69-W Sub-100-fs Yb:YAG Thin-Disk Laser Oscillator

High-power laser oscillators in the sub-100-fs pulse duration regime at megahertz repetition rates are a compact and reliable alternative to multi-stage amplifier systems. Sub-100-fs Ti:sapphire bulk oscillators have been the working horse in ultrafast science, but up to nowadays they have been limited in average power to 3.5 W [ Fig. 1a) ]. Yb-doped gain materials are better suited for high-power operation thanks to their lower quantum defect. Sub-100-fs Yb-based bulk oscillators have already reached 12.5 W. However, further power-scaling in the bulk geometry is strongly limited by thermal effects. The thin-disk geometry is advantageous for higher average powers as it reduces thermal effects in the gain material. Ultrafast thin-disk laser (TDL) oscillators operated already with up to 350 W average power at 940 fs pulse duration [1] and 150 W at 140 fs [2] . However, operation in the sub-100-fs regime still remains challenging. In 2019, we presented an Yb:Lu 2 O 3 TDL oscillator generating 21 W in 95-fs pulses [3] .