光学学报, 2014, 34(1): 0130002, 网络出版: 2014-01-01

基于脉冲石英增强光声光谱的中红外超高灵敏CO探测

Mid-IR Ultra-Sensitive CO Detection Based on Pulsed Quartz Enhanced Photoacoustic Spectroscopy
作者单位

山西大学激光光谱研究所,量子光学与光量子器件国家重点实验室, 山西 太原 030006

摘要
发展了一种超高灵敏的CO痕量气体测量装置,该装置采用4.65 μm脉冲式中红外外腔量子级联激光器作为激发光源,结合石英增强光声光谱技术,对2135~2225 cm-1之间的CO基频振动光谱带R支进行连续光谱扫描。水被加入到被测气体中,以加快较慢的CO分子振动平动弛豫率。在锁相放大器时间常数为3 ms,激光器占空比和扫描速率为50 %和18 cm-1/s时,获得的最小探测极限为4.6×10-8 (体积分数),与之对应的归一化噪声等效吸收系数为1.07×10-8 cm-1W/Hz。
Abstract
An ultra-sensitive gas sensor for trace carbon monoxide (CO) detection is developed. The fundamental ro-vibrational absorption bands of CO from 2135 cm-1 to 2225 cm-1 is continuously measured using a 4.65 μm pulsed external-cavity quantum cascade laser and quartz enhanced photoacoustic spectroscopy. The water vapor, acting as a catalyst for vibrational energy transfer, is added to the targeted analyte mixture to improve signal amplitude. A detection limit of 4.6×10-8 is obtained for 3-ms lock-in amplifier time constant at atmospheric pressure with a laser scan rate of 18 cm-1/s and a 50% duty cycle, which corresponds to a normalized equivalent absorption coefficient of 1.07×10-8 cm-1W/Hz.
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