Study On Mid-infrared Absorber Based On Periodic Structure

Electromagnetic metamaterials are made from assemblies of multiple artificial subwavelength structure units.It is possible to engineer unit cells into the material that have the effect of tailoring its properties to suit specific needs.Compared with traditional electromagnetic wave absorbers,the permittivity and permeability of the metamaterial absorber could be modified by adjusting arrangement and size of the unit,realizing perfect polarization insensitive wide-angle and wide band absorption.It has the advantages of flimsy,easy fabrication and easy to mount.Electromagnetic wave absorbers is widely applied in sensing,stealth technology,imaging and other fields.The absorption bandwidth of current single frequency perfect absorber based on electromagnetic metamaterial is quite narrow.We design an one-dimensional three-layer structure periodic broadband absorber based on magnetic resonance principle.It is shown that absorption rate over 80%from 8μm to14.5μm could be achieved with characteristic of incidence angle independent.This absorber can absorb mid-infrared light with longer wavelength by small unit.The structure parameters are analysized by parallel LC equivalent circuit model.Besides,based on the above results,we design a kind of two-dimensional periodic polarization insensitive absorber,with absorption rate exceeding 70%from 8μm to 11.5μm.Polarization insensitive absorber is generally realized by two dimensional periodic structure which is quite complicated and production difficulties.We presents an one-dimensional periodic single frequency polarization insensitive absorber based on magnetic resonance and guided mode resonance.The proposed structure realized the perfect absorption at with the characteristic of polarization insensitive absorption.In addition,two kinds of polarization insensitive dual-band absorber are proposed.One is designed by vertically stacking multilayer structures based on the different metal-dielectric-metal;another is designed by laterally arranging various sized subunits into one unit cell.The electromagnetic field distribution of the resonant wave strengths indicates that the magnetic resonance and guided mode resonance act on absorption independently.One-dimensional periodic single frequency polarization insensitive absorber has the advantages of easy fabrication,low cost and flexibility,and has great application value.