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Proceedings Paper

Wavelength modulation spectroscopy of water vapor and line center stabilization at 1.462 um for lidar applications
Author(s): Colleen M. Fitzgerald; Grady J. Koch; Audra Michelle Bullock; Amin N. Dharamsi
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Paper Abstract

Wavelength modulation spectroscopy was employed to investigate water vapor absorption lines in the 1.462 micrometer wavelength region using an external-cavity diode laser. These measurements were necessary in the development of a lidar (light detection and ranging) instrument for differential absorption measurement of the concentration and movement of water vapor in the Earth's atmosphere. Differential absorption measurements require that the laser frequency remain stable throughout the duration of the measurement. To ensure this stability, the laser output wavelength is monitored and a feedback control loop set up to minimize laser line drift. Three lines were investigated in the 1.462 micrometer region. The first-harmonic spectroscopic signal of the strongest of these lines was used as an error signal for the stabilization feedback loop. The derivative-like nature of harmonic signals provides a zero crossing for odd harmonics which can be used to determine the polarity of the requisite feedback voltage and compensate the laser wavelength accordingly. The feedback control loop utilized the virtual instrument capabilities of Labview and locking to within plus or minus 5.2 MHz was achieved using this method.

Paper Details

Date Published: 29 March 2000
PDF: 8 pages
Proc. SPIE 3945, Laser Diodes and LEDs in Industrial, Measurement, Imaging, and Sensors Applications II; Testing, Packaging, and Reliability of Semiconductor Lasers V, (29 March 2000); doi: 10.1117/12.380525
Show Author Affiliations
Colleen M. Fitzgerald, Old Dominion Univ. (United States)
Grady J. Koch, NASA Langley Research Ctr. (United States)
Audra Michelle Bullock, Old Dominion Univ. (United States)
Amin N. Dharamsi, Old Dominion Univ. (United States)


Published in SPIE Proceedings Vol. 3945:
Laser Diodes and LEDs in Industrial, Measurement, Imaging, and Sensors Applications II; Testing, Packaging, and Reliability of Semiconductor Lasers V
Geoffrey T. Burnham; S. C. Wang; Geoffrey T. Burnham; Xiaoguang He; Kurt J. Linden; S. C. Wang, Editor(s)

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