Optical analog of particle production in gravitational fields

The abstract discusses the Schwinger effect, where a sufficiently strong electric field can create electron-positron pairs from vacuum. It also notes that a similar phenomenon is predicted for very strong inhomogeneous gravitational fields, but that such conditions have not been observed experimentally due to the required field strengths. Here, the authors propose and demonstrate optical analogs of these extreme gravitational conditions using electromagnetic metamaterial waveguides. They report that waveguide geometries can reach effective gravitational-field strengths up to about 10^24 g and gradients up to about 10^31 s^-2. With these engineered conditions, the system yields an optical analog of particle production in gravitational fields. The abstract further suggests these waveguide geometries could be used to search for axion-like particles that weakly interact with electromagnetic fields.