Instability Study of a High-Power, High Repetition Rate fs-OPCPA Driven Tunable Femtosecond UV Source for FEL Seeding

Tuneable femtosecond UV pulses at high pulse repetition rates and energies are of great interest for a variety of applications. Currently, the FLASH VUV/XUV FEL facility at DESY (Hamburg, Germany) is undergoing a major upgrade to become the first high repetition rate, fully coherent FEL light source worldwide (FLASH2020+) [1]. To reach this goal, the FLASH1 FEL beamline requires a high-power UV lasers system with a highly demanding and unprecedented combination of average power, tunability, pulse timing structure, UV beam quality and extremely low instability in wavelength drifts and jitter (
$<$
2e-4 rms), pulse energy (
$<$
2% rms) and pointing (
$< 20\mu$
rad rms).