LENGTH AND PRESSURE-DEPENDENCE OF THE TUNING SPECTRUM PRODUCED BY CH3F DOUBLE RAMAN LASERS

We have measured the spectrum produced by a tunable Raman FIR laser op erated in a single-pass waveguide configuration using waveguide length s of 50, 120 and 200 cm. For each waveguide a range of pressures was u sed that brackets the pressure at which the maximum output occurs. For nu3 R-branch transitions in (CH3F)-C-12 and (CH3F)-C-13 with 15 less- than-or-equal-to J less-than-or-equal-to 20, the shape of the interlin e spectral profile could be changed significantly with only a modest s acrifice of output power. Using a 200-cm waveguide, for example, the u sual spectral asymmetry weighted towards the higher J number transitio n can be eliminated or reversed by controlling the pressure. A 4-level density matrix model that incorporates pump depletion and signal grow th along the waveguide reproduces some of the trends displayed by the experimental data but is unable to account fully for the large observe d changes in the interline spectral profile.