Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE

Development of SIS mixers for 1 THz

Jonas Stasys Zmuidzinas, J. Kooi, Jonathan H. Kawamura, Goutam Chattopadhyay, B. Bumble, Henry George LeDuc, Jeff A. Stern

Published Jul 31, 1998• 27 citations

Publisher

Abstract

SIS heterodyne mixer technology based on niobium tunnel junctions has now been pushed to frequencies over 1 THz, clearly demonstrating that the SIS junctions are capable of mixing at frequencies up to twice the energy gap frequency (4(Delta) /h). However, the performance degrades rapidly above the gap frequency of niobium (2(Delta) /h approximately equals 700 GHz) due to substantial ohmic losses in the on-chip tuning circuit. To solve this problem, the tuning circuit should be fabricated using a superconducting film with a larger energy gap, such as NbN; unfortunately, NbN films often have a substantial excess surface resistance in the submillimeter band. In contrast, the SIS mixer measurements we present in this paper indicate that the losses for NbTiN thin films can be quite low.

DOI: 10.1117/12.317386

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