Effects of key pulse train parameters on electron dynamics during femtosecond laser nonlinear ionization of silica

The controlled, well-characterized evolution of the amplitude envelope and carrier-frequency sweep of ultrafast laser pulses permits the measurement and control of quantum transitions on a femtosecond time scale. This opens new perspectives to manipulate/adjust/interfere with the transient localized electron dynamics, corresponding material properties and phase change mechanisms, which are critical in laser micro/nano fabrication. This study presents the first-principles calculations of nonlinear electron-photon interactions during femtosecond pulse train ablation of silica. A real-time and real-space time-dependent density functional theory (TDDFT) is used to describe the transient localized electron dynamics such as photon absorption, electron excitation and free electron distribution. The effects of key pulse train parameters (including the pulse separation, the number of pulses per train and temporal pulse energy distribution) on electron dynamics are investigated.