Angular Momentum of Twisted Radiation from an Electron in Spiral Motion

TL;DR

This paper theoretically demonstrates that a free electron in spiral motion naturally emits twisted photons with well-defined orbital angular momentum, especially at relativistic speeds, expanding understanding of angular momentum in radiation.

Contribution

It is the first to show that free electrons in spiral motion emit twisted photons with specific angular momentum properties, highlighting a natural source of such photons.

Findings

Relativistic electrons emit harmonic twisted photons with quantized angular momentum.

Twisted photon emission occurs naturally from free electrons in spiral motion.

The radiation contains harmonic components with well-defined orbital angular momentum.

Abstract

We theoretically demonstrate for the first time that a single free electron in circular/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 l-th harmonic carry lhbar total angular momentum for each. This work indicates that twisted photons are naturally emitted by free electrons and more ubiquitous in laboratories and in nature than ever been thought.