为研究脉冲激光斜入射烧蚀铝靶冲量耦合机理, 直接测量其宏观冲量耦合特性是其中一种手段, 但激光烧蚀包含多种物理过程, 仅仅研究其宏观力学性能难以深入分析冲量形成机理, 脉冲激光烧蚀形成的等离子体羽流喷射是诱发力学效应的重要过程, 因此, 在研究宏观力学性能的基础上, 通过开展脉冲激光斜入射烧蚀铝靶等离子体羽流及发射光谱特性测量研究, 深入分析脉冲激光烧蚀冲量耦合机理。 围绕单脉冲1064nm激光斜入射烧蚀铝靶开展研究, 首先通过构建高速摄影测量系统和发射光谱测量系统, 获得了典型激光能量密度斜入射烧蚀铝靶产生的等离子体羽流图像、 等离子体光谱图像和等离子体发射光谱, 基于等离子体发射光谱, 利用Boltzmann作图法和Stark展宽法, 分别研究了脉冲激光多种斜入射角度下等离子体温度、 电子数密度随能量密度的变化关系; 通过搭建扭摆微冲量测量系统, 研究了脉冲激光多种斜入射角度下, 沿着激光入射方向的冲量耦合系数随能量密度的变化。 研究中遵循从羽流微尺度演化过程到冲量宏观力学性能测量分析的研究思路。 实验结果表明, 随着能量密度的增加, 等离子体羽流发光强度增强, 羽流离化程度增加, 等离子体温度、 电子数密度均先迅速增加, 冲量耦合系数也迅速增加; 当能量密度大于15 J·cm-2时, 由于等离子体屏蔽效应, 等离子体温度、 电子数密度均逐渐趋于饱和, 最终导致冲量耦合系数随着能量密度的增加而减小; 此外, 随着入射角度的增加, 等离子体温度、 电子数密度均逐渐减小, 导致冲量耦合系数也随之减小。 研究结果表明, 利用高速摄影和发射光谱可较好地分析脉冲激光烧蚀冲量耦合机理, 研究结果可为激光空间碎片清除、 空间微推力器、 空间非合作目标消旋等空间应用的关键参数优化提供参考。

To study the impulse coupling mechanism of a pulsed laser ablation aluminum target, the direct measurement of its macroscopic impulse coupling characteristics is one of the means. However, laser ablation involves many physical processes. Therefore, analysing the impulse formation mechanism only by studying its macroscopic mechanical properties is difficult. Plasma plume ejection formed by pulsed laser ablation is an important process to induce the mechanical effect. Hence, based on studying the macroscopic mechanical properties, this paper deeply analyzes the impulse coupling mechanism of pulsed laser ablation by measuring the plasma plume and emission spectrum characteristics. In this paper, a single pulse laser with a wavelength of 1 064 nm is used to ablate aluminum targets. By constructing a fast photogrammetry system and optical emission spectroscopy measurement system, the plasma plume image, the plasma spectral image, and the plasma emission spectrum generated by laser oblique incident ablation of the aluminum target were obtained. Based on optical emission spectroscopy of the plasma plume, the Boltzmann plotting method and Stark broadening method were used to study the variation of plasma temperature and electron number density with the laser fluence at different incidence angles of a pulsed laser, respectively. Moreover, a torsion pendulum system was built to study the trend of the impulse coupling coefficient with the laser fluence along the direction of laser incident at various incident angles. The study follows the research ideas from the plume microscale evolution process to impulse macro mechanical properties analysis. The experimental results show that the luminescence intensity of the plasma plume strengthens with the laser fluence, accompanied by the rise of plume ionization degree. Moreover, the plasma temperature and electron number density increase rapidly, resulting in the impulse coupling coefficient heightening rapidly. When the laser fluence is greater than 15 J·cm-2, the plasma temperature and the electron number density are gradually saturated due to the plasma shielding effect. The change of plasma temperature and electron number density results in the decrease of impulse coupling coefficient with increased laser fluence. In addition, the plasma temperature and the electron number density decrease with the increase of incident angle, which reduces the impulse coupling coefficient. The results show that the coupling mechanism of the ablation impulse can be well analyzed using fast photography and optical emission spectroscopy. The results can provide a reference for optimising key parameters for space applications such as laser space debris removal, space micro-thruster and despinning non-cooperative targets in space.