Triggered by the roadmap of the semiconductor industry, tremendous progress has been achieved in the development of
extreme ultraviolet (EUV) sources and high-quality EUV optical coatings in recent years, opening up also new fields of
applications apart from microlithography, such as metrology, high-resolution microscopy, or surface analysis.
The Laser-Laboratorium Göttingen e.V. has developed a laser-driven plasma source for generation of soft X-rays in the
spectral range 2...20 nm. A Nd:YAG laser (1064 nm, 800 mJ, 6 ns) is focused into a gas-target leading to plasma
formation which in turn emits characteristic soft X-ray radiation. Depending on the employed target gas, narrow-band as
well as broad-band spectra can be obtained. For focusing a Kirkpatrick-Baez optics is used, providing broad-band light
steering due to grazing-incidence reflection. The mirrors of the arrangement are formed by bent silicon wafer slices
allowing continuous tuning to the desired curvatures. The motorized control offers active adaption of surface shape and
incidence angles even in high vacuum, to various experimental demands (e.g. focusing on different sites, beam
For reduction of aberrations the optical system was fine-adjusted with the help of a Hartmann-Shack wavefront sensor
in the visible spectral range. The wave propagation properties were determined and compared to calculations performed
with ZEMAX. From the difference between calculated phase and measured wavefront direct information about the
figure error between perfect and real mirrors could be obtained.