X-ray Optics for Imaging and Spectroscopy

X-rays are used in a wide range of scientific experiments to investigate the structure of matter. They have the ability to penetrate thick samples, and provide information on the elemental and even chemical composition. Moreover, their short wavelength enable excellent spatial resolution down to the atomic scale. In practice, the spatial resolution of x-ray probes and x-ray microscopes are limited by the quality of the available x-ray optics.

Fresnel zone plates can focus x-rays by diffraction. The resolution is limited by the smallest ring width. Typical zone plates have diameters of 100 microns and smallest zone widths below 100 nm

The X-ray Optics and Applications group applies micro- and nanofabrication techniques to produce state-off-the-art diffractive x-ray lenses, such as Fresnel zone plates. The spatial resolution of Fresnel zone plates is limited to the width of their outermost zone Δr. Therefore, we use high-resolution electron-beam lithography to write the zone plate pattern. The pattern must be transferred into suitable materials to provide sufficient absorption or phase shift for the x-rays to achieve optimal diffraction efficiencies. Especially for high photon energies this results in the challenge to produce nanostructures with extreme aspect ratios, i.e., with heights that are much bigger than the width.

The X-ray Optics and Applications group is specialized on pushing the limits of diffractive x-ray optics, for both spatial resolution and diffraction efficiency. We collaborate with many research groups at synchrotron experimental stations to provide tailored optical devices for optimum performance, covering a wide photon energy range from below 100 eV to beyond 10 keV. Moreover, we develop novel optical schemes and application areas, such as advanced Zernike phase contrast microscopy, coherent diffraction imaging, or devices for experiments at XFEL sources.