ULTRASHORT PULSED GAUSSIAN LIGHT-BEAMS

We find a family of solutions of the paraxial wave equation that repre sents ultrashort pulsed Light beams propagating in free space. These p ulsed beams have an arbitrary temporal form and a nearly Gaussian cros s section, while modeling for the pulses emitted by mode-locked lasers with stable two-mirror resonators. We also study the effects arising from their spatiotemporal coupled behavior, such as pulse time delay, distortion, and a frequency shift toward the beam periphery. Time-vary ing diffraction (with diffraction reduction at the first instants of a rrival of the pulsed beam at a given distance) and the dependence of t he spatial distribution of energy on the pulse form are also described . These effects become important for pulsed beams with a few optical o scillations within the pulse envelope.