Planar bifunctional Luneburg-fisheye lens made of an anisotropic metasurface

Luneburg-fisheye lens made of anisotropic metasurface, which features as Luneburg along the horizontal optical axis while as fisheye along the vertical optical axis. We propose a method to control the inhomogeneous indexes of refraction independently along the two optical axes by designing anisotropic and non-uniform metasurface, which can provide the required distributions of refractive indexes approximately for Luneburg and fisheye lenses watching from the two optical axes. Experiments in the microwave frequency demonstrate very good performance of the planar bi-functional Luneburg-fisheye lens. The proposed method opens a venue to design other kinds of bi-functional devices using metasurfaces in the microwave, terahertz, and even optical frequencies.

由各向异性超表面（anisotropic metasurface）制备的Luneburg-鱼眼透镜（Luneburg-fisheye lens），沿水平光轴呈现Luneburg透镜的光学特性，沿垂直光轴则具备鱼眼透镜的光学特性。我们提出一种设计方法，通过构筑各向异性非均匀超表面，实现沿两条光轴的非均匀折射率独立调控，可近似满足双光轴分别对应Luneburg透镜与鱼眼透镜所需的折射率分布。微波频段下的实验结果表明，该平面双功能Luneburg-鱼眼透镜具有优异的光学性能。本研究提出的方法为利用超表面在微波、太赫兹（terahertz）乃至光频波段设计其他类型双功能器件开辟了新的技术途径。