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