Forward and Backward Multibeam Scanning Controlled by a Holographic Acoustic Metasurface

Acoustic metasurfaces have great potential in the field of beam-forming acoustic antennas due to their thin, two-dimensional, and miniature artificial materials that can freely control sound waves. Here, we propose an acoustic metasurface, with multibeam acoustic radiation serving as leaky-wave antennas used for acoustic beam steering. Based on the holographic principle, we pattern a sinusoidal modulated admittance surface, which is designed as a periodic arrangement of cylindrical holes with varying depth profiles. An omnidirectional sound generated from a tiny hole located at the center of the patterned plate creates acoustic surface waves on the modulated surface while simultaneously generating leaky-wave radiation. For multibeam steering, the holographic admittance surfaces are designed with multiple subregions of the metasurface, with each subregion emitting single-beam radiation in the desired direction. Furthermore, the holographic metasurfaces are programmed separately to have forward and backward leaky-wave radiation. In this study, we use three-dimensional additive fabrication to print acoustic holograms to craft the surfaceadmittance variation at subwavelength resolution. Experimental results on these printed holograms show multidirectional acoustic beam steering in close agreement with the theoretical analysis and numerical results. Forward and backward multibeam frequency scanning is also demonstrated by frequency variation. Thus, we expect that this planar surface can be used in applications such as acoustic communications, levitation, and imaging.

Automated summary

Acoustic metasurfaces, with their thin, two-dimensional, and miniature artificial materials that can control sound waves, have great potential in beam-forming acoustic antennas. In this study, we propose an acoustic metasurface that utilizes multi-beam acoustic radiation for acoustic beam steering. By using the holographic principle, a sinusoidal modulated admittance surface is patterned, generating sound surface waves and leaky-wave radiation. Experimental results demonstrate multidirectional acoustic beam steering and forward-backward multibeam frequency scanning. This research holds promise for applications in acoustic communications, levitation, and imaging.