A theoretical and experimental study about the ability of the photothermal modulated mirage technique to characterize vertical interfaces (thermal resistances) separating two different opaque and thermally thick media with thermal conductivities larger than the medium surrounding the sample and with any value in their thermal diffusivities has been carried out. For the calculation of the mirage deflection, a theoretical model that incorporates the mirage parameters (sizes of probe and pump beams, probe beam height) and which is valid for any value of the thermal resistance characterizing the interface is presented. The model is validated by experimental measurements on a fabricated sample having a controlled interface width that separates two pieces of copper and steel. Fitting the model calculations and the experimental data allows one to retrieve the value of the thermal resistance.

This study is on the use of genetic algorithms (GAs) to develop estimation methodologies for the determination of the thermal properties of thin films. The thermal conductivity and two contact resistances are thought to be simultaneously estimated. A GA is used to minimize a least squares objective function containing calculated and measured temperatures. A photo-thermal technique is applied to acquire measured temperatures, while calculated data are obtained from a one-dimensional conductive model. Experiments were performed on ZrO2 thin films of different thickness. The results from the analysis demonstrate that the proposed GA is a useful tool for the thermal characterization of thin films.

This paper presents a theoretical study of the influence of mass diffusion on the photothermal signals detected by the mirage effect. A model is developed for the mirage effect when physical adsorption occurs on a non-porous sample under conditions close to the normal temperature and pressure. It shows that the mass diffusion contribution to the mirage deflection, due to the induced periodic adsorption/desorption of vapour molecules at the solid sample surface, may become more important than the thermal contribution due to the temperature gradient. The model also predicts that the mirage deflection can be used to experimentally determine the mass diffusion coefficient of a binary gas mixture. The limits of validity of this simple one-dimensional theory are discussed and an analysis of the influence of the experimental parameters is presented. An interesting result of this discussion is that the phase of the mirage signal is remarkably sensitive to the adsorbed film growth when the magnitudes of the thermal and the mass diffusion contributions are similar.

Theoretical and experimental possibilities are presented of a modulated photothermal method, laser-induced photoreflectance, for inspecting thermal diffusivities and quality of interfaces in composite materials with micron-scale spatial resolutions. The models are established for semi-infinite materials containing interfaces parallel or perpendicular to the sample surface. The applications concern thermal diffusivity measurements of anisotropic polycrystals and detection of thermal resistance in damaged materials and at interfaces between reinforcements and matrix in composites.

This paper presents the theoretical and experimental possibilities of a modulated photothermal method, laser-induced photoreflectance, for inspecting the quality of interfaces with micronic spatial resolutions. An analytical model is established for semi-infinite materials containing an internal interface perpendicular to the sample surface. Applications are the detection of thermal resistances in damaged materials and at interfaces between reinforcements and matrix in composites.

This paper presents the theoretical and experimental possibilities of a modulated photothermal method, laser induced photoreflectance, for inspecting the quality of interfaces with micronic spatial resolutions. An analytical model is established for semi-infinite materials containing an internal interface perpendicular to the sample surface. The presented application is the detection of thermal resistances in damaged materials.