Inverse Design of Multi-Foci Metalens for Generating Polarization-Dependent Images with Uniform Intensity Distributions

Abstract

Abstract Benefiting from the superior capability in manipulating wavefront of electromagnetic waves, metasurfaces have provided a flexible platform for designing ultracompact and high-performance devices with unusual functionalities. As a typical functional device, multi-foci metalens can realize novel functions (i.e., the large field of view and fully reconfigurable imaging) that are extremely challenging or impossible to achieve with conventional lenses. However, a multi-foci metalens always shows inhomogeneous/chaotical intensity distributions between the multiple focal spots, which is a key challenge in metasurface design and limited to further applications. Here an iterative algorithm is proposed to automatically optimize the in-plane orientation (other than the shape) of each meta-atom in a multi-foci metalens that can generate a plethora of focal spots with uniform intensity distributions. As proof-of-principle examples, inversely designed metalenses for generating circularly-polarized, linearly-polarized, and multi-polarized images with homogeneous intensity distributions are proposed and experimentally demonstrated. The robust approach for simultaneously and accurately modulating the amplitude, phase, polarization as well as intensity distributions of terahertz waves to generate polarization-dependent and uniform intensity of focal spots will open a new avenue in developing compact imaging, face unlock, and motion sensing.