Switching and instabilities of optical vortices in nonlinear dual-core photonic crystal fibre couplers

Abstract

We study switching of an optical vortex launched into one core of a dual-core waveguide coupler in a photonic crystal fibre with self-focusing nonlinearity. We analyse how the beam power and the angular momentum associated with the vortex mode transfer to the second core of the coupler in both linear and nonlinear regimes. We describe three major scenarios of the vortex dynamics and reveal novel symmetry-breaking instabilities associated with the vortex nonzero angular momentum.