Multiple Stokes wavelength generation in H_2, D_2, and CH_4 for lidar aerosol measurements

We report experimental results of multiple Stokes generation of a frequency-doubled Nd:YAG laser in H(2), D(2), and CH(4) in a focusing geometry. The energies at four Stokes orders were measured as functions of pump energy and gas pressure. The characteristics of the Stokes radiation generated in these gases are compared for optical production of multiple wavelengths. The competition between Raman components is analyzed in terms of cascade Raman scattering and four-wave mixing. The results indicate the possibility of using these generation processes for atmospheric aerosol measurements by means of multiwavelength lidar systems. Also this study distinguishes between the gases, as regards the tendency to produce several wavelengths (H(2), D(2)) versus the preference to produce mainly first Stokes radiation (CH(4)).