Title: Circular polarizing filters based on chiral metasurface

Abstract

Chirality is a structural feature in which two objects are mirror images of each other, similar to the left and right hands. For example, we can find the chirality in DNA, cholesteric liquid crystals, screws, and circular metal spirals. Meanwhile, the left circular polarization and right circular polarization light tracks are mirror images, like the above chiral structures. Metal gratings based on the Plasmonics are sensitive to linear polarization light. The 3D helices can be considered as the integral of metal gratings twisted with a constant angle along the propagating direction. By adjusting the twist angle and effective length of the polarization charge oscillation, the anisotropy of a single arc can be successfully transformed into a broadband double anisotropic optical response. Moreover, the chiral metasurface exhibits nearly uniform circular dichroism and asymmetric transmission to circularly polarized light. Therefore, we can use chiral metasurfaces to make circular polarizers. The application of circular polarization imaging is particularly extensive, covering various fields such as biomedical imaging, material science, space remote sensing, and military target recognition, including such as flying airplanes, living cells and tumor lesion detection, which can greatly improve our lives and promote the development of science and technology. For example, when we conduct medical research, the main disadvantage of polarization gating of light backscattered from tissue is that surface reflections affect the image. The combination of images obtained by using linearly polarized and circularly polarized light can produce polarization-gated images without surface reflection, no need additional optical devices and materials. In view of these various types of omni-directional applications, we do need chiral metasurface based circular polarizers.