Resonant photoacoustic detection of trace gas with DFB diode laser
✍ Scribed by Jingsong Li; Xiaoming Gao; Li Fang; Weijun Zhang; Hyungki Cha
- Publisher
- Elsevier Science
- Year
- 2007
- Tongue
- English
- Weight
- 305 KB
- Volume
- 39
- Category
- Article
- ISSN
- 0030-3992
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✦ Synopsis
A resonant photoacoustic detection system based on a low-power distributed feedback diode laser is developed. This sensor has been applied to the detection of acetylene (C 2 H 2 ) using a specifically designed photoacoustic cell operating on its second longitudinal mode. The minimum detectable limit of about 10 parts-per-million volume (SNR ¼ 1) is achieved with an average laser power of 3.5 mW at atmospheric pressure, and an integration time constant of 3 ms; thus, the minimum detectable absorption coefficient normalised by power and bandwidth is 4.0 Â 10 À8 W cm À1 /OHz. The optimum operating pressure buffered with N 2 is also investigated. The realisation of our system is described and experimental results are compared with different modulation techniques and other results reported in the literature. A number of issues arising from the conventional use of mechanical chopping of the beam can be effectively suppressed in wavelength modulation PA spectroscopy (WM-PAS) and second harmonic detection.