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On the possibility of measuring atmospheric OH using intracavity laser spectroscopyIntracavity laser spectroscopy (ILS) has been demonstrated to be useful for measuring extremely weak absorption produced by gases in air. ILS is based on the observation that when there are spectrally narrow losses within the cavity of a broadband laser, the laser output has corresponding spectral holes where the laser oscillation is partially quenched. The depth of the laser output dips can be enhanced by a factor of 10(exp 5) over the depth of the initial cavity loss, and absorptivities of 10(exp -8) cm(exp -1) have been measured in lasers only one meter long. With ILS, one can achieve in a compact space a spectral contrast that would otherwise require kilometers of pathlength. ILS systems typically use quasi-continuous wave dye lasers operating close to threshold. The pump laser is modulated from just below to just above the threshold level for the dye laser, and the dye laser output is spectroscopically observed during a well defined time interval after the onset of lasing (the generation time). The spectral contrast of an intracavity absorber is equivalent to that produced by absorption through a path length equal to the generation time multiplied by the speed of light (assuming the cavity is completely filed with the absorber) up to some limiting time. Thus, if one measures the spectrum after 33 microseconds, the effective path length is 10,000 meters.
Document ID
19940024094
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Mcmanus, J. Barry
(Aerodyne Research, Inc. Billerica, MA, United States)
Kolb, C. E.
(Aerodyne Research, Inc. Billerica, MA, United States)
Date Acquired
September 6, 2013
Publication Date
February 1, 1994
Publication Information
Publication: SRI International Corp., Local Measurement of Tropospheric HO(x)
Subject Category
Environment Pollution
Accession Number
94N28597
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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