[Second-harmonic detection with tunable diode laser absorption spectroscopy of CO and CO2 at 1.58 microm].

Tunable diode laser absorption spectroscopy has been applied in the fields of atmospheric chemistry and monitoring pollutant gases as a new method of measuring trace gases. The technique of remote sensing of CO and CO2 at 760 mm Hg pressure with tunable diode laser absorption spectroscopy in the near-infrared region is introduced. And the relationship between the second-harmonic spectrum of CO2 in Lorentzian line shape and the modulation amplitude is also presented.

[The study of remote sensing CH4 concentration based on tunable diode laser absorption spectroscopy].

In the present paper, a review and analysis of the theory of direct absorption spectroscopy and modulation spectroscopy using tunable diode laser were provided, and a remote sensing system of CH4 was designed. A near infrared tunable diode laser operating at wavelength 1.65 microm at room temperature was used to perform the measurement of CH4, using the R(6) line of, the 2upsilon3 band of methane. Signal to noise ratio and fundamental noise sources were also discussed. This work has laid the foundation for remote sensing of CH4 on-line.