Spatio-temporal evolution scenarios of femtosecond laser pulse filamentation in fused silica

Abstract

We investigated the evolution of femtosecond laser pulses at different wavelengths corresponding to normal, zero, and anomalous regimes of group velocity dispersion (GVD) in fused silica. The laser pulse filamentation in different GVD regimes under the same similarity parameters was first considered. It was established numerically that the scenario of the pulse filamentation depends both on temporal factors, which are determined by pulse GVD and self-phase modulation, and spatial factors associated with Kerr self-focusing and plasma defocusing. In presence of strong normal GVD the dispersive stretching causes, a pulse power decrease followed by lowering of the intensity in filament, electron density reduction in plasma channel, and suppressing of the refocusing. For zero GVD the multipeak regime of radiation propagation is realized in the filament as a result of recurring self-focusings of powerful pulse tail, which was defocused in laser plasma. When GVD is anomalous a sequence of “light bullets” with duration about 10 fs forms in the filament. And the peak intensity in “light bullet” stays the same ≈ 5 × 1013 W/cm2. In the regime of anomalous GVD power is transferred from the pulse edges to its center, where the repeated self-focusings occur and form a “light bullet” sequence.