光谱学与光谱分析, 2015, 35 (8): 2078, 网络出版: 2015-08-25
利用石英增强光声光谱技术在2.0μm处实现高灵敏CO2检测的实验研究
High-Sensitive Carbon Dioxide Detection Using Quartz-Enhanced Photoacoustic Spectroscopy with a 2.0μm Distributed Feedback Laser
石英增强光声光谱 2.0 μm分布反馈激光器 气体传感器 分子弛豫率 Quartz-enhanced photoacoustic spectroscopy 2.0 μm distributed feedback semiconductor laser Gas sensors Molecular relaxation rate
摘要
基于石英增强光声光谱技术,以中心波长为2.0 μm的窄线宽分布反馈式半导体激光器(DFB)为激励光源,采用波长调制及二次谐波解调技术通过改变激光器工作电流实现波长扫描完成了痕量CO2气体检测系统,并通过优化实验参数确定了常压下激光最佳调制深度,实现了高灵敏CO2浓度的检测.通过改变待测气体中的水汽浓度,研究了水汽对CO2气体探测结果的影响,结果显示在水汽浓度低于0.2%范围内,CO2气体光声信号随H2O浓度的上升而明显增强,当浓度高于此值后,H2O浓度的增加对CO2光声信号的增强作用几乎维持不变.数据显示,常温常压下H2O分子通过提高分子弛豫率最多可将二氧化碳R16吸收线的光声信号幅值提高约2.1倍.优化后的装置可以很好的实现大气中CO2浓度的检测.该装置获得的最小探测灵敏度为19 ppm(1σ,300 ms积分时间),相应的归一化噪声等效吸收系数为4.71×10-9 cm-1·W·Hz-1/2.
Abstract
A carbon dioxide (CO2) sensor is developed using quartz enhanced photoacoustic spectroscopy (QEPAS) with a 2.0 μm distributed feedback diode laser.The detection is based on a 2ｆ wavelength-modulation spectroscopy approach by dithering and scanning the laser current.The laser modulation depth is optimized at normal atmosphere pressure and room temperature.The influence of the H2O presence in the sample gas mixture on the CO2 sensor performance is also investigated.The results show that,with 1% CO2 concentration,the H2O in the concentration ranges of 0 to 0.2% has an effect on the CO2 signal amplitude and phase,and the largest amplitude difference is ~2.1 times.When the H2O concentration is over 0.2%,the CO2 signal amplitude is saturated and remains steady.Atmospheric CO2 concentration is well measured using the optimal sensor parameters.Benefiting from the strong absorption line intensity at 4 989.97 cm-1,a detection limit of 19 ppm (1σ,300 ms averaging time) is achieved,which corresponds to a normalized noise equivalent absorption coefficient of 4.71×10-9 cm-1·W·Hz-1/2.
刘小利, 武红鹏, 邵杰, 董磊, 张雷, 马维光, 尹王保, 贾锁堂. 利用石英增强光声光谱技术在2.0μm处实现高灵敏CO2检测的实验研究[J]. 光谱学与光谱分析, 2015, 35(8): 2078. LIU Xiao-li, WU Hong-peng, SHAO Jie, DONG Lei, ZHANG Lei, MA Wei-guang, YIN Wang-bao, JIA Suo-tang. High-Sensitive Carbon Dioxide Detection Using Quartz-Enhanced Photoacoustic Spectroscopy with a 2.0μm Distributed Feedback Laser[J]. Spectroscopy and Spectral Analysis, 2015, 35(8): 2078.
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