Transition Layer Effect on Thermal Radiative Near Field Mode Emission

A spectrally selective thermally emitting device is proposed which takes advantage of near-field surface phonon polariton modes. Surface phonon polariton modes are usually restricted to the emitter surface and do not participate in energy exchange. In this work, the possibility of obtaining desirable spectral properties by using a thin-film surface active material, layered between dielectrics, is explored. This same multilayered structure is proposed to couple the surface modes into radiative modes that can participate in energy transport. This multilayer device is studied in this paper by developing the surface phonon mode dispersion relation to identify the spectral location of the surface modes. The fluctuation-dissipation theorem and impedance boundary condition is used to theoretically describe the near-field spectral radiative properties of the multilayer geometry. The near-field radiative properties show near monochromatic spectral characteristics due to the domination of surface phonon polariton modes.