# $\pi$/2 Mode Converters and Vortex Generators for Electrons

## TL;DR

This paper explores the design of asymmetric quadrupole mode converters in electron optics to generate vortex beams, inspired by optical vortex generation methods, aiming to enhance electron microscopy capabilities.

## Contribution

It introduces novel asymmetric quadrupole designs for electron vortex beam generation compatible with existing microscopes.

## Key findings

- Proposed generalized asymmetric quadrupole configurations.
- Demonstrated potential for high-brilliance electron vortex probes.
- Guidelines for implementation within current electron microscope setups.

## Abstract

In optics, mode conversion is an elegant way to switch between Hermite Gaussian and Laguerre Gaussian beam profiles and thereby impart orbital angular momentum onto the beam and to create vortices. In optics such vortex beams can be produced in a setup consisting of two identical cylinder lenses. In electron optics, quadrupole lenses can be used for the same purpose. Here we investigate generalized asymmetric designs of a quadrupole mode converter that may be realized within the constraints of existing electron microscopes and can steer the development of dedicated vortex generators for high brilliance electron vortex probes of atomic scale.