A potassium dihydrogen phosphate (KDP) crystal is set to be a vital factor in inertial confinement fusion (ICF). This paper focuses on how to reduce the gravitational distortion and increase the second-harmonic generation (SHG) efficiency of the KDP crystal. Multipoint support mounting configurations are proposed. Their influence on distortion and SHG efficiency is analyzed. Mechanical and optical models are established, and the distortion of the KDP crystal is calculated using the finite-element methods. In addition, phase mismatch caused by distortion and SHG efficiency is calculated and analyzed. The numerical results reveal that multipoint support is a suitable mounting configuration as it has little distortion and increases SHG efficiency. Multipoint support mounting configuration is well applied in the ICF facility.
KEYWORDS: Frequency conversion, Crystals, Laser crystals, High power lasers, Photovoltaics, Crystal optics, Interferometers, Laser welding, Solids, National Ignition Facility
In the high power solid laser driver, the frequency conversion unit is of strict requirement to meet the drive condition of ICF. The performance of large caliber KDP crystal, which is the core of frequency conversion of laser, is a vital aspect affecting the overall technical index of the laser driver. In order to get a higher efficiency of frequency conversion, KDP crystal must keep a better surface condition, which asks for high-quality assemblage and adjustment. The current method used in engineering has insufficient knowledge and recognition on surface deformation control of the crystal. Meanwhile, the method itself is of low efficiency on clamping, and lacks of protection for the crystal. Thus, in this article an investigation of crystal clamping method with lower force was performed, factors affecting the surface of crystal were explored, through both imitation and experiment. The clamping method was redesigned and the frequency conversion efficiency was tested. Meanwhile, with the new method, clamping efficiency increases, the optical performance of crystals improves, and the crystals get better protection.
High-energy solid-state laser is an important way to achieve laser fusion research. Laser fusion facility includes thousands of various types of large aperture optics. These large aperture optics should be assembled with high precision and high efficiency. Currently, however, the assembly of large aperture optics is by man’s hand which is in low level of efficiency and labor-intensive. Here, according to the characteristics of the assembly of large aperture optics, we designed three kinds of grasping devices. Using Finite Element Method, we simulated the impact of the grasping device on the PV value and the RMS value of the large aperture optics. The structural strength of the grasping device’s key part was analyzed. An experiment was performed to illustrate the reliability and precision of the grasping device. We anticipate that the grasping device would complete the assembly of large aperture optics precisely and efficiently.
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