Tunable and strong circular dichroism mediated with graphene-Weyl semimetal planar scheme

Strong circular dichroism (CD) has been observed in Weyl semimetals (WSMs) because of the extremely large gyrotropic optical response. However, traditional proposals cannot tune the wavelength of CD peaks continuously without changing the geometric parameters or external magnetic field, which limits the practical application. This study presents a lithography-free platform exhibits near-unity CD in a WSM-graphene-dielectric structure. It is theoretically shown that the proposal possesses different reflectance properties for right-hand circular polarization (RCP) and left-hand circular polarization (LCP) light in the mid-infrared (mid-IR) range. The merits of the wide-angular chiral capacity of CP waves can also be maintained. The CD of the chiral structure can be tuned not only by adjusting the structural parameters, but also the chemical potential of graphene, which may also facilitate the design of more efficient chiral optical devices.