Towards a compact thin-disk-based femtosecond XUV source

The goal of this thesis is to develop a compact high-power
solid-state oscillator capable of superseding existing ultrafast
technology based on low-power Ti:sapphire oscillators. Different
applications such as extra- or intra-cavity XUV generation, seeding
of high-energy low-repetition-rate amplifier systems and
femtosecond enhancement cavities can be dramatically influenced by
the availability of such a reliable, compact femtosecond source. We
applied, for the first time, Kerr-lens mode-locking to a thin-disk
Yb:YAG oscillator, resulting in an unprecedented combination of an
average power 45 W and pulse duration of 250 fs directly available
from the oscillator with repetition rate of 40 MHz and a footprint
of only 1*0.4 m^2. Even shorter emission-bandwidth-limited 200-fs
pulses have been generated with the reduced output coupler
transmission of 5.5% at an average power of 17 W. Moreover, the
oscillator was operating not only in the negative dispersion regime
common to solid-state oscillators but also in the positive
dispersion regime, resulting in a spectrum spanning a range of 20
nm, which is the broadest hitherto reported for Yb:YAG material in
high-power operation. First attempts towards CE phase-stabilized
high-power pulses from such an oscillator are also described.
State-of-the-art XUV generation driven by high-power NIR
femtosecond systems requires methods of separating generated XUV
from NIR radiation. Such a method has been proposed and realized.
It constitutes a glass substrate having a low-loss anti-reflection
coating for NIR wavelengths at grazing incidence of >70° and
serving simultaneously as a high reflector for radiation in the
range of 1-100 nm with reflectivity >60%. The device can be used
for both extra- and intra-cavity XUV generation.