Dual-mode dual-band circular polarization device based on three-layer plasmonic metasurface

In this work, we proposed a three-layer metasurface with rotated gold split-rings as a polarization device that has two adjacent operating bands in two different modes. The proposed metasurface can be used as a circular polarization selector in transmission mode as well as a circular polarization converter in reflection mode. In transmission mode, it can transmit right- and left-handed circularly polarized light at the corresponding wavelengths of 2130 and 3040 nm with transmission efficiencies of 85.3% and 83.8%, respectively. In reflection mode, it can convert two types of circularly polarized light into those of the orthogonal state with conversion efficiencies of 70.3% and 77.3% in the opposite bands, respectively. The results of the theoretical calculation by transfer matrix method are consistent with these simulation results, and the current distribution results illustrate the coupling mechanism under the proposed chiral structure. In addition, the influence of parameters on circular dichroism was investigated, demonstrating the strong robustness of the structure. The proposed metasurface provides a new degree of freedom for multifunctional photonic integrated devices, which can be used for applications in optical communication and imaging.