First demonstration of intense full-coherent soft-X ray laser achieved by advanced accelerator and ultrashort-pulsed laser technologies in Japan
Figure 1. Experimental Setup. High harmonics (HH) radiation is generated by loosely focusing a Ti:S laser (800 nm, 100 mJ, 160 fs FWHM, 30 Hz) in a Xe gas cell (focal length f = 4000 mm), and is separated from the fundamental beam by a SiC mirror. Pt-coated concave mirrors with 8000-mm radius of curvature are used for collimating and focusing HH radiation. The HH radiation is transported by the SiC mirror to the undulator section, overlapped with an electron beam (250 MeV, 300 fs, 30 Hz) spatially and temporally. The seeded FEL is observed by the spectrometer at the end of the beamline. The inset shows the beam profile of HH radiation at the undulator entrance. The spatial profile was measured by a phosphor screen coupled with a multichannel plate (MCP) and CCD camera.
Figure 2. Spectra of seeded (red lines) and unseeded (blue lines) conditions given by experiment (a) and simulation (b).
We achieved 650-hold amplification of the 13th harmonic of near-infrared ultrashort-pulsed intense laser light by the free electron laser (FEL) called SPring-8 Compact SASE Source (SCSS) Test Accelerator. This is the first demonstration of the generation of intense full-coherent light pulses in the extreme ultraviolet region by the high-order harmonic seeded FEL, and paves the way for new frontier research in optical science in the soft-X ray and X-ray regions. This project has been carried out by collaborative efforts made by the researchers in RIKEN, JASRI, University of Tokyo, JAEA, Keio University, NTT Basic Research Laboratories, KEK, and SOLEIL (France).
Tadashi Togashi, Eiji J. Takahashi, Katsumi Midorikawa, Makoto Aoyama, Koichi Yamakawa, Takahiro Sato, Atsushi Iwasaki, Shigeki Owada, Tomoya Okino, Kaoru Yamanouchi, Fumihiko Kannari, Akira Yagishita, Hidetoshi Nakano, Marie E. Couprie, Kenji Fukami, Takaki Hatsui, Toru Hara, Takashi Kameshima, Hideo Kitamura, Noritaka Kumagai, Shinichi Matsubara, Mitsuru Nagasono, Haruhiko Ohashi, Takashi Ohshima, Yuji Otake, Tsumoru Shintake, Kenji Tamasaku, Hitoshi Tanaka, Takashi Tanaka, Kazuaki Togawa, Hiromitsu Tomizawa, Takahiro Watanabe, Makina Yabashi, and Tetsuya Ishikawa, “Extreme ultraviolet free electron laser seeded with high-order harmonic of Ti:sapphire laser,” Optics Express, published 03 January 2011.