Time-varying Metallic Interfaces

Abstract

This paper presents an analytical framework for the analysis of time-varying metallic metamaterials. Concretely, we particularize the study to time-modulated metallic interfaces embedded between two different semi-infinite media that are illuminated by monochromatic plane waves of frequency ω0. The formulation is based on a Floquet-Bloch modal expansion, which takes into account the time periodicity of the structure (Ts = 2π/ωs), and integral-equation techniques. It allows to extract the reflection/transmission coefficients as well as to derive nontrivial features about the dynamic response and dispersion curves of time-modulated screens. In addition, the proposed formulation has an associated equivalent circuit that gives physical insight to the diffraction phenomenon. Finally, some analytical results are presented to validate the present framework. A good agreement is observed with numerical computations provided by a self-implemented finite-difference time-domain (FDTD) method. Interestingly, the present results suggest that timemodulated metallic screens can be used either as pulsed sources (when ωs ω0) or as beamformers (when ωs ∼ ω0) to redirect energy in specific regions of space.