@misc{oai:repo.qst.go.jp:00072599,
 author = {ピロジコフ, アレキサンダー and 福田, 祐仁 and 西内, 満美子 and 桐山, 博光 and 匂坂, 明人 and 小倉, 浩一 and 森, 道昭 and 岸本, 牧 and 榊, 泰直 and ドーバー, ニコラス ピーター and 近藤, 康太郎 and 中新, 信彦 and 黄, 開 and Kanasaki, M and 近藤, 公伯 and 神門, 正城 and ピロジコフ アレキサンダー and 福田 祐仁 and 西内 満美子 and 桐山 博光 and 匂坂 明人 and 小倉 浩一 and 森 道昭 and 岸本 牧 and 榊 泰直 and ドーバー ニコラス ピーター and 近藤 康太郎 and 中新 信彦 and 黄 開 and 近藤 公伯 and 神門 正城},
 month = {May},
 note = {J-KAREN-P [1] is a high-power laser facility aiming at highest beam quality and highest irradiance for performing state-of-the art experiments at the frontier of modern science.
\nWe have recently approached the physical limits of the beam quality: diffraction limit of the focal spot and bandwidth limit of the pulse shape [2]. In particular, we have measured the focal spot after an f/1.3 off-axis parabolic mirror during 0.3 PW operation. The laser beam was attenuated by ten wedges with high surface quality confirmed with interferometry. The resulting focal spot had the effective radius of ~1.0 μm and the Strehl ratio of ~0.5. We thus achieved the highest at-focus irradiance of ~10^22 W/cm^2.
\nWe have also performed full-beam duration measurement, down-collimating the Ø280 mm beam to a few mm using a telescope consisting of the main f = 2,600 mm and additional f = 2.54 mm off-axis parabolic mirrors. The full-beam pulse duration and shape were nearly identical to the duration and shape measured using a few mm diameter pick-off, confirming high spatiotemporal quality of the beam and absence of the spatiotemporal couplings.
\n[1]. H. Kiriyama, M. Mori, A. S. Pirozhkov, et al., "High-Contrast, High-Intensity Petawatt-Class Laser and Applications," IEEE J. Sel. Topics Quantum Electron. 21 1601118-18 (2015).
\n[2]. A. S. Pirozhkov, Y. Fukuda, M. Nishiuchi, H. Kiriyama, A. Sagisaka, K. Ogura, M. Mori, M. Kishimoto, H. Sakaki, N. P. Dover, K. Kondo, M. Kanasaki, K. Kondo, and M. Kando, "Approaching the diffraction-limited, bandwidth-limited Petawatt," (submitted)., Opto 2017 Symposium on Photon and Beam Science},
 title = {Characterization of the J-KAREN-P laser spot at 300 TW and pulse shape at full beam diameter},
 year = {2017}
}