THz thermal emission from a 1D photonic crystal

Abstract

We are exploring the degree to which one can control the spectral emission of heated photonic crystals (or, more generally, electromagnetic crystal) structures in the THz frequency range. Because THz frequencies are well below the room temperature thermal emission maximum, this configuration may realize a low power but extremely low cost incoherent broadband THz source. Electromagnetic crystals are structures whose periodicity either enhances or reduces the associated photonic density of states over some frequency range. Consequently, they either enhance or reduce its thermal emission over the same frequency range. Thermal radiation from electromagnetic crystals has been studied theoretically and experimentally for higher frequency ranges, but usually for infinite lattices. We have experimentally and theoretically investigated a simple 1D, bi-layered electromagnetic crystal structure composed of air and silicon slabs. We have calculated the emissivity using Kirchhoff's thermal radiation law, as well as by calculating the density of states directly, and have compared successfully those results to the experimental values. Our ultimate goal is to be able to control the spectral emission of an electromagnetic crystal in the THz region (or other wavelength ranges, such as the infrared) by engineering its band structure. Controlled thermal emission, i.e., thermal management, could be used for applications as diverse as solar energy convertors, thermoelectric devices, and integrated circuits.