ABSTRACT
At finite temperatures, all materials emit electromagnetic radiation due to the thermally induced motion of particles and quasiparticles. A perfect thermal emitter follows Planck's law of blackbody radiation, which is broadband, incoherent, and isotropic, with a spectral profile and intensity that are dependent on the emissivity of a material, and that vary only with changes in temperature. The electromagnetic spectrum is the range of all possible wavelengths, ranging from gamma ray radiation down to radio wave radiation. All objects that are warmer than their surroundings emit photons within a certain range of wavelengths. The basic method to achieve narrowband absorptivity (emissivity) is the direct use of rare earth oxides, which inherently cause strong absorption at fixed wavelengths. However, the arbitrary control of an emission wavelength or an emission bandwidth is limited to the properties of chosen materials that determine the magnitude of interaction between light and materials.
