激光脉冲喷丸成形系统中高能量脉冲激光矩形光束形成与均匀化技术的研究

In laser peening performing technology, laser peen requires a rectangular laser beam with high laser irradiance (>GW/cm2), short pulse duration (10-30ns) and evenly distributed energy density. This project put forward a shaping technology based on a free-form surface lens system, which changes Gaussian beam to a rectangular laser beam with uniform intensity distribution. Both the uniformity of laser energy density (>90%) and system damage threshold (>5GW/cm2) meet the engineering requirement for laser peening performing. The main research contents include: 1. Research input and output mapping function of laser beam based on the law of conservation of energy and aplanatic principle; 2. Optimize the surface equation of the free-form surface lens using Zemax software; 3. Increase the operating distance of uniform rectangular laser beam by investigating its transmission characteristic based on diffraction theory; 4. Design, construct and characterize the free-form surface lens system for laser peening performing and materials processing. Based on preliminary desirable experimental results measured from optical components designed in our group, we propose to optimize this specific laser beam shaping system for precision engineering of key commercial large aircraft and military aircraft components.

激光脉冲喷丸成形技术中要求功率密度大于GW/cm2，脉宽在10-30ns，能量均匀分布的矩形(或方形)激光束。本项目提出了自由曲面透镜整形技术，将脉冲宽度为ns级的高斯光束转化为能量均匀分布的矩形光脉冲。矩形光斑的能量均匀度大于90%，激光整形系统的能量损伤阈值大于5GW/cm2，满足激光脉冲喷丸成形对脉冲光束质量的要求。主要研究内容：1. 基于能量守恒定律和等光程原理研究激光束输入输出面光束映射函数；2.利用Zemax光学设计软件，优化自由曲面透镜面型方程；3.利用衍射理论研究矩形均匀光束传输特性，提高矩形均匀光束的作用距离；4. 建立自由曲面透镜整形系统，用于激光脉冲喷丸加工中。 实验室初步研究结果表明，我们设计加工的自由曲面透镜整形系统获得了较好的光学效果，我们将继续优化该技术使它能够应用于商业大飞机和军用飞机机翼板等核心部件的精密成形。

本项目研究并建立了用于激光脉冲喷丸技术的均匀化整形系统，系统输出能量均匀分布的矩形（或方形）激光束，能量均匀度大于90%，能量损伤阈值大于5GW/cm2, 满足激光脉冲喷丸技术对脉冲光束质量的要求。主要研究成果包括：1. 利用能量守恒定律、等光程原理以及衍射理论建立了矩形光斑均匀化整形系统输入输出面光束的映射函数关系。2. 利用Zemax光学设计软件，优化自由曲面透镜面型方程，实现了入射激光束（包括高斯和类高斯光束）能量均匀化整形。3. 利用凝聚介质模型，推导了在均匀矩形光斑作用下产生激光诱导等离子体的冲击压力及其传播规律。4. 利用自由曲面透镜均匀化整形系统完成了 LY2 铝合金叶片顶端激光冲击强化实验。