Acoustic black holes in a two-dimensional “photon fluid”

Optical field fluctuations in self-defocusing media can be described in terms of sound waves in a two-dimensional photon fluid. It is shown that, while the background fluid couples with the usual flat metric, soundlike waves experience an effective curved spacetime determined by the physical properties of the flow. In an optical cavity configuration, the background spacetime can be suitably controlled by the driving beam, allowing the formation of acoustic ergoregions and event horizons. An experiment simulating the main features of the rotating black hole geometry is proposed.