超快动态散斑相关函数的理论研究

将散斑场现象的研究推广到超快领域，从超快激光谱分析和散斑统计理论出发，推导出了超快散斑光强自相关函数。由此研究了超快动态散斑随时间和空间的演化规律，发现了超快散斑的一些基本特征，如散斑颗粒中存在干涉条纹结构及其空间周期随时间减小等，其实质在于等效的散射孔径为物面上两个不断向外扩展的对称孔径，它们之间的距离不断增大，从而使相应的观察面上的光波产生干涉而导致散斑结构中出现干涉条纹，并且干涉条纹的间距不断减小，表现为散斑自相关函数呈现不断加快的振荡。

A THEORETICAL STUDY OF THE AUTOCORRELATION FUNCTION OF ULTRAFAST DYNAMIC SPECKLES

This paper extends the studies of speckles to the area of ultrafast optics.Basing on both the spectra analysis of ultrafast lasers and the speckle statistical theory,we derive the autocorrelation function of ultrafast dynamic speckle intensity.We study the spatio-temperal evolution of the speckle fields and find their fundamental characteristics ,such as the interfernce fringe structures in the speckle grain and the decrease of the spatial period.The essence lies in that the scattering system is equivalent to that with a pair of apertures moving outward symmetrically, leading to the interference of light field on the observed plane.Such effect results in the fringe structure in the speckle intensities ,with fringe pitch keeping deminished,and manifesting as oscillation of the speckle autocorrelation function.