New improvements in methane detection using a Helmholtz resonant photoacoustic laser sensor: A comparison between near-IR diode lasers and mid-IR quantum cascade lasers

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• 作者：Agnè ; s Grossel ; Virginie Zeninari ; Lilian Joly ; Bertrand Parvitte ; Daniel Courtois and Georges Durry
• 关键词：Methane detection ; Photoacoustic technique ; Near-IR lasers ; Quantum cascade lasers
• 刊名：Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy
• 出版年：2006
• 出版时间：April 2006
• 年：2006
• 卷：63
• 期：5
• 页码：1021-1028
• 全文大小：860 K

文摘

Atmospheric methane was detected by combining a photoacoustic (PA) sensor with several lasers emitting in both the near- and mid-infrared spectral ranges to check the achievable detection limits. The PA spectrometer is based on differential Helmholtz resonance. Near-infrared telecommunication-type laser diodes of increasing power, from Sensors Unlimited Inc. and Anritsu, were first used to scan the 2ν₃ band of CH₄ near 1.65 μm. The best achieved detection limit is 0.15 ppm of methane at atmospheric pressure and with a 1 s integration time. The PA sensor was then operated in conjunction with a quantum cascade laser from Alpes Lasers emitting near 7.9 μm on the ν₄ band of CH₄. The achieved detection limit is then of 3 ppb. The dramatic improvement in the detection limit obtained with the QC laser is due to the stronger optical power as well as to the capability of reaching the fundamental bands of methane lying in the mid-infrared spectral range.