Spatially resolved amplitude and phase characterization of femtosecond optical pulses

Ultrabroadband pulses exhibit a frequency-dependent mode size owing to the wavelength dependence of free-space diffraction. Additionally, rather compl ex lateral dependence of the temporal pulse shape has been reported for Ker r-lens mode-locked lasers and broadband amplifier chains and in frequency-d omain pulse shapers, for example. We demonstrate an ultrashort-pulse charac terization technique that reveals lateral pulse-shape variations by spatial ly resolved amplitude and phase measurements by use of spectral phase inter ferometry for direct electric-field reconstruction (SPIDER). Unlike with au tocorrelation techniques, with SPIDER we can obtain spatially resolved puls e characterization even after the nonlinear process. Thus, with this method the spectral phase of the pulse can be resolved very rapidly along one lat eral beam axis in a single measurement. (C) 2001 Optical Society of America .