J. Phys. IV France 125 (2005) 365-368
Hyperbolic heat diffusion in photothermal experiments with solidsE. Marín, J. Marín and R. Hechavarría
Facultad de Física, Universidad de La Habana, San Lázaro y L, Vedado 10400, Ciudad de La Habana, Cuba
We will take into account the relaxation or build-up time necessary for the onset of a heat flux after a temperature gradient is imposed on a sample, to derive the hyperbolic heat diffusion equation. It is shown solving this equation that, in photothermal experiments involving intensity modulated laser light, there exists a critical modulation frequency at which the heat flux changes its diffusive character to a wave propagation process with the velocity of sound. On the other hand, in the case of time domain experiments, i.e., when a sample is exposed to an ultra-short laser pulse, our calculations show the existence of thermal waves propagating through the sample, whose behaviour will be discussed.
© EDP Sciences 2005