DISTORTION OF FEMTOSECOND PULSES DUE TO CHROMATIC ABERRATION IN LENSES

We study the pulse propagation through the singlet lens, by solving the diffraction integrals. Several peculiar features around the focal plane are shown, which the geometrical optics approximation cannot predict. Two conceptually different types of time distorsion are clearly distinguished: the group delay dispersion that gives rise to a pulse broadening, and the concavity of the pulse that introduces a time delay across the beam section. Both of them result to be of the same order of magnitude, but appear at different locations. Analytical expressions are obtained for the maxima of the distortions and their position along the axis is discussed.