| Artificial metamaterials have attracted much attention from researchers because of their adjustable electromagnetic parameters,and have been widely used in various devices since their inception.Because the mid-infrared covers the atmospheric transparent window,the metamaterial absorber in the mid-infrared band has important research significance in the military field.At present,metamaterial broadband absorbers in the mid-infrared band are widely used in night vision devices,thermal imaging,and electromagnetic stealth.The multilayer structure and metal materials of traditional metamaterial broadband absorbers make the device have a non-negligible thickness and are susceptible to external environmental changes.Therefore,this paper achieves broadband absorption effect by multiband resonance superposition in a single structure,and its covered surface structure also avoids the influence of metal by the external environment,which greatly improves its application potential in complex scenes,which has potential research value for the study of metamaterial absorbers with simple structure,light and thin,and ultra-wideband.This article mainly studies the absorption mechanism of a background insensitive mid infrared ultra-wideband perfect absorber.The application prospect of broadband absorber based on artificial metamaterial is explored,and the status quo and research progress of metamaterial absorber at home and abroad are reviewed;The absorbing principle of metamaterial perfect absorber is studied through impedance matching principle,scattering parameter inversion theory and surface plasma dispersion relation analysis.Then the principles,advantages and disadvantages of two common numerical simulation methods,finite difference time domain method(FDTD)and finite element method(FEM),are studied and analyzed;A perfect metamaterial absorber with silver split-ring resonator and cross-anchor structure is designed.Analyzed its absorption mechanism by electromagnetic field distribution,current vector diagram and equivalent impedance curve.1.A mid infrared ultra-wideband absorber based on a silver split-ring resonator is designed.Broadband absorption is achieved by excitation of surface plasmon resonance on the resonant ring in the mid infrared band.The numerical results indicate that the MPA achieved a minimum absorption rate of over 90% in the range of 14.6um(9.1um～23.7um),a maximum absorption rate of about 100%,and an average absorption rate of 97.4%.And it has good absorption effect within the range of 1-1.6 background refractive index,and the absorption index and equivalent impedance of the arrow type resonant ring structure have been studied and analyzed.This study provides a design approach for mid infrared absorbers applied in complex environmental conditions.2.An ultra-wideband perfect absorber in the mid infrared band that is insensitive to background and polarization independent is designed.The thickness size of the device was limited to 2μm through calculation and simulation optimization Within.The numerical results indicate that the absorption range can reach up to 15μm(9.1μm～24.1μm)The average absorption rate exceeds 95%,and the relative bandwidth is about 90.36%.By analyzing the surface current vector and electromagnetic field distribution of the structure,it was found that the absorption effect comes from the superposition of resonance absorption excited on the cross-anchor structure and material intrinsic absorption.This ultra-wideband absorber with strong applicability and wide application range has great application potential in night vision devices,thermal imaging,infrared remote sensing,molecular detection and other aspects. |
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