部分相干径向偏振拉盖尔-高斯脉冲光束在大气湍流中传输的光谱移动和光谱开关

Spectral shifts and spectral switches of partially coherent radially polarized Laguerre-Gaussian pulsed beams propagating through atmosphere turbulence

研究了部分相干径向偏振拉盖尔-高斯(partially coherent radially polarized Laguerre-Gaussian,PCRPLG)脉冲光束在大气湍流中传输时的光谱移动和光谱开关。研究发现,在湍流大气传输时,光束轴上点光谱因受湍流影响产生的双谱峰现象会发生跃变,湍流越强,光谱在跃变后相对谱移变化越稳定,而轴外点光谱在越强的湍流中相对谱移变化范围越小。研究还发现,适当增加脉冲宽度会明显减小大气湍流对光束轴上点和轴外点光谱移动的影响。在不同脉宽下,轴上和轴外点光谱均会出现光谱开关,且轴外点光谱会产生两次光谱跃变的独特现象。在固定的传输距离上,拓扑荷越大,轴上点光谱移动越小,近轴范围内光谱相对谱移的变化范围越小,此外,不同拓扑荷下光谱均会出现谱开关。相干度越大时,光谱的变化越稳定,轴外点光谱的光谱开关发生位置越远。本文的研究结果为多普勒激光雷达的应用提供理论依据,PCRPLG脉冲光束本身具有较强抗湍流能力,且通过调控光束参数可以减小光束光谱移动。

The spectral shifts and spectral switches of partially coherent radially polarized Laguerre Gaussian(PCRPLG)pulsed beams propagating through atmospheric turbulence are investigated.It is found that the on-axis spectrum of the beams will shift rapidly in atmospheric turbulence due to the appearance of two spectral peaks caused by the turbulence.The stronger the turbulence is,the more stable the relative spectral shifts are after the rapid shift,and the off-axis spectrum has a smaller variation range of relative spectral shifts in stronger turbulence.It is also found that the influence of atmospheric turbulence on the spectral shifts of the on-axis and off-axis spectra can be significantly reduced by appropriately increasing the pulse width.Under different pulse widths,spectral switches appear in both on-axis and off-axis spectra,and the off-axis spectrum will produce a unique phenomenon of two rapid shifts.For a fixed transmission distance,the higher the topological charges are,the smaller the spectral shift of the on-axis spectrum is,and the smaller the variation range of the relative spectral shifts in the paraxial region is.In addition,spectral switches will appear in different topological charges.The larger the coherent length is,the more stable the spectral shifts are,and the farther the spectral switch occurs in the off-axis spectrum.The results of this paper provide a theoretical basis for the application of Doppler lidar.The PCRPLG pulsed beam itself has a strong anti-turbulence ability,and the spectral shifts of the beams can be reduced by adjusting the beam parameters.