Acoustic Wavefront Manipulation: Impedance Inhomogeneity and Extraordinary Reflection

TL;DR

This paper introduces an impedance-based generalized Snell's law for acoustics, enabling unprecedented wavefront control through impedance manipulation, leading to novel acoustic applications and extraordinary reflection phenomena.

Contribution

It establishes a new impedance-governed mechanism for acoustic wavefront manipulation, distinct from optics, allowing precise control of reflection and wavefronts without abrupt phase-changing materials.

Findings

Extraordinary reflection can be engineered via impedance inhomogeneity.

Ordinary reflection can be switched on or off.

Planar surfaces designed with IGSL enable novel acoustic applications.

Abstract

Optical wavefront can be manipulated by interfering elementary beams with phase inhomogeneity. Therefore a surface allowing huge, abrupt and position-variant phase change would enable all possibilities of wavefront engineering. However, one may not have the luxury of efficient abrupt-phase-changing materials in acoustics. This motivates us to establish a counterpart mechanism for acoustics, in order to empower the wide spectrum of novel acoustic applications. Remarkably, the proposed impedance-governed generalized Snell's law (IGSL) of reflection is distinguished from that in optics. Via the manipulation of inhomogeneous acoustic impedance, extraordinary reflection can be tailored for unprecedented wavefront manipulation while ordinary reflection can be surprisingly switched on or off. Our results may power the acoustic-wave manipulation and engineering. We demonstrate novel acoustic applications by planar surfaces designed with IGSL.