Significant advances on ultra-intense and ultra-short laser technology have led numerous laboratories around the world to develop table-top PW-class laser systems as a means of investigating laser-matter interactions in relativistic regime. The repetition rate of PW-class femtosecond lasers is an important issue for their practical applications. And the development of repetitive PW-class lasers has attracted a great attention in recent years.

Shanghai superintense ultrafast laser facility (SULF) is a large-scale scientific project located in Shanghai, China. The project was formally launched and funded in July, 2016. The SULF facility mainly consists of two laser beamlines, SULF-10 PW beamline operating at one shot per minute and SULF-1 PW beamline operating at 0.1Hz repetition rate. The SULF facility will provide repetitive PW-level and 10 PW-level laser pulses for scientific researches on dynamic of materials under extreme conditions (DMEC), ultrafast sub-atomic physics (USAP), and big molecule dynamics and extreme-fast chemistry (MODEC).

The recent progress on the 1 PW/0.1 Hz laser beamline of SULF is reported on High Power Laser Science and Engineering (Zongxin Zhang, Fenxiang Wu, Jiabing Hu, Xiaojun Yang, Jiayan Gui, Penghua Ji, Xingyan Liu, Cheng Wang, Yanqi Liu, Xiaoming Lu, Yi Xu, Yuxin Leng, Ruxin Li, Zhizhan Xu. The 1 PW/0.1 Hz laser beamline in SULF facility[J]. High Power Laser Science and Engineering, 2020, 8(1): 010000e4). The SULF-1 PW beamline is a typical double-CPA system equipped with a novel temporal filter combining the techniques of cross-polarized wave generation (XPWG) and femtosecond optical parametric ampli?cation (OPA). The SULF-1 PW beamline can generate laser pulses of 50.8 J at 0.1 Hz after the final amplifier, and the shot-to-shot energy fluctuation of the amplified pulse is as low as 1.2% (std). After compression, pulse duration of 29.6 fs is achieved, which can support a maximal peak power of 1 PW. Benefit from the large-energy and high-contrast seed pulses generated by the novel temporal filter, the contrast ratio at -80ps before the main pulse is measured to be 2.5×10^-11 in the SULF-1 PW beamline. After optimization of the angular dispersion in the grating compressor, the maximal focused peak intensity may reach 2.7×10¹⁹ W/cm² even with an f/26.5 off-axis parabolic mirror. Moreover, the horizontal and vertical angular pointing fluctuations in one hour are measured to be 1.89 μrad (std) and 2.45 μrad (std) respectively. The moderate repetition rate, the good stability and the high temporal contrast make the SULF-1 PW beamline a desirable driving laser for laser-matter interactions in relativistic regime.

The SULF-1 PW laser beamline is now in the phase of commissioning, and preliminary experiments of particle acceleration and secondary radiation have been implemented. 300 MeV quasi-monoenergetic electrons was repetitively produced under ~300 TW/0.1 Hz laser condition. Moreover, the maximum proton energy of 14 MeV was also obtained under ~400 TW/0.1 Hz laser condition.

The SULF research group from Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, comments that the progress on the preliminary experiments and the stable daily operation of the laser have demonstrated the availability of SULF-1 PW beamline. The following works would be focused on the further improvement of pulse spatial-temporal quality. By utilization of acousto-optic programmable dispersive filter and deformable mirror, a higher focused peak intensity can be expected in the near future.

The layout of SULF facility and the inset shows the commissioning of SULF-1 PW beamline