Shaping electron beams using light
Marius Constantin Chirita Mihaila b, Philipp Weber b, Matthias Schneller b, Lucas Grandits b, Thomas Juffmann b
a University of Vienna, 1090, Vienna, Austria
b Department of Structural and Computational Biology, Max F. Perutz Laboratories
Proceedings of Electron Beam Spectroscopy for Nanooptics 2021 (EBSN2021)
Online, Spain, 2021 June 14th - 15th
Organizers: Mathieu Kociak and Nahid Talebi
Poster, Marius Constantin Chirita Mihaila, 045
Publication date: 8th June 2021
ePoster: 

Shaping electron beams with light

M. C. Chirita Mihaila (1,2), P. Weber (1,2), M. Schneller (1,2), L. Grandits (1,2), and T. Juffmann (1.2)

1: University of Vienna, Faculty of Physics

2: Department of Structural and Computational Biology, Max F. Perutz Laboratories, University of Vienna, Campus Vienna Biocenter 5, A-1030 Vienna, Austria

 

Introduction

 

The precise control of electron wave function is at the heart of high resolution electron microscopy, where complex multipole lenses [1] have enabled sub-A spatial resolution. Recently, programmable [2] and non-programmable [3][4][5] wave-front shaping techniques have been used for aberration correction, for the production of exotic beams, and for contrast enhancement in biological imaging. Laser based phase-plates have been developed for contrast enhancement [6], and have been proposed for arbitrary and lossless wavefront-shaping [7]. Here, we discuss our progress in developing such a programmable laser phase plate for ultrafast electrons.

 

Methods

The Viennese ultrafast scanning electron microscope (USEM) is based on a commercial SEM, which was modified to enable laser triggered electron emission from a Schottky electron emitter. In the specimen chamber the electron beam interacts with a counter-propagating laser pulse, inducing local phase shifts to the electron wave function that are proportional to the light intensity. The SEM was further modified to enable operation in transmission mode, which allows characterizing the electron-light interaction.

Results

The desired light intensity distribution is generated by a spatial light modulator (SLM) and is situated in a Fourier plane of the interaction region. For finding the required phase patterns on the SLM, a modified Gerchberg-Saxton algorithm was implemented. With a proper choice of initial conditions for the iterative algorithm, undesired intensity fluctuations (speckles) in the reconstructed image and intensity losses along the beam path could be minimized. The spatial and temporal overlap between laser and electrons has been confirmed by measuring electron deflections caused by strong pondemorotive potentials.

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