Fig. 2
From: Producing focused extreme ultraviolet vortex with Fermat-spiral photon sieves
Sketch of the experiment setup for focused OAM and recorded by PMMA (a), detection of AFM (b), (c) and (d) the intensity and phase distribution of the focused OAM with topological charge of -1; e diagonal intensity distribution of experimental results versus the theory; f, g the intensity and phase distribution of the focused OAM with topological charge of +3; h diagonal intensity distribution of experimental results versus the theory