Wide-angle orthogonal polarized metalens for near-infrared imaging

Polarized imaging is capable of displaying the morphological and physicochemical properties of a target and detecting invisible targets, while a large field-of-view (FOV) is of great benefit in obtaining more information about the scene in one imaging session. In this study, we propose a wide-angle orthogonal polarized metalens (WOPM) that works in the near-infrared (NIR) band using a single metasurface-based optical component. The WOPM can focus two orthogonal polarizations at different positions on the focal plane, maintaining high focusing performance even at an off-axis angle over ±30^∘. The average focusing efficiency is over 60% for the two polarizations. In order to further improve the focusing ability of the WOPM, the particle swarm optimization (PSO) algorithm is adopted to optimize the phase profiles, thereby reducing errors between the ideal phase distribution and the actual phase in the metalens. The PSO-optimized WOPM attains a higher average focusing efficiency of 69.0% and 65.3% while achieving a better average polarization extinction ratio of 22.03 and 19.72 dB for <i>x</i>-polarization (<i>x</i>-pol) and <i>y</i>-polarization (<i>y</i>-pol), respectively.