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Proceedings Paper

Quantitative metrics of efficacy of higher harmonic detection in wavelength modulation spectroscopy for precision measurements
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Paper Abstract

A quantitative analysis of Wavelength Modulation Spectroscopy (WMS) signals at various harmonic detection orders for use in precision, non-intrusive measurements is performed. A theoretical analysis of fitting of WMS signals is developed. The detailed structures of WMS signals at various harmonic detection orders are studied and analyzed, using statistical measures. It is shown that the variance of errors increases with mesmatches in linewidth in a particular (Nth order) harmonic signal. However, this rate of increase in variance is characteristic of the harmonic detection order used, thereby demonstrating the advantage in measurements at different harmonics. It is shown that for a constant error in estimation of linewidth of a profile, the variance of errors can be higher for higher detection orders. Therefore, mismatches in fits are more prominent at some optimal detection order. The methods developed can be used to examine subtle effects such as Dicke narrowing in certain molecular spectra. These small perturbations of lineshape profile reveal details of the molecular collision kinetics, and hence yield precise measurements that are difficult to achieve by other techniques.

Paper Details

Date Published: 16 June 2004
PDF: 8 pages
Proc. SPIE 5364, Vertical-Cavity Surface-Emitting Lasers VIII, (16 June 2004); doi: 10.1117/12.529103
Show Author Affiliations
Mohammad A. Khan, Old Dominion Univ. (United States)
Amin N. Dharamsi, Old Dominion Univ. (United States)

Published in SPIE Proceedings Vol. 5364:
Vertical-Cavity Surface-Emitting Lasers VIII
Chun Lei; Kent D. Choquette; Sean P. Kilcoyne, Editor(s)

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