Saturated and Small Signal Gain in CW Laser-Pumped FIR Laser Gases

The gain process in the gases for the FIR Laser can be completely described by the quantum mechanical theory of the three-level system. This paper reports the saturated and the small signal gains of the 7 0 μm and the 119 μm transitions in CH3OH, obtained by solving the density matrix equations for a three-level system /1/ for arbitrary pump- and FIR fields. The results are valid for arbitrary broadenings (Doppler/pressure) of the transitions involved, and also account for the removed M-degeneracy of the molecular levels due to the linearly polarized laser fields.