光纤传输激光驱动飞片实验研究

Fiber-coupled laser-driven flyer plates experiments

构建了一种基于光纤传输高功率激光的飞片发射系统,并测试了飞片速度.飞片膜层为三明治结构:铝烧蚀层、氧化铝隔离层和铝飞片产生层.飞片膜层采用磁控溅射技术沉积在玻璃衬底上,总厚度为5.5μm.激光辐照铝膜层产生高温高压等离子体,驱动剩余膜层产生高速飞片,速度达数km/s.同时,实验研究了光纤传能系统的输出激光空间分布特性和传输激光能量容量,它们决定了飞片的平面性和最大速度.光纤端面损伤是限制光纤传输激光能量容量的关键因素,光纤端面通过精密机械抛光和激光预处理可以获得理想的抗激光损伤能力.采用基于光纤阵列探针的时间序列测试技术获得了飞片的平均速度,并评估了飞片的平面性.采用搭建的基于光纤传输高功率激光的飞片发射系统获得了速度达1.7km/s、直径接近1mm的高速飞片.

A system for the launch of hypervelocity flyer plates is developed,characterized and applied.Laser-driven flyers are launched from substrate backed aluminum-alumina- aluminum sandwiched films.A laser-induced plasma is used to drive flyers with a thicknesses of a 5.5μm and a diameter of less than 1 mm,and typically,the flyer plates can achieve velocities of a few kilometers per second.These flyer plates have several applications ranging from micrometeorite simulation to laser ignition.The flyer plates considered here have three layers：an ablation layer for forming plasma;an insulating layer;and a final thicker layer for forming the final flyer plate.The optical fiber delivery system determines the spatial profile of the laser spot and power capacity.A technique and procedure for coupling high power laser pulse into optical fiber is developed.The surface finish of the fiber is found to be a critical factor.This fiber optic system is successfully used to launch flyer plates.Measurements of the flyer performance including the mean velocities and planarity are made by an optical time-of-arrival （TOA） technique with using an optical fiber array probe.The flyer shows a good planarity and achieves an average velocity of 1.7 km/s.The relationship between flyer velocity and incident laser pulse energy is investigated.