Measurement of near-field thermal radiation of silica grating

This study explores the radiative heat transfer (RHT) between a silica microsphere and a grating, focusing on the nanoscale heat transfer enhancement enabled by engineered nanostructures. The near-field thermal radiation is measured using a custom-fabricated micro-thermocouple with nanometer-scale spatial resolution. The key results reveal the substantial RHT enhancement at subwavelength gaps (<100 nm), driven by surface phonon polariton excitation in the structured silica medium. Theoretical analysis shows that while the effective medium theory qualitatively captures the fundamental coupling mechanisms, it systematically overestimates the heat flux in the deep near-field regime (<50 nm)—highlighting the limitations of homogenization approaches in resolving the nanoscale structural effects. This work underscores the critical roles of nanostructure geometry and material phonon dispersion in regulating the near-field heat flux, providing critical insights for establishing the design principles for next-generation thermal management devices based on phonon-polariton materials.