Acta Optica Sinica, Vol. 40, Issue 2, 0232001 (2020)
Focal Spot Deterioration Analysis of Plasma Mirrors in High-Power Ultrashort Laser Systems
Zhang Dongjun1,2, Zhu Ping1,**, Xie Xinglong1,*, Kang Jun1, Yang Qingwei1, Zhu Haidong1, Guo Ailin1, Sun Meizhi1, Gao Qi1, and Zhu Jianqiang1
- 1Key Laboratory of High Power Laser and Physics, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800, China
- 2Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing 100049, China
Plasma mirrors can be effectively used to improve the signal-to-noise ratio (SNR) of high-power ultrashort laser; however, some experiments conducted using plasma mirrors denote that plasma mirrors may cause focal spot deterioration. Herein, we establish a spatiotemporal focusing multistep propagation algorithm based on plasma expansion and diffraction propagation to quantitatively investigate the plasma-mirror-induced focal spot deterioration. Further, the influences of the plasma expansion time as well as the amplitude and spatial frequency of wavefront error on focal spot deterioration are quantitatively analyzed using a beam quality evaluation function. The simulation results reveal that the plasma-mirror-induced far-field focal spot deterioration can be mainly attributed to the non-uniform plasma expansion based on the plasma expansion time and wavefront error, with the plasma expansion time observed to be the dominant factor. Additionally, higher-amplitude and lower-spatial-frequency wavefront errors have a relatively greater influence on the focusing ability. From the perspective of high SNR ultraintense output capability, the spatiotemporal quality requirement of the pulse is introduced to avoid far-field focal spot deterioration when a plasma mirror is used in a high-power ultrashort laser system.
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