Average power scaling of high repetition-rate femtosecond pulses by cascading multi-pass cw-amplifier

Summary form only given. We discuss the scalability and cascadability of a cw-multipass amplifier for high-average-power femtosecond pulses over 10 W level. For exploring these possibilities, a confocal, reflection-double-pass, cw amplifier using Ti:sapphire was demonstrated as a single-stage gain module. This module produces successfully 5.77-W average-power, small-signal gain of 4.2, and 10.6 % extraction efficiency.