摘要: The group velocity of a short light pulse shaped in space in a form of a Gaussian beam is analyzed. The pulse radiation is represented by the spectral decomposition, and the integration of monochromatic components demonstrates the retardation of a Gaussianbeam pulse with respect to a plane-wave reference pulse. The resulting pulse velocity is not uniform and attains c at the far field, thus providing some excess over c at the part of its optical path. The effect is caused by the influence of a wavelength-dependent Gouy phase shift.