Highly Sensitive Tunable Diode Laser Absorption Spectroscopy of CO₂ Around 1.57μm

he absolute absorption spectrum intensities of carbon dioxide samples has been recorded with a tunable diode laser spectrometer in the spectral range 6350--6364cm^-1, which is suitable for the in-situ sensing of carbon dioxide in the lower stratosphere studied using a commercial telecommunication-type diode laser. It was found that the typical uncertainty of experimental line intensities is about 1% compared with the values listed in the HITRAN database, which are calculated by direct numerical diagonalization. The intensity of the weakest line we detected in this experiment is 1.116×10^-26cm^-1/(molecule.cm^-2) at the pressure of 0.5 Torr, and the corresponding absorption is 3.2×10^-6 with SNR of 4.53.