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17 February 2003 Superconducting hot electron bolometer as mixer for far-infrared heterodyne receivers
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Heterodyne receivers for applications in astronomy need quantum limited sensitivity. In instruments which are currently under development for SOFIA or Herschel superconducting hot electron bolometers (HEB) will be used to achieve this goal at frequencies above 1.4 THz. We present results of the development of a phonon-cooled NbN HEB mixer for GREAT, the German Receiver for Astronomy at Terahertz Frequencies, which will be flown aboard SOFIA. The mixer is a small superconducting bridge incorporated in a planar feed antenna and a hyperhemispherical lens. Mixers with logarithmic-spiral and double-slot feed antennas have been investigated with respect to their noise temperature, conversion loss, linearity and beam pattern. At 2.5 THz a double sideband noise temperature of 2200 K was achieved. The conversion loss was 17 dB. The response of the mixer was linear up to 400 K load temperature. The performance was verified by measuring an emission line of methanol at 2.5 THz. The measured linewidth is in good agreement with the linewidth deduced from pressure broadening measurements at millimeter wavelength. The results demonstrate that the NbN HEB is very well suited as a mixer for far-infrared heterodyne receivers.
© (2003) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Heinz-Wilhelm Huebers, Alexei Semenov, Heiko Richter, Manfred Birk, Michael Krocka, Ulrich Mair, Konstantin Smirnov, Gregory N. Gol'tsman, and Boris M. Voronov "Superconducting hot electron bolometer as mixer for far-infrared heterodyne receivers", Proc. SPIE 4855, Millimeter and Submillimeter Detectors for Astronomy, (17 February 2003);


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