OPTIMIZATION OF THE OUTPUT BEAM HOMOGENEITY OF SHORT-PULSE KRF AMPLIFIERS

The output beam of short-pulse excimer amplifiers exhibits an inhomoge neous spatial intensity distribution caused by diffraction effects at laser windows and mirrors. Theoretical and experimental studies show t hat the amplification parameters of a KrF amplifier can be optimized w ith respect to the output beam homogeneity by proper choice of the ene rgy density in the amplifier. The homogenized intensity distribution i s 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 tha t the amplification parameters for the best output homogeneity are clo se to the ones previously found for optimal energy extraction efficien cy. (C) 1997 Optical Society of America.