Filamentation of Double Femtosecond Laser Pulses in Fused Silica

Based on the pulse shaping technique, filamentation of double femtosecond pulses in fused silica is studied experimentally and theoretically. It is shown in experiments that the filamentation onset and length, as well as the intensity can be continuously changed with the delay time. Theoretical studies reveal that the onset of filamentation depends on the peak power of the superposed double pulses, while the filamentation length and intensity are mainly influenced by the evolution of the electron density generated by the superposition of the two pulses. Moreover, both experiment and theory results indicate that the filamentation can be more robust when appropriate delay times are set.