In high power laser system, the upstream flaw could induce light intensification in the downstream, thus damaging the optical component. In most of the research, the shape of the defect model is ideal, for example, Gaussian shape. However, the defect in the real system is non-ideal with different shapes. In this paper, the light intensification effect caused by defects with different shapes are compared by numerical simulation. Results show the shape dependence of downstream light intensification caused by flaws. When only the linear effect is considered, the change of defect shape could change the maximum light intensification factor and the downstream location for the maximum intensity. When the nonlinear effect is also considered, the light intensification effect will be more sensitive to the shape of defects. This research can provide some reference for the beam quality control and defect management in the high power laser systems.
The latest progress on high power laser facilities in NLHPLP was reported. Based on a high power laser prototype, damage behavior of 3ω optics was experimentally tested, and the key influencing factors contributed to laser-induced damage in optics were deeply analyzed. The latest experimental results of advanced precision measurement for optical quality applied in the high power laser facility were introduced. At last, based on the accumulated works of 3ω elements damage behavior status in our laboratory, beam expanding scheme was presented to increase the total maximum output 3ω energy properly and decrease the laser induced damage risking of ω optics simultaneously.
A new high power laser facility with 8 beams and maximum output energy of one beam 5kJ/3.4ns/3ω has been performed and operated since 2015. Combined together the existing facilities have constructed a multifunction experimental platform including multi-pulse width of ns, ps and fs and active probing beam, which is an effective tool for Inertial Confinement Fusion (ICF) and High Energy Density (HED) researches. In addition another peculiar high power laser prototype pushes 1ω maximum output energy to 16kJ in 5ns and 17.5kJ in 20ns in flat-in-time pulse, this system is based on large aperture four-pass main amplifier architecture with 310mm×310mm output beam aperture. Meanwhile the near field and far field have good quality spanning large energy scope by use of a wide range of technologies, such as reasonable overall design technique, the integrated front end, cleanness class control, nonlinear laser propagation control, wave-front adaptive optics and precision measurement. Based on this excellent backup, 3ω damage research project is planning to be implemented. To realize the above aims, the beam expanding scheme in final transport spatial filter could be adopted considering tradeoff between the efficient utilization of 1ω output and 3ω damage threshold. Besides for deeply dissecting conversion process for beam characteristic influence of 1ω beam, WCI (Wave-front Code Image) instrument with refined structure would be used to measure optical field with simultaneous high precision amplitude and phase information, and what’s more WCI can measure the 1ω, 2ω and 3ω optical field in the same time at same position, so we can analyze the 3ω beam quality evolution systematically, and ultimately to improve the 3ω limited output.
In a word, we need pay attention to some aspects contents with emphasis for future huger laser facility development. The first is to focus the new technology application. The second is to solve the matching problem between 1ω beam and the 3ω beam. The last is to build the whole effective design in order to improve efficiency and cost performance.
Enhancing performance status of final optics assembly on high power laser at 351nm laser is experimentally studied. We experimentally demonstrate 61 shots of 310mm × 310mm laser. The maximum laser energy flux is 5.5J/cm2. The laser energy conversion efficiency is more than 72%. And the laser perforation efficiency across 800μm at 3000J is more than 96%. These results provide valuable information to improve final optics assembly performance research of high power laser.
Beam-guiding system (BGS) in the target area of a laser-driver maps the rectangular arrangement at the main lasers to a spherical geometry configuration of shooting lasers at the target chamber. It also ensures that all the laser beams share the same light path length when they arrive at the target chamber center. With the output energy raising from 2MJ to 5MJ@3ω, the laser beam quantity will increase to more than 500. In this situation, researches were conducted on the relationship among the beam quantity, beam combination fashion in the target area and the radius of the target chamber. Also, beam transmission units (BTU), including transmission models of main lasers and shooting lasers and the switch manner between them, was put forward to simply the BGS arrangement work. Then we discussed the factors that determine the BTU configuration and general target area shape. Based on the beam combination fashion and BTU, the entire BGS arrangement in the target area of a 5.76MJ@3ω indirect-drive laser facility with 576 laser beams was figured out.