Department of Electrical and Computer Engineering, The University of Texas at Austin, Austin, Texas 78712, USA.
Photonics Initiative, Advanced Science Research Center, City University of New York, New York, New York 10031, USA.
Phys Rev Lett. 2018 Jun 22;120(25):254301. doi: 10.1103/PhysRevLett.120.254301.
Willis coupling in acoustic materials defines the cross-coupling between strain and velocity, analogous to bianisotropic phenomena in electromagnetics. While these phenomena have been garnering significant attention in recent years, to date their effects have been considered mostly perturbative. Here, we derive general bounds on the Willis response of acoustic scatterers, show that these bounds can be reached in suitably designed scatterers, and outline a systematic venue for the realistic implementation of maximally bianisotropic acoustic inclusions. We then employ these inclusions to realize acoustic metasurfaces for bending and steering of sound with unitary efficiency.
声材料中的 Willis 耦合定义了应变和速度之间的交叉耦合，类似于电磁学中的双各向异性现象。尽管这些现象近年来受到了广泛关注，但迄今为止，它们的影响大多被认为是微扰性的。在这里，我们推导出了声学散射体 Willis 响应的一般边界条件，表明这些边界条件可以在适当设计的散射体中达到，并概述了实现最大双各向异性声学夹杂的系统方法。然后，我们利用这些夹杂实现了具有单位效率的声超表面，用于声的弯曲和转向。
