Numerical Investigation of Opto-Energy Phenomena in Thin Gold Films Irradiated by Femtosecond Pulse Laser Considering Quantum Effects

Abstract

Nonequilibrium energy transport and optical characteristics in thin gold film structures irradiated by a femtosecond pulse laser are examined numerically. With the use of a two-temperature model, the quantum effect is considered to determine various thermo-optical properties such as electron heat capacity, electron thermal conductivity, collision frequencies, reflectivity, and absorption rates. As a result, estimation on the electron temperature considering the quantum effect is in better agreement with measurements than those without considering quantum effect. During a femtoseond laser pulse, it is found that the electron and lattice are in nonequilibrium, the electron thermal conductivity changes rapidly with time, and reflectivity decreases substantially because of the changes in dielectric function and refractive index of gold films.