Trace Carbon Monoxide Detection with a Cavity Ring-Down Spectrometer
CHEN Bing1, ZHOU Ze-yi2, KANG Peng1, LIU An-wen1, HU Shui-ming1*
1. Hefei National Laboratory for Physical Sciences at Microscale, University of Science and Technology of China, Hefei 230026, China 2. National Institute of Metrology, Beijing 100013, China
Abstract：A cavity ring-down spectrometer (CRDS) was built based on telecom distributed feedback (DFB) diode lasers. The ring down cavity was formed by mirrors of 99.997% reflectivity with a separation of 130 cm, with an empty ring down time of about 150 μs. A minimum detectable absorption coefficient of 5×10-12 cm-1 was obtained by averaging about 1 000 recorded spectra. The ring down cavity is thermo-isolated, and used as an interferometer to calibrate the recorded spectrum. A feedback control scheme was applied to step scan the laser frequency, successively matching each of the longitudinal modes of the cavity. By measuring the CO contents in a standard gas sample, the quantitative capability of the CRDS instrument was demonstrated, and a CO detection limit of 4 ppb was achieved. The instrument was applied to monitor the CO concentration in ambient air.
Key words：Cavity ring down spectroscopy;DFB diode lasers;CO;Atmospheric monitoring
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