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Updated: Mar 6, 2026

Magnetic Tweezers for the Measurement of Twist and Torque
Published on: May 19, 2014
Angular Momentum of Twisted Radiation from an Electron in Spiral Motion
M Katoh1,2, M Fujimoto1,2, H Kawaguchi3
1Institute for Molecular Science, National Institutes of Natural Sciences, Okazaki 444-8585, Japan.
Abstract:
We theoretically demonstrate for the first time that a single free electron in circular or spiral motion emits twisted photons carrying well-defined orbital angular momentum along the axis of the electron circulation, in adding to spin angular momentum. We show that, when the electron velocity is relativistic, the radiation field contains harmonic components and the photons of lth harmonic carry lℏ total angular momentum for each. This work indicates that twisted photons are naturally emitted by free electrons and are more ubiquitous in laboratories and in nature than ever thought.
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