扭曲的涡旋光束在海洋湍流中的传输因子

基于扩展惠更斯-菲涅尔原理和维格纳分布函数(Wigner distribution function,WDF)二阶矩,推导了部分相干扭曲涡旋光束(partially coherent twisted vortex beam,PCTVB)在海洋湍流中传输时的M2因子和角扩展θ(z)。通过数值模拟方法详细研究了海洋湍流对光束M2因子和角扩展θ(z)的影响,结果表明温度方差耗散率ΧT和温度盐度贡献比w越大、动能耗散率ε和各向异性因子ξ越小时对PCTVB的M2因子和角扩展θ(z)的影响越大。此外研究发现,相较于非扭曲涡旋光束(PCVB),PCTVB有更好的抗海洋湍流的能力,且增大拓扑荷数m以及扭曲因子绝对值｜μ｜后,PCTVB的M2因子和角扩展θ(z)显著减小,光束的抗海洋湍流能力增强。并且增大束腰宽度w0和波长λ,以及减小初始相干长度δηη(η=x,y)同样可以增加光束抗海洋湍流的能力。本文的数值研究结果对海洋光通信具有重要意义。

Propagation factors for twisted vortex beams throughoceanic turbulence

In this paper,analytical formulas of M2 factor and angular extension θ(z) of partially coherent twisted vortex beam (PCTVB) propagating in oceanic turbulence are derived based on the extended Huygens Fresnel principle and the Wigner distribution function (WDF) second moment. The effects of oceanic turbulence on M2 factor and angular spread θ(z) of PCTVB are studied in detail by numerical simulation methods,and the results show that the M2 factor and θ(z) of PCTVB is greatly affected by oceanic turbulence with the large rate of dissipation of mean square temperature and large relative strength of temperature and salinity undulations as well as the small rate of dissipation of turbulent kinetic energy per unit mass of fluid and small anisotropic factor. In addition,it is found that the PCTVB has better resistance to ocean turbulence compared to the non twisted vortex beam (PCVB),and the M2 factor and angular extension θ(z) of the PCTVB are significantly reduced and the beam′s resistance to ocean turbulence is enhanced by increasing the topological charge m as well as the absolute value of the distortion factor |μ|. And increasing the beam waist width w0 and wavelength λ as well as decreasing the initial coherence lengths δηη(η=x,y) can likewise increase the beam′s resistance to ocean turbulence. The numerical results in this paper are of great significance for ocean optical communications.