Pulse duration dependence of dry laser peening effects in the femtosecond-to-picosecond regime

Abstract

We found an optimum pulse duration for dry laser peening in the femtosecond-to-picosecond regime, in which the laser intensity exceeds the air breakdown threshold. A pulse duration of 1 ps produced the most effective peening effects under conditions wherein the laser energy was constant; this was caused by a decrease in the laser fluence due to a beam expansion of less than 1 ps, in addition to an increase in the thermal effect above 1 ps. When the laser intensity exceeds the air breakdown threshold, it is necessary to select the pulse duration while considering laser–air and laser–metal interactions.