Metagratings for Waterborne Sound: Various Functionalities Enabled by an Efficient Inverse-Design Approach

A controllable and steerable transport of acoustic wave signals along preferred paths with unitary efficiency is highly desired for underwater acoustic applications such as underwater communication, navigation, and tracking. Here we present a systematical study of a class of simply structured acoustic metagratings containing iron cylinders only. Through diffraction analysis and a genetic-algorithm-assisted optimization process, we propose a powerful inverse-design approach that can faithfully and promptly produce desired wave-front manipulation effects. Various interesting diffraction-engineering functionalities such as perfect beam splitting, anomalous reflection and transmission, retroreflection, and highly asymmetric transmission response are unambiguously demonstrated with unitary efficiency. These simply structured metagrating configurations, as well as the efficient inverse-design methodology behind them, are expected to be useful in the design of multifunctional acoustic planar devices for diverse underwater applications.