Comparison of Yb:YAG single crystal fiber with larger aperture CPA pumped at 940 nm and 969 nm

We compare the characteristics of a two-pass chirped pulse amplifier based on a Yb:YAG single crystal fiber and the performance of Yb:YAG rods with a larger aperture. As a pump source, high brightness laser diodes with a total power of up to 140 W at 940 nm and 100 W at 969 nm were used. The seed pulses emitted from the fiber laser were amplified up to ~30W in a single crystal fiber and up to ~50W in a larger diameter rod with unguided pump propagation, both of which are characterized by a beam quality M² ~ 1.1. The amplified pulses were compressed by a diffraction grating up to ~ 600 fs with an efficiency of 80 %.