Tunable Circular Dichroism Based on Graphene-Au Chiral Metasurface Structure

In this study, we present a chiral metasurface structure based on graphene-Au elliptical hole arrays. Circular dichroism of up to 0.91 is achieved by varying the rotation angle of the elliptical hole. Circular dichroism (CD) typically expresses the chiral response. The structure has excellent absorption of right circularly polarized light while reflecting left circularly polarized light, and it is theoretically analyzed using the Jones matrix. By incorporating graphene between the gold hole array and the dielectric, the CD can be finely tuned. The CD response decreases from 0.88 to 0.55 when the Fermi energy level of graphene is changed from 0.3 eV to 1.0 eV, as indicated by computational studies. In addition, the periodic cell structure based on this metasurface can realize the digital imaging function and the dynamic modulation of the imaging state can be achieved by adjusting the Fermi energy level, which has potential applications in fields like communication encryption.