Temporal interfaces in complex electromagnetic materials: an overview [Invited]

Time-varying metamaterials are currently at the forefront of research, offering immense possibilities for intriguing wave manipulations. Temporal modulations of metamaterials have paved the way for unconventional realizations of magnetless nonreciprocity, wave amplification, frequency conversion, pulse shaping, and much more. Here, we overview the fundamentals and recent advancements of temporal interfaces in isotropic, anisotropic, and bianisotropic materials and metamaterials. Delving into the fundamentals of temporal scattering in media of different material classes, we draw insightful comparisons with phenomena observed at spatial interfaces. We specifically emphasize the potential of time-switched anisotropic and bianisotropic metamaterials in unlocking extraordinary temporal scattering phenomena. Furthermore, an overview of possible platforms to realize time-varying bianisotropic metamaterials is provided. Concluding with a glimpse into the future, we make a research outlook for time-varying anisotropic and bianisotropic metamaterials, highlighting their potential in obtaining exotic photonic time crystals and other dynamic electromagnetic structures.