Two thermoelectrically cooled mid-infrared distributed feedback quantum cascade lasers operated in pulsed mode have been used for the quasi-simultaneous determination of NO and NO2 in the sub-parts per million meter (sub-ppm-m) range. Using a beam splitter, the beams of the two lasers were combined and sent to a retro-reflector. The returned light was recorded with a thermoelectrically cooled mercury cadmium telluride detector with a rise time of 4 ns. Alternate operation of the lasers with pulse lengths of 300 ns and a repetition rate of 66 kHz allowed quasi-simultaneous measurements. During each pulse the laser temperature increased, causing a thermal chirp of the laser line of up to 1.3 cm−1. These laser chirps were sufficient to scan rotational bands of NO centered at 1902 cm−1 and NO2 located at 1632 cm−1. In that way an absorption spectrum could be recorded from a single laser pulse. Currently achieved limits of detection are 600 parts per billion meter (ppb-m) for NO and 260 ppb-m for NO2 using signal averaging over 1 min. This work presents the first steps toward a portable stand-off, open-path instrument that uses thermoelectrically cooled detector and lasers.
Vol. 9, Iss. 2 Virtual Journal for Biomedical Optics
Christoph Reidl-Leuthner and Bernhard Lendl, "Toward Stand-Off Open-Path Measurements of NO and NO2 in the Sub-Parts Per Million Meter Range Using Quantum Cascade Lasers (QCLs) in the Intra-Pulse Absorption Mode," Appl. Spectrosc. 67, 1368-1375 (2013)
References are not available for this paper.
OSA is able to provide readers links to articles that cite this paper by participating in CrossRef's Cited-By Linking service. CrossRef includes content from more than 3000 publishers and societies. In addition to listing OSA journal articles that cite this paper, citing articles from other participating publishers will also be listed.