The CW optically pumped 12.08µm Raman laser theory and experiments for high power-conversion efficiency

A model is developed to predict the performance of the continuous-wave CO2-pnmped 12.08 μm NH3laser which is operated by a two-photon or Raman-like process. The local gain and pump absorption are determined from a two-wave three-level treatment based on the density matrix formalism. A ring cavity configuration is considered and interaction of the two intensities inside the cavity are described using coupled wave equations. The subsequent 12.08μm output intensity is calculated for a wide range of operational parameters (injected pump intensity, NH3gas pressure, pump frequency offset, gain length, output coupling,... ). For a well optimized system, power-conversion efficiencies of 10-30 percent should be realistically obtained by pumping with a conventional CW CO2laser. Experiments illustrating the major conclusions are described.