Step-wise constant-amplitude waves in non-Hermitian disordered media

Multi-reflection interference of sound waves is ubiquitous in our daily life, and suppressing any such distortions of a wave's free propagation and achieving counter-directional adaptation is a challenging task, with many applications in acoustics. Here, we propose a non-Hermitian Fabry-Perot resonance unit, which demonstrates unidirectional invisibility in opposite directions at the so-called exceptional points by adjusting its geometric configuration and intrinsic acoustic parameters. Then, we extend the principle and design a waveguide containing six inclusion-membrane pairs in which a unique property of step-wise constant-amplitude waves in two opposite directions has been realized, irrespective of whether the distribution of inclusions is periodic or random. Our method breaks through the limitation of the impedance, amount, position of the inclusions, and the incident direction of the waves, revealing potential applications in acoustic sensing, noise control engineering, and other related wave disciplines. (C) 2022 Author(s).All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY)license (http://creativecommons.org/licenses/by/4.0/).

Automated summary

In this study, a non-Hermitian Fabry-Perot resonance unit is proposed to achieve unidirectional invisibility at exceptional points by adjusting the device's geometric configuration and acoustic parameters. Furthermore, a waveguide consisting of six inclusion-membrane pairs is designed to realize step-wise constant-amplitude waves in two opposite directions. The method breaks through the limitations of inclusions and exhibits potential applications in various wave disciplines.