Development of DIAL for CO2 and CH4 in the atmosphere

Development of a mid-infrared differential absorption LIDAR system around 2.0 and 2.3 mum wavelength is proposed for remote sensing of greenhouse-effect gases, such as CO2 and CH4. A model calculation shows that the 1.6 to 2 mum wavelength region is also suitable for the CO2 Measurements. A widely tunable self-injection seeded Ti3+: sapphire laser in combination with a Raman shifter is used for a tunable mid-infrared laser source. This combination could allow a wide tuning range between 1.6 and 2.3 mum. The spectral width of the Ti3+: sapphire laser was measured around 0.04 cm(-1) and stability of the laser source was also studied by a Fabry-Perot interferometer in order to determine the accuracy of the DIAL measurement. Currently, output energy is limited to only a few mJ limiting the detection sensitivity. Nevertheless improved output characteristics should meet the requirements satisfactorily to monitor CO2 and CH4 gases in the atmosphere.