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Proceedings Paper

Wide-band-tunable sources using photomixing in laser-assisted field emission
Author(s): Mark J. Hagmann
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Paper Abstract

Quantum theory shows that tunneling electrons have a resonant interaction with a radiation field, and because of this resonance a highly-focused amplitude-modulated laser diode (670 nm, 30 mW) changes field emission current enough to be seen with an oscilloscope. The emitting tip is much smaller than the optical wavelength, so the potential of the tip follows each cycle of the radiation field. Electron emission responds to the total electric field (DC + radiation) with a delay τ < 2 fs, and the current-voltage characteristics of field emission are highly nonlinear. Thus, quantum simulations show that two lasers can cause current oscillations by photomixing, which can be tuned from DC to 500 THz (1/τ) by shifting the frequency offset of the lasers. Microwave prototypes for 1-10 GHz are being tested. The output power is proportional to the resistive part of the impedance that is seen by the current oscillations. However, the electric field at the mixer frequency, which is proportional to this impedance, causes negative feedback to reduce the current oscillations, so there is an optimum impedance for maximum output power. Analyses with equivalent circuits are used to optimize the design. Simulations suggest that 1 μW may be obtained in CW operation, or 10 mW in pulsed operation, using 10 mW laser diodes as the pump sources.

Paper Details

Date Published: 8 April 2004
PDF: 17 pages
Proc. SPIE 5354, Terahertz and Gigahertz Electronics and Photonics III, (8 April 2004); doi: 10.1117/12.529765
Show Author Affiliations
Mark J. Hagmann, Deseret Electronics Research Corp. (United States)

Published in SPIE Proceedings Vol. 5354:
Terahertz and Gigahertz Electronics and Photonics III
R. Jennifer Hwu, Editor(s)

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