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Proceedings Paper

0.5-THz waveguide SIS mixers with NbN/AlN/NbN technology
Author(s): Jing Li; Masanori Takeda; Zhen Wang; Sheng-Cai Shi
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Paper Abstract

Heterodyne mixers based on superconducting SIS (superconductor-insulator-superconductor) tunnel junctions have been demonstrated to be the most sensitive coherent detectors at millimeter and submillimeter wavelengths. In fact, conventional superconducting SIS mixers with Nb/AlOx/Nb junction and Nb/SiO2/Nb tuning circuit have shown good performances with the noise temperature reaching as low as three times the quantum limit below 0.7THz, which is the gap frequency of Nb-based SIS junctions. However, due to the large loss in Nb thin-film superconducting microstrip lines, the noise performance of Nb SIS mixers deteriorates significantly above 0.7THz. With a gap frequency double that of Nb-based SIS junctions, NbN-based SIS junctions are of particular interest for the development of heterodyne mixers in the terahertz region. Considering the bandwidth and output power of local-oscillator (LO) signal sources are quite limited around 1THz, we firstly develop a waveguide NbN-based SIS mixer at 0.5THz. Three types of SIS junctions, i.e., long junction, parallel-connected tunnel junction (PCTJ) and distributed junction array (DJ) are investigated. They are all comprised of NbN-AlN-NbN tri-layer fabricated on an MgO substrate and have the same current density (Jc) of 10kA/cm2. In this paper, we describe their design, fabrication and preliminary experimental results.

Paper Details

Date Published: 4 January 2008
PDF: 8 pages
Proc. SPIE 6840, Terahertz Photonics, 684013 (4 January 2008); doi: 10.1117/12.755407
Show Author Affiliations
Jing Li, Purple Mountain Observatory (China)
Graduate School of Chinese Academy of Sciences (China)
Masanori Takeda, Kobe Advanced ICT Research Ctr. (Japan)
Zhen Wang, Kobe Advanced ICT Research Ctr. (Japan)
Sheng-Cai Shi, Purple Mountain Observatory (China)

Published in SPIE Proceedings Vol. 6840:
Terahertz Photonics
Cunlin Zhang; Xi-Cheng Zhang, Editor(s)

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