Holographic and diffractive x-ray imaging using waveguides as quasi-point sources

Abstract

We report on lensless nanoscale imaging using x-ray waveguides
\nas ultra-small sources for quasi-point-like illumination. We first give a brief
\naccount of the basic optical setup, an overview of the progress in waveguide
\nfabrication and characterization, as well as the basics of image formation. We
\nthen compare one-step holographic and iterative ptychographic reconstruction,
\nboth for simulated and experimental data collected on samples illuminated
\nby waveguided beams. We demonstrate that scanning the sample with
\npartial overlap can substantially improve reconstruction quality in holographic
\nimaging, and that divergent beams make efficient use of the limited dynamic
\nrange of current detectors, regardless of the reconstruction scheme. Among
\ndifferent experimental settings presented, smallest source dimensions of 29 nm
\n(horizontal) ×17 nm have been achieved, using multi-modal interference effects.
\nThese values have been determined by ptychographic reconstruction of a Ta
\ntest structure at 17.5 keV and have been corroborated by simulations of field
\npropagation inside the waveguide.