Design And Characteristic Analysis Of Polarization Insensitive Metamaterial Absorber In Terahertz Band

Terahertz waves are located in a special position in the electromagnetic spectrum,so they have many unique electromagnetic properties,which have been widely concerned.However,there are very few substances in nature that can respond to terahertz waves,and the production,detection and manipulation of terahertz waves still need to be perfected in theoretical research,and there are some limitations in experimental conditions.The theory of electromagnetic metamaterials and the development of microstructure processing technology provide a new way of studying terahertz waves,because electromagnetic metamaterials that respond to terahertz waves can be designed by artificially selecting suitable materials,using different structures and controlling the physical dimensions of structures.Since then,terahertz devices have developed rapidly in just a few years and have achieved fruitful results.Compared with the traditional absorbers,the metamaterials absorbers has the advantages of good absorption performance,thin thickness and portability,which is widely used in electromagnetic stealth,thermal detector,filtering,imaging and other related fields,becoming one of the research hotspots in academia.This paper focuses on the design of polarization insensitive metamaterials absorbers in terahertz band,and puts forward two kinds of absorbing structures in terahertz band: a broadband polarization insensitive absorber and a dual-frequency polarization insensitive absorber:(1)A terahertz polarizing insensitive broadband absorber with a coupling resonant ring is proposed and designed,first of all,a single-peak polarization insensitive absorber is designed,and the structural unit is stacked vertically.By adjusting the thickness of the medium layer between each layer and the structural parameters of the surface metamaterials layers,the layers are coupled with each other,matching the impedance of free space.Finally,the bandwidth with the absorption rate of more than 90% can reach 1.91 THz,among which the bandwidth with the absorption rate of more than 97% is about 1.65 THz,and the absorption rate of the central resonance frequency point can reach 99.9%,achieving nearly 100% perfect broadband absorption.Because the structure of the broadband absorber has central symmetry,it has the characteristic of polarization insensitive absorption.The simulation results show that the designed wideband absorber still has good absorption characteristics at a certain incidence Angle.By comparing it with the structure with the coupling resonance ring removed,it is verified that the resonance ring can enhance the coupling between layers.(2)A terahertz dual-frequency polarization insensitive absorber based on a typical metal-media-metal sandwich structure is proposed and designed.The numerical simulation shows that it generates two resonance absorption peaks in the terahertz band,with the central resonance frequency of 1.95 THz and 3.20 THz,respectively,and the absorption rate at 1.95 THz reaches 99.9% and that at 3.20 THz reaches 99.4%.The influence of the structure parameters of the dual-frequency wave absorber on the absorption performance is studied,and the polarization insensitive characteristic is verified.The absorption spectrum curves obtained by the simulation at different incident angles also show that the absorption structure has wide angle absorption characteristics,which will play an important role in the practical application.