Kerr-lens mode-locking of directly LD pumped Yb:YAG laser

Yb:YAG is an attractive material for high-power and ultra-short pulse laser because of its high quantum efficiency exceeding 90% and wide gain spectrum larger than about 10 nm. Our research is development of high-average power Kerr-lens mode-locked Yb:YAG laser. A Kerr-lens mode-locked laser has been designed with thin-rod Yb:YAG for high average power oscillator. Thin and long Yb:YAG crystal is used for gain medium and it was pumped directly by stacked LD bar. The Z-folded cavity was designed by simple ABCD matrix law. An additive Kerr-medium is used for stable mode-locked operation instead of semiconductor saturable absorber mirrors (SESAM), because Kerr-effect of the Yb:YAG crystal is weak. SF57 glass is used to stabilize the mode-locked oscillation to decrease the intra-cavity loss to increase the oscillation bandwidth for transform limited pulse generation. The Group Delay Dispersion (GDD) of the optical element in the laser cavity was compensated by SF10 prism pair. The output is expected to be the transform limited ultrashort pulses of sub 200 fs width with a high average output power around 60 W with 200 W pump power.