Beam-quality-determining processes in high-energy atomic iodine amplifiers

The disturbance of the optical homogeneity of high-energy, 1.315 μm atomic iodine amplifier systems by gas density changes, produced by gas-dynamic effects following nonuniform photolysis, has been analyzed for a wide range of line-broadening buffer gases. Mechanisms of photolysis gas heating and the relative merit of different buffer gases for minimizing density changes are discussed. An experimental study of the buffer gas dependence has shown good agreement with the gas-dynamic analysis. The model has been used to determine conditions for diffraction-limited amplification for varying pump times and buffer gas composition for typical large amplifier pumping profiles, showing the possibility for significantly increasing pump pulse duration.