Resonance Control of VO2 Thin-Film-Based THz Double-Split Rectangular Metamaterial According to Aspect Ratio

Abstract

The resonance characteristics of a double-split rectangular metamaterial based on a vanadium dioxide (VO2) thin film were controlled according to the aspect ratio of the rectangle in the terahertz (THz) frequency region. The VO2 thin film line was etched between the double-split rectangular gaps so that the resonance band could be switched by varying the characteristics of the VO2 thin film. When the VO2 thin film is in an insulator state, the rectangle is separated and resonates individually; thus, it resonates in the high-frequency band. When the VO2 thin film changes from an insulator to a conductor with a change in the temperature, the divided rectangles are electrically connected to operate as a single resonator, and the resonant frequency shifts to a low-frequency band. Varying the aspect ratio of the rectangle changes the resonant frequency and resonance strength of the double-split rectangular metamaterial. If the aspect ratio is increased by fixing the width of the unit cell of the metamaterial and adjusting the height, the resonant frequency is lowered in all situations, regardless of the state of the VO2 thin film and the polarization of the incident THz wave. The resonant frequency and resonance strength of the double-split rectangular metamaterial proposed in this paper could be controlled stably through a change in only the aspect ratio, not the overall unit cell size. The proposed double-split rectangular metamaterial based on an etched VO2 thin film is expected to be essential for THz tag, sensing, and wireless communication applications.