Product Code: ICAL06_M302

Modeling of Ultrafast Laser Ablation into Vacuum
Authors:
Cho Lik Chan, University of Arizona; Tucson AZ USA
Mark Squires, University of Arizona; Tucson AZ USA
Presented at ICALEO 2006

Laser-matter interaction is a very complicated phenomenon. There exist three principal regimes for laser pulses, namely long, short, and ultrashort pulse lasers. In the ultrashort regime, the target material is ionized more rapidly than the characteristic heat transfer time scale, and the material is ablated without any transfer of heat to the surrounding lattice. The absence of heat transfer to the surrounding lattice provides important advantages to micromachining: reducing both the material property change due to heating and the deposition of slag. To further understand the ablation process into vacuum, a solver using the Space-Time Conservation Element Solution Element Method is used to describe the material removal. The model uses a coordinate transformation for the expanding boundary, allowing the size of the computational domain to be fixed. The ablation process is considered to be a Coulomb explosion. This process may be modeled using the Euler equations and an appropriate equation of state. The equation of state is based on a one term virial equation of state with the coefficient of ionization playing a role in the virial coefficient. Material ablation rates are compared for various laser intensities and levels of ion recombination.