X‐ray waveguide arrays: tailored near fields by multi‐beam interference

A novel 1‐D X‐ray waveguide, the Mo/C waveguide array (WGA), is introduced to tailor the optical near field distribution by precisely designed and controlled multi‐beam interference at 19.9 keV hard X‐ray energy. Seven precisely controlled guiding layers with optimized layer thickness variation were fabricated by high‐precision direct‐current magnetron sputtering of amorphous carbon (C) and molybdenum (Mo). The thickness variations are designed in such a way to introduce the desired phase shifts between the guided output beams, to act as a quasi‐focusing device. The WGA and the layer thicknesses are characterized by X‐ray reflectivity, transmission electron microscopy, and measurement of the synchrotron radiation far‐field intensity pattern. Based on the measurements and simulations, a reliable Mo/C multilayer layers combination can be verified. With the layers thicknesses, simulations inside the WGA and in the optical near field behind it show that multi‐beam interference with the designed phase shifts lead to a relative beam intensity of 0.59 in a quasi‐focal plane 0.08 mm behind the exit, with a spot size of 23.8 nm.