Electrically terahertz switchable device based on superconducting composite structure metamaterial

In this work, we experimentally demonstrate an electrically tunable superconducting composite structure metamaterial capable of modulating terahertz (THz) waves. Compared with other superconducting switching devices, our device is composed of golden structures and niobium nitride (NbN) film junctions together. Its unique structural characteristics allow our device to achieve relatively large amplitude modulation effects with the smallest superconducting films. With a 4 V bias voltage, a modulation depth of 73.8% for this switch can be achieved at 0.308 THz. The experimental results agree well with the simulations. To better illustrate the physical mechanism behind the resonance mode transition, a hybrid coupling model was introduced. Our work provides an alternative tuning method and delivers a promising approach for designing active and miniaturized devices in THz cryogenic systems.