Numerical simulation research of circular dichroism based on a catenary-shaped ultrathin metasurface

Abstract

The circular dichroism (CD) produced by chiral materials in nature is usually very weak, and is not easy to be detected and analyzed in experiment. In this paper, a catenary-shaped chiral metasurface (CCMS) is proposed to achieve giant CD. The unit of the CCMS is composed of a metal–insulator–metal structure. Its upper and lower layers are composed of catenary-shaped metal elements. Under the excitation of left circularly polarized light and right circularly polarized light, the coupling modes of the equivalent electric dipole moments on the upper and lower metal surfaces are different, which leads to giant CD approaching 0.55. In addition, the CD properties can be tuned by structure parameters, such as the thickness of the intermediate dielectric layer, the length of the catenary-shaped metal elements, the twisted angle of the catenary-shaped metal surfaces of the upper and lower layers, and the period of the structure. By optimizing structure parameters, the maximum CD signal can reach 0.68. The present results would be helpful for designing chiral structures with enhanced CD signal.