Stimulated Raman scattering process for nonlinear Raman lidar monitoring atmospheric carbon dioxide

The lidar technique based on stimulated Raman scattering (SRS) process has been extensively used in monitoring trace gas concentrations in the atmosphere. To monitor the atmospheric CO2 concentration, a nonlinear Raman lidar based on the SRS process was devised. A third harmonic Nd:YAG laser wave (354.7 nm) was injected into the Raman cells filled with high-pressure gases, CO2 and N2. The first order Stokes lights 371.66 nm(CO2) and 386.7 nm(N2) were generated by the stimulated Raman scattering process. The energy of the first order Stokes lights was measured by changing the gas pressure in the Raman cell and the Nd:YAG laser system output energy. The optimum pressures of CO2 and N2 in the Raman cell were achieved, which were 0.8 MPa and 3.5 MPa respectively. The principles of this physics