2 research outputs found
Generalization of Kirchhoff's Law of Thermal Radiation: The Inherent Relations Between Quantum Efficiency and Emissivity
Planck's law of thermal radiation depends on the temperature, , and the
emissivity, , of a body, where emissivity is the coupling of heat to
radiation that depends on both phonon-electron nonradiative interactions and
electron-photon radiative interactions. Another property of a body is
absorptivity, , which only depends on the electron-photon radiative
interactions. At thermodynamic equilibrium, nonradiative interactions are
balanced, resulting in Kirchhoff's law of thermal radiation that equals these
two properties, i.e., . For non-equilibrium, quantum
efficiency () describes the statistics of photon emission, which like
emissivity depends on both radiative and nonradiative interactions. Past
generalized Planck's equation extends Kirchhoff's law out of equilibrium by
scaling the emissivity with the pump-dependent chemical-potential ,
obscuring the relations between the body properties. Here we theoretically and
experimentally demonstrate a prime equation relating these properties in the
form of , which is in agreement with a recent
universal modal radiation law for all thermal emitters. At equilibrium, these
relations are reduced to Kirchhoff's law. Our work lays out the fundamental
evolution of non-thermal emission with temperature, which is critical for the
development of lighting and energy devices.Comment: 14 pages, 16 figures. arXiv admin note: substantial text overlap with
arXiv:2104.1013