In-line holography and coherent diffractive imaging with x-ray waveguides

A Fresnel coherent diffraction imaging experiment with hard x rays is here presented, using two planar
crossed waveguides as optical elements, leading to a virtual pointlike source. The coherent wave field obtained
with this setup is used to illuminate a micrometric single object having the shape of a butterfly. A digital
two-dimensional in-line holographic reconstruction of the unknown object at low resolution 200 nm has been
obtained directly via fast Fourier transform FFT of the raw data. The object and its twin image are well
separated because suitable geometrical conditions are satisfied. A good estimate of the incident wave field
phase has been extracted directly from the FFT of the raw data. A partial object reconstruction with 50 nm
spatial resolution was achieved by fast iterative phase retrieval, the major limitation for a full reconstruction
being the nonideal structure of the guided beam. The method offers a route for fast and reliable phase retrieval
in x-ray coherent diffraction.