A Research Of Tunable Metamaterial Absorber Based On Graphene

Metamaterials are a kind of artificial electromagnetic materials with extraordinary physical properties.The common metamaterials are usually composed of subwavelength metal unit structures,which arrange and combine periodically.They have unique physical properties that natural materials do not have,such as perfect absorption,negative refractive index and optical stealth.The appearance of metamaterials improves the performance of traditional devices.This paper mainly researches the absorbers based on metamaterials.Compared with the traditional absorbers,the metamaterial absorbers have the advantages of strong absorption,light and thin.However,the size of the structure is fixed,it can only work at the certain frequency as the structure is shaped.If it needs to achieve high absorption in other frequency bands,the structure should be designed and made again,which increases the production cost and consumes many resources.In recent years,the tunable work frequency of the metamaterial absorber is a new research direction.With definite structure of the absorber,we use some materials with tunable dielectric properties to tune the absorption peak position.In this paper,we mainly add graphene into the structure,the resonance frequencies are tuned through tuning the surface conductivity of graphene.Based on the above analysis,several kinds of metamaterial absorbers are designed in this paper.The absorbing characteristic and resonance principle are analyzed in detail.The main research contents are as follows:1.A tunable single band metamaterial absorber based on graphene is proposed.The combination of the metamaterial absorber and the two-dimensional material graphene realizes the dynamic movement of the absorption peak.The gate voltage is applied to control the Fermi energy level of graphene.A perfect absorption peak with an absorption rate higher than 99% was observed at the resonance wavelength.The absorption mechanism of the structure and the influence of relevant parameters on its performance were explored.2.For the above single band metamaterial absorber,if the size of the upper resonance unit is different,the value of the resonance wavelength will also be different.Based on this,an independent tunable dual-band metamaterial absorber based on graphene is proposed.The dual-band absorption is realized by using the bimetal resonance structure in the unit,the graphene strips are placed under the different metallic resonance structures by the interdigital arrangement,so two bands can be tuned independently.At the wavelength of 6.94 μm and 10.68 μm,two absorption bands with peaks higher than 99% were formed.The absorption peaks at 6.94 μm and 10.68 μm shifted by 1.8909% and 4.4019%,respectively.The blue shift at the long wavelength is more obvious.The phenomenon was analyzed by the calculation formula of graphene and the electric field distribution on the surface of metamaterials.When the incident angle of electromagnetic wave increases to 70°,the absorption rate is still greater than 90%,which shows that the proposed dual-band absorber has excellent wide-angle characteristics.3.The resonance absorption peaks of the metamaterial absorber mainly come from the upper metal resonance units,so the multi frequency or wide frequency absorber can be designed by increasing the number of resonance units.According to this method,a tunable triple-band absorber based on graphene is proposed.The peaks of the three absorption bands are 0.998,0.962 and 0.945,respectively.On the basis of the triple-band absorber,tunable broadband absorber was achieved by simple deformation.A wider frequency band is obtained by continuous absorption peak coupling.Compared with the single band absorbers mentioned above,the Half height and width of the absorption curve here increases by about 1.5 μm.4.A single band metamaterial absorber based on split ring resonator(SRR)loading medium is researched.A peak value of 0.999 was observed at the resonance wavelength.The influence of the parameters on the absorption curve was researched.Double SRRs loading media with different sizes are nested in the center,so a dual-band metamaterial absorber is obtained.The resonance wavelengths are 17.3 μm and 22.4 μm,the peaks are 0.985 and 0.988.The absorption peaks are shifted by changing the opening medium of the inner and outer structure.The frequency shift range of two absorption peaks is 0.15 μm and 2.41 μm,respectively.The obvious difference of the frequency shift range was analyzed by the theory of equivalent circuit model.The variation of the absorber’s characteristics with the opening position of the outer ring and the relative rotation angle of the inner ring were researched.The results are valuable for the development and application of SRR structure metamaterial absorber.