Near-field thermal radiation between two closely spaced glass plates exceeding Planck’s blackbody radiation law

TLDR

The study experimentally investigates radiative heat transfer between two parallel glass plates. Micron‑scale gaps were created using polystyrene spacers between optical flats, and measurements were performed in high vacuum to isolate radiative heat transfer. Measured heat flux across micron gaps surpassed the far‑field Planck limit and matched theoretical predictions.

Abstract

This work reports experimental studies on radiative heat flux between two parallel glass surfaces. Small polystyrene particles are used as spacers to maintain a micron-sized gap between two optical flats. By carefully choosing the number of particles and performing the measurement in a high-vacuum environment, the experiment is designed to ensure that the radiative heat flux is the dominant mode of heat transfer. The experimental results clearly demonstrate that the radiative heat flux across micron-sized gaps can exceed the far-field upper limit given by Planck’s law of blackbody radiation. The measured radiative heat flux shows reasonable agreement with theoretical predictions.