Initial considerations on the relationship between the optical absorption and the thermal conductivity in dielectrics

Abstract

The absorption of modulated or pulsed light leads to non-radiative processes that generate a photoacoustic (PA) wave. The standard model assumes that the amplitude of the PA wave is proportional to the optical absorption. In previous reports we have demonstrated experimentally and theoretically that from this proportionality: (1) one can obtain quantitative measurements of the optical properties of dielectric thin films and (2) that there may exist a relationship between the amplitude of the PA wave and the thermal conductivity of a given sample. Here we present analytic results that clearly show that the optical absorption and the thermal conductivity are coupled to the amplitude of the PA wave in the modulated regime and that this correlation holds for any type of macroscopic optical and thermal transparency. In particular, the present analysis shows that the product of the optical absorption and the thermal conductivity is related to the PA amplitude via a partition function.