Multi-mJ kHz cw-Pumped Femtosecond Yb,Na:CaF 2 Amplifier

We demonstrate a cw-diode-pumped close-loop-cooled Yb doped regenerative amplifier with the output energies scalable to multi-millijoule level due to gain-narrowing suppression by inhibiting ground-state absorption. Amplitude shaping of seed pulses allows achieving sub-200-fs pulse duration.