Recent progress in submillimeter and terahertz heterodyne receivers with superconducting mixers.
Abstract
The last five years have seen a major progress in the development of very sensitive superconductor based submillimeter heterodyne mixers. For Superconductor - Insulator - Superconductor (SIS) receivers up to 700 GHz, less than 5 photons double-sideband sensitivities are now common. Above the gap frequency of Niobium at 700 GHz, the sensitivities drop substantially due to the signal loss in the necessary integrated matching circuits, though the SIS junctions themselves are capable of quantum mixing up to almost twice the gap frequency. This situation could change with the recently introduced Niobium - Titanium - Nitride films which should allow similar sensitivities up to about 1.2 THz. Above 1.2 THz, and possibly up to more than 10 THz, a new mixer technololgy based on fast superconducting hot-electron bolometers with IF bandwidths in the GHz range is now emerging. The local oscillator power requirement of 50nW - 1μW is even less than that for SIS mixers, which makes new concepts for THz local oscillators feasible. This paper discusses the physical principles of quasiparticle tunneling (SIS) and hot-electron bolometer (HEB) mixers and their fundamental and practical frequency limits. Specific results of SIS and HEB mixer devices obtained at KOSMA and the concept for the KOSMA heterodyne mixers planned for the SOFIA instrumentation are presented.
- Publication:
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Astronomy and Technology in the 21st Century
- Pub Date:
- 1998
- Bibcode:
- 1998attc.conf..163J
- Keywords:
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- Heterodyne Spectrometers: Sub-MM Radiation;
- Heterodyne Spectrometers: Space Instrumentation