LASER-MATERIAL INTERACTIONS - FUNDAMENTALS AND APPLICATIONS

The interaction of light with matter leads to electronic excitation by the absorption of photons. A large fraction of the high excitation en ergy of the electrons is transformed into heat on a time scale of abou t one picosecond in many circumstances. With lasers, power flux densit ies or intensities exceeding a terawatt/cm2 are readily achieved and a ny material may be converted into a high temperature plasma. The mater ial response has been investigated over a wide range of intensities an d irradiation times. Applications include heat treatment and ablation of surfaces, cutting, drilling and welding of a wide variety of materi als, laser recording and printing, and laser surgery. Phase transition s induced by ultrashort femtosecond laser pulses enlarge our understan ding of materials under extreme conditions of pressure and temperature .