An analytical approach to microscale heat transfer with a frequency domain examination of metal film thermomodulation experiments

A Green's Function solution to a non-Fourier heat transfer equation is presented. This analytical solution is applicable to thermal waves and femtosecond pulsed laser thermomodulation of thin metal films. A one dimensional solution of the two-step parabolic model for sinusoidal heat input is applied to frequency domain analysis of previously obtained results. Calculated electron temperatures are consistent with selected experimental measurements in the literature. The least squares method is applied to frequency domain parameter estimation of the ratio of electron-phonon coupling factor to thermal conductivity and the optical radiation penetration coefficient. The estimates of the latter indicate that the heat input for the back surface is distributed as expected for a classical approach, but the film surface receiving the pulse is flooded with energy. For a constant heat transfer coefficient of accepted macroscale values, the estimates of electron-phonon coupling factor agree with previously published values.