Nonlinear acoustic metasurface for simultaneous higher-harmonic generation and demultiplexing
Nonlinear acoustic metasurface for simultaneous higher-harmonic generation and demultiplexing
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DOI：
10.1117/12.2612932
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发表时间：
2022-04
期刊：
影响因子：
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通讯作者：
Zhen Lin;Yuning Zhang;Kon-Well Wang;S. Tol
中科院分区：
文献类型：
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作者：
Zhen Lin;Yuning Zhang;Kon-Well Wang;S. Tol
近年来，声学/弹性亚表面因其结构紧凑、重量轻、具有控浪能力而受到越来越多的研究关注。亚表面是主介质中的一层薄层，由一系列亚波长尺度图案组成，它在波传播路径中引入突变的相移，并根据广义斯奈尔定律调整波前。现有的亚表面主要依赖于结构的线性动力行为，而对其非线性特性的研究还很少。最近的几项尝试显示了在声学超表面设计中引入非线性的方法，从而导致非线性效应，如二次谐波产生(SHG)。然而，这些研究主要集中在高次谐波的产生和最大化，而对相位调制和波前剪裁能力的研究较少。我们的研究推进了技术水平，并提出了一种新的声学准表面设计，该设计采用曲线梁形式的局部共振非线性元件。我们用解析框架和数值框架研究了该系统的非线性现象，特别是倍频现象。结果表明，所提出的非线性亚曲面可以在传输的声波场中实现倍频，同时通过引导不同的方向对不同的频率分量进行解复用(即从基频分量中分离出二次谐波分量)。这项研究提供了新的理论和数值平台来探索声学亚表面的幅度相关行为，扩展了它们的波前剪裁能力和功能，并为高效的声波操纵技术开发了新的潜力。
Recently, acoustic/elastic metasurfaces have gained increasing research interests due to their ability to control waves with compact and lightweight structures. A metasurface is a thin layer in the host medium composed of an array of subwavelength-scaled patterns, which introduces an abrupt phase shift in the wave propagation path and tailors wavefront based on generalized Snell’s law. The existing metasurfaces mainly depend on the linear dynamic behavior of the structures, while their nonlinear features have not been studied extensively. A couple recent attempts have shown means of introducing nonlinearity in acoustic metasurface designs, resulting in nonlinear effects such as second-harmonic generation (SHG). However, these studies mainly focus on generating and maximizing the higher-order harmonics, while the phase modulation and wavefront tailoring capability are less explored. Our study advances the state of the art and proposes a novel acoustic metasurface design with locally resonant nonlinear elements in the form of curved beams. We explore the nonlinear phenomenon, specifically SHG, of the proposed system using both analytical and numerical frameworks. Our results show that the proposed nonlinear metasurface can achieve SHG in the transmitted acoustic wavefield, and simultaneously demultiplex for different frequency components (i.e., split the second-harmonic component from the fundamental frequency component) by steering them into different directions. This study presents new theoretical and numerical platforms to explore the amplitude-dependent behavior of acoustic metasurfaces, expands their wavefront tailoring capabilities and functionalities, and develops new potentials towards efficient technologies to manipulate acoustic waves.