Acoustic Wave Splitting and Wave Trapping Designs

Acoustic metasurfaces use the phase gradient of a single layer to reflect/refract waves in any direction. This study shows that other than wave steering, acoustic metasurfaces can exhibit wave splitting or trapping through the geometry design. Previous studies focused on the generalized Snell's law when developing metasurfaces and attempted to prevent wave leakages. On the contrary, this study exploits the periodicity of metasurfaces to accomplish acoustic wave splitting, which leads to a similar concept to metagrating. For acoustic wave trapping, we show that through proper arrangements, an acoustic wave can be localized in a specific region without using any boundaries based on the generalized Snell's law. A design formula is provided to trap waves from any incident angle or at any frequency. The analytical and numerical results are in good agreement, verifying the effectiveness of the proposed concept for wave splitting and trapping. This study shows the versatile applications of acoustic metasurfaces and is useful for interferometry and energy harvesting.