A theoretical study for photothermal deflection for the thermal conductivity measurement of anisotropic materials

We have analyzed the three-dimensional thermal conduction in anisotropic materials using nonsymmetric-Fourier transforms. The distribution of temperature fields which corresponds to the variation of the anisotropic ratio of thermal conductivities was obtained. The differences of the temperature fields for each material give rise to distinctions in the deflection of a probe beam. By using the relation between the temperature fields and the deflection of the probe beam, a complete theoretical treatment of the photothermal deflection has been performed for thermal conductivity measurement in an anisotropic medium. Principal and effective thermal conductivity were determined from the deflection angle and phase angle with the relative position between the heating and probe beams. The influence of the parameters, such as modulation frequency of the heating beam, the thermal conductivity, the angle between crystalline direction and probe beam direction, was investigated. Consequently, the overall effects between both thermal properties of anisotropic materials and experimental parameters and deflection signals were proposed in this study.