The Penrose process in nonlinear optics

Penrose process is a mechanism by which energy may be extracted from the rotation of a Kerr black hole. The goal of this Perspective is to describe the elements that combine to allow a tabletop nonlinear optics experiment involving laser propagation in a medium to provide a versatile platform for elucidating the intimate details of the Penrose process. Key elements include propagation in a thermo-optic medium viewed as a photon fluid, rotating black hole geometries in a photon superfluid, and the Zel'dovich effect, and we highlight connections to the work of Roger Penrose throughout. In addition, we point out how the Penrose process has led to the notion of geometry-induced phase-matching in nonlinear optics, thereby highlighting the synergy between the fields of nonlinear optics and analog black holes.