Differential calorimetric measurement of thermal emission from individual nanostructures

Distinct optical properties of nanostructures have enabled infrared light sources with high spatial and/or spectral coherence and offered IR absorption/emission cross sections well beyond the physical dimensions. Yet, the implementation of such structures for heat dissipation through radiation or enhanced conduction via polaritons is still in the nascent stage. While thermal emissivity could reveal information critical to radiation and light-matter interactions, direct experimental measurements of individual nanostructures' emissivity have long been impeded due to the extremely small signal with respect to the thermal background. In this study, we introduce a platform to quantify the far-field thermal emission from nanoscale samples, which allows for the detection of small signals through differential calorimetry employing a Wheatstone bridge scheme. Experimental validation through measurements of the emissivity of SiO2 nanoflakes demonstrates good agreement with simulation results, highlighting size-dependent emissivity trends and distinct resonant behavior in the Reststrahlen band. This platform provides a route for characterizing small thermal emission signals, which can be used to probe the thermal radiation properties of various nanostructures, thereby aiding in the fundamental understanding of nanostructures' thermal emissivity for the design of novel IR emitters and effective strategies for microdevice thermal management.