Acoustic Metagrating Circulators: Nonreciprocal, Robust, and Tunable Manipulation with Unitary Efficiency

TL;DR

This paper introduces a simple, efficient acoustic circulator using metagratings and fluid flow, achieving nonreciprocal signal routing with high efficiency, tunability, and robustness, suitable for underwater communication and sensing.

Contribution

The work presents a novel design of acoustic circulators based on metagratings and fluid flow, demonstrating nonreciprocal operation with unitary efficiency and tunability, which was not previously achieved with such simplicity.

Findings

Achieved nonreciprocal acoustic circulation with high efficiency.

Demonstrated robustness over various flow velocities and profiles.

Enabled tunable switching and reversal of circulation direction.

Abstract

Nonreciprocal signal operation is highly desired for various acoustic applications, where protection from unwanted backscattering can be realized so that transmitting and receiving signals are processed in a full-duplex mode. Here we present the realization of a class of nonreciprocal circulators based on simply structured acoustic metagratings, which consist only of a few solid cylinders and a steady fluid flow with low velocity. These innovative metagratings are intelligently designed via a diffraction analysis of the linearized potential flow equation and a genetic-algorithm-based optimization process. Unitary reflection efficiency between desired ports of the circulators are demonstrated through full-wave numerical simulations, confirming nonreciprocal and robust circulation of the acoustic signal over a broad range of flow velocity magnitude and profile. Our design provides a feasible degree of tunability, including switching from reciprocal to nonreciprocal operation and reversing the handedness of the circulator, presenting a convenient but efficient approach for the realization of nonreciprocal acoustic devices from wavelength-thick metagratings. It may find applications in various scenarios including underwater communication, energy harvesting, and acoustic sensing.