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The thin disk laser design enables the operation of a quasi-three-level laser active medium, e. g. Yb:YAG, in the high power regime with high optical efficiency. This requires a high absorption efficiency, which is realized by multiple pump beam passes through the crystal in a quasi-end pumped configuration. Our experimental setup utilizes 16 absorption passes of the pump radiation. Scaling of the output power can then be realized by scaling the pumped area using one or more disks. The experimental investigations yield to a maximum output power of 650 W at 51 % optical efficiency for one crystal and of 1070 W with 48 % optical efficiency for four crystals at a temperature of the cooling water of 15 °C.

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A thin-disk regenerative amplifier based on Yb-doped potassium yttrium tungstate is operated at 40 kHz with an output pulse energy of 116 microJ and a pulse duration of 250 fs. Dispersive stretching of the pulse during amplification instead of an external stretcher is used to avoid high peak intensities. The small amount of the laser active material in the amplifier inherent for the thin-disk laser design and a large beam radius in the Pockels cell reduce nonlinear effects further. Consequently the output pulses can be compressed to 250 fs using a pair of diffraction gratings.