Broadband achromatic acoustic vortex generator based on integrated-resonant meta-atoms

Abstract

Acoustic vortex generator based on metamaterials is of great importance in acoustic communication, particle manipulation, and other applications. However, most of these applications are limited by narrow bandwidth due to strong dispersion. In this work, we numerically and experimentally present a broadband achromatic acoustic vortex generator (BAAVG) based on integrated-resonant meta-atoms (IRMs). The proposed IRMs, composed of a straight channel with side-loaded resonators and a large cavity, demonstrate linear phase shifts with high transmission efficiency and guarantee the existence of broadband vortex resulting from constant phase difference between adjacent IRMs. Based on the proposed BAAVG, conversion from plane wave to high purity vortex (with average purity 0.9) is demonstrated from 2187 to 2787 Hz. Good agreement between numerical and experimental results verifies the effectiveness of the proposed BAAVG. The high vortex purity of BAAVG exhibits broadband conversion properties quantitatively compared with traditional acoustic vortex generator. Our study provides an avenue to construct broadband achromatic acoustic vortex generators, which advances the capability of designing broadband acoustic vortex beams for versatile applications.