Terahertz multi-foci metalens enabling high-accuracy intensity distributions and polarization-dependent images based on inverse design

Abstract

A multi-foci metalens can realize unprecedented functions (i.e., the large field of view and fully reconfigurable imaging) that are extremely challenging to achieve by conventional lenses. However, a traditional multi-foci metalens shows inhomogeneous/chaotical intensity distributions between multiple focal spots, which is a key challenge in metasurface design and limited for further applications. Herein, an inverse design method is proposed to automatically optimize the in-plane orientation (rather than the shape) of each meta-atom in terahertz multi-foci metalenses that can generate a plethora of focal spots with high-accuracy intensity distributions. The inverse design of multi-foci metalenses for generating circularly polarized and linearly polarized images (rather than holograms) with nearly homogeneous intensity distributions is proposed and experimentally demonstrated. The robust approach for simultaneously and accurately modulating the amplitude, phase, polarization, and intensity distributions of terahertz waves to generate polarization-dependent images with high-accuracy intensity of each focal spot will open an avenue in developing compact imaging, face unlock, and motion sensing.