Thermal conductivity and thermo-optic coefficient measurements of transparent thin films using quantitative phase microscopy

The temperature increase of a thin film as a result of laser irradiation causes phase shift to the transmitted light. This phase shift can be quantitatively imaged by quantitative phase microscopy (QPM). Since the phase shift is a function of the thermal conductivity and thermo-optic coefficient (TOC), the recorded phase shift can be used to extract the thermal conductivity and TOC of the thin film by modeling the heat transfer within the thin film and its substrate. In this study, the laser-induced phase shift of three different transparent thin films deposited on transparent substrates is recorded by QPM. The thermal conductivity and TOC of the thin films obtained based on our heat transfer model show reasonable agreement with the values obtained from other methods. This method is simple yet cost-effective, which is advantageous compared with other available methods such as the thermoreflectance method.