Switchable terahertz metamaterial device for multi-frequency narrowband absorption and polarization conversion

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A multifunctional terahertz metamaterial based on VO 2 with tunable phase transition is proposed, integrating narrowband absorption and polarization conversion. The device features a multilayer VO 2 /SiO 2 structure that exhibits excellent phase-transition responsiveness. In the metallic state, the device exhibits absorption exceeding 99% at 0.40, 1.15, 1.37, and 1.75 THz. In the insulating state, it serves as a polarization converter, realizing linear-to-cross polarization at 0.49-0.57, 1.06, and 1.52 THz, linear-to- left-hand circular polarization (LHCP) at 0.37-0.44, 0.68-1.04, and 1.20-1.49 THz, and linear-to- right-hand circular polarization (RHCP) at 1.08 and 1.57 THz, with normalized ellipticity approaching ±1. The device exhibits stable performance under varying polarization and incident angles, offering promising applications in spectral sensing, polarization control, and adaptive stealth.