Thermal emission from finite photonic crystals

We present a microscopic theory of thermal emission from finite-sized photonic crystals and show that the directional spectral emissivity and related quantities can be evaluated via standard bandstructure computations without any approximation. We then identify the physical mechanisms through which interfaces modify the potentially super-Planckian radiation flow inside infinite photonic crystals, such that thermal emission from finite-sized samples is consistent with the fundamental limits set by Planck’s law. As an application, we further demonstrate that a judicious choice of a photonic crystal’s surface termination facilitates considerable control over both the spectral and angular thermal emission properties.