Nonlinear changes in plasma and crater properties during laser ablation of Si

A dramatic change in plasma characteristics, as well as a significant increase in the quantity of ablated mass were observed at a laser power density threshold of 20 GW/cm2. The electron number density and temperature of the laser-induced plasma show dramatic changes in their nonlinear behavior in the range of 2 - 80 GW/cm2. The crater volume undergoes some type of phase explosion at the threshold. Mechanisms such as inverse bremsstrahlung and self-regulation were used to describe the behavior below threshold. Self-focusing and critical temperature are discussed to explain the dramatic changes at the threshold. copyright 1999 American Institute of Physics