The emergence and development of acoustic artificial materials stimulate a large number of applications for the manipulation of ultrasonic and elastic waves. Most of the reported metasurfaces and metamaterials only work effectively at a given frequency and target a fixed functionality. Reconfigurable designs may solve this problem, to a certain extent, but require the introduction of complex active control components. Here, by integrating multiple functionalities on a conformally mapped Mikaelian lens with a hyperbolic secant refractive-index distribution, a broadband passive lens is presented and accomplished on an elastic plate. Just by adjusting the location and type of source, different regulations of flexural waves can be switched from one sort to another. Through projecting the refractive-index profile onto the thickness of the plates, the proposed Mikaelian lens is designed and fabricated. Theoretical prediction and experimental results demonstrate beam scanning at an angle of up to 120° from 30 to 180 kHz and achromatic subwavelength focusing with a full width at half maximum of around 0.3λ from 30 to 120 kHz. Without using locally resonant materials or active control elements, this work provides a feasible way to construct multifunctional flexural-wave devices.

中文翻译：

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弹性板上的超宽带和多功能消色差 Mikaelian 透镜

声学人造材料的出现和发展激发了对超声波和弹性波操纵的大量应用。大多数报告的超表面和超材料仅在给定频率下有效工作并针对固定功能。可重构设计可以在一定程度上解决这个问题，但需要引入复杂的主动控制组件。在这里，通过在具有双曲线正割折射率分布的共形映射 Mikaelian 透镜上集成多种功能，在弹性板上呈现并实现了宽带无源透镜。只需调整源的位置和类型，弯曲波的不同调节就可以从一种切换到另一种。通过将折射率分布投影到板的厚度上，所提出的 Mikaelian 透镜是设计和制造的。理论预测和实验结果表明，在 30 至 180 kHz 范围内以高达 120° 的角度进行光束扫描，并且半峰全宽约为 0.3 的消色差亚波长聚焦λ从 30 到 120 kHz。这项工作在不使用局部谐振材料或有源控制元件的情况下，为构建多功能弯曲波器件提供了一种可行的方法。