Asymmetric conversion of arbitrary vortex fields via acoustic metasurface

Abstract

Asymmetric manipulation of acoustic waves has gained significant attention due to its rich physical properties and potential application prospects. In this study, we design and demonstrate a planar acoustic metasurface (AM) that enables asymmetric conversion for vortex fields with arbitrary orbital angular momentum (OAM) to different plane waves by placing the same vortex source at different focusing points of above and below. This asymmetric effect is caused by the spatial asymmetry of vortex wave, and AM achieves the conversion of two types of waves through directional compensation of phases. Numerical demonstrations and acoustic experiments further validate this asymmetric phenomenon, and the deflection angle of converted plane waves is qualitatively and quantitatively confirmed by a more general formula. Our work enriches the research meta-system of acoustic wave physics and holds potential applications in underwater acoustic communication and OAM-based devices.