Directly Metering Light Absorption and Heat Transfer in Single Nanowires Using Metal–Insulator Transition in VO₂

A near-field powermeter that directly quantifies light absorption and heat transfer in single nanowires is demonstrated. The mechanism is based on the metal-insulator transition in single-crystal VO₂ microbeams, where the domain wall exhibits distinct optical contrast between the two phases. The powermeter is contactless and optically readable, allowing quick determination of optical absorbance, thermal conductivity, and contact thermal resistance of single nanostructures.