0.5-THz waveguide SIS mixers with NbN/AlN/NbN technology

Jing Li; Masanori Takeda; Zhen Wang; Sheng-Cai Shi

doi:10.1117/12.755407

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4 January 2008 0.5-THz waveguide SIS mixers with NbN/AlN/NbN technology

Jing Li, Masanori Takeda, Zhen Wang, Sheng-Cai Shi

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Proceedings Volume 6840, Terahertz Photonics; 684013 (2008) https://doi.org/10.1117/12.755407
Event: Photonics Asia 2007, 2007, Beijing, China

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/AlO_x/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 (J_c) of 10kA/cm². In this paper, we describe their design, fabrication and preliminary experimental results.

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Jing Li, Masanori Takeda, Zhen Wang, and Sheng-Cai Shi "0.5-THz waveguide SIS mixers with NbN/AlN/NbN technology", Proc. SPIE 6840, Terahertz Photonics, 684013 (4 January 2008); https://doi.org/10.1117/12.755407

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