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Near-infrared trace-gas sensors based on room-temperature diode lasers

: Werle, P.; Mücke, R.; D'Amato, F.; Lancia, T.

Applied Physics. B 67 (1998), S.307-315 : Ill., Lit.
ISSN: 0340-3793
ISSN: 0721-7269
ISSN: 0946-2171
ISSN: 1432-0649
Fraunhofer IFU; 2002 in Helmholtz-Gesellschaft integriert

Semiconductor lasers continue to find an increasing number of applications as tunable sources for highresolution spectroscopy. Substantial improvements in sensitivity and detection speed have been achieved and many laserbased gas monitoring applications have been reported. In this paper the relevant characteristics of currently available semiconductor lasers with respect to spectroscopic gas analysis will be discussed. Experimental data from a C02 monitor designed for field applications using room-temperature diode lasers are presented. Near-infrared DFB lasers operating at 1.57 mu m and around 2.0 mu m have been used for C02 measurements. At ambient concentration levels a resolution of more than two orders of magnitude has been demonstrated at 1. 57 mu m at 2 mu m the precision is in the order of 0. 1 ppm CO2, and for trace analysis a detection limit of 10 ppb has been obtained. The measurements demonstrate the capability of near-infrared DFB diode lasers for the precise determination of C02 concentrations as required for climatological, medical, or industrial applications.