Frequency resolved wavefront retrieval and dynamics of diffractive focused ultrashort pulses

In this work we demonstrate the ability of the spatiotemporal characterization technique STARFISH to retrieve the wavelength dependent wavefront of focused ultrashort laser pulses. The high resolution achievable with this technique allows measuring the wavefront at the focal spot. In particular, the method is applied to study the effects of focusing with a kinoform diffractive lens. The evolution from converging to diverging wavefronts as the pulse propagates along the focal region is analyzed for each wavelength. The spatiotemporal intensity and spatially resolved spectrum structure of the pulses, as well as their profiles on axis, are also presented. Numerical simulations of the propagation of such pulses confirm the experimental results. ? 2012 Optical Society of America.