Measurement of Thermal Diffusivity Based on the Photothermal Displacement Technique Using New Phase Method

A new analysis method of measuring the thermal diffusivity of a solid using photothermal displacement is proposed. To obtain an expression for the photothermal deformation, a homogeneous and isotropic infinite plate of finite thickness with stress-free boundaries is considered. Theoretical study was carried out to investigate the influence of the parameters, such as the radius and modulation frequency of the pump beam and the sample thickness. We obtained the thermal diffusivity from the phase of the signal by two methods. The first method for finding the thermal diffusivity of the theoretical result uses the bi-section method to minimize the standard deviation between experimental and theoretical phase curves. The second method uses the relation between the normalized thermal diffusion length and normalized minimum position. The experimental data obtained by applying these methods for different samples were in good agreement with the literature values.