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

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 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 nonreciprocal 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 is demonstrated through full-wave numerical simulations, confirming nonreciprocal and robust circulation of the acoustic signal over a broad range of flow velocity magnitudes and profiles. 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 and efficient approach for the realization of nonreciprocal acoustic devices from wavelengththick metagratings. It may find applications in various scenarios, including underwater communication, energy harvesting, and acoustic sensing.

Automated summary

Nonreciprocal signal operation is achieved through the use of simply structured acoustic metagratings, which provide nonreciprocal and robust circulation of the acoustic signal over a broad range of flow velocity magnitudes and profiles. The design allows for tunability, including switching between reciprocal and nonreciprocal operation, and reversing the handedness of the circulator, offering a convenient and efficient approach for the realization of nonreciprocal acoustic devices from wavelength-thick metagratings.