Low-noise submillimeter-wave NbTiN superconducting tunnel junction mixers

Creators: Kawamura, Jonathan; Chen, Jian; Miller, David; Kooi, Jacob; Zmuidzinas, Jonas; Bumble, Bruce; LeDuc, Henry G.; Stern, Jeff A.

Abstract

We have developed a low-noise 850 GHz superconductor–insulator–superconductor quasiparticle mixer with NbTiN thin-film microstrip tuning circuits and hybrid Nb/AlN/NbTiN tunnel junctions. The mixer uses a quasioptical configuration with a planar twin-slot antenna feeding a two-junction tuning circuit. At 798 GHz, we measured an uncorrected double-sideband receiver noise temperature of TRX = 260 K at 4.2 K bath temperature. This mixer outperforms current Nb SIS mixers by a factor of nearly 2 near 800 GHz. The high-gap frequency and low loss at 800 GHz make NbTiN an attractive material with which to fabricate tuning circuits for SIS mixers. NbTiN mixers can potentially operate up to the gap frequency, 2Delta/h~1.2 THz.

Additional Information

©1999 American Institute of Physics. (Received 2 August 1999; accepted 27 October 1999) This work was supported in part by NASA/JPL and its Center for Space Microelectronics Technology, by NASA Grant Nos. NAG5-4890, NAGW-107, and NAG2-1068, by the NASA/USRA SOFIA instrument development program, and by the Caltech Submillimeter Observatory (NSF Grant No. AST-9615025). One of the authors (J.C.) acknowledges support from the Japanese Ministry of Education, Science, Sports, and Culture.

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