This paper shows the enhanced sensitivity of the optothermal interference technique in the detection of local differences (non-homogeneity in thickness and optothermal parameters), compared to the conventional optical interference, when...
moreThis paper shows the enhanced sensitivity of the optothermal interference technique in the detection of local differences (non-homogeneity in thickness and optothermal parameters), compared to the conventional optical interference, when investigating layered transparent structures. The measured signal is sensitive to the reflectance variation at the distinct interfaces, function of temperature, as well as to the optical phase lag between the reflected beams. Measurements made on solar cells show contrast of the order of 100% in the optothermal interference, while the conventional optical interference presents a contrast of only 15%. A model based on the reflectance variation at each interface describes the signal behavior as a function of modulation frequency.
