Analysis of near field radiation among lithography-free metal-dielectric-metal perfect absorbers with a combined numerical method

Abstract

An integrated analysis is developed to determine the far-field and near-field radiation of lithography-free metal-dielectric-metal (MIM) structures. Directional spectral emissivity determined with the integrated analysis shows good agreement with the directional spectral absorptivity from verified full wave simulation. With the integrated analysis, we identified that the condition of Fabry–Perot resonance used to design broadband wide-angle perfect light absorbers/emitters with MIM structures could trigger the waveguide modes of the dielectric layer. The waveguide modes can amplify the thermal electric field for photon tunneling between two MIM structures across a 100 nm level gap. Adding an additional pair of waveguides that can amplify evanescent waves in the gap formed with two MIM structures can further enhance the strength of photon tunneling. The enhanced photon tunneling shows high-intensity quasi-monochromatic near-field radiation in TM mode across a 100 nm gap at specific wavelengths. We expect even stronger photon tunneling for high-intensity quasi-monochromatic near field radiation across a more significant gap can occur when the MIM structure made with lower loss metal is combined with structures providing stronger amplification of evanescent wave.