Lehmann Lucien, Bouillet Stéphane, Leymarie Christophe, Ameil-Schuh Christel, Benoit Melusine, Rouyer Claude
Appl Opt. 2022 Feb 20;61(6):1545-1551. doi: 10.1364/AO.451256.
In the framework of high-power lasers, surface defects on optics can generate strong light intensification and induce damage sites on downstream optics. To evaluate this intensification during high-energy laser shots, a three-step method is proposed. First, a dedicated measurement bench is designed to measure the intensification induced by defects on a wide variety of optics, including amplifier slabs, KDP crystals, mirrors, gratings, and vacuum windows, for propagation distances up to 2000 mm. A multi-resolution single-beam multiple-intensity reconstruction phase retrieval algorithm is then used to reconstruct a model of the defect, in both amplitude and phase, from a set of intensification measurements. Finally, the impact of the modeled defect on downstream optics is evaluated with a simulation of the high-power laser system. This method is experimentally validated through a case study of damage identified on one of the Laser Mégajoule (LMJ) beams, characterized with the method presented in this paper. The long-distance impact on the LMJ beam is estimated by simulation and compared to a direct near-field measurement.
在高功率激光的框架下，光学元件上的表面缺陷会产生强光增强，并在下游光学元件上引发损伤点。为了评估高能激光脉冲期间的这种增强效应，提出了一种三步法。首先，设计一个专用测量台，用于测量各种光学元件（包括放大器板、磷酸二氢钾（KDP）晶体、镜子、光栅和真空窗口）上的缺陷所引起的增强效应，传播距离可达2000毫米。然后，使用多分辨率单光束多强度重建相位恢复算法，从一组增强测量值中重建缺陷的幅度和相位模型。最后，通过对高功率激光系统的模拟来评估建模缺陷对下游光学元件的影响。通过对激光兆焦耳装置（LMJ）的一束光束上识别出的损伤进行案例研究，对该方法进行了实验验证，该损伤用本文提出的方法进行了表征。通过模拟估计了对LMJ光束的长距离影响，并与直接近场测量结果进行了比较。
