Temporal boundaries in electromagnetic materials

Temporally modulated optical media have amazing potential to amplify signals. Here we investigate the behaviour of temporal boundaries, and show that traditional approaches that assume constant dielectric properties, with loss incorporated as an imaginary part, necessarily lead to unphysical solutions. Furthermore, although physically reasonable predictions can be recovered with a narrowband approximation, we show that appropriate models should use materials with a temporal response and dispersive behaviour. We indicate recent experiential demonstrating temporal boundaries.