Achieving bi-anisotropic coupling through uniform temporal modulations without inversion symmetry disruption

Abstract

Temporal modulations provide a new approach for realizing metamaterials. In this study, through the imposition of uniform temporal modulations, we achieve two types of reciprocal bi-anisotropic metamaterials. Notably, these achievements do not rely on any spatial modulation, preserving inversion symmetry at any instantaneous time. This stands in sharp contrast to the scenario of traditional bi-anisotropic metamaterials, where the disruption of inversion symmetry by spatial arrangements is necessary. Conditions for realizing nonzero bi-anisotropic coupling are discussed and verified through full-wave simulations. Our work will stimulate research in the field of temporal bi-anisotropic metamaterials, as well as the application of temporal modulations in manipulating photonic spin angular momentum.