Zeng Tao, Gui Ya, Yi Yuliang, Li Nan, Zhang Zhi, Guo Jiewei, Shang Binpeng, Guo Lanjun
Chongqing Key Laboratory of Micro & Nano Structure Optoeletronics, School of Physical Science and Technology, Southwest University, Chongqing 400715, China.
Chongqing Vocational College of Transportation, Chongqing 402247, China.
Sensors (Basel). 2023 Oct 10;23(20):8364. doi: 10.3390/s23208364.
Air lasers induced by femtosecond laser filaments play an important role in remote sensing applications. Few studies have been dedicated to the spatial distribution of external-seeded air laser radiation in the laser filament based on the numerical simulation method, which can pave the way to understanding the mechanism of the external-seeded air lasing process during filamentation. In this study, numerical simulations of the propagation of an air laser seeded by an external plane wave with a wavelength of 391 nm during femtosecond laser filamentation were performed. The results indicated that the air laser's beam intensity distribution varies from a ring pattern to a donut pattern when the filament length and nitrogen ion density are raised as a result of the defocusing and lasing effects of the filament plasma. Here, the ring pattern is formed by several thin rings, while the donut pattern refers to a notably thicker, ring-like structure. In addition, it has been demonstrated that the air laser's beam power would increase exponentially versus the filament length and the nitrogen ion density. The knowledge about the angular distribution of air lasing could be important for optimizing the detection geometry of the LIDAR setup, including the view angle and the size of the collecting optical component.
飞秒激光细丝诱导产生的空气激光在遥感应用中发挥着重要作用。基于数值模拟方法，很少有研究致力于探讨基于激光细丝的外种子空气激光辐射的空间分布，这可以为理解细丝化过程中外种子空气激光过程的机制铺平道路。在本研究中，对波长为391 nm的外部平面波种子在飞秒激光细丝化过程中产生的空气激光的传播进行了数值模拟。结果表明，由于细丝等离子体的散焦和激光效应，当细丝长度和氮离子密度增加时，空气激光的光束强度分布从环形图案变为甜甜圈图案。这里，环形图案由几个细环形成，而甜甜圈图案是指明显更厚的环状结构。此外，已经证明空气激光的光束功率将相对于细丝长度和氮离子密度呈指数增加。关于空气激光角度分布的知识对于优化激光雷达装置的探测几何结构可能很重要，包括视角和收集光学元件的尺寸。
