Dissipative optical flow in a nonlinear Fabry-Perot cavity

We describe a classical nonlinear optical system that displays superfluidit y and its breakdown. The system consists of a self-defocusing refractive me dium inside a Fabry-Perot cavity with a cylindrical obstacle. We have numer ically solved for the transmitted beam when an incident plane wave strikes the cavity at an oblique angle. The presence of the incident beam pins the steady-state phase of the output, preventing the formation of vortices or t ime-dependent flow. When the incident beam is switched off, a transient wak e of moving optical vortices is produced. This is analogous to the breakdow n of superfluidity above a critical velocity.