大气湍流中贝塞尔-高斯涡旋光束传播性能分析

摘要

In order to study the transmission characteristics of vortex beams in atmospheric turbulence,based on the generalized Huygens-Fresnel principle,the transmission process of Bessel-Gaussian beams(BGB)in atmospheric turbulence was analyzed theoretically and simulated numerically by using power spectrum inversion method based on fast Fourier transform.Harmonic compensation method was used to generate random phase screen to simulate atmospheric turbulence,which solved the problem that low frequency components were not enough.The results show that,besides turbulence strength,transmission distance,topological charge number and laser wavelength also become the main factors that could affect the vortex beam's communication quality.With the increasing of turbulence strength,the annular intensity decreases,phase distortion becomes more serious,intensity fluctuation is more obvious and beam will gradually degenerate into ordinary Gaussian beam.With the increase of transmission distance,vortex beam has the significant broadening and finally degrades into ordinary Gaussian beam.The longer the laser wavelength is,the stronger the ability which vortex beams restrain turbulence,the stronger annular light intensity is.In the meanwhile,the degree of phase distortion becomes weaker.The smaller topological charge number is,the weaker phase distortion is,and vortex beam would degenerate into ordinary Gaussian beams more easily.The results are helpful for the study of the propagation of vortex beams in free space optical communication.%为了研究涡旋光束在湍流大气中的传输特性,根据广义的惠更斯-菲涅耳原理,采用基于快速傅里叶变换的功率谱反演法,对贝塞尔-高斯光束在大气湍流中的传输过程进行了理论分析和数值仿真;采用次谐波补偿法产生随机相位屏来模拟大气湍流,解决了大气湍流模拟时存在低频成分不足的问题.结果表明,除了湍流强度外,传输距离、拓扑荷数、激光波长等也成为影响贝塞尔-高斯涡旋光束质量的主要因素;湍流越强,光束的环形光强越弱,相位畸变越严重,光强起伏越明显,且逐渐退化为普通高斯光束;随着传输距离的增加,涡旋光束扩散现象明显,最终退化为普通高斯光束;波长越长,则涡旋光束抑制湍流能力越强,环形光强越强,相位畸变程度会得到逐步改善;拓扑荷数越小,涡旋光束会最先退化为普通高斯光束,相位畸变程度越弱.该结果对于研究涡旋光束在自由空间光通信中的传输是有帮助的.