Reconstruction of the near-field distribution in an X-ray waveguide array

Abstract

Iterative phase retrieval has been used to reconstruct the near-field distribution behind tailored X-ray waveguide arrays, by inversion of the measured far-field pattern recorded under fully coherent conditions. It is thereby shown that multi-waveguide interference can be exploited to control the near-field distribution behind the waveguide exit. This can, for example, serve to create a secondary quasi-focal spot outside the waveguide structure. For this proof of concept, an array of seven planar Ni/C waveguides are used, with precisely varied guiding layer thickness and cladding layer thickness, as fabricated by high-precision magnetron sputtering systems. The controlled thickness variations in the range of 0.2 nm results in a desired phase shift of the different waveguide beams. Two kinds of samples, a one-dimensional waveguide array and periodic waveguide multilayers, were fabricated, each consisting of seven C layers as guiding layers and eight Ni layers as cladding layers. These are shown to yield distinctly different near-field patterns.

Introduction to the special issue on high-resolution X-ray diffraction and imaging

“…(iv) Coherent (phase-sensitive) X-ray imaging is presented in three articles, focused on the investigation of the near-field wavefront produced by a waveguide (Zhong et al, 2017), on the issue of resolution in holographic and coherent diffraction imaging (Hagemann & Salditt, 2017), and on the coherent imaging of a single semiconductor nanorod (Davtyan et al, 2017).…”