Femtosecond Electronic Thermal Oscillation in Electron Temperature Dynamics in Thin Gold Film

Abstract

High intense femtosecond laser pulse is irradiated on thin gold film. Electron temperature was evaluated using the two-temperature and the dual- phase lag models. Numerical results showed a thermal oscillation in electron temperature dynamics. To assess thermal oscillation, analytical solution of the characteristic equation for heat conduction was obtained by the Laplace transformation method and implied with the Van Neumann condition. More than one temperature locations in the surface of thin gold film were observed. Another feature was also observed from the numerical solutions was the shallow concentration of temperature distribution of the film. Instabilities and non-homogeneous temperature distribution on front surface of the gold target were also studied in terms of plume expansion. Plume expansion (in vacuum) in terms of Knudsen layer thickness will be presented for different laser fluence and pulse duration. These results suggest that the laser parameters can influence the plume characteristics. Plume expansion in two dimensions of the surface exposed to the laser will be presented in order to show that the plume expansion was abroad and can be interpreted in terms of laser fluence. Keywords - femtosecond laser pulse, gas dynamics, laser plume expansion, thin film gold foil, two-temperature model.