Self-guided propagation of ultrashort IR laser pulses in fused silica

We report self-guided propagation of ultrashort IR laser pulses in fused silica over several Rayleigh lengths. Self-guiding is accompanied by pulse splitting and time compression. Numerical simulations involving pulse self-focusing, temporal dispersion, and multiphoton ionization are found to be in good agreement with the experimental results. They show that a quasidynamic equilibrium between multiphoton ionization and self-focusing drives the filamentation process, while temporal dispersion plays a negligible role.