Broadband achromatic mid-infrared metalens with polarization-insensitivity
Chenchen Sha, Wenhui Xiong, Baifu Zhang, Jianping Ding
Abstract
Metasurfaces have shown excellent ability in manipulating light fields. However, the intrinsic chromatic aberration impairs the quality of their broadband operation, which is a serious problem restricting the application of metadevices, especially metalenses. In this paper, a polarization-independent broadband achromatic metalens composed of engineered structures that have spatially varying gradient sizes is devised to focus the light over the mid-infrared region from 3 to 5 µm. The proposed dielectric metalens is constructed by an array of meta-units with a hollowed square pillar. By tuning its structural parameters, the optical response of the meta-unit turns out to be broadband achromatic, insensitive to the polarization state, and of high efficiency. Numerical simulation results show that the designed metalens can significantly suppress chromatic aberrations over a broad mid-infrared and hold a focusing efficiency of nearly 75%. Our work is beneficial to improving the mid-infrared broadband imaging quality and detection efficiency.