Self-sustaining Thermophotonic Circuits.

Significance Photon-based systems that convert heat to electricity have been limited by low power density. Thermophotonic systems have the potential to significantly enhance the power density. This potential has not been realized in practice, due in part to the fundamental thermodynamic difficulty in designing a self-sustaining circuit that enables steady-state power generation. Current construction instead uses batteries which lower system efficiency and adds complexity. We overcome such difficulty by introducing an electronic circuit where multiple photons can be generated from a single electron. Our design enables a self-sustaining thermophotonic circuit that can achieve a steady-state power density exceeding traditional thermophotovoltaic systems by many orders of magnitude. This work highlights possibilities for constructing heat engines with light as the working medium.