大气湍流对斜程传输准单色高斯-谢尔光束空间相干性的影响

由湍流大气中斜程传输时准单色高斯-谢尔(GSM)光束互相干函数的解析式导出了该光束的复相干度.然后,利用表征光束空间相干性的横向相干长度,研究了斜程传输时大气湍流对准单色GSM光束空间相干性的影响.研究结果表明:1)当传输路径偏离水平方向较大(即θ≤88°)时,准单色GSM光束横向相干长度随传输距离均为先迅速增加,后缓慢增加,最后基本保持不变.2)当传输路径接近水平方向(即θ≥89°)时,准单色GSM光束横向相干长度随传输距离均为先增大,达到一个最大值后开始下降并持续减小.3)空间相干性不同的准单色GSM光束在湍流大气中传输一定距离后空间相干性趋于相同.最后,对以上结果在物理上给予了解释.

By using the mutual coherence function of quasi-monochromatic Gaussian Schell-model (GSM) beams propagating in a slant path through the turbulent atmosphere, the complex degree of coherence of those beams is derived analytically. By employing the lateral coherence length (that can be derived from the complex degree of coherence) of quasi-monochromatic GSM beams to characterize their spatial coherence, the effect of atmospheric turbulence on the spatial coherence of the beams was studied. The result shows that: (1) When theta <= 88 degrees, the lateral coherence length increases firstly and then keeps unchanged as the beam propagates in the turbulent atmosphere. (2) When theta >= 89 degrees, the lateral coherence length increases firstly and then reaches a maximum value after the beam propagates a certain distance in the turbulent atmosphere, then begins degrading and keeps decreasing with increasing distance. (3) Three beams with different lateral coherence lengths at the source plane (z = 0) will have almost the same lateral coherence length after they propagate a certain distance in the turbulent atmosphere. Lastly, a physical explanation was given to the results.