量研学術機関リポジトリ「QST-Repository」は、国立研究開発法人 量子科学技術研究開発機構に所属する職員等が生み出した学術成果（学会誌発表論文、学会発表、研究開発報告書、特許等）を集積しインターネット上で広く公開するサービスです。 Welcome to QST-Repository where we accumulates and discloses the academic research results(Journal Publications, Conference presentation, Research and Development Report, Patent, etc.) of the members of National Institutes for Quantum and Radiological Science and Technology.
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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).
Characterization of the J-KAREN-P laser spot at 300 TW and pulse shape at full beam diameter
