Low-noise 0.5 THz all-NbN superconductor-insulator-superconductor mixer for submillimeter wave astronomy

We report the detection of spectral line emission from CO (J=4-3) at 0.46 THz using a low-noise 0.5 THz superconductor-insulator-superconductor (SIS) mixer incorporating NbN/AlN/NbN tunnel junctions (with an energy gap of 5.6 meV) and a NbN/MgO/NbN tuning circuit, which is installed on a 30 cm submillimeter telescope. Uncorrected receiver noise temperatures as low as 149 K are measured on the telescope from 0.45-0.50 THz for an unoptimized device. Moreover, the 0.5 THz all-NbN SIS mixer exhibits high stability in a considerably large dc bias range and low noise at significantly high temperatures compared with a 0.5 THz Nb SIS mixer. (c) 2008 American Institute of Physics.