Photothermally induced temperature variations in a low-absorption sample via backside absorption

In order to make the photothermal effect detectable from a sample with low optical absorption, an optically opaque layer must be applied on its surface. A model of optically induced temperature variations for such a structure is derived, with a very thin coating applied on the non-illuminated (back) side of the sample and neglecting heat flux dissipation in the coating. Validation of the model is performed by comparing the obtained results with the results for the corresponding two-layer structure model. The influence of optical absorption on surface temperature variations of both optically transparent and semi-transparent film, whether the film is a good or poor thermal conductor, is analyzed. It is shown that the effects of optical absorption in the coated structure can be observed through variations in the measured temperature, despite the low absorbance of the sample.