基于全光学光声光谱的超高灵敏度痕量气体检测技术研究

Trace gas detection technology plays an important role in applications such as environmental pollution gas monitoring, characteristic gas analysis of electrical equipment, safety supervision in coal mine and medical exhalation gas diagnosis. Ultra-high sensitive detection of target gas contributes to accurate analysis and early warning. To further improve the sensitivity of trace gas detection, an all-optical photoacoustic spectroscopy based ultra-high sensitive detecting scheme is proposed. A distributed feedback laser is used as the photoacoustic excitation source. Meanwhile, cantilever-cavity double resonance enhancement mechanism is introduced. Moreover, optical cross-correlation method is studied for high-precision acoustic demodulation. As a result, a new enhanced all-optical photoacoustic spectroscopy system is designed. The main research contents include: study of the sensing technology of the high sensitive fiber-optic cantilever microphone, research of the optical cross-correlation dynamic demodulation technology for fiber-optic Fabry-Perot acoustic sensor, research of double resonance enhancement method of optical cantilever beam and acoustic resonant cavity. Finally, the integration and testing of the all-optical photoacoustic spectroscopy based trace gas detection system will be completed. It is expected that the detection sensitivity of the tested acetylene gas can be improved by one order of magnitude, and the detection limit can be reached to less than 10 ppt. This research project is of great significance for the development and application of trace gas detection technology.

痕量气体检测技术在环境污染气体监测、电气设备故障特征气体分析、煤矿安全生产监测和医学呼出气诊断等应用中发挥着重要作用，对目标气体的超高灵敏度检测有助于精准分析与早期预警。为进一步提高痕量气体检测的灵敏度，本项目提出一种基于全光学光声光谱的超高灵敏度气体检测技术方案：采用分布反馈激光器作为光声激发光源，引入悬臂梁-谐振腔双共振增强机制，结合基于光学互相关解调的高灵敏度光纤声波探测技术，构成新的增强型全光学光声光谱系统。研究重点为：高灵敏度光纤悬臂梁声波传感器的设计与优化；光纤法布里-珀罗声波传感器的光学互相关解调技术研究；光学悬臂梁与声学谐振腔的双共振增强方法研究。最终完成全光学光声光谱痕量气体检测系统的集成与测试，预期在近红外波段将乙炔气体的检测灵敏度提高1个数量级，检测极限达到10ppt以下。本项目研究工作的开展对于痕量气体检测技术的发展与应用具有重要的意义。

本项目提出了一种基于全光学光声光谱的超高灵敏度气体检测技术方案：采用分布反馈激光器作为光声激发光源，引入悬臂梁-谐振腔双共振增强机制，结合基于光学互相关解调的高灵敏度光纤声波探测技术，构成新的增强型全光学光声光谱系统。优化设计了高灵敏度光纤MEMS悬臂梁声波传感器，1 kHz频率下的等效噪声声压达到0.2 μPa/Hz1/2。研究了光纤法布里-珀罗声波传感器的光学互相关解调技术，解调速度达到500Hz。研究了光学悬臂梁与声学谐振腔的双共振增强方法，光声信号的信噪比相比传统的单共振方法提高了8倍。构建了1套全光学光声光谱痕量气体检测系统，归一化噪声等效吸收（NNEA）系数达到4.2×10−10 cm−1·W·Hz−1/2，其中，乙炔气体的检测极限达到27ppt。项目研究成果已在国家电网得到应用，本项目的实施对于痕量气体检测技术的发展具有重要意义。