采用波长2 μm附近的可调谐半导体激光二极管作为光源，结合多步吸收光程和光纤传输技术，通过激光吸收光谱直接测量方法对CO2分子浓度进行测量研究。实验在标定了激光器调谐范围内17条CO2吸收谱线的波长及相应的吸收带跃迁的基础上，研究了不同压力下纯CO2气体在2008 nm附近的吸收光谱，由吸收信号随气体压力的变化关系得到低气压下实验装置的系统刻度因子。并进一步对样品气体的CO2浓度进行测量，测量给出CO2分子浓度为(2.754±0.145)×1016 cm-3，测量误差主要来源于目前实验中所使用的气压计的精度和读数局限性。该研究为气体分子浓度测量、同位素含量分析提供了一种光谱测量方法。

The technology of the directly laser absorption spectroscopy for CO2 concentration measurement is described. A tunable diode laser near 2 μm is used as optical source. The multi-pass absorption technology combined with optical fiber transmission technique is improved for this method. Seventeen absorption lines of CO2 are observed and the corresponding spectral parameters (i.e. positions, the transition of absorption band) are presented. The absorption line of CO2 molecule near 2008 nm is recorded in different pressures, from which calibration factor of experimental system at low pressures is retrieved. A CO2 molecule concentration of (2.754±0.145)×1016 cm-3 in the sample gas is also achieved. The resulting accuracy in the retrieved values of gas concentration could be strongly limited by an accuracy of a vacuum gauge using in our measurements. It is proved that this spectral measurement method is an attractive tool for gas concentration monitoring application and isotope abundance analysis.