Ultrathin Acoustic Holography

Abstract

How to realize acoustic holography via ultradeep‐subwavelength structures is a challenging problem in the past decades, which is thought impossible due to the linear proportional relationship between the structural thickness and acoustic wavelength. In this article, the methodology of ultrathin holography by patterning holes in an acoustic insulation plate with an ultradeep‐subwavelength thickness is introduced. The transmitted sound field can be manipulated arbitrarily to form a desired shape by designing the ultrathin pattern based on the nonlocal wave interaction theory. The physical mechanism of the nonlocal behavior to achieve a sophisticated hologram is revealed due to the interaction among the sound wave components themselves. Furthermore, the experiments are designed to map out the pressure amplitude field of a “sun” pattern in air and water, respectively. The work demonstrates the advantage of nonlocal ultrathin holography in the applications of ultrathin acoustic devices and provides inspiration for the holographic wave manipulation.

Decorated bacteria-cellulose ultrasonic metasurface

“…The wave scattering problem with the Fredholm integral equation has been solved in quantum mechanics as the Lippmann-Schwinger equation. We discretize the meta-skin and divide it into a regular unit array to derive the discretization equation 41 . The acoustic pressure distribution on the metasurface can be further calculated from the nonlocal coupling between square holes at different positions, where is the pressure from the unit , is the area of each unit, is the Green’s function between two units and , is the pressure from the unit .…”

“…Therefore, the question of obtaining the target acoustic field is attributed to a ‘0–1’ programming on the discretized meta-skin. It is effective to solve the ‘0–1’ programming via the optimization method 41 , 42 . Details of the optimization algorithm are given in Supplementary Note 4 .…”

“…The acoustic scattering properties are derived from the nonlocal coupling between square holes at different positions. Therefore, meta-skin holography can be regarded as reshaping the propagation behavior of ultrasound through the interaction between acoustic waves themselves rather than the interaction between acoustic waves and metamaterial with an interior space 41 . In the incident ultrasound wave, the reflected and transmitted waves interact and change their wave fields synergistically through the nonlocal effects between the arranged through-holes.…”

Acoustic metascreen for broadband wavefront manipulation with stationary phase gradients

“…Building on the foundational concepts of the generalized Snell law (GASL) [11], the (a) E-mail: zhmgu@tongji.edu.cn (corresponding author) (b) E-mail: yongli@tongji.edu.cn (c) E-mail: jiezhu@tongji.edu.cn modulatory capacity for the transmitted and reflected wavefronts of gradient acoustic metamaterials and metasurfaces has been elucidated. As a result, diverse gradient metamaterials and metasurfaces have been instrumental in unveiling novel phenomena such as anomalous refraction/reflection [27][28][29][30], innovative acoustic holography techniques [31][32][33][34][35], and unique approaches to acoustic focusing [36][37][38][39][40] and bending [41][42][43][44][45]. Multiple unit cell architectures have been examined in the context, encompassing Helmholtz resonators [46][47][48][49], membrane-based structures [50][51][52][53], and coiling spaces [54][55][56], with the objective of achieving metamaterials and metasurfaces characterized by transversal gradient impedance or phase profiles.…”