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ST405 - Characterization of MgB2 Superconducting Hot Electron Bolometers

Characterization of MgB2 Superconducting Hot Electron Bolometers

D. Cunnane1, J. H. Kawamura1, M. A. Wolak2, N. Acharya2, T. Tan2, X. X. Xi2, and B. S. Karasik1
1Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 USA
2Physics Department, Temple University, Philadelphia, PA 19122 USA 
Abstract — Hot-Electron Bolometer (HEB) mixers have proven to be the best tool for high-resolution spectroscopy at the Terahertz frequencies. However, the current state of the art NbN mixers suffer from a small intermediate frequency (IF) bandwidth as well as a low operating temperature. MgB2 is a promising material for HEB mixer technology in view of its high critical temperature and fast thermal relaxation allowing for a large IF bandwidth. In this work, we have fabricated and characterized thin-film (~ 15 nm) MgB2-based spiral antenna-coupled HEB mixers on SiC substrate. We achieved the IF bandwidth greater than 8 GHz at 25 K and the device noise temperature < 4000 K at 9 K using a 600 GHz source. Using temperature dependencies of the radiation power dissipated in the device we have identified the optical loss in the integrated microantenna responsible as a cause of the limited sensitivity of the current mixer devices. From the analysis of the current-voltage (IV) characteristics, we have derived the effective thermal conductance of the mixer device and estimated the required local oscillator power in an optimized device to be ~ 1 µW. 
Keywords (Index Terms) — Hot Electron Bolometers, MgB2, Superconducting Devices, Terahertz Mixers 
IEEE/CSC & ESAS SUPERCONDUCTIVITY NEWS FORUM (global edition), October 2014.
Received August 26, 2014; Selected September 16, 2014.  Reference ST405; Category 4.
Preprint of ASC 2014 manuscript 1EOr1C-02 submitted to IEEE Trans. Appl. Supercond. for possible publication.