Impulse Photothermal Evaluation of Materials Via Frequency Modulated Optical Reflectance I: Theory

Recently, laser induced thermal wave based technologies have provided a powerful class of techniques for the evaluation of solid state materials [1,2]. Through the use of tightly focussed optical beams modulated at high frequencies, it has been possible to both generate and interrogate highly localized thermal wave phenomena in materials with spatial resolutions approaching 1 µm [2]. The unique capability for thermal depth profiling of optically opaque materials is possible with surface thermal wave measurements because of the rather obvious relationship between the vertical depth of a buried feature and the transit time of thermal energy to the sample surface