Switching of plasmonic resonances in multi-gap resonators at terahertz frequencies

Switching plasmonic resonance modes in metamaterials have drawn enormous attention in recent years due to its great potential in applications in electromagnetic modulation and sensing. The switching process is essentially dependent on the connection way in the gaps of the metamaterial structure. In this work, we experimentally investigate the resonance switching effect in a multi-gap metamaterial structure at terahertz frequencies. It is found that a new inductor-capacitor circuit (LC) resonance would generate if the center gaps are totally connected. By decomposing the types of the connection in the center gaps, it is found that under horizontally polarized incidences, such switching effect is attributed to the horizontal connection (HC), while the vertical connection (VC) cannot bring any change in the transmission. This characteristic is further theoretically generalized to an active modulator by replacing the metallic HC to vanadium dioxide (VO2) HC, where the dynamic switching effect is observed. The detail study in the resonance switching effect may broaden the avenues toward the control of terahertz waves and the development of modulators and sensors in the terahertz band.