Acoustic Reflection And Refraction Control Technology Based On Metasurface

Acoustic metasurfaces refer to ultra-thin acoustic devices that are composed of sub-wavelength-sized unit structures that are densely arranged and combined into complex structures.The unit structure can be reasonably designed to control the wavefront of the sound wave,so that the phase of the sound wave can be distributed from 0° to 360°,thereby realizing some peculiar physical phenomena.However,these unit structures are usually composed of subwavelength-sized multi-folded channels or independent cylindrical structures,which have disadvantages such as low beam steering efficiency and poor rigidity,which limit their application in practical engineering.Here we propose a metasurface-based acoustic wavefront manipulation technique for the design of a highly efficient anomalous beam splitter that etches one to two semicircular grooves per cycle on a flat acoustic surface,enabling acoustic wave peculiar physical phenomena such as anomalous reflection/refraction,retroreflection,and specular reflection.Compared with the previous gradient structure or cylindrical structure,this design can split the incident acoustic wave into a specific direction,and has high directional reflection efficiency.This paper designs three acoustic models on this basis.The first is a symmetrical abnormal reflection beam splitter,which is used to realize the symmetrical reflection beam splitting of acoustic waves;the second is an asymmetric abnormal reflection beam splitter,which is used to realize asymmetric reflection beam splitting of acoustic waves;the third is the abnormal transmission acoustic metasurface,which is used to achieve the abnormal transmission of acoustic waves.Our design avoids thin-walled and freestanding cylindrical structures,so this acoustic metasurface structure can be used to achieve specific reflection and refraction modulation of low-frequency acoustic waves compared to previously established systems.The design is modeled under the framework of diffraction theory of gratings and genetic optimization algorithms.This paper discusses the interaction mechanism between incident acoustic waves and artificial structures in depth,and systematically studies the scattering properties and anomalies of periodic acoustic metasurface structures.The physical properties provide a reference for the wavefront manipulation of acoustic waves and the fabrication of acoustic planar devices.