Optimization of the output beam homogeneity of short-pulse KrF amplifiers

The output beam of short-pulse excimer amplifiers exhibits an inhomogeneous spatial intensity distribution caused by diffraction effects at laser windows and mirrors. Theoretical and experimental studies show that the amplification parameters of a KrF amplifier can be optimized with respect to the output beam homogeneity by proper choice of the energy density in the amplifier. The homogenized intensity distribution is obtained at the plane of the output window of the amplifier and can be transferred by optical imaging onto a target plane. It is shown that the amplification parameters for the best output homogeneity are close to the ones previously found for optimal energy extraction efficiency.