A tunable ultra-wideband terahertz metamaterial filter based on vanadium dioxide

Currently, terahertz (THz) filters face challenges such as narrow bandwidth and insufficient tuning capability, which hinder their applications in THz communication and sensing. To address these issues, this paper proposes a tunable ultra-wideband THz metamaterial filter based on vanadium dioxide (VO₂). The filter comprises a three-layer periodic structure: the front and back layers are VO₂-metal composite layers, the middle layer is a metal mesh layer, and each layer is separated by polyimide dielectric spacers. The physical mechanism is elucidated through impedance matching theory and the equivalent circuit model. When VO₂ is in the insulating state, the filter exhibits ultra-wideband bandpass characteristics with a transmission coefficient exceeding 90% in the frequency range of 3.15–8.81 THz, achieving a relative bandwidth of 116% and shielding effectiveness below 1 dB within the passband. When VO₂ transitions to the metallic state upon heating, the transmission coefficient drops below 15% across 0.1–8.78 THz, with a maximum transmission modulation depth of 91.5%. Additionally, the SE exceeds 20 dB within 0.1–8.72 THz. The filter demonstrates excellent polarization insensitivity and angular stability for transverse electric and transverse magnetic polarization modes. Featuring a simple structural design, wide passband, and tunability, this filter holds significant application potential in 6G communication and electromagnetic shielding.