that the switching takes place well below the collapse threshold. The switching is more effective for the inner-ring excitation since it triggers more sharply and for the powers low enough to avoid the vortex instability and breakup.