Study of superconducting transmission lines based on NbTiN/Al and pumping of Nb/AlN/NbN SIS junctions in the frequency range above 1 THz

Superconducting transmission lines based on NbTiN/Al were studied as rf lines for operation at frequencies up to 1.1 THz. Circuits for studying damping in thin-film structures consisting a receiving slot THz antenna, a set of NbTiN/Al microstrip transmission lines, and two THz detectors based on the “superconductor–insulator–superconductor” Nb/AlN/NbN tunnel junction matched to the line were numerically simulated and fabricated. An experiment was carried out to register an external source signal (backward wave oscillator) at a frequency of about 1.1 THz, demonstrating the successful operation of the developed NbTiN/Al transmission lines at frequencies above 1 THz, where traditional Nb-based transmission lines are not applicable. The analysis of the heating effect is made when the detector is affected by external rf signal, which leads to a powerful pumping of the tunnel junction.