Reflected acoustic wavefront manipulation by an ultrathin metasurface based on three-dimensional generalized Snell’s law

Abstract

We theoretically derive three-dimensional (3D) generalized Snell’s law which is demonstrated by reflected wavefront manipulations based on ultrathin quasi-3D acoustic metasurfaces. Acoustic metasurfaces with a deep subwavelength thickness of λ/10 are constructed with 16 unit cells composed of a straight pipe and two ring-like Helmholtz resonators. Based on the 3D generalized Snell’s law, many fascinating reflected wavefront manipulations in 3D space are realized separately, including anomalous reflections, point focusing, line focusing in two perpendicular directions, non-diffracting Bessel beam and self-bending beam. Our results provide a new design methodology for 3D sound wavefront manipulations and practical applications of 3D sound devices.