Vortex beam with a high topological charge generated using a partially coherent X-ray

The generation and propagation characteristics of partially coherent X-ray vortex beams are investigated using a numerical simulation method based on the four-dimensional mutual coherence function. The simulation results show that the vortex beams can be constructed even under low-coherence conditions using one-dimensional fork-shaped gratings with a high topological defect. In the experiment, the 4th-order diffraction vortex was successfully observed at 200 eV, demonstrating the generation of an X-ray vortex carrying a topological charge as high as 160. The experimental results demonstrated that the photon flux governs the generation of high topological charge vortex beams rather than the coherence properties of the source. Moreover, the coherence singularities of the vortex beams propagating through the two-dimensional fork-shaped grating are analyzed. The simulation results indicate that the fork-shaped grating can diffractively map the coherence singularities of the input vortex beam onto the vortex array.