Superconducting Complementary Metamaterial-Based Switchable Device for Terahertz Wave Manipulation

Herein, a tunable superconducting switch that can modulate terahertz waves is designed and experimentally demonstrated. The switchable device consists of two symmetrical split ring resonator antistructures made from niobium nitride film in one unit cell. The relatively high modulation depths of 88.5% can be obtained at resonance peaks of 0.328 THz by applying a very low bias voltage of 0.8 V. Due to the presence of higher-order resonance modes, the superconducting device also demonstrates a multiband tuning ability at 1.03 and 1.16 THz. To further analyze the modulation mechanism of the superconducting device, the temperature dependence of the switchable device is also measured. The trends of conductivity change are calculated based on the Bardeen-Cooper-Schrieffer theory and the simulations agree well with the experimental results. During the experiment, this device not only owns a good switching capability but also shows significant frequency selective bandpass characteristics. This study delivers a promising approach for designing active and miniaturized devices, especially for applications in THz cryogenic systems.