Monitoring laser-energy coupling to solid materials: Plasma-shielding and phase change

For many laser-material processes, new methods are needed to monitor laser-energy coupling to solid materials. Different methods will be presented which can detect changes in laser-energy coupling due to plasma shielding, phase change, and surface alterations. The techniques used are inductively coupled plasma-atomic emission spectroscopy (ICP-AES), mechanical stress power (MSP), and photothermal deflection (PTD). This work demonstrates that the onset of plasma shielding can be detected for ns and ps laser interactions with solids, using ICP-AES and MSP, and that the onset of melt at a surface can be detected using PTD. (C) 1997 Elsevier Science S.A