Space-Time Modulation Induced Non-reciprocity in Electromagnetic Metasurfaces

TL;DR

This paper demonstrates how space-time modulation of electromagnetic metasurfaces induces non-reciprocal wave transmission, using rigorous theoretical methods and numerical simulations to confirm the phenomenon under oblique incidence.

Contribution

It introduces a novel approach to achieve non-reciprocity in metasurfaces through space-time modulation of surface susceptibilities, supported by rigorous analytical and numerical methods.

Findings

Non-reciprocal wave transmission confirmed under oblique incidence

Space-time modulation creates inherent asymmetry in wave propagation

Floquet mode expansion effectively computes scattered fields

Abstract

Space-time modulation induced non-reciprocity in EM metasurfaces is proposed and numerically demonstrated using rigorous Generalized Sheet Transitions Conditions (GSTCs) under oblique plane-wave incidence. It is phenomenologically shown that the space-time modulation of surface susceptibilities create an inherent asymmetry with respect to the directional perturbation on the metasurface and the transverse wave momentum of the input wave, between forward and backward propagations, resulting in non-reciprocal wave transmission. Exploiting the periodicity of the surface susceptibilities in both time and space, Floquet mode expansion method is used to rigorously compute the scattered fields from, inherently dispersive metasurfaces, by solving GSTCs in combination with causal Lorentzian surface susceptibilities. Various harmonic solutions are shown and the non-reciprocal wave transmission has been confirmed under oblique plane-wave incidence.