INTERPLAY OF LINEAR AND NONLINEAR EFFECTS IN THE FORMATION OF OPTICAL VORTICES IN A NONLINEAR RESONATOR

We study the role played by nonlinearities in the formation of optical vortices when the boundary conditions determine the pattern formation in a Fabry-Perot resonator. Particular care is taken to avoid trivial vortices coming from particular Gaussian modes or from the cavity alignment. We show that, while the existence of optical vortices is a generic linear property of the superpositions of Gaussian modes, their actual appearance in the transmitted patterns is controlled by the nonlinearity itself.