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 a full-duplex mode. Here we present the realization of class nonreciprocal circulators based on simply structured metagratings, which consist only few solid cylinders steady fluid flow with low velocity. These innovative metagratings intelligently designed via diffraction analysis linearized potential equation genetic-algorithm-based optimization process. Unitary reflection efficiency between ports demonstrated through full-wave numerical simulations, confirming robust circulation over broad range velocity magnitude profile. Our design provides feasible degree tunability, including switching reciprocal to reversing handedness circulator, presenting convenient but efficient approach devices wavelength-thick metagratings. It may find applications scenarios underwater communication, energy harvesting, sensing.