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Proceedings Paper

Pulsed and widely tunable terahertz sources for security: imaging and spectroscopy
Author(s): Mark J. Hagmann; B. A. McBride; Zulaima S. Hagmann
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Paper Abstract

Terahertz imaging and spectroscopy are being studied for inspecting packages and personnel, but advanced THz sources with much greater power are needed to increase the signal-to-noise ratio, and much greater frequency bandwidth to obtain more information about the target. Photomixing in resonant laser-assisted field emission is a new method that shows potential for increasing both the output power and frequency bandwidth by more than an order of magnitude. Tunneling electrons have a resonance with a radiation field, so a highly focused laser diode (670 nm, 30 mW) increases the emitted current enough to be seen with an oscilloscope, in good agreement with simulations. The electron-emitting tip is much smaller than optical wavelengths, so the surface potential follows each cycle of the incident radiation. Electron emission responds to the electric field with a delay τ< 2 fs, and the current-voltage characteristics of field emission are highly nonlinear. Thus, photomixing in laser-assisted field emission can cause current oscillations that may be tuned from DC to 500 THz (1/delay). A field emission current density of 1012 A/m2 can be generated using a 20 pJ 70 fs pulse from a Ti:sapphire laser, to provide 200 W THz pulses. Microwave prototypes for 1-10 GHz are now being tested.

Paper Details

Date Published: 8 September 2004
PDF: 17 pages
Proc. SPIE 5411, Terahertz for Military and Security Applications II, (8 September 2004); doi: 10.1117/12.540808
Show Author Affiliations
Mark J. Hagmann, Deseret Electronics Research Corp. (United States)
B. A. McBride, Deseret Electronics Research Corp. (United States)
Zulaima S. Hagmann, Deseret Electronics Research Corp. (United States)

Published in SPIE Proceedings Vol. 5411:
Terahertz for Military and Security Applications II
R. Jennifer Hwu; Dwight L. Woolard, Editor(s)

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