Multilayer Rectangular Broadband Metamaterial Absorber

A multilayer rectangular absorber with wide band and high absorption rate is designed based on multilayer waveguide structure and hybrid coupling theory. The absorber unit is composed of a rectangular slot antenna and a multi-layer metal-dielectric-metal rectangular structure. We use finite-difference time-domain method to analyze the absorption characteristics of the multilayer rectangular absorber under the conditions of wide band, different polarization states and large angle oblique incidence. Numerical results reveal that the absorption band of the absorber is 400-1400 nm, and its average absorption rate can reach 95%, showing a certain polarization insensitivity, and it can still maintain an average absorbance of 93% at 60 degrees oblique incidence. By monitoring the electromagnetic field distribution at the resonance frequency point, we find that the high-absorption characteristics of the absorber in a broadband which is mainly caused by Fabry-Perot resonance, slow-wave effects, local surface plasmon resonance, and the hybrid coupling among them. The proposed metamaterial absorber is expected to play a role in invisible devices, solar cells and other fields owing to its wide bandwidth, high absorption, insensitivity to polarization and oblique incidence angle.