Thin disk picosecond pump laser for jitter stabilized kHz OPCPA

We report on the initial performance of the first ELI-Beamlines high repetition rate, thin disk-based OPCPA pump laser. The laser is designed to produce a pulse train with pulse energies of 10-30 mJ at a 1 kHz repetition rate and is intended to be used as a pump source for an OPCPA amplifier. While the preliminary tests and analysis show that these target energies are well within the capabilities of the equipment available, the output energies of the current design are limited by self-phase modulation. We discuss the sources of this modulation and a new amplifier design to reduce these nonlinear effects. The efficiency of the second harmonic conversion of the thin disk amplifier output is measured to be higher than 65% and scaling to higher energies is discussed.