Semi-empirical approach for the analysis of infrared photothermal microscopy

Thermal diffusivity measurement by IR photothermal microscope is analyzed in this article. In order to avoid artifacts in thermal diffusivity estimation, data must be carefully analyzed with a model including signal distortions coming from diffraction and nonlinearity in IR emission. We present an alternative method for signal analysis. The key aspect is the possibility to estimate the quantities involved in the signal description directly from the experimental data obtained for properly selected conditions. This approach is particularly useful when the distortions are relevant, as in case of shifted spectral bandwidth toward the short wavelength of the IR detector with respect to the typical range 2–12 μm. This situation is typical when a CO 2 laser is used as pump beam to investigate visible transparent samples. The method is applied to estimate the thermal diffusivity of an uncoated BK7 glass sample.