Cloaking, Trapping and Superlensing of Lamb Waves with Negative Refraction

TL;DR

This paper demonstrates experimental and numerical methods to manipulate Lamb waves using negative refraction, enabling cloaking, trapping, and superlensing effects in elastic media, advancing elastic wave control technologies.

Contribution

It introduces a practical elastic superlens combining negative refraction with metalens concepts, surpassing diffraction limits for Lamb wave imaging.

Findings

Negative refraction enables wave cloaking and trapping.

Evanescent waves can be converted into propagating waves.

The work advances towards elastic superlens development.

Abstract

We report on experimental and numerical implementations of devices based on the negative refraction of elastic guided waves, the so-called Lamb waves. Consisting in plates of varying thickness, these devices rely on the concept of complementary media, where a particular layout of negative index media can cloak an object with its anti-object or trap waves around a negative corner. The diffraction cancellation operated by negative refraction is investigated by means of laser ultrasound experiments. However, unlike original theoretical predictions, these intriguing wave phenomena remain, nevertheless, limited to the propagating component of the wave-field. To go beyond the diffraction limit, negative refraction is combined with the concept of metalens, a device converting the evanescent components of an object into propagating waves. The transport of an evanescent wave-field is then possible from an object plane to a far-field imaging plane. Twenty years after Pendry's initial proposal, this work thus paves the way towards an elastic superlens.