Terahertz Characterization of External Resonant Systems by High- T c Josephson Junctions

High- T c Josephson technology looks promising for THz applications. One of the remaining problems, important both for detection and emission of THz radiation, is an optimum coupling of high- T c junctions with environment. Recently, we have demonstrated a possibility to characterize electromagnetic systems integrated with high- T c junctions using dc I - V curves of these junctions. Here, we report in details on modification of the dc I - V curves of rm YBa 2 rm Cu 3 rm O 7 - rm x bicrystal junctions, related to interaction of Josephson oscillations with terahertz resonance antennas. Thin-film log-periodic antennas with various resonance structures were fabricated on the same substrate as Josephson junctions and were excited by Josephson oscillations. Frequency-dependent admittances of the antennas were derived from fine log-periodic structures on the dc I - V curves of the junctions and compared with the results of numerical simulations. Data obtained can be used for optimization of coupling between the junctions and antennas.