Multifunctional reflection in acoustic metagratings with simplified design

In this work, we propose and demonstrate a simple acoustic metagrating with binary phase modulation that can be employed to achieve multifunctional reflection with high efficiency, including three-channel retroreflection, quasi-retroreflection, and specular reflection. Although only two sub-elements are designed for the acoustic metagratings, the efficiency of multifunctional reflection is well preserved. By changing the desired retroreflection angle, the incident range of quasi-retroreflection and specular reflection can be effectively tuned. Our work provides an alternative way for planar acoustic devices with versatility and enables the development of acoustic metasurfaces with a simplified design.