Few-layer metasurface with gold split-rings for high-efficiency asymmetric circular polarization conversion

摘要

Controlling the polarization state of light has important applications in optical communications, imaging, and detection. The latest developments in metamaterials can miniaturize optical components to the sub-wavelength range. The previous work cannot simultaneously take into account the two aspects of simple structure and high efficiency. Here, we propose a simple and effective circular polarization converter, which is composed of three layers of rotated gold split-rings and SiO_2 substrate. It can convert LCP and RCP into orthogonally polarized light in two adjacent bands, with conversion efficiencies of 70% and 52%, respectively. Meanwhile, an asymmetric transmission of about 0.5 is achieved efficiently. The error caused by allowable changes of structural parameters will not affect the efficiency of asymmetric polarization conversion, indicating the high stability of our converter. As an ultra-thin planar optical element, the proposed metasurface can be used in integrated photonics, optical sensing and other fields. The asymmetric transmission in adjacent frequency bands may contribute to information encoding and decoding in applications of optical communication.