Abstract
We report on an interband cascade laser (ICL)-absorption spectrometer for absolute, calibration-free, atmospheric CO amount fraction measurements, addressing direct traceability of the results. The system combines first-principles direct tunable diode laser absorption spectroscopy (dTDLAS) with a metrological validation. Using a multipath cell with 76 m path length, our detection limit is 0.5 nmol/mol at . The system is highly linear (slope: ) in the amount fraction range of 0.1–1000 μmol/mol and thus is interesting for industrial as well as environmental applications. The sensor repeatability at 300 nmol/mol is 0.06 nmol/mol (with ). The sensor’s absolute response is in excellent agreement with the gravimetric values of a set of primary gas standards used to test the sensor accuracy. The relative expanded uncertainty () of the measured CO amount fraction is 2.8%. Due to this performance and the calibration-free approach, the spectrometer may be used as an optical transfer standard (OTS) if gas standards are for whatever reason not available or applicable, e.g., for airborne instruments. Our dTDLAS approach has shown excellent stability and accuracy in detection [Appl. Phys. B 116, 883 (2014) [CrossRef] ] even when compared to primary standards. We therefore deduce that the ICL spectrometer (after its adaptation to field conditions, similar to our spectrometers) has good potential to meet the 2 nmol/mol compatibility goal stated by the World Meteorological Organization for atmospheric CO measurements, and serve as an OTS which does not need frequent calibrations using reference gases.
© 2017 Optical Society of America
Full Article | PDF ArticleMore Like This
Robert Provencal, Manish Gupta, Thomas G. Owano, Douglas S. Baer, Kenneth N. Ricci, Anthony O’Keefe, and James R. Podolske
Appl. Opt. 44(31) 6712-6717 (2005)
Anatoliy A. Kosterev, Frank K. Tittel, Rüdeger Köhler, Claire Gmachl, Federico Capasso, Deborah L. Sivco, Alfred Y. Cho, Shawn Wehe, and Mark G. Allen
Appl. Opt. 41(6) 1169-1173 (2002)
E. A. Curtis, G. P. Barwood, G. Huang, C. S. Edwards, B. Gieseking, and P. J. Brewer
J. Opt. Soc. Am. B 34(5) 950-958 (2017)