Polariton-enhanced emittance of metallic-dielectric multilayer structures for selective thermal emitters

This study proposes a tungsten grating structure with SiO₂-W-SiO₂ multilayer films on a tungsten substrate as a thermal emitter for transverse-magnetic waves in a broad spectral region. The rigorous coupled-wave analysis method is employed to analyze the spectral emittance. Three close-to-unity peaks on the emittance spectrum lift the emittance in the wavelength range from 0.7μm to 2.0μm for the proposed thermal emitter. To quantify the applicability of the proposed emitter, parametric studies are performed regarding the effects of grating geometrical parameters, emission angle, metallic/dielectric layer thicknesses, and mismachining tolerance. The normal emittance of the proposed emitter is shown to be wavelength-selective and direction-insensitive. The mechanisms of excitations of surface plasmon polariton (SPP), gap plasmon polariton (GPP), and magnetic polariton (MP) in the multilayer structure are elucidated to evaluate their contributions on the emittance under different conditions. The results provide a useful reference to design and optimize selective thermal emitters with excellent performance.