FEMTOSECOND LASER-HEATING OF MULTILAYER METALS .2. EXPERIMENTS

Femtosecond thermoreflectivity experiments are performed to investigate energy deposition and transport during the very early period of short-pulsed laser heating of gold and chromium multi-layer metal films. The chromium layer underneath the top gold layer is found to produce significant effects on the laser-energy deposition process. Experimental results show that radiation absorption by free electrons and the subsequent heating of the lattice occur not only at different times but also at different locations in a multi-layer metal film. The conventional radiation heating model fails to predict these results, and a more rigorous two-step model agrees well with the measured data.