大气湍流对高斯-谢尔模型光束孔径平滑因子的影响

Effects of Atmospheric Turbulence on the Aperture Averaging Factor of the Gaussian-Schell Model Beams

大气湍流严重影响了无线激光通信系统的性能，而孔径平滑效应能有效抑制湍流引起的光强闪烁效应。采用包含内外尺度影响的修正vonKarman湍流谱模型，并根据Tatarskii给出的孔径平滑因子定义式和波场交叉谱密度函数的互相干函数近似原理，得到了高斯-谢尔模型（GSM）光束的闪烁孔径平滑因子。讨论了光源相干参量、湍流强度及湍流内外尺度对高斯-谢尔模光束闪烁孔径平滑效应的影响。结果表明：随着湍流的增强，部分相干光抑制湍流效应的作用逐渐减弱，并且湍流越强孔径平滑因子达到饱和的速度越快；湍流外尺度对孔径平滑因子的作用可忽略，内尺度对孔径平滑因子的影响显著，在分析光强闪烁问题时内尺度应作为重要影响参数之一。

The performance of wireless laser communication can be affected due to atmospheric turbulence and the aperture averaging can effectively inhibit scintillation caused by turbulence. The aperture averaging factor of scintillation for Gaussian-Schell mode （GSM） beams is derived according to the expression of aperture averaging factor given by Tatarskii and the relationship between mutual coherent function and cross-spectral density function for narrow-band wavefield. The effects of coherent parameter of the source,the strength of turbulence, inner scale and outer scale of the turbulence on the aperture averaging factor of scintillation for GSM beams are discussed. It is shown that the effects of the coherent parameter on the aperture averaging factor become smaller with the turbulence increase. The aperture averaging factor reaches saturated more quickly with stronger turbulence, and further increasing of the aperture of receiver becomes no longer valid in reduction of scintillation. The inner scale of turbulence has a significant effect on aperture averaging factor, while the influence of outer scale can be neglected. The inner scale of turbulence plays an important part in analysis of scintillation.