Ultrathin Acoustic Metasurface Holograms with Arbitrary Phase Control

Huaping Wang,Zehao Wang,Rongrong Zhu,Weijie Gao,Zhiwei Xu,Bin Zheng

doi:10.3390/app9173585

Abstract

Holograms show great potential in optical or acoustical waves applications due to their capability to reconstruct images. In this paper, we propose a novel scheme to realize acoustic holograms based on an ultrathin metasurface with arbitrary phase control ability. Compared with the conventional imaging method, e.g., concave mirror, which has a bulky size and limited imaging effects, the acoustic metasurface comprises a single layer of Helmholtz-like elements that can largely reduce the complexity of production. With this ultrathin reflective metasurface, acoustic holograms are constructed through a subtle structure design for single and multiple focal imaging, while the potential thermoviscous effects are minimized. We further demonstrate that the metasurface has the capability of arbitrary phase control in a certain frequency range, where the reflected phase dispersion is linear. Our proposed ultrathin metasurface holograms would be very useful in numerous applications, such as acoustic sensing, medical imaging, and so on.

Highlights

Acoustic imaging and acoustic focusing have many essential uses in modern science and industry, such as diagnosing disease [1], sensing natural gas seepage [2], visualizing earthquake sources [3], and microfluidic particle separation [4]
The hologram can be generated by calculating the phase distribution of the field on the hologram and transforming the phase information into unit structures, a method known as computer-generated holography (CGH) [9,10,11]
To demonstrate the flexibility of the acoustic metasurface hologram, we introduced multifocal holography based on the same methods that single-focal holography uses

Summary

Introduction

Acoustic imaging and acoustic focusing have many essential uses in modern science and industry, such as diagnosing disease [1], sensing natural gas seepage [2], visualizing earthquake sources [3], and microfluidic particle separation [4] Structures such as the concave mirror, convex mirror, and wedge are used to realize focal and imaging effects. Sci. 2019, 9, 3585 is thin, compact, and capable of controlling phases Owing to these advantages, the metasurface is opening the path to various applications, such as ultrathin flat lenses [20,21,22], carpet cloaks [23,24,25], and polarization conversion [26]. Simulations are performed, and the results all possess good consistency with the theoretical prediction, validating the effectiveness in our design

Results and Discussion

Simulated

Conclusions