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Atomic inner-shell laser at 1.5-ångström wavelength pumped by an X-ray free-electron laser

Nature volume 524, pages 446449 (27 August 2015) | Download Citation


Since the invention of the first lasers in the visible-light region, research has aimed to produce short-wavelength lasers that generate coherent X-rays1,2; the shorter the wavelength, the better the imaging resolution of the laser and the shorter the pulse duration, leading to better temporal resolution in probe measurements. Recently, free-electron lasers based on self-amplified spontaneous emission3,4 have made it possible to generate a hard-X-ray laser (that is, the photon energy is of the order of ten kiloelectronvolts) in an ångström-wavelength regime5,6, enabling advances in fields from ultrafast X-ray spectrosopy to X-ray quantum optics. An atomic laser based on neon atoms and pumped by a soft-X-ray (that is, a photon energy of less than one kiloelectronvolt) free-electron laser has been achieved at a wavelength of 14 nanometres7. Here, we use a copper target and report a hard-X-ray inner-shell atomic laser operating at a wavelength of 1.5 ångströms. X-ray free-electron laser pulses with an intensity of about 1019 watts per square centimetre7,8 tuned to the copper K-absorption edge produced sufficient population inversion to generate strong amplified spontaneous emission on the copper Kα lines. Furthermore, we operated the X-ray free-electron laser source in a two-colour mode9, with one colour tuned for pumping and the other for the seed (starting) light for the laser.

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The experiment was performed at SACLA with the approval of JASRI and the program review committee (grant numbers 2012B8014, 2013A8013, 2013B8020, 2014A8008). We acknowledge the supporting members of the SACLA facility. This research was partially supported by Grant-in-Aids for Scientific Research (A) (25247093) and (S) (23226004), by the Photon Frontier Network Program and by the Global COE Program ‘Center of Excellence for Atomically Controlled Fabrication Technology’ from the Ministry of Education, Sports, Culture, Science and Technology, Japan (MEXT).

Author information


  1. Institute for Laser Science, University of Electro-Communications, Chofu, Tokyo 182-8585, Japan

    • Hitoki Yoneda
    • , Kazunori Nagamine
    •  & Yurina Michine
  2. RIKEN SPring-8 Center, Sayo, Hyogo 679-5148, Japan

    • Hitoki Yoneda
    • , Yuichi Inubushi
    • , Haruhiko Ohashi
    • , Kazuto Yamauchi
    • , Hidekazu Mimura
    • , Tetsuya Ishikawa
    •  & Makina Yabashi
  3. Japan Synchrotron Radiation Research Institute (JASRI), Sayo, Hyogo 679-5198, Japan

    • Yuichi Inubushi
    • , Haruhiko Ohashi
    • , Hirokatsu Yumoto
    •  & Tetsuo Katayama
  4. Graduate School of Engineering, Osaka University, Suita, Osaka 565-0871 Japan

    • Kazuto Yamauchi
  5. Department of Precision Engineering, The University of Tokyo, Bunkyo, Tokyo 113-8656, Japan

    • Hidekazu Mimura
  6. Department of Physics, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan

    • Hikaru Kitamura


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H. Yoneda and Y.I. conceived the basic experiment. H. Yoneda, Y.I., K.N., Y.M. and M.Y. designed the research. M.Y. and T.I. are responsible for SACLA and the SACLA beamline. H.M., K.Y., H. Yumoto, H.O. and M.Y. designed and constructed the two-stage focusing system at SACLA. H. Yoneda, Y.I., K.N., Y.M. and T.K. performed the experiment. H. Yoneda and H.K. performed theoretical analyses and numerical simulations. H. Yoneda and M.Y. wrote the first draft of the manuscript with discussion and improvement from all authors.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to Hitoki Yoneda.

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