Electron holography for vortex beams

A combined technology of vortex beam technique and electron holography has been developed. A range about 10 times the diameter of the grating opening was irradiated and two-wave interference between a Bragg diffraction wave as a vortex beam and a transmitted wave from and around a fork-shaped grating was recorded as a hologram. Reconstruction by using the Fourier transform method was simultaneously performed for amplitude and phase distributions. Furthermore, by using a wave aberration function, the amplitude and phase distributions at various propagation positions were reconstructed numerically, resulting in the confirmation of vortex beam twists.