Theory of thermal radiation from a nanoparticle array

Thermal radiation has diffusive and broad emission characteristics. Controlling emission spectrum and direction is essential for various applications. Nanoparticle arrays, supporting collective lattice resonances, can be employed for controlling optical properties. However, thermal emission characteristics remain unexplored due to the lack of a theoretical model. Here, we develop an analytical model to predict thermal radiation from a nanoparticle array using fluctuation–dissipation theorem and lattice Green's functions. Our findings reveal that the periodicity and particle size of the particle array are main parameters to control both emission spectrum and direction. The derived simple expression for thermal emission enables insightful interpretation of physics. This model will lay a foundation for analytical derivation of thermal radiation from metasurfaces. Our study can be useful in engineering infrared thermal sources and radiative cooling applications.