NUMERICAL STUDY OF ULTRASHORT LASER PULSE INTERACTIONS WITH METAL FILMS

Abstract

A dual-hyperbolic two-step radiation heating model is presented to investigate ultrashort laser pulse interactions with metal films. This model extends Qiu and Tien's theory by including the effect of heat conduction in the lattice. In addition, the depth distribution of laser intensity is modified by adding the ballistic range to the optical penetration depth. The effects of temperature dependence of the thermophysical properties also are examined. For comparison, the proposed model and the existing theories, the parabolic two-temperature model, Qiu and Tien's theory, and Fourier's law, are solved using a mesh-free particle method. Numerical analysis is performed with gold films; the results are compared with experimental data of Qiu, Jubhasz, Suarez, Bron, and Tien, and Wellershoff, Hohlfeld, Gudde, and Matthais. It is shown that this current model predicts more accurate thermal response than the existing theories considered in this study. It is also found that the inclusion of the ballistic effect to the depth distribution of laser intensity significantly improves the melting threshold fluence prediction.