Rotating black hole geometries in a two-dimensional photon superfluid

Photon fluids have recently found applications in the simulation of a variety of physical phenomena such as superfluidity, vortex instabilities, and artificial gauge theories. Here we experimentally demonstrate the use of a photon fluid for analog gravity, i.e., the study of the physics of curved spacetime in the laboratory. While most analog gravity experiments are performed in 1+1 dimensions (one spatial plus time) and thus can only mimic 1+1D spacetime, we present a (room-temperature) photon superfluid where the geometry of a rotating acoustic black hole can be realized in 2+1D dimensions by an optical vortex. By measuring the local flow velocity and speed of waves in the photon superfluid, we identify a 2D region surrounded by an ergosphere and a spatially separated horizon.