Optical analog of Schwinger effect: https://arxiv.org/abs/1903.12263
Strong enough electric field is predicted to spontaneously create electron-positron pairs in vacuum via Schwinger effect. A similar effect is also predicted to occur in sufficiently strong gravitational field. However, due to necessity of very large field strength, these effects were never observed in the experiment. Here we demonstrate that optical analog of a very strong gravitational field (up to ~10^24 g) may be created in electromagnetic metamaterials, leading to an optical analog of Schwinger effect in a metamaterial waveguide. Such waveguide geometries may also potentially be used to search for axion-like particles weakly interacting with electromagnetic field.