Method and apparatus for the detection of trace gas species using multiple line integrated absorption spectroscopy

Abstract

An apparatus and method are used to enhance the sensitivity of a spectrometer (sensor) for trace gas species detection by employing an external cavity continuously tunable CW quantum cascade laser and integrating the absorption spectra across multiple lines of the species. With this method the absorption spectra of NO2 is continuously recorded across the R-branch from 1628.8 cm−1 to 1634.5 cm−1. By integrating the resulting spectra, the detection sensitivity for NO2 is improved by a factor of 15 compared to the sensitivity achieved using single line laser absorption spectroscopy with the same apparatus. This procedure offers much shorter data acquisition times for the real-time monitoring of trace gas species compared with adding repeated scans of the spectra to improve the signal-to-noise ratio.

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