Temporal boundaries in electromagnetic materials

Gratus, Jonathan and Seviour, Rebecca and Kinsler, Paul and Jaroszynski, Dino A. (2021) Temporal boundaries in electromagnetic materials. New Journal of Physics, 23: 083032. ISSN 1367-2630

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Abstract

Temporally modulated optical media are important in both abstract and applied applications, such as spacetime transformation optics, relativistic laser-plasma interactions, and dynamic metamaterials. 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. Further, 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.