风控热晕对双模涡旋光束大气传输的轨道角动量和相位奇异性的影响  

Influence of wind-dominated thermal blooming on orbital angular momentum and phase singularity of dual-mode vortex beams

作　　者：徐梦敏 李晓庆[1] 唐荣 季小玲[1] Xu Meng-Min;Li Xiao-Qing;Tang Rong;Ji Xiao-Ling(College of Physics and Electronic Engineering,Sichuan Normal University,Chengdu 610068,China)

机构地区：[1]四川师范大学物理与电子工程学院,成都610068

出　　处：《物理学报》2023年第16期112-120,共9页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:61775152,61505130);四川省科技厅项目(批准号:2022NSFSC1836)资助的课题.

摘　　要：本文研究了不同风向和风速下大气非线性热晕效应对双模涡旋光束轨道角动量(orbital angular momentum,OAM)和相位奇异性的影响.由于不同模式叠加的双模涡旋光束具有不同的对称性,热晕效应对其的影响不仅与风速有关,还与风向密切相关.研究发现:在一定风向角度下,风速越小,热晕效应越强,OAM值越大,即热晕效应促进了双模涡旋光束的OAM增大.因此,在一定风向以及风速下双模涡旋光束可以获得大于自由空间的OAM,并且大于单模涡旋光束的OAM.模式越高的光束需要更小的风速才能使得OAM值大于自由空间中的OAM值.此外,构成双模涡旋光束的两束子光束的拓扑荷数相差越大,不同风向下其OAM值越稳定.另一方面,还研究了风控热晕效应对线刃型位错奇点演化的影响,研究表明:线刃型位错线和风向垂直时,位错线消失;线刃型位错线和风向平行时,位错线始终存在;线刃型位错线和风向为钝角或锐角时,位错线演化为光学涡旋对.上述研究结果对激光大气传输和光通信领域具有理论指导意义.The effects of thermal blooming on orbital angular momentum(OAM)and phase singularity of dual-mode vortex beams under different wind directions and wind speeds are studied in this paper.Owing to the different symmetries of dual-mode vortex beams superimposed by different modes,the effects of thermal blooming on them depend on not only wind speed,but also wind direction.Based on the scalar wave equation and the hydrodynamic equation,a four-dimensional(4D)computer code to simulate the time-dependent propagation of dual-mode vortex beams in the atmosphere is devised by using the multiphase screen method and finite difference method.It is found that for a certain wind direction,the value of OAM increases with the wind speed decreasing because the thermal blooming becomes more serious,i.e.the thermal blooming effect promotes the OAM of dual-mode vortex beam to grow.For example,when the angle between the wind direction and the beam is 0<q<50°,the OAM of the dual-mode vortex beams with a topological charge difference of 2 increases with wind speed decreasing,and there is an optimal angle(θ≈20°)to maximize OAM.Therefore,for a certain wind direction and wind speed,the OAM of dual-mode vortex beam propagating in the atmosphere can be larger than that in free space,and can be larger than the OAM of single-mode vortex beam.The dual-mode vortex beam with higher modes requires smaller wind speed to make its OAM larger than the OAM in free space.In addition,the larger the difference in topological charge between the two element beams of a dual-mode vortex beam,the more stable the OAM of the dual-mode vortex beam is.On the other hand,the evolution of linear edge dislocation singularity under atmospheric thermal blooming is also investigated in this paper.When the wind direction is perpendicular to the dislocation line,the linear edge dislocation singularity disappears.If the wind direction is parallel to the dislocation line,the linear edge dislocation singularity always exists.At other angles,the linear edge dislocation si

关 键 词：双模涡旋光束 风控热晕效应 轨道角动量 线刃型位错奇点 

分 类 号：O43[机械工程—光学工程]