Application of differential absorption lidar system for CO<inf>2</inf> monitoring at different wavelengths around 1.6 μm and 2 μm

Comparative study is performed for a mid-infrared differential absorption lidar system with different wavelengths around 1.6 μm and 2 μm for remote sensing of green-house effect gas CO2. Simulation based on lidar equations is performed for estimating detectable range and detectable concentration per unit volume. Different approaches for developing the coherent light sources, such as a KTiOPO4 nonlinear optical crystal based optical parametric oscillator, widely tunable Ti3+:sapphire laser based Raman shifter are also considered and the effect of strong and weak absorption lines, spectral width and output energy of the coherent light source on the detection sensitivity is investigated at different wavelengths of interests. Simulation results show that DIAL system around 1.6 μm can provide a long range measurement with a narrow spectral width (0.03 cm-1) of the light source. However, with a wider spectral width (0.3 cm-1) the detectable range is comparable to that of the DIAL system around 2 μm wavelength. The detection sensitivity is also limited by the available output energy from the light source.