FDTD method study on the effects of Geometric parameters on the W- Al2O3 nano-structure thermal emitter.

In this paper, a 2D periodic structure made of tungsten(W) grating patch on a thin Al2O3 spacer and an opaque W film is proposed, as a broadband selective thermal emitter. We numerically investigated the spectral emissivity of the structure from the deep by finite-difference time-domain (FDTD) method. Geometric parameters effects on the emissivity are discussed and the mechanisms of magnetic polaritons in the structure are further analyzed in detail. In addition, by adding another metal-dielectric stack upon the pre-existing grating structure, the emissivity of the composite structure can be further enhanced, and the normal emissivity exceeds 0.95 in the wavelength range of 0.65~1.95 μm, some even close to unity. Furthermore, the composite structures are found to exhibit insensitivity to polar angle and polarization.