The wavelength-selective radiative property is becoming a noticeable requirement in various technological fields. There are many researches that have been focused on the radiative properties of metal periodic microstructure surface. However, the spectral bandwidth of high absorptance is often too narrow if excited by the conventional grating structures. In order to solve this problem, two novel periodic grating structures are proposed in this paper, which can increase the effective bandwidth of high absorption peaks. One of the new periodic grating structures, called dual-groove grating, is constructed by adding a rectangular groove at the bottom of the simple grating's groove through a secondary microscale processing. The other grating structure, which is called complex dual-groove grating, is constructed by superposing a dual-groove grating with a simple grating within one period. Aluminum grating structure is taken as an example to show the advantage of proposed structures on increasing effective bandwidth of high absorption peaks 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 shows that, two close absorption peaks and three connecting absorption peaks are obtained respectively for the two periodic grating structures. The effective bandwidth of high absorption peaks within interested wavelength band is improved obviously by these two microscale grating structures.
