TABLE OF CONTENTS With the invention of the laser, it was soon recognised that the high amplitude of shock waves required for a SP process could be achieved by using confined plasma generated at the metal surface by means of a high-intensity laser beam with a pulse duration in the tens of nanoseconds range (Dane et al., 1997).
The physics and mechanisms of laser-induced shock wave generation has been investigated intensively (Fairand et al., 1974; O'Keefe and Skeen, 1972; Hoffman, 1974; Yang, 1974; Romain et al., 1986; Ling and Wight, 1995; Couturier et al., 1996). In early experiments (White, 1963; Skeen and York, 1968), the irradiated material was placed in a vacuum and the plasma generated by the laser pulse expanded freely. The resulting peak plasma pressure ranged from 1 GPa up to 1 TPa when the laser power density was varied from about 0.1 GW/cm 2 to 10 6 GW/cm 2. The time duration of the plasma pressure was roughly equal to the laser pulse duration, typically 50 ns in length, because of the rapid adiabatic cooling of the laser-generated plasma in the vacuum (Fairand and Clauer, 1978; Clauer et al., 1981).
There are three wavelengths use of most commonly in LSP processes, 1.064 ?m (near infrared, IR), 0.532 ?m (green) or 0.355 ?m (ultraviolet, UV). The near infrared wavelength has only a modest absorption coefficient in a water overlay, sufficient interaction with the metal surface and a high dielectric...
