Achieving total mode conversion from longitudinal to shear waves for a broad incident angle has been a big scientific challenge in elastic fields, which was impossible to be achieved in classical elastic wave theory. In this paper, we propose and realize a refractive transmodal elastic metasurface that can convert an incident longitudinal wave to a shear wave for a broad incident angle. Here, the total mode conversion is achieved via a sufficiently large phase gradient, while the full transmission is achieved with the impedance-matched single-layered metasurface. Numerical and experimental investigations show that the proposed metasurface can provide almost total mode conversion for a broad incident angle from −20.4 ° to 22.3 °. We expect that the proposed refractive transmodal metasurface can be applied in various ultrasonic systems.

中文翻译：

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广角折射跨模态弹性超表面

在宽入射角下实现从纵波到横波的全模式转换一直是弹性场中的一项重大科学挑战，这在经典弹性波理论中是不可能实现的。在本文中，我们提出并实现了一种折射跨模态弹性超表面，可以将入射纵波转换为宽入射角的横波。在这里，总模式转换是通过足够大的相位梯度实现的，而完全传输是通过阻抗匹配的单层超表面实现的。数值和实验研究表明，所提出的超表面可以为从 -20.4° 到 22.3° 的宽入射角提供几乎全模式转换。我们期望所提出的折射跨模态超表面可以应用于各种超声系统。