Chaplain Gregory J, De Ponti Jacopo M, Colombi Andrea, Fuentes-Dominguez Rafael, Dryburg Paul, Pieris Don, Smith Richard J, Clare Adam, Clark Matt, Craster Richard V
Department of Mathematics, Imperial College London, London, SW7 2AZ, UK.
Department of Civil and Environmental Engineering, Politecnico di Milano, Piazza Leonardo da Vinci, 32, 20133, Milano, Italy.
Nat Commun. 2020 Jun 29;11(1):3267. doi: 10.1038/s41467-020-17021-x.
Elastic waves guided along surfaces dominate applications in geophysics, ultrasonic inspection, mechanical vibration, and surface acoustic wave devices; precise manipulation of surface Rayleigh waves and their coupling with polarised body waves presents a challenge that offers to unlock the flexibility in wave transport required for efficient energy harvesting and vibration mitigation devices. We design elastic metasurfaces, consisting of a graded array of rod resonators attached to an elastic substrate that, together with critical insight from Umklapp scattering in phonon-electron systems, allow us to leverage the transfer of crystal momentum; we mode-convert Rayleigh surface waves into bulk waves that form tunable beams. Experiments, theory and simulation verify that these tailored Umklapp mechanisms play a key role in coupling surface Rayleigh waves to reversed bulk shear and compressional waves independently, thereby creating passive self-phased arrays allowing for tunable redirection and wave focusing within the bulk medium.
沿表面传播的弹性波在地球物理学、超声检测、机械振动和表面声波器件等领域有着广泛应用；精确操控表面瑞利波及其与极化体波的耦合是一项挑战，而这一挑战有望为高效能量收集和减振装置解锁所需的波传输灵活性。我们设计了弹性超表面，它由附着在弹性基底上的渐变棒状谐振器阵列组成，结合声子 - 电子系统中倒逆散射的关键见解，使我们能够利用晶体动量的转移；我们将瑞利表面波模式转换为形成可调波束的体波。实验、理论和模拟验证了这些定制的倒逆机制在将表面瑞利波独立耦合到反向体剪切波和压缩波方面起着关键作用，从而创建了无源自相位阵列，可在体介质内实现可调重定向和波聚焦。
