x

## 留言板

 引用本文:
 Citation:

## Influence of spherical aberration on beam quality of high-power laser beams propagating upwards in the atmosphere

Huang Zi-Yue, Deng Yu, Ji Xiao-Ling
PDF
HTML
• #### 摘要

地基激光空间碎片清除等激光烧蚀推进在太空中的应用中, 激光功率已远超过大气非线性自聚焦临界功率, 因此自聚焦效应是影响光束质量的重要因素. 此外, 由于高功率激光产生过程中的非线性效应, 光束常伴有球差. 本文采用数值模拟方法, 研究了球差对高功率激光上行大气传输光束质量的影响. 研究表明: 对于大尺寸(光束发射尺寸)光束, 利用正球差可提高靶面光强. 然而, 对于小尺寸光束, 则需利用负球差提高靶面光强. 并且, 大尺寸比小尺寸光束更适合地基激光空间碎片清除等应用. 在线性衍射效应和非线性自聚焦效应共同作用下, 存在一个最佳发射功率使得靶面光强最大化, 本文拟合出了大尺寸光束的最佳发射功率的公式. 另一方面, 由于衍射、自聚焦和球差均导致焦移, 这使得靶面光束质量变差. 本文推导出了大尺寸光束情况下透镜修正焦距公式, 这样可把将实际焦点移至靶面, 从而提高靶面光束质量. 本文所得结论具有重要的理论和实际应用意义.

#### Abstract

For laser ablation propulsion’s applications in space (e.g., space-debris removal, etc.), the laser power is well above the critical power for self-focusing in the atmosphere. Therefore, the self-focusing effect on the beam quality is very significant. In addition, a high-power laser beam is usually accompanied with spherical aberration due to nonlinear effects in its generation process. In this paper, the influence of spherical aberration on the beam quality of high-power laser beams propagating upwards in the atmosphere is studied by using numerical simulation. It is shown that for the large beam size case, the target intensity may be improved by applying the positive spherical aberration. However, for the small beam size case, the target intensity may be improved by using the negative spherical aberration. Furthermore, a laser beam with a large size is more suitable for laser ablation propulsion’s applications in space than that with a small size. Owing to the linear diffraction effect and the nonlinear self-focusing effect, there exists optimal beam power to maximize the target intensity. The formula of the optimal beam power is fitted for the large beam size case in this paper. On the other hand, the focal shift appears due to diffraction, self-focusing and spherical aberration, which results in a degradation of the beam quality on the target. For the large beam size case, to move the actual focus to the target and improve the beam quality on the target, the formula of the modified focal length is also derived in this paper. The results obtained in this paper are of important theoretical significance and practical value.

#### Authors and contacts

###### Corresponding author: Ji Xiao-Ling, jiXL100@163.com
• Funds: Project supported by the National Natural Science Foundation of China (Grant No. 61775152).

#### 施引文献

• 图 1  靶面光强I (r, z = L)分布　(a), (b) 大尺寸光束, w0 = 1.414 m, β = 5.9275; (c), (d) 小尺寸光束, w0 = 0.821 m, β = 1.03

Fig. 1.  Intensity distributions on the target I (r, z = L): (a), (b) For a large beam size, w0 = 1.414 m, β = 5.9275; (c), (d) for a small beam size, w0 = 0.821 m, β = 1.03.

图 2  靶面峰值光强I (r = 0, z = L)随相对发射功率P/PcrGs的变化　(a) 大尺寸光束, w0 = 1.414 m, β = 5.9275; (b) 小尺寸光束: w0 = 0.821 m, β = 1.03

Fig. 2.  Peak intensity on the target I (r = 0, z = L) versus the relative beam power P/PcrGs: (a) For a large beam size, w0 = 1.414 m, β = 5.9275; (b) for a small beam size, w0 = 0.821 m, β = 1.03.

图 3  (5)式的验证. 相对最佳发射功率Popt/PcrGs随初始束宽w0和球差系数kC4的变化. 黑点: 数值模拟计算结果, 曲面: (5)式计算结果

Fig. 3.  Confirmation of the formula of Eq. (5). Relative optimal beam power Popt/PcrGs versus the initial beam radius. w0 and the spherical aberration coefficient kC4. Black dots: results by using numerical simulation method; surfaces: results by using Eq. (5).

图 4  (9)式的验证. 束宽w随距离z的变化

Fig. 4.  Confirmation of the formula of Eq. (9). Beam width w versus the propagation distance z

图 5  透镜修正焦距Fmod随球差系数kC4和相对发射功率P/PcrGs的变化, w0 = 1.414 m, β = 5.9275

Fig. 5.  Modified focal length Fmod versus the spherical aberration coefficient kC4 and the relative beam power P/PcrGs, w0 = 1.414 m, β = 5.9275.

图 6  靶面光强分布, w0 = 1.414 m, β = 5.9275, P = 2000PcrGs　 (a) 修正焦距前; (b) 修正焦距后

Fig. 6.  Intensity distributions on the target. w0 = 1.414 m, β = 5.9275, P = 2000PcrGs: (a) For the unmodified focal length case; (b) for the modified focal length case.

• 文章访问数:  1546
• PDF下载量:  42
• 被引次数: 0
##### 出版历程
• 收稿日期:  2021-06-30
• 修回日期:  2021-07-21
• 上网日期:  2021-08-17
• 刊出日期:  2021-12-05

## 球差对高功率激光上行大气传输光束质量的影响

• 四川师范大学物理与电子工程学院, 成都　610068

/