Wavefront Propagation Modeling and Verification of the SG-II Updated Laser Facility

Ailin, 郭爱林 Guo; Haidong, 朱海东 Zhu; Zeping, 杨泽平 Yang; Ende, 李恩德 Li; Xinglong, 谢兴龙 Xie; Jianqiang, 朱健强 Zhu; Zunqi, 林尊琪 Lin; Weixin, 马伟新 Ma; Jian, 朱俭 Zhu

doi:10.3788/aos201333.0214001

Cited by 3 publications

(2 citation statements)

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“…High-energy laser systems usually have large beam diameters with relatively low energy density on optical elements due to the limited damage threshold problem, and large diameter laser systems have the inherent wave front deviation. The influence on spatial output characteristics by wave front deviation has been analyzed by mature means 11 . However the discussed temporal characteristic by wave front deviation is confined to the pulse width 12 , without considering the temporal contrast degradation by wave front deviation.…”

Section: Introductionmentioning

confidence: 99%

Analysis of temporal contrast degradation due to wave front deviation in large aperture ultra-short pulse focusing system

et al. 2014

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In extremely intense laser system used for plasma physics experiments, temporal contrast is an important property of the ultra-short pulse. In this paper, we theoretically study the temporal contrast degradation due to wave front deviation in large aperture ultra-short pulse focusing system. Two-step focusing fast Fourier transform (FFT) algorithm with the coordinate transform based on Fresnel approximation in space domain and Fourier integral transform method in time domain were used to simulate the focusing process spatially and temporally, in which the spatial distribution of ultrashort pulse temporal contrast characteristics at the focal spot is related to the wave front in large aperture off-axis parabolic mirror focusing optical system. Firstly, temporal contrast degradation due to wave front noise with higher spatial frequency is analyzed and appropriate evaluation parameter for large aperture ultra-short pulse focusing system is put forward from the perspective of temporal contrast. Secondly, the influence of wave front distortion with lower spatial frequency on temporal contrast is revealed comparing different degradation characteristics of various aberrations. At last, a method by controlling and optimizing the wave front to prevent temporal contrast degradation in large aperture ultrashort laser system is proposed, which is of great significance for high temporal contrast petawatt laser facilities.

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Section: Introductionmentioning

confidence: 99%

Analysis of temporal contrast degradation due to wave front deviation in large aperture ultra-short pulse focusing system

et al. 2014

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“…中国的神光 II升级装置于 2015年建成并投入运行, 共8束纳秒激光, 单束基频最大输出能力为8 kJ/5 ns方波, 可支持三倍频到靶总能量 24 kJ/3 ns方波物理实验打靶 [8,9] . 随着物理实验的开展, 物理对装置不断提出更高的能量要求, 尤其是新型激光聚变点火研究, 提出了集高峰值功率、长脉宽、大能量、三角波形为一体的复杂打靶要求 [10,11] .…”

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Improvement of fundamental frequency performance of SGII-UP laser facility

Xie,

Wang,

Liu

et al. 2023

Acta Phys. Sin.

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The SGⅡ-UP laser facility is one of the most important high power laser systems in China and one of the few inertial confinement fusion laser devices in the world that operate all year round. In order to further improve its output capacity to meet higher physical requirements, measures such as increasing the number of neodymium glasses, adopting new N41 neodymium glasses, and improving the energy configuration of xenon lamps are taken to improve the gain capacity of the main amplifier. Calculation of the new main amplifier construction model predicts the small gain coefficient will reach 4.9%. And further modulation of the laser device shows a reduction of injection energy from 5J to 1.26J when a 10kJ fundamental frequency energy output is demanded, which supports a higher output energy as well as a stronger commission ability. Furthermore, B integral is analyzed with a result of a obvious reduction under different laser pulses injection conditions of 1ns, 5ns, 10ns, which means a better near-filed quality of the beams. Accordingly small-size modulation suppression of induced by non-linear phase shift while high fluence laser passing is expected before and after the improvement, which is a key prerequisite to a higher commission energy. Based on these analyses, fundamental frequency output energies with different pulse injections are calculated and an improvement from 8kJ to 12.5kJ commission is expected under 10ns square pulse condition. Tests show that the small signal gain coefficient of the device increases from 4.15%/cm to 4.94%/cm, consistent with simulation results and the mean gain multiple of a single beam increases from 9000 to 118000 with more than an order of magnitude. Commission verifies the fundamental frequency output capacity exceeding 12.5kJ under 10ns square pulse as well as a small-size modulation suppression around 0.16mm<sup>-1</sup> as a result of joint action of non-linear phase shift and spatial filtering. After the significant improvement, the SGⅡ-UP laser facility will strongly support more ambitious physical experiment targets.

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