基于分层散射介质传输模型的概念,建立了综合考虑非线性光学效应、湍流扰动及粒子散射的飞秒激光云雾传输模型。利用该模型数值模拟了大气湍流和粒子散射等大气扰动类型对飞秒激光传输成丝动态演化过程的影响。结果表明,大气湍流能使脉冲形状产生不规则变化,对自聚焦成丝过程中的脉冲能量流动有重要影响;粒子散射可以使脉冲能量明显衰减,从而影响光丝的形成过程;飞秒激光在云雾环境中传输时,粒子数浓度越高,粒子半径越大,则形成光丝的长度越短,成丝过程中能量衰减越快,脉冲能量的总衰减量越多。研究结果可为真实大气条件下飞秒激光实际应用效能评估提供一定的理论依据。

In this study, a femtosecond laser cloud and fog transmission model, which considers the nonlinear optical effect, turbulence disturbance, and particle scattering, is established based on the concept of the stratified scattering medium transmission model. Further, the influence of atmospheric disturbances, including atmospheric turbulence and particle scattering, on dynamic evolution of the femtosecond laser transmission filaments is numerically studied. The results show that atmospheric turbulence can cause the pulse shape to change in an irregular manner; in addition, atmospheric turbulence significantly affects the pulse energy flow during the self-focusing filamentation process. The attenuation of pulse energy can be attributed to particle scattering, thereby affecting the formation process of optical filaments. As the femtosecond laser travels through the cloud and fog, the length of the optical filament will decrease, the energy attenuation during the filamentation process will be accelerated, and the total deposited pulse energy will increase with the increasing particle number concentration and particle radius. The results presented here can provide some theoretical basis to evaluate the efficiency of the femtosecond laser related applications under real atmospheric conditions.