Nootz Gero, Matt Silvia, Kanaev Andrey, Judd Kyle P, Hou Weilin
Appl Opt. 2017 Aug 1;56(22):6065-6072. doi: 10.1364/AO.56.006065.
The propagation of a laser beam through Rayleigh-Bénard (RB) turbulence is investigated experimentally and by way of numerical simulation. For the experimental part, a focused laser beam transversed a 5 m×0.5 m×0.5 m water filled tank lengthwise. The tank is heated from the bottom and cooled from the top to produce convective RB turbulence. The effect of the turbulence on the beam is recorded on the exit of the beam from the tank. From the centroid motion of the beam, the index of refraction structure constant Cn2 is determined. For the numerical efforts RB turbulence is simulated for a tank of the same geometry. The simulated temperature fields are converted to the index of refraction distributions, and Cn2 is extracted from the index of refraction structure functions, as well as from the simulated beam wander. To model the effect on beam propagation, the simulated index of refraction fields are converted to discrete index of refraction phase screens. These phase screens are then used in a split-step beam propagation method to investigate the effect of the turbulence on a laser beam. The beam wander as well as the index of refraction structure parameter Cn2 determined from the experiment and simulation are compared and found to be in good agreement.
通过实验和数值模拟的方式研究了激光束在瑞利 - 贝纳德（RB）湍流中的传播。在实验部分，一束聚焦激光束纵向穿过一个长5米×宽0.5米×高0.5米的装满水的水箱。水箱从底部加热，从顶部冷却以产生对流RB湍流。湍流对光束的影响在光束从水箱出口处记录下来。根据光束的质心运动确定折射率结构常数Cn2。在数值研究中，对相同几何形状的水箱模拟了RB湍流。将模拟的温度场转换为折射率分布，并从折射率结构函数以及模拟的光束漂移中提取Cn2。为了模拟对光束传播的影响，将模拟的折射率场转换为离散的折射率相位屏。然后在分步光束传播方法中使用这些相位屏来研究湍流对激光束的影响。比较了从实验和模拟中确定的光束漂移以及折射率结构参数Cn2，发现两者吻合良好。
