Thermal Radiation Engineering Via Quantum Nonlinear Mixing Of Photons

We show that the nonlinear mixing of thermally generated photons in a resonant system can be used to overcome the fundamental blackbody limit on thermal emission, and to introduce nontrivial statistics $(g^{(2)}\, 6 =2)$ and biphoton intensity correlations at two distinct frequencies in the emission spectrum. These effects can be observed by heating a properly designed photonic system without using any external signal. Our work goes beyond all investigations of thermal radiation phenomena involving materials exhibiting linear response, into the nonlinear regime where fundamental questions related to thermal equilibrium and detailed balance require careful analysis. It motivates new interdisciplinary inquiries combining the fields of nonlinear photonics, quantum optics and thermal science.