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.