Palermo Antonio, Marzani Alessandro
Department of Civil, Chemical, Environmental and Materials Engineering - DICAM, University of Bologna, Bologna, 40136, Italy.
Sci Rep. 2018 May 8;8(1):7234. doi: 10.1038/s41598-018-25503-8.
Metasurfaces of mechanical resonators have been successfully used to control in-plane polarized surface waves for filtering, waveguiding and lensing applications across different length scales. In this work, we extend the concept of metasurfaces to anti-plane surface waves existing in semi-infinite layered media, generally known as Love waves. By means of an effective medium approach, we derive an original closed-form dispersion relation for the metasurface. This relation reveals the possibility to control the Love waves dispersive properties by varying the resonators mechanical parameters. We exploit this capability to manipulate the metasurface refractive index and design two gradient index (GRIN) metalenses, i.e. a Luneburg lens and a Maxwell lens. We confirm the performance of the designed lenses using full 3D finite element simulations. Our work demonstrates the possibility of realizing wave control devices for anti-plane waves.
机械谐振器的超表面已成功用于控制面内偏振表面波，以实现跨不同长度尺度的滤波、波导和透镜应用。在这项工作中，我们将超表面的概念扩展到半无限分层介质中存在的反平面表面波，即通常所说的乐甫波。通过有效介质方法，我们推导出了超表面的原始封闭形式色散关系。该关系揭示了通过改变谐振器的机械参数来控制乐甫波色散特性的可能性。我们利用这一能力来操纵超表面折射率，并设计了两种梯度折射率（GRIN）金属透镜，即伦伯格透镜和麦克斯韦透镜。我们使用全三维有限元模拟证实了所设计透镜的性能。我们的工作证明了实现反平面波的波控器件的可能性。
