Research on the Vortex States of Partially Coherent Vortex Beams

The Mutual Optical Intensity (MOI) model is further developed to simulate the propagation of partially coherent X-ray vortex beams through free space. The intensity, phase, and amplitude distributions of the degree of coherence in the far field zone are numerically calculated using the MOI model. The effects of the coherence property and topological charge on the vortex beam are analyzed. For Gaussian Schell-model vortex beams, a vortex structure appears around the coherence singularity at the amplitude distribution of the degree of coherence relative to the central point. The number and rotation direction of the vortex structure are consistent with the magnitude and sign of the topological charge of the partially coherent vortex beam. As the spatial coherence decreases, the size of the vortex structure for the phase and amplitude distributions of the degree of coherence gradually increase until they disappear. The intensity of the dark hollow region increases with increasing topological charge. In addition, for the Laguerre–Gaussian Schell-model vortex beam, there is no singularity or vortex structure at the amplitude distribution of the degree of coherence relative to the central point. Therefore, the vortex structure around the coherence singularity at the amplitude distributions of the degree of coherence relative to the central point can be used to measure the vortex beam types and topological charge.