A generalized temporal transfer matrix method and its application to modeling electromagnetic waves in time-varying chiral media

Chiral metamaterials have attracted significant attention in recent years due to their unique properties in both the microwave and optics regimes. However, most existing works rely on engineering the desired properties of spatial interfaces, and the concept of time-varying chirality has only recently begun to be explored. As a consequence, there is currently a lack of suitable tools for evaluating the propagation of electromagnetic (EM) waves in time-varying chiral media. As such, this paper presents the theoretical formulation for temporal reflection and transmission of EM waves in time-varying chiral media using the temporal transfer matrix method (TTMM). The developed TTMM tool will then be utilized to explore several application examples including a structure with an arbitrary temporal profile, optical activity generated from time interfaces, and anti-reflection temporal coatings. In addition, we employ a specialized finite-difference time-domain (FDTD) technique, known as BI-FDTD, in all the scenarios to validate the proposed theory.