Chiral metasurface absorbers with tunable circular dichroism in the mid-infrared via phase transition of vanadium dioxide

Chiral metasurface absorbers are vital for many applications such as polarization imaging, CD spectroscopy, and thermal emitters. Herein, we present a chiral metasurface integrated with eta-shaped vanadium dioxide (VO2) to achieve dynamic tuning of circular dichroism (CD) in the mid-infrared region. The proposed chiral absorber can achieve near-perfect absorption due to the excitation of strong magnetic dipole (MD) resonance under the illumination of the right-handed circularly polarized (RCP) light, while the absorption is comparably low in the case of the left-handed circularly polarized (LCP) light as the electric dipole (ED) mode associated with the LCP light is weak, thus broadband CD effect with maximum CD of 0.63 can be realized due to the remarkable chiral-selective absorption performances. In addition, the CD value and the absorption peak of the chiral metasurface can be dynamically tuned by changing the volume fraction of the metallic state of VO2, and good CD effect can be maintained even if the structural parameters are significantly altered.