Thermally tunable broadband circular dichroism with Weyl semimetal/vanadium dioxide planar structure

Weyl semimetals (WSMs) have lately attracted significant interest because of the intrinsic large gyrotropic optical response and strong chiral anomaly. This study presents a mid-infrared (mid-IR) lithography-free platform exhibits broadband near-unity circular dichroism (CD) with WSM-vanadium dioxide (VO2) dual layers. The optical responses with mid-IR radiation have been explored with the generalized 4 × 4 transfer matrix algorithm. It is theoretically shown that the proposal possesses different absorption characteristics for right-handed circularly polarized (RCP) and left-handed circularly polarized (LCP) light. Theoretical results show that a CD in absorption reaching 0.936 and a g factor of 1.76 under 300 K temperature. The merit of the wide-angular chiral capacity can be maintained. The magnitude and resonance of CD can be tuned not only by adjusting the structural parameters, but also the insulator-to-metal transition (IMT) of VO2, which may facilitate the design of more efficient chiral optical devices.