Conditions for optimum photothermal discrimination of subsurface thermal inhomogeneities

We present calculated photothermal contrast functions arising from lateral scanning of buried stripe and disk-shaped deviations in thermal conductivity k. From the theoretical findings we derive the measuring conditions in terms of the modulation frequency for which optimal photothermal discrimination of subsurface thermal inhomogeneities can be achieved. The theoretical results have been verified experimentally by measuring model samples, in which localized inhomogeneities were embedded.