Space-coiling Acoustic Metasurface with Independent Modulations of Phase and Amplitude

TL;DR

This paper introduces a novel acoustic metasurface design that independently modulates phase and amplitude at sub-wavelength scales, enabling advanced control of acoustic wavefronts for applications like acoustic illusions.

Contribution

The work presents a simple space-coiling structure with an air layer that allows independent tuning of phase and amplitude, expanding capabilities of acoustic metasurfaces.

Findings

Achieved full 2π phase control and amplitude modulation of one.

Demonstrated acoustic illusion effect with the metasurface.

Validated independent modulation of phase and amplitude.

Abstract

In this work, we propose a design of acoustic meta-surfaces in sub-wavelength scale enabling independent modulations of phase and amplitude. Each unit cell of the acoustic meta-surface consists of simple conventional space-coiling structure added with an air layer, which can be analyzed as two equivalent slabs with non-dispersion effective parameters. The amplitude depends on the space-coiling structure regardless of the air layer, and the phase can be further adjusted by the air layer independent to the amplitude. The acoustic meta-surface covers an entire phase change of 2-pi and amplitude change of one. We demonstrate an acoustic illusion effect by using the acoustic meta-surface screen, which works well as a full-control discontinuous boundary to support phase and amplitude differences between the original and illusion patterns. The incident field of a point source is transformed into a target field of the point source scattered by an object with shadow area behind it.