提出了一种利用振幅关联函数来分析超短脉冲中时空耦合效应的方法。定义了振幅关联度和关联带宽来衡量时空耦合的严重程度。给出了不同空间啁啾程度的脉冲光束的时空分布图。采用振幅关联函数研究了超短脉冲中的一些振幅耦合效应，如由角色散元件引起的一阶空间啁啾和角色散效应以及由衍射引起的二阶空间啁啾效应，并给出了相应的振幅关联度的解析表达式。结果表明，由于宽带激光脉冲的衍射和折射与频率密切相关，导致其振幅关联度下降并出现时空耦合。具体地，角色散引起的空间啁啾将会随着传输距离的增大而减弱直至趋于一定值。另外，由自由空间衍射引起的二阶空间啁啾效应也会随着传输距离的增大而减弱。最后，由角色散元件引起的角色散效应并不会随着传输距离的变化而变化。

A novel approach for analyzing spatiotemporal couplings in ultrashort pulses is presented using amplitude correlation functions. Amplitude correlation degrees and correlation bandwidth are defined, which can readily indicate the severity of spatiotemporal couplings. Intuitive pictures of pulses with different amounts of spatial chirp are given. With amplitude correlation functions, the amplitude couplings in ultrashort pulses, such as the first-order spatial chirp and angular dispersion caused by angular dispersion elements and the second-order spatial chirp caused by diffraction effects, are studied, and corresponding analytical expressions for the amplitude correlation degrees are given. It can be found that the refraction and diffraction of broadband optical pulses are frequency dependent, resulting in the decrease of amplitude correlation degree and leading to a coupling of spatial and temporal effects. Specifically the severity of the spatial chirp caused by an angular disperser increases with the increase of propagation distance and finally tends to be constant. Moreover, as the diffraction of ultrashort pulsed Gaussian beams is frequency dependent, the second-order spatial chirp of ultrashort pulsed Gaussian beams caused by diffraction effects will decrease during propagation. Finally, the severity of angular dispersion caused by an angular disperser does not vary as the beam propagates in the free space.网络出版日期: 2013-12-11