Influence of the pump power and of the addition of helium on the energy parameters of an electron-beam-pumped Ar — Xe laser

An investigation was made of the influence of the addition of helium on the lasing and amplifying characteristics of an electron-beam-pumped Ar — Xe laser emitting in the near-IR part of the spectrum. The efficiency of this laser was far from maximal when the pressure of the two-component laser mixture was ~1 bar and the electron current density had the maximum (in the present investigation) value j ~ 1.4 A cm^–2. A major improvement in the energy parameters was obtained by reducing the electron current density or by adding helium to the active medium. The results obtained were interpreted by compensation of the excess pump power as a result of a reduction in the rates of the processes of mixing of laser-active levels by electron collisions on lowering the secondary-electron concentration in the former case or as a result of electron cooling in collisions with light helium atoms in the latter case. A record (for electron-beam-pumped lasers) efficiency of 4.5% was achieved with a mixture of the Ar:Xe = 200:1 composition at a pressure of 1 bar for j = 0.2 A cm^–2.