Aiming to minimize the surface distortion of large-aperture laser transport mirrors in high-power laser facilities, an assembly design and mounting method are proposed for the mirror. First, a theoretical model on the mirror surface deformation is established. With a new assembly design, the mirror is fastened on its neutral plane and its optical surface distortion can be precisely compensated through several adjustable forces on the sides, which will generate bending moments on the mirror body. Furthermore, a dynamic kinematic joint is designed, in which a corresponding relationship between spring compression and screw rotation ensures the accurate control of the magnitude of mirror preload. Finally, the performance of the presented method has been validated through field experiments and numerical simulations. This transport mirror assembly and mounting design have obvious technical advantages on simple mechanical structure, high operational efficiency, and precise preload control. The results show that the assembly design and optimized mounting strategy can keep the total surface distortion of the mirror within 350 nm (peak-valley).
Due to the unique mechanical and optical characteristics, it is difficult to carry out experimental research and online measurement for large-aperture ICF frequency converters. To analyze and optimize the performance of the frequency converters under complex process loads, we present an integrated optomechanical method that correlates actual process loads with laser critical characteristics. Based on the established optomechanical model, the key factor that induces the loss of harmonic generation efficiency is identified. In addition, the proposed method is conductive to rapid evaluation, prediction, and optimization of comprehensive performance of frequency converters. Thereby, we propose an adaptive frequency conversion system (AFCS). The results indicate that AFCS can not only minimize the phase mismatching of second harmonic generation doubler but also significantly improve the quality of far-field focal spot.
Large aperture KDP crystals are mainly used in the final optic assembly of inertial confinement fusion facility to change the frequency of laser light incident into them. For the optimization of the surface of large aperture KDP crystals, this paper proposes an assembly scheme based on point support and calculates the surface state of KDP crystal under different installation postures and different preload force distributions and magnitudes by numerical simulation. The results show that the assembly scheme can effectively reduce the surface distortion of KDP crystal after assembly. For example, in the horizontal state, the surface PV value of the KDP crystal can be controlled below 5um and the frequency conversion efficiency can reach 83.7% after assembly.
In huge-scale high peak power laser facility, the frequency conversion unit is responsible for the conversion of fundamental infrared wave at 1053nm into ultraviolet wave at 351nm. In this paper, the mechanism of service performance degradation of frequency doubling crystal is revealed by combining field experiments and numerical simulations. Moreover, we propose a flexure support method that can effectively reduce crystal surface distortion. Further, an experiment platform for offline mounting of frequency conversion crystal is built, and the mechanical and optical characteristics are verified by the experimental results. Finally, online verification is carried out in China’s high peak power laser facility. The results show that the proposed mounting method can significantly modify the crystal surface figure, improve its online performance and increase the highest efficient output power of high peak power laser facility.