Acoustic Coherent Perfect Absorbers as Sensitive Null Detectors

TL;DR

This paper experimentally demonstrates acoustic coherent perfect absorbers (CPAs) that can serve as highly sensitive null detectors, showing nearly 1000-fold modulation of output power and detecting minute differences between incident waves.

Contribution

The study introduces the first experimental realization of acoustic CPA with diverse symmetric scatterers, highlighting their potential as sensitive null detectors for wave differences.

Findings

Nearly 1000 times modulation of output power achieved

27% change in scattering strength per degree phase deviation

Effective detection of small differences between incident waves

Abstract

We report the experimental realization of acoustic coherent perfect absorption (CPA) of four symmetric scatterers of very different structures. The only conditions necessary for these scatterers to exhibit CPA are that both the reflection and transmission amplitudes of the scatterers are 0.5 under one incident wave, and there are two collinear and counter-propagating incident waves with appropriate relative amplitude and phase. Nearly 1000 times in the modulation of output power has been demonstrated by changing the relative phase of the incident waves over 180{\deg}. We further demonstrate that these scatterers are sensitive devices to detect the small differences between two nearly equal incident waves. A 27 % change in the strength of the scattering wave has been demonstrated for every degree of phase deviation from the optimum condition between the incident waves.