Electron Vortex Beams and Their Control

Abstract

Electron vortex beams are considered as probes for next generation electron beam instruments with unprecedented measurement capabilities because vortex beams carry intrinsic orbital angular momenta. In order to clarify the performance of vortex beams, we generated vortex beams by using fork-shaped gratings manufactured by focused ion beam instruments. In vortex beam generation experiment, we found that shapes and sizes of grating openings were superimposed on rings of diffraction spots, typical behavior of vortex beams. This paper discusses experimental results on the generation and control of vortex beams by changing grating opening shapes and sizes.

Fig. 8 Effect of opening shapes on diffraction ring shapes: (a) circular opening, (b) triangular opening, (c) square opening, (d) pentagonal opening, and (e) star-shaped opening. The fork-shaped gratings have the third order edge dislocation and their average grid spacing is 400 nm.