Atomic simulation of irradiation of Cu film using femtosecond laser with different pulse durations

Abstract

It is necessary to understand the light-matter interaction for application of femtosecond laser micro/nanoprocessing. In this work, the authors investigated the melting and disintegration behavior of a Cu film irradiated by a femtosecond laser with different pulse durations in the range of 35–500 fs by using a combined two temperature model (TTM) and molecular dynamics (MD) method. On the basis of TTM-MD, the temperature and stress evolution of the Cu film were analyzed. The result indicated that the Cu film disintegrates when the pulse duration is shorter than 100 fs but melts at a pulse duration of 200 fs. The photomechanical and thermomechanical evolutions induced by the femtosecond laser were also analyzed. The stress wave and increasing temperature were the main reasons for film disintegration and vibration. The snapshots of the Cu film indicate the melting and disintegration processes on an atomic scale. It shows that the melting occurs homogeneously, whereas the disintegration occurs at the center of the film. These results are helpful to understand the mechanism of femtosecond laser materials ablation.