Bianisotropic metasurfaces for scattering-free manipulation of acoustic wavefronts

TL;DR

This paper introduces a new acoustic bianisotropic metasurface design that achieves near-ideal wavefront control with high efficiency, enabling scattering-free redirection of sound waves at large angles.

Contribution

It proposes a novel acoustic cell architecture for bianisotropic metasurfaces that reduces losses and enhances control over wavefront manipulation.

Findings

Achieved over 90% efficiency in redirecting acoustic waves.

Demonstrated control of wavefronts at 60°, 70°, and 80° angles.

Outperformed conventional Snell's law-based designs in efficiency.

Abstract

Recent advances in gradient metasurfaces have shown that only by locally controlling the bianisotropic response of the constituent cells can one ensure full control of refraction, i.e., arbitrarily modify the direction of the incident waves without producing scattering into unwanted directions. In this work, we propose and experimentally verify the use of a new acoustic cell architecture that provides enough degrees of freedom to fully control the bianisotropic response and minimizes the implementation losses produced by resonant elements. The versatility of the approach is shown through the design of three different anomalous refractive metasurfaces capable of redirecting a normally incident plane wave to 60, 70 and 80 degrees on transmission. The effciency of the bianisotropic designs is over 90%, much higher than the corresponding designs based on the conventional generalized Snells law (81%, 58%, and 35%). The proposed strategy opens a new way of designing practical and highly effcient bianisotropic metasurfaces for different functionalities, enabling nearly ideal control over the acoustic energy flow through thin metasurfaces.