Terahertz chiral metasurface with tunable VO₂ dual-frequency phase transition: anomalous reflection and near-field...

Addressing the limitations of current chiral metasurfaces with narrow operational bandwidths and monotonous functionality, this paper proposes a dual-frequency phase-change tunable terahertz chiral metasurface device based on vanadium dioxide (VO₂). This innovation achieves functions such as anomalous reflection and near-field densification. This design employs temperature-controlled regulation of VO₂ conductivity to achieve strong circular dichroism (CD) responses of 0.81 and -0.82 at 3.17 and 3.87 THz, respectively. When arrayed, the metasurface generates approximately ±20^∘ chiral anomalous reflection at both operating frequencies and supports near-field encryption imaging based on its mirroring properties. This device holds significant application value in the fields of terahertz absorption, polarization conversion, and chiral imaging.