卷曲空间型超表面对声波的调控

声学超表面具有天然材料所不具备的独特属性,为声学器件的设计提供了多样性。以广义斯涅尔定律为理论基础,设计了具有多种声波调控能力的折射型相位梯度超表面。该超表面由8个具有不同结构参数的卷曲空间单元结构组合而成,在中心频率3 500 Hz附近,8个单元结构的相位覆盖π范围且声波透射率较高。通过合理地设计超表面水平方向上的相位梯度变化,能够实现对声波的任意调控,在理论和有限元仿真上依次实现了异常折射、无衍射贝塞尔声束和声聚焦。这种厚度薄、透射率高的声超表面,在声学器件设计方面具有潜在的应用价值。

Acoustic wave regulation and control by coiling up space typed metasurface

The acoustic metasurface has unique properties which are not possessed by natural materials, it provides diversity for the design of acoustic devices. In this paper, it is theoretically demonstrated that the generalized Snell''s law can be used for designing acoustic gradient metasurface to achieve acoustic wavefront regulation and control. The metasurfaces are constructed by eight coiling up space units of a solid structure having different structural parameters. The eight units can provide discrete phase shifts covering. span and have the extraordinary acoustic transmission coefficient around the frequency of 3 500 Hz. Arbitrary regulation and control of acoustic wavefront can be achieved by appropriately designing the phase gradient profiles in the transverse direction of the metasurface. The theoretical and numerical results show that some excellent wavefront regulations, such as anomalous refraction, non-diffracting Bessel beam and sub-wavelength flat focusing, can be achieved. The ultrathin metasurfaces with high transmission coefficient has potential application in acoustic devices.