Vanadium dioxide-assisted switching of a half-wave and quarter-wave plate to a dual-band absorber for the terahertz wave

In this study, we present a broadband, multi-functional, and switchable metamaterial for terahertz (THz) waves. The metamaterial design achieves high polarization conversion efficiency and can seamlessly transition between a polarization converter (PC) and a dual-band absorber through the phase transition behavior of vanadium dioxide (VO 2 ). Our design facilitates linear to-cross (Half-wave plate) and linear to-circular (Quarter-wave plate) polarization conversion across a bandwidth extending from 0.58 THz to 0.88 THz, and 0.35 THz to 0.50 THz respectively. Near-perfect absorption at 0.35 THz and 0.99 THz was observed when VO 2 changed its phase from an insulator to a conductor. These broadband features are realized through a straightforward metamaterial design incorporating only a reflector, a dielectric spacer, and an antenna (meta-atom resonator). Our designed structure demonstrates impressive angular stability for incident angles ranging from 0° to 45°. The proposed switchable metamaterial holds promise for advancing the development of tunable polarization rotating devices and on/off switching LPC devices, offering broad applications in THz detection, sensing, and communications.