甚低频极微弱光声信号拾取关键技术研究

高精度光声光谱多组分气体检测中，由于光声腔内光声效应激发效率低、甚低频声波信号探测难度大和极微弱信号解析困难等问题，导致痕量气体最低检测阈值受限。本项目将围绕高效率光声效应、高灵敏信号拾取和高精度声波反演等关键科学及技术问题，拟开展受激光声效应形成过程中光致声高效率产生机理的研究，探索光与气体分子在腔内相互作用过程中光-热-声的演化机理，从而提升受激光声效应产生效率。通过揭示声光耦合机理，优化设计和制备多腔抗扰拾音器，实现对甚低频极微弱光声信号的高灵敏拾取，引入声光协同滤波方法和经验模态分解噪声抑制算法，降低系统噪声水平，从而降低痕量气体的检测阈值，分析混合态光声信号，实时反演有效声纹信息，最终获取多组分痕量气体的含量。本项目通过揭示复合场甚低频光声耦合机理和解决极微弱光声信号高精度解析的难题，为高精度、低阈值、多组分的光声光谱痕量气体检测提供理论依据和技术参考。

In high-precision photoacoustic spectroscopy multi-component gas detection, the minimum detection threshold of trace gas is limited to the low excitation efficiency of the photoacoustic effect in the photoacoustic cavity, the difficulties of detecting very low frequency acoustic signals and analyzing extremely weak signals. This project will focus on the key scientific and technical issues of high-efficiency photoacoustic effect, high-sensitivity signal pickup and high-precision acoustic wave inversion. It intends to conduct the research on the mechanism of high-efficiency laser-induced-acoustic generation in the process of formation of stimulated photoacoustic effect, and explore the evolution mechanism of laser-thermo-acoustic in the process of light-gas molecules interaction in cavity. Thus it will enhance the generation efficiency of stimulated photoacoustic effect. By revealing the acousto-optic coupling mechanism, then optimal designing and preparing the multi-cavity anti-interference pickups, it can achieve highly sensitive picking up of the extremely weak photoacoustic signals at very low frequency. Acousto-optic collaborative filtering method and empirical mode decomposition noise suppression algorithm are introduced to reduce the system noise level. Accordingly, it will decrease the detection threshold of trace gases. Finally, it can obtain the multi-component trace gases content by analysis mixed state photoacoustic signals and inversion effective voiceprint information in real time. This project provides a theoretical foundation and technical reference for high-precision, low-threshold, multi-component photoacoustic spectroscopy trace gas detection by revealing the mechanism of compound field photoacoustic coupling at very low frequency and solving the difficulties of high-precision analysis of extremely weak photoacoustic signals.