In this submission, we report a maximum 638-W fiberized chirped-pulse-amplification (CPA) laser system with a bulk reflection grating compressor. The system is able to emit 338-W compressed pulses of 624 fs centered at 1 µm, corresponding to a pulse energy of 1.3 µJ at a pulse repetition rate of 258 MHz. The output beam quality factor M 2 is measured to be <1.3, without observing transverse-mode instability. The standard deviation of the power fluctuation is quantified to be 0.6 W over a time span of more than 1 hour, at an output power of up to 100 W.

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A diode-pumped continuous-wave mode-locked (CWML) femtosecond Yb+3:(Gd0.1Y0.9)2SiO5 (Yb:GYSO) laser at 1058.5 nm with a semiconductor saturable absorber mirror (SESAM) was successfully realized and demonstrated. Pulses with a duration of 186 fs were obtained at a pulse repetition rate of 80.1 MHz with a maximum average output power of 564 mW, corresponding to a maximum single pulse energy of 7.04 nJ and peak power of 37.9 kW. To the best of our knowledge, this is the highest peak power ever obtained from a mode-locked femtosecond Yb:GYSO laser.