Research Activities
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5. Development of the superconducting elements for operation at frequencies up to 1 THz IIn order to increase an operation frequency of the integrated superconducting receiving devices and to expand the frequency band in the terahertz region a number of new technological procedures and techniques have been developed for fabrication of the superconducting tunnel junctions with unique parameters. In particular, Nb-AlN-NbN junctions with gap voltage Vg up to 3.55 mV and extremely low leakage currents (Rj/Rn > 30) have been developed. On the base of such junctions the integrated microcircuits comprising superconducting local oscillator (flux flow oscillator, FFO) and harmonic mixer have been designed, fabricated and tested. For the first time the radiation from such circuits has been measured at frequencies up to 700 GHz. It was demonstrated that employment of niobium nitride electrodes does not result in the appearance of additional noise. For example, FFO linewidth as low as 3.5 MHz has been measured at frequency 600 GHz, that allows us to phase lock up to 70 % of the emitted by FFO power and to realize very low phase noise (of about -90 dBc).
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