"J-KAREN"; High intensity laser

Kiriyama, Hiromitsu; Mori, Michiaki; Nakai, Yoshiki; Shimomura, Takuya*; Tanoue, Manabu*; Akutsu, Atsushi; Okada, Hajime; Motomura, Tomohiro*; Kondo, Shuji; Kanazawa, Shuhei; Sagisaka, Akito; Ogura, Koichi; Orimo, Satoshi; Nishiuchi, Mamiko; Pirozhkov, A. S.; Ma, J.-L.; Yogo, Akifumi; Kando, Masaki; Kotaki, Hideyuki; Fukuda, Yuji; Chen, L.-M.; Daito, Izuru; Kawase, Keigo; Homma, Takayuki; Kameshima, Takashi; Hayashi, Yukio; Hayakawa, Takehito; Shizuma, Toshiyuki; Fujiwara, Mamoru; Bulanov, S. V.; Daido, Hiroyuki; Kimura, Toyoaki; Tajima, Toshiki

One of the main bottlenecks for the applications of ultrashort and ultrahigh-peak power lasers in high-field physics is a temporal contrast of the pulses. In ultrahigh-peak power lasers, a nanosecond background of the amplified spontaneous emission (ASE) is generated at the same time as the femtosecond pulse. This background is mostly generated in the preamplifier (regenerative, multipass amplifier). Even though the contrast level is usually in the range from 10 to 10, this level is not sufficiently low at relativistic intensities greater than 10W/cm to avoid unwanted pre-plasmas generation. We demonstrated a high-contrast, high-peak power laser with optical parametric chirped-pulse amplification (OPCPA). With the use of OPCPA, contrast is enhanced to better than 710 in a few picoseconds before the main pulse, which corresponds to an improvement of three to four orders in magnitude compared with conventional systems.