Theoretical evaluation of the buffer gas effects for a self-sustained discharge ArF laser

The effect of buffer gases on the operating performance of a self-sustained discharge ArF laser employing a charge transfer excitation circuit has been analyzed theoretically. By the analysis of the electron kinetics, the ArF* formation, the ArF* relaxation, and the absorption of the B→X laser radiation, the pump rate dependence of intrinsic efficiency, small-signal gain, and absorption could be clarified for the Ne- and He-diluted mixtures. It is found that there is no appreciable difference in the intrinsic efficiency of the ArF laser between Ne- and He-diluted mixtures when employing a laser resonator with a strong output coupling. After optimizing output coupling in each case, a higher efficiency is obtainable for the Ne diluent than for the He diluent. For a 4-atm mixture of 4.9% Ar and 0.1% F2 in Ne, an intrinsic efficiency of 4% is obtainable, while less than 2% is obtainable for the He-diluted mixtures. However, a higher specific output energy is achievable for the He-diluted mixtures than the Ne-diluted mixtures because the use of He-diluted mixtures can efficiently transfer the stored energy to the laser discharge load.