Tunable and strong circular dichroism metamaterial absorber based on gold-VO2 hybrid structure

Abstract

The existing terahertz chiral absorber faces a series of issues, including low efficiency, un-tunable absorption, and complex structure. We present a chiral metamaterial absorber integrated with gold and phase-change material vanadium dioxide (VO2) to address the issues above. Our designed metamaterial absorber’s maximum circular dichroism (CD) value, as an ideal chirality-selective meta-absorber, reaches 0.95 when VO2 behaves as a metallic state. However, when VO2 is in the insulator state, the CD value is merely 0.003. Notably, the intrinsic mechanisms of the CD effect are revealed by analyzing the difference in electromagnetic response under left-handed circularly polarized (LCP) and right-handed circularly polarized (RCP) illumination. The designed chiral metamaterial absorber supports the free switching of the CD signal between ‘on’ and ‘off’ states by continuously adjusting the conductivity of VO2 with a CD value ranging from 0 to 0.95. Moreover, the absorption performance of chiral metamaterials is affected by geometric parameters and the angle of incidence. To evaluate the capability of chiral structure in biosensing, three typical avian influenza viruses are sensed by detecting changes in their resonant frequencies and CD values. Finally, the presented chiral-selective absorber with phase-change materials has an important reference value in the terahertz range for constructing chiral light detectors, chiral thermal switching, biosensors, and tunable chiral photonics.