扰动大气中部分相干光束的光谱特性

对扰动大气中传输的部分相干光束的光谱演化特性进行了研究。利用推广的惠更斯一菲涅耳原理．得到了扰动大气中部分相干光束的交叉光谱密度，据此分析了在大气扰动影响下部分相干光束的频移效应以及空间相干度的变化规律。结果表明：由于大气扰动的影响，在光束传输过程中，轴上光谱先是出现蓝移，蓝移量先增大后减小，传输足够远距离之后将出现红移，并且光束的相干性越差，就需要传播越远的距离才会发生红移；而光束的空间相干度随传输距离增大到一定程度之后开始减小，最终将趋于零。通过与自由空间中部分相干光的传输特性比较，发现当光束的传输距离比较小时．大气扰动效应对光谱特性的影响很小，只有在传输距离足够远时，大气扰动对光谱特性的影响才会明显地表现出来。

Spectrum Properties of Partially Coherent Beams in Turbulent Atmosphere

The spectrum properties of partially coherent beams propagating in turbulent atmosphere are studied. Basing on the extended Huygens-Fresnel principle, an analytical propagation formula for the cross-spectral density of partially coherent beams in turbulent atmosphere is derived. The degree of spatial coherence and spectral shift of partially coherent beams through turbulent atmosphere are analyzed by using the derived formula. The results show that the spectrum of the partially coherent beam on axis in turbulent atmosphere is blueshifted in the beginning, the mount of the shift firstly increases, afterwards decreases, and finally a red shift appears with the increase of propagation distance. The lower the beam coherence is, the farther propagation distance is needed when red shift appears. At first the degree of spatial coherence increases, then decreases and approaches to zero finally. Comparing with the propagation of the partially coherent beam in free space, the atmospheric turbulence has small influence on the spectrum properties of the partially coherent beam in a short distance propagation, while has a strong influence on it in a sufficient long distance propagation.