Temperature-controlled terahertz chirality and imaging in a nested split-rings metasurface

Chiral metasurfaces exhibit vast application prospects in near-field imaging, polarization conversion, and chiral sensing. In this work, we theoretically propose a temperature-tunable terahertz (THz) chiral absorber based on a metasurface of Ag–VO2 nested split-rings. Perfect absorption of left-handed circularly polarized light (LCP) exceeding 99% and weak absorption of only about 6% of right-handed circularly polarized light (RCP) are achieved at 7.24 THz in frequency. The discrepancy in absorption responses of LCP and RCP results in a large circular dichroism (CD) of 0.94. The CD value in the THz region can be actively modulated between 0.02 and 0.94 by controlling the phase transition of VO2, which is closely related to the ambient temperature. Moreover, near-field imaging and encrypted presentation are realized by leveraging the metasurface and its mirror-image properties. Our work holds significant promise in widespread fields including THz intelligent absorption, imaging, and chiral detection.