Abstract
We consider use of a variable polarizing undulator for generating brilliant x-ray beams carrying orbital angular momentum. We find that higher harmonics of the radiation correspond to Laguerre-Gaussian modes with azimuthal mode indices equal to one less than the harmonic number when the undulator is operated to produce circularly polarized light. Beams with nonzero carry orbital angular momentum quantized in units of per photon. When operated to produce linear polarization, the harmonics correspond to Hermite-Gaussian modes. Selection of these modes with conventional monochromator optics opens the door for new research with x-ray synchrotron and free-electron laser sources.
- Received 9 September 2007
DOI:https://doi.org/10.1103/PhysRevLett.100.124801
©2008 American Physical Society