Full-coherent free electron laser seeded by 13th- and 15th-order harmonics of near-infrared femtosecond laser pulses

Sato, Takahiro*; Iwasaki, Atsushi*; Owada, Shigeki*; Yamanouchi, Kaoru*; Takahashi, Eiji*; Midorikawa, Katsumi*; Aoyama, Makoto; Yamakawa, Koichi; Togashi, Tadashi*; Fukami, Kenji*; Hatsui, Takaki*; Hara, Toru*; Kameshima, Takashi*; Kitamura, Hideo*; Kumagai, Noritaka*; Matsubara, Shinichi*; Nagasono, Mitsuru*; Ohashi, Haruhiko*; Oshima, Takashi*; Otake, Yuji*; Shintake, Tsumoru*; Tamasaku, Kenji*; Tanaka, Hitoshi*; Tanaka, Takashi*; Togawa, Kazuaki*; Tomizawa, Hiromitsu*; Watanabe, Takahiro*; Yabashi, Makina*; Ishikawa, Tetsuya*

By introducing 13th- (61.7 nm) and 15th-order harmonics (53.4 nm) of femtosecond laser pulses at 800 nm into an undulator of SCSS (SPring-8 Compact SASE Source) test accelerator at RIKEN, these harmonic pulses were amplified by a factor of more than 10 with a high contrast ratio through the interaction between accelerated electron bunches and the harmonic pulses. From numerical simulations of the amplification processes of high-order harmonic pulses in the undulator, optimum conditions of the electron bunch duration interacting with the high-order harmonic pulses were investigated for generating full-coherent and intense pulses in the extreme ultraviolet wavelength region.