One-dimensional photothermal characterization of subsurface interfaces utilizing the virtual wave concept

This work presents one-dimensional photothermal results for estimating subsurface interface parameters using the virtual wave concept. The performed study demonstrates the capability of the virtual wave concept as a feature extraction method for estimating the depth position and thermal mismatch of subsurface interfaces within layered materials. The mathematical relationship between the reflection coefficient of the thermal wave and the signal of the virtual wave is demonstrated for exact one-dimensional solutions. For experimental validation, pulsed thermography in the pulse-echo configuration for different metallic specimens is applied. This method yields a very good estimation of the interfacial parameters for the analyzed samples. In summary, a feasible and fast one-dimensional photothermal evaluation of subsurface interfaces using the virtual wave concept is demonstrated.