Characteristics of an electron beam pumped KrF laser amplifier with an atmospheric‐pressure Kr‐rich mixture in a strongly saturated region

Amplifier characteristics of a KrF laser were investigated as a function of Kr concentration for a wide range of input intensity. The experiments were performed with atmospheric‐pressure mixtures excited by a 65‐ns (full width at half‐maximum), 160‐A/cm2 electron beam. The extracted intensity (output intensity minus input intensity) from a single‐pass (50 cm) amplifier was maximized at an input intensity around 5 MW/cm2 and then, the power efficiencies were 12.6, 13.7, 13.3, and 11.3% for Kr concentrations of 10, 20, 40, and 99.4%, respectively. The small‐signal gain, absorption coefficient, and saturation intensity were determined for each mixture by using an analysis due to Rigrod [J. Appl. Phys. 36, 2487 (1965)]. The KrF* formation efficiency and the extraction efficiency were also obtained as a function of Kr concentration.