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Optical Engineering

Laser diode coherence length variation for balancing fiber optic interferometers
Author(s): Douglas A. Christensen; James R. Rotge; Andrew T. Klemas; Gary C. Loos; David Merriman
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Paper Abstract

A visible light (675-nm) laser diode is used as a variable coherence length source to allow the rapid adjustment to equal optical pathlengths of a fiber interferometer. The diode's spectral width, measured for decreasing drive current, changes from less than 0.2 to 16 nm. The corresponding change in coherence length is from 2.3 mm to 28 μm, bridging a significant portion of the gap between a gas laser and a broadband source. The fiber interferometer's air paths are first adjusted with the laser at high drive current, then fine tuned as the current is reduced below threshold. An experimentally observed interferogram confirms the theoretical prediction for fringe visibility at a current near threshold.

Paper Details

Date Published: 1 June 1994
PDF: 5 pages
Opt. Eng. 33(6) doi: 10.1117/12.169738
Published in: Optical Engineering Volume 33, Issue 6
Show Author Affiliations
Douglas A. Christensen, Univ. of Utah (United States)
James R. Rotge, Rockwell Power Systems (United States)
Andrew T. Klemas, Air Force Phillips Lab. (United States)
Gary C. Loos, Air Force Phillips Lab. (United States)
David Merriman, Rockwell Power Systems Co. (United States)

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