Related Experiment Video
Updated: Apr 22, 2026

Fabrication And Characterization Of Photonic Crystal Slow Light Waveguides And Cavities
Published on: November 30, 2012
First characterization of coherent optical vortices from harmonic undulator radiation
E Hemsing1, M Dunning1, C Hast1
1SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA.
Abstract:
We describe the experimental generation and measurement of coherent light that carries orbital angular momentum from a relativistic electron beam radiating at the second harmonic of a helical undulator. The measured helical phase of the light is shown to be in agreement with predictions of the sign and magnitude of the phase singularity and is more than 2 orders of magnitude greater than the incoherent signal. Our setup demonstrates that such optical vortices can be produced in modern free-electron lasers in a simple afterburner arrangement for novel two-mode pump-probe experiments.
Related Concept Videos
Standing Waves in a Cavity
Atomic Nuclei: Larmor Precession Frequency
Electromagnetic Waves in Matter
Consider the electromagnetic wave passing through a dielectric medium. In such a case, Maxwell's equations get modified. In Ampere's law, ε0 , the dielectric permittivity of free space is replaced with ε, the permittivity of dielectric. Also, the vacuum permeability μ0 is replaced by the permeability of the medium,...
The Wave Nature of Light
Interference and Diffraction
Plane Electromagnetic Waves I
The EM field is assumed to be a...

