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

•A thermal emitter with high emittance in a broad spectral region is proposed.•The polariton excitations are elucidated to evaluate their contributions.•The normal emittance is wavelength-selective and direction-insensitive.•The 0th order diffraction is the absolute contributor on the emission peaks.

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 0.7 μm to 2.0 μm 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.