Saturation energy density and line profile of the atomic iodine laser transition at high pressure

The saturation energy density of an iodine laser amplifier is proportional to the homogeneous medium linewidth and inversely proportional to the Einstein coefficient. For good energy extraction high values of the saturation energy density are needed, thus also requiring large values of the medium linewidth, especially when the Einstein coefficient increases with pressure, as inferred from fluorescence measurements recently reported in the literature. In order to check this conclusion, we measured the saturation energy density in the pressure range between 0.5 and 4 bar for the buffer gases Ar, SF
6
, and Xe and also the medium linewidth at a pressure of 2 bar for Ar, SF
6
, and Xe. It is found that, at least in this pressure range, the Einstein coefficient is constant and does not change with pressure. This is in contrast to the results published in the paper mentioned earlier. From our experimental data an optimum pressure range for high-power iodine laser amplifiers of large extraction efficiency is also inferred.