Thermal radiation in asymmetrically driven coupled non-linear photonic cavities

We study thermal radiation from a system of two coupled photonic cavities including the nonlinear Kerr effect, using numerical simulations and analytical methods. The general system, which can be implemented as two cavities in a waveguide, is asymmetrically driven with a monochromatic pumping from a single side. We describe the eigenmodes in the linear and nonlinear regime as well as the transmission of the coupled system. These results are then employed to understand the thermal radiation exhibited from both sides as each part of the system is coupled to a bath at a different temperature. Interestingly, the radiation spectrum is complicated, and can present up to four peaks due to the rich nonlinear coupling features. Furthermore, in certain regimes these spectra can drastically change upon variation of the bath temperatures. In addition, interference between the emitted and reflected radiation can lead to dips in the thermal radiation. Moreover, the system can exhibit self-pulsing, leading to comblike spectra for thermal radiation with peaks of very large amplitude. Our proposed analytical model for thermal radiation in the stable regime fits very well with the numerical results and describes a general class of devices.