The paper is devoted to the study of plasma effects, which are present in laser ablation at relatively high intensity (I ≥ 1012 W/cm2). We start from the classical “two temperature model” of laser ablation (“cold solid approximation”) and we extend it to higher intensities where laser-induced heating and laser-induced changes in the background material become relevant. The new model is also compared to experimental results on laser ablation of solid targets from short pulse lasers at high intensities (up to 1014 W/cm2). Finally, we consider the effects on laser-ablation of laser-generated fast electrons.

We propose the use of Focused Ion Beam/Scanning Electron Microscope (FIB/SEM) devices for the analysis of ablation results. Ablated samples have been obtained by irradiating an Al planar target with an optically smoothed iodine laser working at 0.44 μm. The interpretation of FIB images shows the high potentiality of the technique.

The model of plasma production by laser radiation onto a solid target was developed taking into account plasma heating by the emitted electrons and target heating by ion bombardment, as well as by the laser radiation. The near target plasma structure was analyzed. The space charge sheath was studied solving the Poisson equation and taking into account the volume charge of accelerated electrons and ions. The kinetics of atoms evaporated from the target and the back-flow of atoms and ions from the plasma towards the surface was analyzed. A system of equations, including equations for solid heat conduction, plasma generation and the plasma expansion was formulated. The calculation for Cu target, laser spot radius 100 μm, pulse duration 1 ms, 103, 10, 1ns and laser power density qL = 10−3–1 GW/cm2 was conducted. The ratio of net evaporation rate to the total evaporated mass flux was determined. It was shown that the plasma mainly generated in the electron emission beam relaxation region and there the plasma flow is subsonic. The electric field at the target surface is relatively large and therefore the ion current to the surface in the space region is large and comparable with the electron emission current. A large contribution of the plasma energy flux in the target heat regime was obtained, showing that the laser generated plasma significantly converts the absorbed laser energy to kinetic and potential energy of the plasma particles, which transport part of the energy through the electrostatic sheath to the solid surface.