The wavelength-selective radiative properties are becoming noticeable requirements in various technological fields. There have been many researches focus on the radiative properties of periodic microstructured surface of metals. However, the spectral bandwidth of high absorptance is often too narrow by applying the conventional grating structures. In order to solve this problem, in this paper we propose two novel periodic grating structures, which can widen the spectral bandwidth of high absorptance. One of the new periodic grating structures, called dual-groove grating, is constructed by adding a rectangular groove at the bottom of the simple binary grating’s groove through a secondary microscale processing. The other novel grating structure, which is called complex dual-groove grating, is constructed by superposing a dual-groove grating and a simple binary grating within one period. Aluminum grating structure is taken as an example to show how the geometric parameters based on the novel structure widen the spectral bandwidth of high absorptance within mid-infrared and far-infrared spectra. The rigorous coupled-wave analysis (RCWA) is used to calculate the absorptance of periodic grating structures. The results show that, two close absorption peaks and three connecting absorption peaks are obtained respectively for the two novel periodic grating structures. These two novel structures may widen the effective spectral bandwidth of high absorptance of the microscale periodic grating structures.

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