近红外外差光谱温室气体柱浓度的探测方法

Measurement Method of Atmospheric Column Concentration of Greenhouse Gas Based on Near Infrared Heterodyne Spectroscopy

搭建了一套以1.57μm近红外半导体激光器作为本振光源的小型化被动式激光外差探测系统,并将其用于大气环境监测。为对该系统的性能进行评估,以窄线宽近红外外腔激光器岀射的光作为信号光,与本振光混频,得到系统的带宽为0.032 cm^(-1),最小可探测灵敏度为25 pW,为光电探测器暗电流噪声功率的1/68。利用该系统对大气CO_2太阳光谱信号进行测量,并反演了其中两条主要强吸收线所对应的体积分数,结果均约为396×10^(-6),误差为7.6×10^(-6),测量结果与实际整层大气中的CO_2柱浓度一致,验证了该系统的可行性。

A miniaturized passive laser heterodyne detection system is built for monitoring atmospheric environment with a near infrared diode laser operating at 1.57μm as the local oscillator light source.In order to evaluate the performance of the system,we use light emitted by an external cavity laser with narrow linewidth as the signal light mixing with the local oscillator light.The bandwidth of the system is 0.032 cm^-1 and the minimum detectable sensitivity is 25 pW,which is 1/68 of the dark current noise power of photodetector.CO2 solar spectral signal is measured with the system.The volume fractions of two main absorption lines are inverted,and the values are all around 396×10^-6 with measurement error of 7.6×10^-6.The measured results are consistent with the actual CO2 column concentration in the whole atmosphere,and the feasibility of the system for atmospheric environment monitoring is verified.