Development of a high-contrast, high beam-quality, high-intensity laser

Kiriyama, Hiromitsu; Mori, Michiaki; Nakai, Yoshiki*; Shimomura, Takuya; Sasao, Hajime*; Tanaka, Momoko; Ochi, Yoshihiro; Tanoue, Manabu*; Kondo, Shuji; Kanazawa, Shuhei; Daito, Izuru; Okada, Hajime; Wakai, Daisuke; Sasao, Fumitaka*; Suzuki, Masayuki; Kosuge, Atsushi  ; Kondo, Kiminori; Sugiyama, Akira; Bulanov, S. V.; Bolton, P.; Yokoyama, Atsushi; Daido, Hiroyuki; Kawanishi, Shunichi; Kimura, Toyoaki*; Tajima, Toshiki

This paper reviews the temporal contrast and spatial beam quality improvement techniques in a high intensity Ti:sapphire laser system that is based on chirped-pulse amplification (CPA). We describe a low gain optical parametric chirped-pulse amplification (OPCPA) preamplifier that uses high energy, clean pulse seeding and is shown to significantly improve the contrast to better than 10-10 relative to the peak of the main femtosecond pulse. We also report the use of a diffractive optical element for beam homogenization of a 100 J level Nd:glass green pump laser, achieving a flat-topped spatial profile with a filling factor near 80 %.