The present paper is aimed at discussing thermo-mechanical processes of pulsed laser target effects and at evaluating laser ablation induced changes of characteristic parameters of optical materials, components or devices under different temporal and spectral exposure conditions in a broad range of energy densities or power densities, respectively. Particular interest is actually in plasma sustained energy transfer, both in single pulse and repetitively pulsed modes of operation. In this latter case, high peak power densities and average power densities are attained simultaneously. Investigations are described, which were carried out with solid state lasers and gas lasers available at ISL. Depending on power densities applied and pulse half widths which are differing by more than nine orders of magnitude, from milliseconds in the case of long duration pulses to few picoseconds in the case of mode-locked pulses, energy transfer is governed by different mechanisms which are evaluated both experimentally and numerically by means of simulation. (C) 2003 Elsevier B.V. All rights reserved.