Research On Spectral Properties And Applications Based On Graphene-Metamaterials

Metamaterials are of significance for modern highly integrated nanophotonic devices,manipulating the perfect absorption and selective transmission of light fields at the sub-wavelength scale.However,once we fabricated an optical device based on that,we need to refabricate a new one if we want to change the operating frequency or intensity subsequently.This issue has hindered the development of metamaterials applications.A viable action to this problem has been provided by the finding of excellent photovoltaic properties of graphene,a two-dimensional material,such as high electrical conductivity and dynamical tunability of the Fermi level via applied bias voltage or chemical doping.In this paper,we combine graphene with metamaterials,numerically simulate the proposed structure with the Finite Difference Time Domain method,analyze the spectral properties,and discuss potential application directions related to the spectral properties exhibited by different parameters.The specific studies are as follows:Firstly,we proposed a composite structure of dual size silicon strip-graphene-silica dielectric layer-silver substrate.The proposed simple structure achieved multi-narrowband perfect absorption in the near-infrared region,with average absorption efficiencies above 99%,the full width at half maximum not exceeding 1.5 nm,and the quality factor reached an order of magnitude of 10~3,which is an order of magnitude improvement over previous studies,and was expected to be applied in high sensitivity fields.The resonant cavity formed by the silicon strips is highly localized for plasma fields in the finite space,strengthening the graphene field coupling,exciting graphene plasmons that are difficult to be excited in the near infrared region,and enhancing the optical absorption of graphene sheet.Moreover,the tuning of the Fermi level of graphene enabled the manipulation of the spectral intensity,which is a promising property for potential applications in optical modulators.Secondly,we have designed an all-dielectric metamaterials structure coupling graphene with dielectric silicon and silica.The asymmetrical structure has successfully produced four extremely narrow resonances at 1100-1400 nm with modulation depth nearly 100%and further discussing the main contributing modes in the multipole electromagnetic excitation in each Fano resonance using multipole decomposition in Cartesian coordinates.The adjustment of geometrical parameters had an influence on the transmission spectrum of the structure,i.e.,transmission intensity,resonance wavelength,transmission bandwidth.When the Fermi level of graphene was tuned from0.5 e V to 1 e V,the modulation depth reaches 95%,which indicated its potential promise as optical switching.Further increasing the Fermi level provided tunability of the operating wavelength while maintaining high transmittance.In addition,the proposed all-dielectric structure was sensitive to ambient media,with a maximum sensitivity of447.5 nm/RIU,and could achieve fast and sensitive responses to samples with different refractive indices,such as liquid,gas and so on,which is widely used in biological and medical fields.