斜程湍流大气中部分相干艾里光束的偏振特性研究

偏振是激光通信中保密编码的重要参数,研究斜程湍流大气中的偏振特性对激光通信具有重要意义。利用广义惠更斯-菲涅尔原理和偏振-相干统一理论,推导了无衍射的部分相干艾里高斯光束在斜程湍流大气传输中的偏振度解析式,详细研究了湍流参数、相干长度、天顶角、截断因子和分布因子对偏振度的影响。研究结果表明:与水平湍流相比,光束在斜程湍流下恢复到初始偏振需要更长的传输距离。天顶角、接收高度、截断因子、分布因子越大和相干长度越小,光束偏振度峰值也越大。高相干性的高斯光束比艾里光束更易于保持偏振度不变。无衍射艾里光束中选取合适的光学参数更有利于信息传输与编码,本文结果对激光大气通信领域有着潜在的应用价值。

Polarization changes of partially-coherent Airy-Gaussian beams in a slanted turbulent atmosphere

Investigating polarization changes in a turbulent atmosphere holds great significance because polarization is one of the most important parameters in laser communication.Based on the extended Huygens-Fresnel principle and the unified theory of coherence and polarization,an analytical expression for the degree of polarization(DoP)in partially-coherent Airy-Gaussian beams propagating in a slanted turbulent atmosphere is derived.It is then used to study the dependence of polarization changes in turbulent parameter,coherence length,zenith angle,truncation and distribution factor.The polarization between the slanted and horizontal paths is also compared.Compared with horizontal turbulence,the beams traverse a longer distance to recover their initial polarization in slanted turbulence.An increase in the zenith angle,receiving height and truncation factor,or a decrease in the coherence length can increase the DoP.A smaller distribution factor or a higher coherence length is beneficial to reducing the effect of the zenith angle on the polarization.Analysis of the influence of the distribution factor on polarization also shows that maintaining the polarization of a Gaussian beam with higher coherence in a horizontally turbulent atmosphere has a greater advantage to that of a pure Airy beam from the view of keeping polarization invariance.The results show that optical information encoding can be achieved by selecting appropriate parameters,which is useful for studying atmospheric communication.