Reflection-type quantitative phase microscopy for thermal conductivity and thermo-optic coefficient measurements of substrates and thin films

Abstract

Thermo-optic properties are critical for high-performance devices where both heat and light significantly affect their performance in different kinds of applications. However, methods for accurately characterizing these properties remain limited. This study demonstrates the development of quantitative phase microscopy (QPM) to simultaneously measure the thermal conductivity and thermo-optic coefficient (TOC) of various materials, including transparent and opaque substrates and transparent thin films on opaque substrates. The thermal conductivity values obtained using QPM are in good agreement with those measured via thermal wave analysis, and the TOC measurements align with the reported values in the references. Furthermore, the observed phase difference provides insights into the relative contributions of the thermal expansion coefficient and TOC to the overall phase shift. This approach is robust, cost-effective, and versatile compared to existing techniques, offering a valuable tool for characterizing thermo-optic properties in diverse material systems.