Recently, the research team of the Thin Film Optics Laboratory of the Shanghai Institute of Optics and Fine Mechanics of the Chinese Academy of Sciences has made new progress in the optimization of sub-nanosecond laser pretreatment of DKDP crystals. The related results were published in Optics Express, Vol. 29, No. 22, 35993-36004].

DKDP (KDxH(2-x)PO4) crystal is the only nonlinear optical crystal material used in ICF (Inertial Confinement Fusion) engineering, but its damage problem seriously restricts the service life of the components and the output of the laser. Laser pretreatment technology is one of the methods that can effectively improve the anti-laser damage performance of DKDP crystals. In recent years, research at home and abroad has found that the pulse width of the pretreatment laser (especially in the sub-nanosecond order) has a great influence on the improvement of the pretreatment effect. By optimizing the parameters of the sub-nanosecond laser, the DKDP crystal will be able to obtain higher resistance. Laser damage performance.

The research team innovatively proposed a scheme to optimize the laser preprocessing effect based on the pulse time waveform, and used sub-nanosecond laser pulses with different combinations of rising and falling edges to carry out research on the laser preprocessing process. The research results show that the speed of the pulse rising front has a significant impact on the pretreatment effect of the DKDP crystal. The pretreatment effect of the sub-nanosecond laser with a slow rising pulse front on the DKDP crystal is 20% higher than that of the Gaussian sub-nanosecond laser. ; and the damage morphology has also changed significantly, manifesting as local microcracks, which indicates that sub-nanosecond laser pretreatment with slow rising pulse fronts can more thoroughly thermally modify the damage precursors in DKDP crystals, with better to improve the anti-laser damage performance of the crystal.

This research can provide important ideas and references for the improvement of the laser damage resistance of DKDP crystals and other nonlinear optical crystals.

Relevant work has been supported by the National Key R&D Program, the National Natural Science Foundation of China, the Chinese Academy of Sciences’ Strategic Pilot Science and Technology Project, and the Chinese Academy of Sciences’ Special Research Assistant Project.

Fig.1 R-on-1 laser-induced damage thresholds of DKDP crystals after sub-nanosecond laser pretreatment with different time waveforms

Fig. 2 Nanosecond laser-induced damage morphology of DKDP crystals after sub-nanosecond laser pretreatment with different time waveforms (the induced laser parameters are 3ω, 8ns, 23J/cm2)