A continuously tunable sequential Stokes Raman laser

We have obtained continuously tunable coherent radiation in the m region via sequential Raman scattering of pulsed-dye-laser radiation in hydrogen. A multiple-pass-cell was used to enhance the Raman gain and produce an overall quantum conversion efficiency of at least 45 percent in the wavelength range from 0.9 to 5μm. At 5 μm, an energy output of 1 mj in a 7 ns pulse at a 10 Hz repetition rate has been obtained. Inherent four-wave mixing initiates the sequential Stokes conversion to the infrared and produces single transverse mode (TEM00) radiation in a 0.2 cm^-1bandwidth. We have developed a nonlinear model of the process that includes the effects of diffraction, four-wave mixing, and temporal pulse shape and gives numerical outputs in agreement with experiment.