High-energy, diode-pumped, picosecond Yb:YAG chirped-pulse regenerative amplifier as a pump source for optical parametric chirped-pulse amplification

Akahane, Yutaka; Aoyama, Makoto; Ogawa, Kanade; Tsuji, Koichi; Tokita, Shigeki*; Kawanaka, Junji*; Nishioka, Hajime*; Yamakawa, Koichi

We have developed a narrowband Yb:YAG chirped-pulse regenerative amplifier using gain-narrowing, which is suitable for direct OPCPA pumping without pulse compression. A chirped-seed pulse was amplified and compressed in the regen, simultaneously, which generated the picosecond pulses with 7.5-mJ of energy without a pulse compressor. In the experiment, output pulse from a mode-locked oscillator was split into two beams, which were used as seed pulses for both Yb:YAG regen and OPCPA. The seed pulse for the regen was positively chirped to 1.2 ns by a PANDA fiber before amplification. An Yb:YAG was cooled by a liquid-nitrogen cryostat and fiber-coupled laser diode was used to pump the regen. A gain narrowed amplified bandwidth (from 17 nm to 0.5 nm) corresponded to 35 ps (FWHM) duration. We also performed a parametric amplification by using the frequency-doubled, 25-ps pump pulse. We have observed OPA spectra at 850 and 1200 nm, simultaneously, with the maximum OPA gain of 10.