Generation and Application of Bessel Beams in Electron Microscopy

TL;DR

This paper systematically explores the holographic generation of electron Bessel beams, optimizing fabrication for high efficiency and tunability, and discusses their potential applications in electron microscopy.

Contribution

It provides a detailed theoretical and experimental framework for generating and controlling electron Bessel beams with high efficiency and tunability in electron microscopy.

Findings

Electron Bessel beams achieved with 37% efficiency.

Beam properties can be tuned for interferometry or imaging.

Phase structure characterized and controlled.

Abstract

We report a systematic treatment of the holographic generation of electron Bessel beams, with a view to applications in electron microscopy. We describe in detail the theory underlying hologram patterning, as well as the actual electro-optical configuration used experimentally. We show that by optimizing our nanofabrication recipe, electron Bessel beams can be generated with efficiencies reaching $37 \pm 3\%$. We also demonstrate by tuning various hologram parameters that electron Bessel beams can be produced with many visible rings, making them ideal for interferometric applications, or in more highly localized forms with fewer rings, more suitable for imaging. We describe the settings required to tune beam localization in this way, and explore beam and hologram configurations that allow the convergences and topological charges of electron Bessel beams to be controlled. We also characterize the phase structure of the Bessel beams generated with our technique, using a simulation procedure that accounts for imperfections in the hologram manufacturing process. Finally, we discuss a specific potential application of electron Bessel beams in scanning transmission electron microscopy.