Stimulated Raman scattering in hydrogen pumped with a tunable, high power, narrow linewidth alexandrite laser

The conversion efficiencies and the linewidth of the Stokes components which result from stimulated Raman scattering (SRS) in hydrogen gas pumped with a high power alexandrite laser have been studied. The pump laser was operated at 742 nm giving first and second Stokes components at 1074 nm and 1935 nm respectively. The pump laser could be operated either in the normal Q-switched configuration with a linewidth of the order of 0.2-0.3 nm or with injection seeding which narrowed the linewidth to 1-2 pm. Measurements of the Stokes components under these varying conditions reveal that there is no effect on the conversion efficiency by the narrowing of the pump linewidth and that the linewidth of the first Stokes component is broader than the expected linewidth of the injection seeded pump. Modelling of the conversion from the pump to the Stokes components shows a strong dependence of this conversion on a specific, resonant four wave mixing process. The study gives a complete set of information about the radiation resulting from SRS in molecular hydrogen pumped with a high power, narrow linewidth, tunable solid-state laser.