title: Direct phase and amplitude characterization of femtosecond laser pulses undergoing filamentation in air.
abstract: Measurement of the temporal (spectral) phase and amplitude of a 50 fs laser pulse approaching and exceeding the critical power for self-focusing (P(crit)) in air reveals the formation of an isolated 17 fs pulse at 3P(crit). The dynamics of self-shortening are measured directly in the filament using transient-grating cross-correlation frequency-resolved optical gating with a noble gas serving as the nonlinear medium. Our results support recent filamentary propagation simulations, suggesting that a Kerr-dominated temporal reshaping process toward the end of the filament is largely responsible for the generation of short pulses.
authors.affiliation: Department of Chemistry and Center for Advanced Photonics Research, Temple University, Philadelphia, Pennsylvania 19122, USA.
authors.forename: Johanan
authors.initials: J
authors.lastname: Odhner
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Levis