Impact of wavefront aberrations on the duration of few-cycle laser pulses.

It is generally difficult to define the duration of few-cycle laser pulses in the presence of spatiotemporal coupling. The pulse temporal width can indeed vary locally across the pulse front and spatially varying delays can complicate the definition of the temporal pulse length over the whole pulse front. However, the simple formalism of the global pulse length can be used to define the duration of such pulses. The variation of the rms temporal pulse width and the maximum instantaneous intensity of this global pulse is used here to investigate the impact of various aberrations. This is done for a collimated Gaussian few-cycle pulse propagating in a vacuum with no dispersion as a perfect plane wave of uniform, Gaussian, and super-Gaussian spatial profiles and for various local temporal pulse widths. It is shown that the temporal global profile of an aberrated pulse front can lose its Gaussian profile even for low amplitudes of aberration. This results in an increase of the rms temporal width and a decrease of the maximum instantaneous intensity of the global pulse, depending on the type of aberration. This is generally associated with a decrease in the performance for optical systems using few-cycle pulses.