可调共振型超表面对透射声波的三维波前调控

Three-dimensional wavefront manipulation of transmitted acoustic waves by a tunable resonant metasurface

为实现对透射声波波前的灵活调控,本文设计了带有开口的可旋转共振筒单胞,通过旋转单元内筒即可调节开口的大小,进而改变透射声波的相位。依据广义Snell定律,结合设定的工作频率和预期的功能如三维异常折射、聚焦以及波束自弯曲等,利用此可重构单胞构建双向梯度共振型超表面,并进行有限元软件数值模拟。结果表明:本文设计的可调超表面可实现对三维声场的有效和灵活操控。

To realize the flexible modulation of the transmitted acoustic waves, a unit cell consisting of a rotational resonant cylinder with openings is designed in this paper. The opening angle can be changed by simply rotating the inner cylinder;thus, the phase of the transmitted acoustic waves can be modulated flexibly. Then, based on the generalized Snell′s law, resonant metasurfaces with bidirectional phase gradients are constructed by using this reconfigurable unit cell according to the set working frequency and the expected functions, including three-dimensional(3-D) abnormal refraction, focusing, and beam self-bending. Numerical simulations are performed by using finite element software. The results show that the tunable metasurface designed in this paper can effectively and flexibly manipulate the 3-D sound field.