Propagation dependence of chirp in Gaussian pulses and beams due to angular dispersion

The chirp acquired by a Gaussian ultrashort pulse due to angular dispersion, unlike that of plane waves, increases nonlinearly with propagation distance and eventually asymptotes to a constant. However, this interesting result has never been directly measured. In this Letter, we use two-dimensional spectral interferometry to measure the propagation dependence of the chirp for Gaussian ultrashort pulses and beams with angular dispersion. The measured chirp as a function of propagation distance agreed well with theory. This work verifies both an equation and a measurement technique that will be useful for predicting or determining the pulse's chirp in ultrafast optics experiments that contain angular dispersion.