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Implementation of a Hot Electron Bolometer (HEB) for THz Detection

Implementation of a Hot Electron Bolometer (HEB) for THz Detection. Matthew Kelley, Rogier Braakman, and Geoffrey Blake – Division of Chemistry and Chemical Engineering, California Institute of Technology

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Implementation of a Hot Electron Bolometer (HEB) for THz Detection

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  1. Implementation of a Hot Electron Bolometer (HEB) for THz Detection Matthew Kelley, Rogier Braakman, and Geoffrey Blake – Division of Chemistry and Chemical Engineering, California Institute of Technology Daniel Santavicca, Matthew Reese, and Daniel Prober – Department of Applied Physics, Yale University Ohio State International Symposium on Molecular Spectroscopy – June 18, 2007

  2. Motivations • High resolution gas phase THz spectra are difficult to acquire but have application to: • Astronomy • Chemical Physics • Atmospheric Chemistry

  3. Molecular nozzle mirrors Wire grid polarizer (R~99%) THz photomixer 50:50 beam splitters 1.5 m Er doped fiber Amplifier e.g. P,  meter Heterodyne HEB THz mixer 3 dB coupler Mirror (R>99.99%) mirror Amplifier, filters Fixed tuned 1.55 m DFB laser Tunable 1.55 m Agilent laser Applications/Interest • THz spectroscopy is hard to implement in a lab setting. • Direct Detector • Measurement of absorption spectrum with an appropriate light source. • As a Heterodyne Mixer (Braakman WI03 2006) • Hope to replicate the unparalleled success of Flygare’s FT-MW.

  4. How A HEB Detector Works • As incoming radiation is absorbed, the device (Nb Microbridge) heats up and changes resistance. • Near the superconducting regime, the device is most sensitive.

  5. Sensitivity vs. Saturation • Length and size determine: • Bandwidth/Reset speed • Saturation power • Two cooling mechanisms prevail: • Diffusion cooling (fast) • Electron-phonon interaction (slow) Burke, P. J., Schoelkopf, R. J., Prober, D. E., Skalare, A., Karasik, B.S., Gaidis, M. C., McGrath, W. R., Bumble,B., and LeDuc, H. G. Appl. Phys. Lett., 1999, 85, 1644-1653.

  6. Experimental Setup • Chopping at 330 Hz • Hot vs. Cold Load (77 K) • Optocoupler separates device from preamp -> Bias stability improved

  7. Noise Performance • Noise is white above 100 Hz. • Chopping tests give accurate noise performance • S/N ~ 160

  8. Responsivity Calculation • ΔV=0.7 mV • G=2000 • λ~0.10 • Tu=290 K • Tl=77K • νl~1 THz • νl~2 THz • R~2 kV/W

  9. Calculated Results from Prober Group (Yale)

  10. Current Work • FTS Tests • Limited by Signal/Noise (~2.5) • Switch to 4 Wire Bias • Closed loop feedback • Lowers noise in one channel • Adds stability to the bias point • Improve Optical Coupling FTS Diagram4 4: Benford, D.J., Kooi, J. W., and Serbyn, E. 1998, Proc. Ninth Intl. Symp. Space Thz. Tech., 405.

  11. Conclusions • The Nb HEBs presented here are suitable THz detectors for laboratory environments: • High sensitivity • Moderate bandwidth • Resistant to saturation • Optical coupling is the key. • Single mode dipole antenna imposes strict limits

  12. Acknowledgements • Caltech: • Prof. Geoff Blake and group: • Rogier Braakman • Prof. Jonas Zmuidzinas and group: • Dave Miller • Tasos Vayonakis • Chip Sumner • Frank Rice • Yale: • Prof. Dan Prober and group: • Matthew Reese • Daniel Santavicca • Prof. Charlie Schmuttenmaer • Funding: • NASA • NSF

  13. Zitex filters

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