Enhanced sensing and conversion of ultrasonic Rayleigh waves by elastic metasurfaces

TL;DR

This paper introduces an elastic metasurface device that enhances Rayleigh wave rainbow trapping and enables mode conversion to shear waves, advancing wave manipulation on deep elastic substrates.

Contribution

It presents the first experimental demonstration of elastic Rayleigh wave rainbow trapping combined with mode conversion on deep elastic substrates.

Findings

Successful experimental creation of Rayleigh wave rainbow trapping.

Effective mode conversion from Rayleigh to shear waves.

Potential applications in energy harvesting and wave filtering.

Abstract

Recent years have heralded the introduction of metasurfaces that advantageously combine the vision of sub- wavelength wave manipulation, with the design, fabrication and size advantages associated with surface excitation. An important topic within metasurfaces is the tailored rainbow trapping and selective spatial frequency separation of electromagnetic and acoustic waves using graded metasurfaces. This frequency dependent trapping and spatial frequency segregation has implications for energy concentrators and associated energy harvesting, sensing and wave filtering techniques. Different demonstrations of acoustic and electromagnetic rainbow devices have been performed, however not for deep elastic substrates that support both shear and compressional waves, together with surface Rayleigh waves; these allow not only for Rayleigh wave rainbow effects to exist but also for mode conversion from surface into bulk waves. We design, and test experimentally, a device creating not only elastic Rayleigh wave rainbow trapping, but also selective mode conversion of surface Rayleigh waves to shear waves.