High-efficiency nonlocal focusing waterborne acoustic metasurfaces

Abstract

A type of nonlocal waterborne acoustic metasurfaces (WAMs) is proposed to improve the low focusing efficiency of conventional WAMs. Based on the generalized Snell′s law, this nonlocal design enhances the long-range interaction and takes the effects of fluid-solid interaction into account. The theoretical models of the local and nonlocal designs are developed respectively using the finite element simulation software COMSOL Multiphysics, and the focusing cases of the two designs under different incidence conditions are presented. Comparing the simulation results, the focusing efficiency is improved from 35.70% to 48.73%. Additionally, the nonlocal design appears more robust to fluctuations in the incidence frequency, angle, and focal distance. The device is easy to implement in underwater signal communication and high-resolution ultrasonic imaging.