Superconducting hot electron bolometer (HEB) mixers are a competitive alternative to other technologies in the terahertz frequency range because of their ultrawide bandwidth, high conversion gain, and low intrinsic noise level. A process to fabricate stacked YBaCuO / PrBaCuO ultra-thin films (in the 15 to 40 nm range) etched to form 0.4 μm × 0.4 μm constrictions, elaborated on MgO (100) substrates, has been previously described. HEB structures were fabricated on such stacks, covered by log-periodic planar gold antennas, aiming at spanning the 0.9 to 7 THz range. Ageing effects were observed, however, with the consequence of increased electrical resistance, significant degradation of the regular bolometric response, so preventing HEB mixing action. Several measures have been attempted to address these problems, mainly by considering the embedding technological issues related to the YBaCuO constriction electrical coupling to the antenna and the intermediate frequency (IF) circuitry. For this purpose, the YBaCuO impedance was analyzed, and mismatch to antenna and IF strip was considered. Besides, THz antenna simulations were performed and validated against experiments on scaled models at GHz frequencies. Electromagnetic coupling to the incoming radiation was also studied, including crosstalk between neighbor antennas forming a linear imaging array.

Date Published: 24 April 2010
PDF: 10 pages
Proc. SPIE 7671, Terahertz Physics, Devices, and Systems IV: Advanced Applications in Industry and Defense, 767103 (24 April 2010); doi: 10.1117/12.850228

Published in SPIE Proceedings Vol. 7671:
Terahertz Physics, Devices, and Systems IV: Advanced Applications in Industry and Defense
Mehdi Anwar; Nibir K. Dhar; Thomas W. Crowe, Editor(s)