Tunable compressed hydrogen infrared Raman laser

An investigation was made of a Raman laser utilizing compressed hydrogen (50–60 atm) in a cell 1 m long with an optical diameter of 70 mm. The pump source was a tunable neodymium laser with a central frequency $\nu_p=9460\pm50$ cm$^{-1}$ emitting 50 nsec pulses of radiation with a spectral width $\Delta\nu_p\lesssim0.05$ cm$^{-1}$. A raster focusing system was used in combination with a light guide of square 1X1 cm cross section to ensure spatially homogeneous pumping of the active region of the Raman laser. Tunable emission was obtained at the first Stokes component ($\nu_s =5305\pm50$ cm$^{-1}$, $\lambda_s=1.867-1.903\mu$) with an energy efficiency of 10 % and an output power up to 30 MW. Moreover, tunable emission was also obtained at the second Stokes component ($\nu_{ss}=1150\pm50$ cm$^{-1}$, $\lambda_{ss}=8.33-9.091\mu$) with an energy efficiency of $\sim 1$ % and an output energy of up to 0.5 J per pulse. The absorption spectrum of water vapor in the atmosphere was measured with a high resolution by means of this Raman laser.