On the basis of the design parameters from Table 1, field propagation in the WGA and the WGM were simulated in the near field by FD calculations, with the incoming plane wave of unit intensity and 13.8 keV photon energy. The simulations are for waveguide lengths L1 = 0.26 mm [(a) and (c) for the WGA and WGM, respectively] and L2 = 0.52 mm [(b) and (d), respectively]. (e) The field distribution of a single WG (Ni [52 nm] / C [18 nm] / Ni [52 nm]) on a Ge substrate are also calculated for the length L1. (f) The intensity profiles in the exit plane for the WGA [purple line, (a)], the WGM [black line, (c)] and the single WG [dark-blue line, (e)] are compared. (g) Comparison of intensity profiles in the downstream planes, for the WGA (light-blue line) at a distance of 0.48 mm from the exit, for the WGM (red line) at a distance of 0.22 mm from the exit, and for the single WG (green line) at a distance of 0.02 mm from the exit. The corresponding intensities I/I0 of the WGA, the WGM and the single layer at the central positions are 0.1239, 0.0747 and 0.0852, respectively.