氨气高精度激光光谱检测装置的设计及实现

Design and achievement of a device for high-precision ammonia gas detection based on laser spectroscopy

氨气排放会对环境以及人体健康造成危害,因此对环境中氨气浓度的高精度监测显得尤为重要。本文基于具有高灵敏度、高响应速度等优点的离轴积分腔输出光谱技术(OA-ICOS)对氨气高精度检测装置进行设计。使用基长30 cm装有反射率为99.99%的高反镜的光学谐振腔作为气体吸收池,实现了近3000 m的光程,将中心波长为1528 nm的分布反馈式激光器(DFB)调谐至6548.611 cm^(−1)和6548.798 cm^(−1)附近,在常温18.6 kPa的气压下对1×10^(−5)~5×10^(−5)范围内NH3进行了检测。测量结果表明NH3浓度与信号幅值的线性拟合度R2可达0.99979。使用Allan方差对实验数据进行分析得到13 s后系统的平均检测极限为9.8×10^(−9),在103 s时系统的最低检测极限可达7×10^(−9)(S/N~1)。实验结果表明,该检测装置具有良好的稳定性与高灵敏度,满足对氨气高精度检测的需求,本文研究为国内自主研发痕量气体高精度检测设备提供了技术经验。

Ammonia emission will cause harm to the environment and human health,so it is particularly important that the ammonia concentrations are measured with high precision.Off-Axis Integrating Cavity Output Spectroscopy(OA-ICOS),which has the advantages of high sensitivity and high response speed,is used to design a high-precision ammonia detection device.The gas absorption cell is composed of two high reflection mirrors with a reflectivity of 99.99%,and the base length of the optical resonator is 30 cm.Finally,an optical path of nearly 3000 m was realized.The Distributed Feedback Laser(DFB)with a central wavelength of 1528 nm is tuned to 6548.611 cm^(−1)and 6548.798 cm^(−1).The concentration of NH3 is changed from 1×10^(−5)to 5×10^(−5)and is detected under an atmospheric pressure of 18.6 kPa at room temperature.The measurement results show that the linear fit R2 between NH3 concentration and signal amplitude can reach 0.99979.The Allan variance is used to analyze the experimental data,and the minimum detection limit of the system can reach 7×10^(−9)at 103 s.The experimental results show that the detection device has good stability and high sensitivity,meets the demand for the high-precision detection of ammonia gas,and also provides technical experience for the domestic independent research and development of high-precision detection equipment for trace gases.