科研之友
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摘要
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.
