Abstract
In this paper, we design a three-part-period grating based on alternating Fe/SiO 2 sandwich structure, which can achieve an ultra-broadband absorption from 750.0 nm to 5351.6 nm. In particular, the absorbing efficiency can reach to more than 95% within 2158.8 nm, which is due to the well impedance matching of Fe with the free space, as well as due to the excitation of localized surface plasmon resonance and surface propagation plasmon resonance in the proposed structure. Furthermore, multiple period gratings are also discussed to broaden the absorption band. These results are very promising for applications in high-performance photovoltaics, nonlinear optics devices and protective equipment for laser weapons.