Monochromatization of Electron Beams with Spatially and Temporally Modulated Optical Fields

TL;DR

This paper proposes a method to monochromatize electron beams by matching chirped optical fields with chirped electron wave packets, improving spectral resolution in ultrafast electron imaging.

Contribution

It introduces a novel approach using chirped optical fields and electron wave packets to achieve partial monochromatization of electron spectra.

Findings

Electron spectra can be narrowed by a factor of 5.

26% of electrons can be confined in a monochromatized energy band.

Matching chirp parameters enhances spectral purity.

Abstract

Inelastic interaction between coherent light with constant frequency and free electrons enables periodic phase modulation of electron wave packets leading to periodic side-bands in the electron energy spectra. In this Letter we propose a generalization of the interaction by considering linearly chirped electron wave packets interacting with chirped optical fields. We theoretically demonstrate that when matching the chirp parameters of the electron and light waves, the interaction leads to partial monochromatization of the electron spectra in one of the energy side-bands. Depending on the coherence time of the electrons, the electron spectrum may be narrowed down by a factor of 5-times with 26% of the electron distribution in the monochromatized energy band. This approach will improve the spectral resolution and reduce color aberrations in ultrafast imaging experiments with free electrons.