Simulations of spiral phase plate interactions for x-ray diffraction contrast imaging

Abstract

We present a hard-x-ray spiral phase contrast optic for Bragg-diffraction microscopy, consisting of a spiral phase plate inserted at the back focal plane. The optic performs a radial Hilbert transform on the dynamically diffracted exit wave, and an orbital-angular-momentum coupling between the optical spiral and any topological phase winding carried by a defect's displacement field converts phase topology directly into intensity contrast. The optic was designed and validated entirely through forward simulation, combining a fully three-dimensional Takagi-Taupin solver with an FFT-based Fourier-optics propagator. A charge-matching rule between the optical topological charge and the defect winding number governs which features become bright cores and which produce dark regions of controlled order. Applications include single-shot Burgers-vector sign classification of dislocations and chirality/charge-state imaging of ferroelectric domain walls.