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/cm(2). 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/cm(2). 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. (C) 1999 American Institute of Physics. [S0003-6951(99)02935-6].