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Generation of Circularly Polarized X-ray Free-Electron Laser (Press Release)

Release Date
23 Apr, 2014

Japan Synchrotron Radiation Research Institute (JASRI)

Key Points
• Successful installation of an optical device that can generate circularly polarized X-ray free-electron laser beams at SACLA
• Demonstration of full control of X-ray polarization states of XFEL using a diamond crystal
• Possible applications to observation of ultrafast dynamics of electron spins as well as chiral structural dynamics

A research group of RIKEN (President, Ryoji Noyori) and JASRI (President, Yoshiharu Doi) has installed a new instrument at the X-ray free-electron laser (XFEL) facility, SACLA[1], for full control of polarization states[2] of XFEL radiation. This device has successfully worked to generate a circularly polarized XFEL beam. The beam would be a powerful tool for exploring new scientific fields including ultrafast magnetization dynamics in magnetic materials and chiral structural dynamics in inorganic/organic materials. The research group was led by Motohiro Suzuki (senior scientist) of Research & Utilization Division, JASRI (visiting scientist at RIKEN) and Makina Yabashi (group director) of Beam Line Research and Development Group, RIKEN SPring-8 Center (Director, Tetsuya Ishikawa).

XFEL radiation is generally a linearly polarized electromagnetic wave, for which the electric field vector is oscillating in the horizontal plane. Researchers have desired XFEL beams in other polarization states of which the electric field vector is rotating spirally, namely, circular polarization. Circularly polarized XFEL can extend the range of SACLA's applications, making it feasible to observe electron spin motions in magnetic materials and structural dynamics of chiral materials in biological systems in the time scale shorter than 1 picosecond. In the present research, a synthetic diamond crystal was used as a transmission-type polarizer to convert a linearly polarized XFEL beam generated from SACLA into circular polarization. The spiral direction of the resulting circularly polarized XFEL beam can be quickly switched between right- and left-handed by changing the angle of the diamond crystal. With the newly installed device, SACLA has become the only facility that can provide circularly polarized XFEL beams. This extended capability of SACLA will likely produce a number of leading-edge studies particularly in magnetic and chiral materials. Possible innovations include development of novel magnetic memory devices that can be working hundreds times faster than current ones.

This work was supported by SACLA User's Equipment Development Proposal of RIKEN and JASRI. The paper was published online in the British scientific journal, Journal of Synchrotron Radiation on 3 April 2014.

"Polarization control of an X-ray free-electron laser with a diamond phase retarder"
Motohiro Suzuki*†‡, Yuichi Inubushi‡, Makina Yabashi‡, Tetsuya Ishikawa‡
†Japan Synchrotron Radiation Research Institute (JASRI), 1-1-1 Kouto, Sayo, Hyogo 679-5198, Japan
‡RIKEN SPring-8 Center, RIKEN, 1-1-1, Kouto, Sayo, Hyogo 679-5148, Japan
Journal of Synchrotron Radiation, 2014, 21, pp .466–472
DOI: 10.1107/S1600577514004780
Publication Date (Web): 3 April 2014


Fig. 1 Conversion of X-ray polarization states using a diamond crystal.
Fig. 1 Conversion of X-ray polarization states using a diamond crystal.

A linearly polarized XFEL beam from SACLA is going through a diamond crystal and converted into circular polarization.

Fig. 2 The instrument installed at the SACLA beamline.
Fig. 2 The instrument installed at the SACLA beamline.

A diamond crystal is placed in the vacuum chamber.

Fig. 3 Degrees of circular polarization as a function of the angle of diamond crystal.
Fig. 3 Degrees of circular polarization as a function of the angle of diamond crystal.

Dots show the experimental result, and the line shows the result of theoretical calculation. Right- (left-) handed circular polarization was generated at a crystal angle of –31 (+31) arcsec.

《Supplementary explanations》

SACLA is a Japanese X-ray free-electron laser (XFEL) facility and was constructed jointly by RIKEN and JASRI. It is a system for generating an X-ray laser from electrons oscillating coherently. SACLA has been developed as one of the national core technologies. Its construction and preparation was launched in FY2006 in a five-year project and was completed in March 2011. The name SACLA is short for SPring-8 angstrom compact free-electron laser.

[2]Polarization, linear polarization, circular polarization
Light and X-rays are types of electromagnetic waves. An electromagnetic wave oscillating in a fixed direction or regular manner is defined as 'polarized light (X-rays)'. Linear polarization refers to a light (X-ray) wave with which the electric field vector is oscillating in a plane; circular polarization refers to a wave with which the electric field vector is rotating spirally.

[3]Chiral material
Material that has a helical structure in the atomic arrangement. Typical chiral materials include some organic molecules: amino acid, sugar, adrenaline, and inorganic crystals: quartz, and tellurium. Some chiral materials may be applied to development of novel multifunctional materials for the next-generation electronic devices.

For more information, please contact:
 Motohiro Suzuki (JASRI)
  TEL: 0791-58-2750