  In this work, we designed and studied a feasible dual-layer binary
metagrating, which can realize controllable asymmetric transmission and beam
splitting with nearly perfect performance. Owing to ingenious geometry
configuration, only one meta-atom is required to design for the metagrating
system. By simply controlling air gap between dual-layer metagratings,
high-efficiency beam splitting can be well switched from asymmetric
transmission to symmetric transmission. The working principle lies on
gap-induced diffraction channel transition for incident waves from opposite
directions. The asymmetric/symmetric transmission can work in a certain
frequency band and a wide incident range.Compared with previous methods using
acoustic metasurfaces, our approach has the advantages of simple design and
tunable property and shows promise for applications in wavefront
manipulation,noise control and acoustic diode.
