Orbital Angular Momentum Transfer and Beam-Quality Limits in Fork-Grating Electron Diffraction
Abstract
We analyze fork-grating generation of electron vortex beams beyond the ideal single-mode approximation. The incident beam is described as a paraxial Gaussian ensemble with finite transverse momentum spread and a first electromagnetic Hartree phase accumulated before the grating. Within Fresnel propagation we derive an analytical expression for each diffraction order and determine the corresponding orbital-angular-momentum statistics. The mean OAM of a selected order remains fixed by the topological rule, ⟨ Lz⟩m=mpℏ, while its variance is set by the residual transverse momentum spread of the beam prepared at the grating. For the Gaussian mixture, the transverse purity is 𝒫⊥,m=[1+2(ΔLz,m/ℏ)2]−1. The observed annular profile is governed by a separate propagation-dependent blurring scale, so a beam can retain well-defined mean OAM while having low transverse purity or a partially filled vortex minimum. Within the radial phase-screen approximation, the Hartree self-field modifies the propagated profile while preserving the full-plane OAM moments and transverse purity.
Related
- Probing Orbital Angular Momentum Distributions in Elastic Vector Meson Production in Longitudinally Polarized Electron--Proton Scattering
- Electron Dynamics in a Wakefield Accelerator Driven by Laser Pulses Carrying Orbital Angular Momentum
- Laser-Driven Electron Emission Carrying Orbital Angular Momentum from Carbon Nanotubes
- Spectral density of angular momentum transfer from a swift electron to a large spherical nanoparticle
- Spin-to-orbital angular momentum conversion in dielectric metasurfaces
BibTeX
@misc{tsiopa2026orbital,
title = {{Orbital Angular Momentum Transfer and Beam-Quality Limits in Fork-Grating Electron Diffraction}},
author = {P. K. Tsiopa and S. S. Baturin},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.18401},
eprint = {2610.18401},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.18401},
}
RIS
TY - UNPB
TI - Orbital Angular Momentum Transfer and Beam-Quality Limits in Fork-Grating Electron Diffraction
AU - P. K. Tsiopa
AU - S. S. Baturin
PY - 2026
DA - 2026/10/13
PB - arXiv
DO - 10.48550/arxiv.2610.18401
UR - https://arxiv.org/abs/2610.18401
AB - We analyze fork-grating generation of electron vortex beams beyond the ideal single-mode approximation. The incident beam is described as a paraxial Gaussian ensemble with finite transverse momentum spread and a first electromagnetic Hartree phase accumulated before the grating. Within Fresnel propagation we derive an analytical expression for each diffraction order and determine the corresponding orbital-angular-momentum statistics. The mean OAM of a selected order remains fixed by the topological rule, ⟨ L_z⟩_m=mpℏ, while its variance is set by the residual transverse momentum spread of the beam prepared at the grating. For the Gaussian mixture, the transverse purity is 𝒫_⊥,m=[1+2(ΔL_z,m/ℏ)^2]^−1. The observed annular profile is governed by a separate propagation-dependent blurring scale, so a beam can retain well-defined mean OAM while having low transverse purity or a partially filled vortex minimum. Within the radial phase-screen approximation, the Hartree self-field modifies the propagated profile while preserving the full-plane OAM moments and transverse purity.
ER -