非均匀步长分步傅里叶算法的改进

研究了大气湍流中斜程路径上激光波束的传输模拟过程中的步长取值问题。针对分步傅里叶算法中大步长情况下的边界反射问题,首先对已有的吸收边界法进行了数值实验,得到了吸收边界法的步长取值上限。提出了滤波函数法,进一步解放了对步长的限制,利用真空中的波束传输模拟,证明了滤波函数法的有效性及其有效区域。结合这两种方法,给出了一种斜程路径上的相位屏设置方式,模拟了激光在此路径上的传输并统计计算了激光光斑的相干长度和闪烁指数。数值结果与理论吻合,证明了滤波函数法可以有效地增大分步算法中步长的上限,从而提升大气湍流中激光波束远距离斜程传输仿真效率。

Improvement of split-step Fourier algorithm with inhomogeneous step length

The problem of step length in the numerical simulation of laser beam propagation in atmospheric turbulence along slant path is studied.For boundary reflection under large step length in split-step Fourier algorithm,numerical experiments for absorbing boundary method are carried out,and the upper bound of the step length is obtained.The filter function method is proposed to further release the limit for the step length.The effectiveness of filter function method and its effective region are proved by the beam propagation simulation in vacuum.Combining these two methods,a setting way of phase screen on slant path is given.The propagation of laser beam on this path is simulated,and the coherence length and scintillation index of the laser spot are calculated.The numerical results are in good agreement with the theory,which proves that the filter function method can effectively increase the upper bound of the step length in the slip-step algorithm,thus improving the simulation efficiency of laser beam over long range transmission in atmospheric turbulence.