Generation of topologically diverse acoustic vortex beams using a compact metamaterial aperture

TL;DR

This paper introduces a compact, tunable metamaterial-based acoustic vortex generator that efficiently produces diverse vortex modes, including non-integer ones, with simple geometry and electronic control, advancing acoustic wave manipulation.

Contribution

The authors develop a novel metamaterial aperture that generates topologically diverse acoustic vortex beams using a wrapped leaky wave antenna, offering a simpler and more compact alternative to existing methods.

Findings

Successfully generated both integer and non-integer vortex modes.

Demonstrated tunability via frequency-dependent refractive index.

Achieved a compact design suitable for high-density systems.

Abstract

Vortex waves, which carry orbital angular momentum, have found use in a range of fields from quantum communications to particle manipulation. Due to their widespread influence, significant attention has been paid to the methods by which vortex waves are generated. For example, active phased arrays generate diverse vortex modes at the cost of electronic complexity and power consumption. Conversely, analog apertures, such as spiral phase plates, metasurfaces, and gratings require separate apertures to generate each mode. Here we present a new class of metamaterial-based acoustic vortex generators, which are both geometrically and electronically simple, and topologically tunable. Our metamaterial approach generates vortex waves by wrapping an acoustic leaky wave antenna back upon itself. Exploiting the antennas frequency-varying refractive index, we demonstrate experimentally and analytically that this analog structure generates both integer, and non-integer vortex modes. The metamaterial design makes the aperture compact and can thus be integrated into high-density systems.