Study On Abnormal Refractive Index And Perfect Absorption Of Periodic Nanostructure

Electromagnetic metamaterial is a kind of material composed of artificial structure composite material which has abnormal properties compared with natural materials.The abnormal properties include negative refractive index,zero refractive index and perfect absorption,which are widely used in fields of cloaking,super-resolution imaging and sensing,and in particular,the electromagnetic metamaterial can be used to solve electromagnetic field fluctuated on the atomic size in such as the infrared,visible and ultraviolet wavelengths.However these features are not easy to realize in high-frequency waveband,and there are a lot of problems.For example,abnormal characteristics of the electromagnetic metamaterial strongly depend on the choice of material and the design of the structure,so there are a lot of defects,including high loss of metal in high-frequency waveband,the narrow bandwidth of double negative resonance mechanism,and abnormal characteristics cannot be tuned based on the structural design.The absorption performance are affected seriously because of a part of electromagnetic metamaterials are sensitive to different polarized light.In order to solve these problems,firstly we used the chiral structure form multi-band negative refractive index and Kagome structure to form dual-band zero refractive index.Then,based on the local field enhancement and extinction phenomenon of surface plasmon resonance structure we get nearly perfect or perfect absorption performance.Finally,we embed graphene in the surface plasmon resonance structure and get the adjustable absorption characteristics through the chemical potential of graphene.To realize electromagnetic metamaterial has certain difficulty because of high losses of double negative mechanism,especially in high-frequency such as infrared and visible.But,permittivity or permeability of chiral structure is negative in realization of negative refractive index,which is able to reduce the loss brought by the resonance.Based on this principle,we present a double conjugate four ”C” type hollow-out resonant-rings chiral periodic nanostructure.With the effect of chirality,the structure can realize multi-band negative index characteristics for the left handed circularly polarized light and right handed circularly polarized light of infrared and visible light respectively.Similar to negative refractive index metamaterial,zero refractive index metamaterial is achieved when permittivity and permeability are zero or one of them is zero.So we present a Kagome periodic nanostructure,and the structure realized dual-band zero refractive index electromagnetic metamaterials which permittivity is zero and permeability is approximate zero under electromagnetic resonance mechanism in visible and ultraviolet wavelengths.Two perfect electromagnetic metamaterial structures were designed based on surface plasmon resonance of hybridization and electric dipole resonance.One is the double cross elliptical metal plates periodic nanostructure,and the influence of materials and geometric parameters on absorption performance on different polarized light were studied.The other is a double cross elliptical holes periodic nanostructures of which the second layer surface plasmon resonance of the structure is strengthened by extraordinary optical transmission of the first layer of elliptical hole,so higher absorption performance than that of elliptical metal plates nanostructure was achieved.The abnormal electromagnetic characteristics of electromagnetic metamaterial is usually not adjustable because of strongly rely on material selection and structure design,which greatly limits the application of electromagnetic metamaterial.Studies found that both the layers and positions of graphene in double cross Ag elliptical holes periodic nanostructures absorption performance.First,the absorption performance can be enhanced with the chemical potential of graphene,but there is cut-off value.Second,the absorption performance is very stable with the temperature graphene,except improved slightly in the extremely low temperatures.