Technology Review: In 2009 a team of researchers used metamaterials in a lab to create a structure that mathematically resembled a black hole. Now, Daniele Faccio and her colleagues at Heriot-Watt University in Scotland propose that it should be possible to turn such black hole analogues into lasers. In its theoretical proposal, the Heriot-Watt team creates analogues of a black hole and a white hole (a spacetime region that emits light and matter but can’t be entered) and separates them by only a few hundred micrometers, which is just enough to form a cavity between the two holes’ event horizons. Light fired into the cavity would be reflected back and forth between the two horizons. However, the light would be amplified by the Hawking radiation emitted at the horizons. Faccio’s work suggests that this setup could be created using metamaterials whose refractive index depends on the intensity of the light. A pulse of light in such a material would result in extreme gradient changes in the material’s refractive index at the front and back edges of the pulse, creating the black and white holes, respectively.