Two-junction tuning circuits for submillimeter SIS mixers

THz SIS mixers with normal-metal Al tuning circuits

Nb-based superconductor–insulator–superconductor (SIS) mixers with Nb tuning circuits have demonstrated good results up to the Nb gap frequency. Above the gap frequency the performance is expected to degrade quickly because RF loss in Nb becomes significant. In this paper we present the results of an effort to extend Nb-based SIS mixers to THz frequencies by employing lower-loss normal-metal Al...

Simulated performance of multi-junction parallel array SIS mixers for ultra broadband submillimeter-wave applications

SIS Junctions for Millimeter and Submillimeter Wave Mixers

We have developed a process for the fabrication of highquality Nb/AlOx/Nb tunnel junctions with small area and high current densities for the heterodyne mixers at millimeter and submillimeter wavelengths. Their dc I-V curves are numerically studied, including the broadening of quasiparticle density of states resulting from the existence of an imaginary part of the gap energy of Nb. We have foun...

NbTiN/SiO2/NbTiN and NbTiN/SiO2/Al tuning circuits for 1 THz waveguide SIS mixers

Waveguide SIS mixers are presented in which Nb/Al-AlOx/Nb tunnel junctions are integrated with both NbTiN/SiO2/NbTiN and NbTiN/SiO2/Al tuning circuits. The mixers with a NbTiN/SiO2/NbTiN tuning circuit yield relatively low receiver noise temperatures between 700 and 830 GHz, but their sensitivity drops significantly above ~ 850 GHz. In contrast, low-noise heterodyne mixing near 1 THz is observe...

Low-Noise THz SIS Mixers Incorporating NbTiN/SiO2/Al and Al/SiO2/Al Tuning Circuits

The development of the Heterodyne Instrument for the Far-Infrared (HIFI) requires lownoise SIS mixers for frequencies up to 1.25 THz. Past work has shown that the integration of a NbTiN/SiO2/Al tuning circuit with standard Nb SIS junctions enables the development of state-of-the-art heterodyne receivers for frequencies up to at least 1 THz [1-3]. Following from the results of this previous work...