Non-Hermitian acoustic metamaterial for the complete control of sound by accessing the exceptional points

TL;DR

This paper presents a non-Hermitian acoustic metamaterial that leverages exceptional points to achieve complete control over sound, including decoupled tuning of phase and amplitude, demonstrated through acoustic holography.

Contribution

It introduces a novel non-Hermitian acoustic metamaterial design that utilizes exceptional points for independent control of sound wave properties.

Findings

Decoupled tuning of phase and amplitude achieved

Experimental demonstration of acoustic hologram

Control of sound via loss engineering at exceptional points

Abstract

Non-Hermitian systems always play a negative role in wave manipulations due to inherent non-conservation of energy as well as loss of information. Recently, however, there has been a paradigm shift on utilizing non-Hermitian systems to implement varied miraculous wave controlling. For example, parity-time symmetric media with well-designed loss and gain are presented to create a nontrivial effect of unidirectional diffraction, which is observed near the exceptional points (EPs) in the non-Hermitian systems. Here, we report the design and realization of non-Hermitian acoustic metamaterial (NHAM) and show that by judiciously tailoring the inherent loss, the phase and amplitude of reflection can possibly be tuned in a decoupled manner. Such decoupled tuning of phase and amplitude is closely related to the EPs. As a demonstration of functionality, we experimentally generate a high-quality acoustic hologram via NHAM. Our work may open a new degree of freedom for realizing the complete control of sound.