Design of acoustic metasurfaces with independent phase and amplitude control

Abstract

We address the problem of designing acoustic metasurfaces for independent amplitude and phase control of acoustic waves. The reflection and transmission amplitude and phase of an acoustic wave are governed by the geometry of the acoustic metasurface. The geometry is modeled by discretizing the continuous space into a finite number of elements, where each element can either be filled with air, or solid material. Full wave simulations on the COMSOL Multiphysics software are performed to obtain the acoustic outputs for a given geometry. In case of smaller-sized elements, it is computationally infeasible to consider all geometries, which correspond to all possible combinations of solid or air-filled elements. To address this challenge, we propose a novel ‘acoustic domain space expansion algorithm’ that starts with a few geometries and adaptively adds geometries to the set such that they span the entire domain of the desired acoustic outputs, using only a small fraction of all the possible geometries. Our algorithm simulated only 24 000 geometries out of the 563 trillion possible geometries, which can be used to obtain any feasible combination of the acoustic outputs with a tolerance of 5.4% in the individual outputs.