Holographic acoustic admittance surface for acoustic beam steering

Abstract

Efficient beam steering using elements in the subwavelength scale is an exciting field, which can significantly miniaturize the existing acoustic systems and may lead to promising applications of sonic devices. In this study, we build an acoustic metasurface, which functions as a holographic leaky wave antenna and achieves effective beam steering in the designed direction. It is demonstrated that carefully designing the depth of the cylindrically grooved elements, arranged in a hexagonal pattern, allows the refractive index and surface admittance to be manipulated and can be used to generate acoustic surface modes below the cutoff frequency. The hologram principle, originally used for holographic reactance surfaces in the electromagnetic regime, is used to introduce admittance patterns, which allow effective beam steering results. We present a detailed construction methodology of the holographic acoustic admittance surface and verify its beam steering effectiveness both experimentally and numerically. The present work presents an effective method for acoustic beam steering and brings us one step closer in achieving freely steering wave beams.