Plasma effect on propagation of filamented femtosecond laser pulse in fused silica

Abstract

Propagation of filamented femtosecond laser pulses in fused silica is studied using microscopic techniques of time-resolved femtosecond optical polarigraphy and transient absorption. Basing on the value of induced absorbance measured at the trailing edge of propagating pulse, it is concluded that the filament is refilled by energy flux from a reservoir. Light energy and plasma density in the filament core, along with the corresponding changes in refraction index, are estimated. Reshaping of the laser pulse caused by expulsion of light from the plasma-occupied area is directly observed. Transformation of axially symmetric shape of the pulse into asymmetric Z-like one is also found.