High repetition and high average power solid-state laser for EUV lithography

A stable and reliable front-end based on cw fiber laser has been developed. A fast LN modulator switches out arbitrary pulse shape with response time of 250 ps. Laser pulses from the modulator are amplified by 3 stage fiber amplifiers up to 1 muJ. Amplification properties of the main amplifier chain was measured. A 6.6-W Yb:S_iO₂ fiber front end operating at a repetition rate of 100 kHz with 13 ns of pulse duration was served as the seed oscillator. An output power of 35 W was achieved from the first 4-mm rod amplifiers and guided to the main amplifier chain. Output power of 5.24 kW at 30.4 kW of pumping power was obtained from the main amplifier chain. Input and output pulses were almost identical in the case of the high repetition mode.