Acoustic Vortex Filter Based on Tunable Metasurfaces

TL;DR

This paper introduces a tunable acoustic vortex filter using metasurfaces that can selectively filter acoustic vortices with specific orbital angular momentum by mechanically adjusting the metasurface orientation.

Contribution

It presents a novel tunable metasurface-based acoustic vortex filter capable of selective filtering of multiplexed vortices with different topological charges.

Findings

Successfully filters acoustic vortices with opposite topological charges

Demonstrates tunability via mechanical rotation of the metasurface

Validates filtering capability through theoretical and experimental results

Abstract

In this paper, we present an acoustic vortex filter (AVF) based on tunable metasurfaces, which can selectively filter the incident multiplexed vortices that carry different orbital angular momentum (OAM). Our metasurface-based AVF is composed of an upper acoustic metasurface (UAM) and a lower acoustic metasurface (LAM), of which the intrinsic topological charge (ITC) can be tuned by mechanically rotating the UAM along its central axis. Due to the critical order of the propagating vortex modes in waveguide, controlling the ITC of the AVF allows for the selective filtering of incoming multiplexed acoustic vortex beams based on the sound vortex diffraction in phase-gradient metasurface, which endows the vortex filter the capability that let the incident vortex of specific OAM pass through it. In the following demonstration, both in theory and experiment, we design the AVF and effectively filter the acoustic vortices with two opposite topological charges (TCs) by simply altering the orientation angle of the UAM. Based on this, we further demonstrate its application in asymmetric acoustic wave transmission. Our work offers an approach to selectively filter the incident acoustic vortex, which improves the capability to control the acoustic OAM via metasurfaces.