The Research Of Broadband Absorbers Based On Metamaterials

Electromagnetic metamaterial absorber is a sort of artificial periodic unit structure,which has the advantages of flexible design,thin thickness and wide application.In recent years,the research on the absorption characteristics of electromagnetic metamaterials has become a hot topic.The research of metamaterial absorber is mainly carried out from two aspects:one is the research of narrow-band absorber,which is mainly used in sensors and optical switches;Second,the broadband absorber is studied to broaden the absorption band as much as possible,and the absorption characteristics are not affected by the incidence Angle and polarization state.This type of absorber plays an important role in the design of photothermal conversion and stealth devices.Based on the the energy conversion requirements in the thermal photovoltaic system,this paper focus on the design of electromagnetic metamaterials broadband absorber,and the finite time-domain difference method is used for simulation calculation.We designed the electromagnetic metamaterial wideband absorber in the near-infrared and terahertz bands respectively:1.Based on the principle of Propagation Surface Plasmon(PSP)and Localized Surface Plasmon(LSP),an electromagnetic metamaterial absorber is designed in the near-infrared band.In the wavelength range from 924 nm to 2175nm,more than 90%of the incident near-infrared light can be effectively absorbed by our metamaterial absorber The broadband absorption is caused by a combination of LSP resonance at 1601nm and PSP resonance at 948nm.In addition,the effects of polarization angle,incidence angle and structural parameters on the properties of the metamaterial absorber are simulated.2.Based on magnetic resonance principle,an electromagnetic metamaterial absorber in terahertz band is proposed.By combining multiple resonant units of different sizes within a metamaterial structure period,the superposition of different resonance peaks can be realized,which lead to broadening the absorption bandwidth of the metamaterial absorber.In the frequency range from 2.48THz to 3.25THz,the bandwidth with absorption above 90%can reach 770GHz,and the relative bandwidth of the terahertz metamaterial broadband absorber is calculated to reach about 26.9%.Moreover,there are two peaks of the absorption spectrum in the absorption band,the first peak is 2.65THz and the second peak is 3.10THz.According to the simulation results of electromagnetic field distribution and surface current distribution at resonance frequency,the physical mechanism of the designed metamaterial wideband absorber is explained.Meanwhile,the electromagnetic metamaterial samples are processed and the absorption performance of the metamaterial is tested by experiments.