摘要
实际高能激光器(如半导体激光器、光谱合束系统)出射的激光存在椭圆分布的现象。高能激光在大气中传输时会遭遇非线性热晕效应,大气热晕效应对椭圆高斯光束传输特性的影响还未见报道。用解析和数值模拟方法研究了风控热晕下椭圆激光光束质量的优化问题,推导出了热畸变扭曲参数的解析公式,并证明了其正确性。研究表明:由于椭圆光束像散特性,大气热晕效应对其传输特性的影响与风向密切相关。当源平面处迎风方向的束宽越大(光斑面积相等)时,聚焦椭圆高斯光束受热晕效应的影响越弱,靶面光斑对称性越好,能量集中度越高,即靶面光束质量越好。因此,在实际工作中,聚焦椭圆高斯光束的短轴沿着大气的总体风向更有利于减弱热晕效应。并且,聚焦椭圆高斯光束达到稳态热晕的时间与源平面处沿风方向的束宽成正比。研究结论对高能激光大气传输的应用具有理论指导意义。
Objective In practice,the beam produced by a high-energy laser is more nearly elliptical in its cross section,such as a semiconductor laser and a spectral beam combining system.When a high-energy laser propagates in the atmosphere,a fraction of the laser power is absorbed by the atmosphere along the propagation path.The absorbed power first heats the air and alters the refraction index of the path,and then causes laser distortion and divergence.This self-induced effect is called thermal blooming.Moreover,the energy transmission efficiency of a high-energy laser is severely limited by the thermal blooming effect.Thermal blooming depends on the distribution of the laser beam and the state of the atmosphere.Until now,the effect of thermal blooming on an elliptical Gaussian beam(EGB)propagating in the atmosphere has not been reported.In this paper,the beam quality optimization of an EGB under wind-dominated thermal blooming is studied analytically and numerically.The results obtained in this paper are useful for the applications of high-energy lasers propagating in the atmosphere.Methods Thermal blooming of a laser beam propagating through atmosphere can be described by the paraxial wave equation and the hydrodynamic equation.When the diffraction effect is neglected under the geometric optics approach,the intensity expression for steady-state thermal blooming and the distortion parameter of an EGB propagating in the atmosphere are respectively derived,and their correctness is proved.Besides,numerical simulation is very useful to study thermal blooming.We design 4D computer code of the time-dependent atmospheric propagation of a focused EGB by using the multi-phase screen method and the finite difference method.A grid size of 512×512 is used.The numerical calculation results remain almost constant when the number of grid size increases.The transient-state thermal blooming and steady-state thermal blooming are investigated in this paper.Results and Discussions In this paper,the intensity expressions for steady-state t
作者
邓凌
李晓庆
穆轶
季小玲
Deng Ling;Li Xiaoqing;Mu Yi;Ji Xiaoling(College of Physics and Electronic Engineering,Sichuan Normal University,Chengdu,Sichuan 610068,China)
出处
《中国激光》
EI
CAS
CSCD
北大核心
2022年第4期29-39,共11页
Chinese Journal of Lasers
基金
国家自然科学基金(61775152,61505130)。
关键词
大气光学
大气传输
热晕效应
椭圆高斯光束
光束质量
atmospheric optics
atmospheric propagation
thermal blooming effect
elliptical Gaussian beam
beam quality
