Surface wave non-reciprocity via time-modulated metamaterials

TL;DR

This paper explores how spatio-temporal modulation of resonators on a surface can induce non-reciprocal behavior in Rayleigh waves, enabling wave filtering and conversion with potential applications in elastic wave control.

Contribution

It introduces an analytical and numerical framework for understanding non-reciprocal Rayleigh wave interactions with time-modulated resonators on elastic surfaces, providing design guidelines for experiments.

Findings

Spatio-temporal modulation induces non-reciprocal wave spectrum features.

Wave filtering and frequency conversion are achieved via modulation.

Parameter bounds for stable and accurate modeling are identified.

Abstract

We investigate how Rayleigh waves interact with modulated resonators located on the free surface of a semi-infinite elastic medium. We begin by studying the dynamics of a single resonator with time-modulated stiffness. In particular, we evaluate the accuracy of an analytical approximation of the resonator response and identify the parameter ranges in which its behavior remains stable. Then, we develop an analytical model to describe the interaction between surface waves and an array of resonators with spatio-temporally modulated stiffness. By combining our analytical models with full-scale numerical simulations, we demonstrate that spatio-temporal stiffness modulation of this elastic metasurface leads to the emergence of non-reciprocal features in the Rayleigh wave spectrum. Specifically, we show how the frequency content of a propagating signal can be filtered and converted when traveling through the modulated medium, and illustrate how surface-to-bulk wave conversion plays a role in these phenomena. Throughout this article, we indicate bounds of modulation parameters for which our theory is reliable, thus providing guidelines for future experimental studies on the topic.