湍流大气中的准直激光束III.分形结构与相位不连续点饶瑞中
Collimated laser beam in a turbulent atmosphere: Fractal structure and phase branch points
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摘要: 利用数值方法研究了不同起伏条件下准直激光束在湍流大气中的传播，分析了光斑的分形维数以及相位不连续点数目的统计特征。结果表明：随着起伏条件的增大，光斑的分形维数以及相位不连续点数目增大；光斑的分形维数与锐度（描述光斑质量的参量）有一定的关系，但相位不连续点数目与光斑质量不存在确定的关系。在本文的计算条件下，分形维数一直随起伏条件的增大而增大，没有出现类似于闪烁饱和的现象。在一定的起伏条件下，相位不连续点数目具有一定的统计分布，而不是一个确定的值，并且具有相当的发散性。Abstract: The statistics of the fractal dimension of the intensity image and the number of phase branch points in the light field of a collimated laser beam propagating through a turbulent atmosphere are evaluated for a series of numerically-generated field and intensity patterns. Some results are summarized as follows. The fractal dimension and the number of phase branch points increase with the fluctuation condition. The fractal dimension has definite relation with the pattern sharpness, but there is no relation between the number of phase branch points and the sharpness. In the situation considered here, no saturation phenomenon is found for the fractal dimension, and the number of phase branch points has a probability distribution instead of a definite value under a certain fluctuation condition
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Key words:
- beam pattern /
- light propagation /
- atmospheric turbulence /
- fractal structure /
- branch point.
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