A Waveguide NbTiN SIS Mixer for THz Array Applications

In this paper we will present the design and realization of a double sideband SIS heterodyne mixer for the frequency range of 780-950 GHz. A NbTiN high Tc superconductor in combination with aluminum is used for a SIS junction tuning circuit. We use a double side waveguide probe with a fixed backshort tuner design which was optimized by means of a 3D EM-modeling software. Compact mechanical envelope of the mixer allows for a combination of several units in a focal plane array. We will present results of instantaneous bandwidth measurement for seven mixer units and compare it with theoretical predictions. We also present a heterodyne sensitivity test results for these mixers with the best achieved DSB mixer noise temperature of about 250 K (physical temperature 4.2 K) which is only several times higher than a quantum noise limit for these frequencies.