Flexible Manipulation of the Reflected Wavefront Using Acoustic Metasurface with Split Hollow Cuboid.

Limei Hao,Li Zhang,You Xie,Zhi Chen,Shaofang Pang,Yujia Li,Xiaole Yan,Xi Chen

doi:10.3390/ma15031189

Abstract

This work proposes a method for actively constructing acoustic metasurface (AMS) based on the split hollow cuboid (SHC) structure of local resonance, with the designed AMS flexibly manipulating the direction of reflected acoustic waves at a given frequency range. The AMS was obtained by precisely adjusting any one or two types of structural parameters of the SHC unit, which included the diameter of the split hole, the length, width, height, and shell thickness of the SHC. The simulation results showed that the AMS can flexibly manipulate the direction of the reflected acoustic waves, and the anomalous reflection angle obeys the generalized Snell’s law. Furthermore, among the five structural parameters, the AMS’s response frequency band is widest with the hole diameter and height, followed by the length and width, and narrowest with the shell thickness. It is worth noting that comprehensive manipulation of two parameters not only broadens the response frequency band, but also strengthens the effect of the anomalous reflection at the same response frequency. The subwavelength size of the AMS constructed with such a comprehensive method has the advantages of a small size, wide response band, simple preparation, and flexible modulation, and can be widely used in various fields, such as medical imaging and underwater stealth.

Highlights

The manipulation of wavefront distribution is a hotspot in physics and engineering technology
acoustic metasurface (AMS) with the positive phase gradients were constructed by arranging ten split hollow cuboid (SHC) according to the reflected phase from small to large, and the flexible modulation of the reflected acoustic waves were achieved in the desired frequency band
When the acoustic wave is vertically incident to a metasurface with the phase gradient, the reflected acoustic wave is emitted in a nonvertical direction, resulting in an anomalous reflection

Summary

Introduction

The manipulation of wavefront distribution is a hotspot in physics and engineering technology. Zhao et al [24] designed ultrathin acoustic metasurfaces based on membrane and cavity structures, and anomalous modulation of the transmitted acoustic waves was achieved. Zhao and Zhai [27] designed the AMS with a structure unit with a split cavity and an annular split cavity, and the anomalous modulation of the reflected acoustic waves was attained by changing the rotation angle of the inner split cavity. Liang et al [28] designed a reflected acoustic hypersurface with Schroeder diffusers based on a subwavelength local resonance unit In all these reported works, the main problem with the local resonance AMS is that the prepared method is relatively single, and the frequency range of adjustment of the reflected wavefront distribution is relatively fixed, which makes it difficult to satisfy the engineering design needs at the various working frequency bands. Comprehensive manipulation of two structural parameters was studied

Model and Simulation

Results and Discussion

Effect of the Hole Diameter

Effect of the Length

Conclusions