Band-switchable Terahertz Metamaterial Based on an Etched VO2 Thin Film

We propose a band-switchable terahertz metamaterial based on an etched vanadium dioxide (VO2) thin film. A line of etched VO2 thin film was placed in the center gap of the split square-loop shape for the tunability of the metamaterial. The resonance frequency of the metamaterial can be switched from the 1.4 THz band to the 0.7 THz band, according to the insulator-metal phase transition in the VO2 thin film. The absolute difference in the transmittance of the metamaterial was 78.5% and 65.8% at 0.7 THz and 1.4 THz respectively, according to the band switching. The differential phase shift was around 90 degrees, and the transmittance was stably maintained between 40% and 60% in the middle band of the two switchable resonance-frequency bands.