Steering Thermal Radiation

Thermal radiation is a physical phenomenon exhibiting dual characteristics of both light and heat. Sunlight, serving as the primary source of energy, emanates as thermal radiation from a high-temperature surface at 5,700 K. It is also responsible for the feeling of warmth experienced when individuals congregate and non-contact measurement of body temperature. Thus, thermal radiation exists everywhere in our daily life. However, in the early 20th century, thermal radiation posed a challenge to physicists. The endeavor to elucidate the spectrum of thermal radiation led to the concept of light as photons, therefore signaling the advent of quantum physics. It is known that thermal radiation uniformly emits, irrespective of its direction and polarization, with the spectrum dictated by Planck’s law. Yet, this commonplace should be modified when thermal radiation encounters the principle of nanophotonics. Herein lies the ability to modulate the intensity of thermal radiation across desired wavelengths, directions, and polarizations. In this article, we will delve into the latest research findings concerning the manipulation of thermal radiation and its promising applications.