(a) Schematic of the experimental setup. The X-ray waveguide array (WGA) is positioned at f, which is the distance from the exit of the Kirkpatrick–Baez (KB) device to the sample. The incoming beam with photon energy E and primary intensity I0 is coupled into the Ni/C WGA with working length L, which tailors the near field to the desired shape. The far-field intensity distribution is recorded at a distance of D behind the WGA exit by a two-dimensional pixel detector. (b) A schematic of the structure of the WGA, consisting of seven guiding layers in red (di, ) and eight cladding layers in purple (cj, ). After the pre-focus beam has been coupled, the guided mode is produced in the different guiding layers. With the working length L, the exit phase from the corresponding guiding layers i can be controlled by the variation of the layer thickness di. The parameters at the exit of the WGA can be optimized such that the lines of the exit phase describe a circle with radius R, resulting in constructive interference in a quasi-focal spot (F) outside the WGA. The phase of the reference sample with length L is , with the corresponding guiding layer d0 and cladding layers c0. (c) Sketch of a slab waveguide with two cladding layers cj and cj+1. Under the influence of the electric field inside the waveguide , the symmetrical guided modes () and the asymmetrical mode propagate inside the guiding layer depending on the different layer thickness di.