基于长光程近红外光声光谱的微量气体探测研究

Research on trace gas detection based on long pass and near infrared photoacoustic spectrum

针对采用高功率激光光源或外加功率放大设备以提高光声光谱探测灵敏度时存在系统成本较高和复杂度较大的缺点,基于普通一阶共振式光声池,引入Herriott型多次反射池技术,设计了一种基于长光程近红外光声光谱的微量气体探测系统.该系统通过Herriott结构使光束穿过光声池的光程增加,提高待测气体的吸收光强,并利用光声信号在光声池内共振增强的特性,实现在不增加光源功率的情况下有效增加光声转换功率,提高系统探测灵敏度.以NH 3为例进行的验证实验结果表明,在平均时间为100 s时,对NH 3的最低检测限达2.69×10^-7,1σ归一化等效噪声吸收系数为9.87×10^-11 W·cm^-1·Hz^-1/2,该系统结构简单,成本低廉,可以广泛应用于微量气体探测领域.

Aiming at the shortcomings of higher system cost and complexity when using high-power laser light sources or external power amplification equipment to improve the sensitivity of photoacoustic spectrum detection,based on the ordinary first-order resonant photoacoustic cell and the introduction of Herriott multiple reflection cell technology,a trace gas detection system based on long optical path near infrared photoacoustic spectrum was designed.The system increased the optical path of the beam through the photoacoustic cell through the Herriott structure,and improved the absorption light intensity of the gas to be measured.The resonance of the photoacoustic signal was enhanced in the photoacoustic cell,which effectively increased the conversion power of photoacoustic without increasing the power of the light source,and improved the detection sensitivity of the system.The results of verification experiments using NH 3 as an example showed that when the average time was 100 s,the minimum detection limit of NH 3 was 2.69×10^-7,and the normalized equivalent noise absorption coefficient of 1σwas 9.87×10^-11 W·cm^-1·Hz^-1/2.It showed that the system had simple structure and low cost,and could be widely used in the field of trace gas detection.