在可调谐红外激光器的基础上发展的新的痕量气体监测分析方法，已在大气化学研究和污染气体监测领域中得到了应用。在无法通过增加光程长度来提高系统检测灵敏度的环境中，降低噪声、提高信噪比，是提高TDLAS二次谐波检测技术系统检测灵敏度的途径之一。介绍了TDLAS的噪声来源并对短吸收光程下的CO和CO₂的近红外波段二次谐波进行了测量研究和噪声分析。获得CO和CO₂的最小检测灵敏度分别为0．73%和0．98%。这一结果能够满足某些对于测量要求不是很高的情况下的环境监测的需要。

As a new advanced method of measuring trace gases,the technology of tunable diode laser absorption spectroscopy(TDLAS)has been applied in the fields of atmospheric chemistry and pollutant gases monitoring. When the absorption optic length can not be effective increased in the system,the noise of system will limit the capabilities of the system and should be reduced to increase the detection limit of TDLAS system. The origin of noise of TDLAS system is introduced and the second-harmonic detection of CO and CO₂ with shortpath optic length at atmosphere pressure in the near-infrared wavelength also presented. The detection limit of CO is 0.73% and the one of CO₂ is 0.98%. It is obvious that the TDLAS system is fit for the environmental monitor with the high detection limit.