Investigation on the tunable spectral characteristics of a nanofacet-sandwiched structure

Spectral radiative characteristics of the nanofacet-sandwiched structure can be effectively tailored by tuning the geometric parameters. The finite-difference time-domain (FDTD) method for electromagnetics is employed to numerically predict the spectral transmittance and absorptance of a sandwiched structure with the nanofacets periodically distributed. Compared with the basic case (a classical three-layer planar configuration), changing the pertinent parameters can transform the radiative behavior from transmittance enhancement to absorptance enhancement. The effects of the width and thickness of the nanofacet, the gap between facets and the facet material are discussed respectively. The results indicate that at small facet thickness and width with large gap, the radiative characteristics exhibit a transmittance-enhancement mode (average transmittance of 0.83), and on the contrary, the absorptance-enhancement mode is achieved (peak absorptance of 0.97). The facet thickness, facet width and the gap between facets donate significant influences on the overall transmittance and absorptance, while the matrix thickness has little effect. Besides, the transmittance-enhancement mode is mainly dominated by the structural parameters, almost independent of the facet material. Whereas, the spectral absorptance presents different extra peaks while changing the facet material.