Precision control of gamma-ray polarization using a crossed helical undulator free-electron laser

Jun Yan, Jonathan M. Mueller, Mohammad W. Ahmed, Hao Hao, Senlin Huang, Jingyi Li, Vladimir N. Litvinenko, Peifan Liu, Stepan F. Mikhailov, Victor G. Popov, Mark H. Sikora, Nikolay A. Vinokurov, Ying K. Wu

Research output: Contribution to journalArticlepeer-review

7 Citations (Scopus)


Polarized gamma-ray beams are a precise and selective probe for studying fundamental questions about nuclear structure and hadron properties. Improvements to this probe require new experimental approaches that can produce high-flux gamma-ray beams with easily switchable pure polarization states. Here, we report an optics-free method to precisely control the polarization of a Compton gamma-ray beam. Using a free-electron laser (FEL) oscillator with two helical undulator magnets of opposite helicities, we have produced a linearly polarized FEL beam with a variable polarization direction and an unprecedented degree of linear polarization, PLin = 0.997. With this FEL as a photon drive, we are able to generate Compton gamma-ray beams having either left/right-circular polarization or rotatable linear polarization. The linearly polarized gamma-ray beam has been characterized and shows PLin = 0.97. This demonstrated polarization control technique is well suited for high-flux gamma-ray production with any level of FEL power.

Original languageEnglish
Pages (from-to)629-635
Number of pages7
JournalNature Photonics
Issue number9
Publication statusPublished - 1 Sep 2019




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