Absorption of femtosecond laser pulse in fused silica: experiments and modelling (original) (raw)

Interaction of femtosecond laser pulses with dielectric materials: insights from numerical modelling

2009

To shed light on ultra-short laser interactions, we study the laser ionization processes leading to the energy absorption and reflection. In particular, we investigate the ratio of the energy deposited to the material to the total incident energy. The absorbed energy density is studied as a function of pulse width and laser intensity. It is shown that the maximum absorption takes place at a given incident laser intensity that is considered as ablation threshold. For pulses shorter than 100 fs, only a small fraction of laser energy is deposited to the matrix, causing heating and leading to the thermal and/or mechanical modifications of the target material. We connect these results with the electronic excitation and the ionization processes leading to the changes in reflectivity and consuming electron energy. The obtained numerical results explain several recent experiments.

Thermal and nonthermal effects in femtosecond laser ablation and damage of transparent materials

Proceedings of SPIE - The International Society for Optical Engineering

There are considered non-thermal and thermal processes of femtosecond laser-induced damage and ablation of wide band-gap transparent materials. Dominating of one or other of them depends on radiation and material parameters among which pulse repetition rate, focal spot size and absorption play key role. Non-thermal mechanisms of damage and ablation can dominate at initiating stage and at low repetition rates (below 10 kHz). They are attributed to nonlinear electrodynamical processes such as higher harmonic generation and formation of shock electromagnetic waves. Considering interaction of shock electromagnetic wave with a particle (single charged particle and a dipole) placed in potential well, we derive expression for threshold of laser-induced ionization and delocalization. Thermal mechanisms can dominate at later stages of damage and ablation at repetition rates above 10 kHz. It is considered possibility of their description within modified two-temperature model. There are also d...