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Proceedings Paper

Candidate THz sources: the history and future of velocity-modulated devices
Author(s): Thomas H. Lee
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Paper Abstract

Compelling applications for terahertz technology include medical diagnostics and imaging, extremely wideband communication (XWB), pollution monitoring and security threat detection. One impediment is a lack of practical sources in the 1-10THz frequency range. Room-temperature CW operation, high spectral purity, tunability, and power levels above the milliwatt range are additional requirements that compound the challenge. Continued scaling of feature sizes will enable traditional semiconductor devices to provide good small-signal performance at THz frequencies, but practically obtaining the desired output power levels is much less certain. Traditional coherent optical sources encounter downward frequency scaling difficulties as the energy state differences approach 25meV (corresponding to approximately 6THz, or 50μm free-space wavelength). Electronic devices dependent on velocity modulation obey rather different scaling laws and are strong candidates for bridging the "terahertz gap." As relatively few contemporary engineers are familiar with vacuum electronic devices (VEDs), and fewer still with velocity modulation, this paper reviews the history of velocity-modulated VEDs, starting with the observations of Barkhausen and Kurz in 1919, and proceeding to practical devices, such as the klystron, magnetron, traveling-wave tube (TWT) and backward-wave oscillator (BWO). We additionally consider how modern process technology enables a reconceiving of classical VEDs to produce devices capable of practical operation in the 1-10THz region.

Paper Details

Date Published: 7 March 2006
PDF: 12 pages
Proc. SPIE 6120, Terahertz and Gigahertz Electronics and Photonics V, 61200E (7 March 2006); doi: 10.1117/12.660967
Show Author Affiliations
Thomas H. Lee, Stanford Univ. (United States)

Published in SPIE Proceedings Vol. 6120:
Terahertz and Gigahertz Electronics and Photonics V
R. Jennifer Hwu; Kurt J. Linden, Editor(s)

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