Research On The Regulation And Application Of Localized Magnetic Field Enhancement In Metamaterials

Surface plasmons(SPs)refer to the collective oscillation of free electrons on the metal surface when incident light hits the interface between metal and medium,and its optical properties are closely related to the metal composition material,geometry and surrounding dielectric environment.Due to the characteristics of SPs in nanoscale space and breaking through the light diffraction limit,the research on SPs has attracted widespread attention.With the increasing development of modern micro-nano processing technology,miniaturization,integration and versatility are the future trends in the development of micro-nano photonic devices.The combination of SPs technology and metamaterials can further enhance the interaction between light and matter at the sub-wavelength scale,and will have important application prospects in the fields of bioinformation storage,solar cells,superfraction imaging,negative refractive index materials and biosensing.First,this thesis introduces the principle,excitation mode and related applications of SPs.Then,this thesis introduced the characteristics of metamaterials,the concept of magnetic surface plasmons resonance(MSPR)and the principle of refractive index sensors,the research progress of graphene absorbers based on SPs,and electromagnetic calculation simulation software.Finally,this thesis innovatively investigate the magnetic field enhancement effect and its sensing performance in metamaterials,and explore the application of this magnetic field enhancement in monolayer graphene light absorption enhancement.The main content of this thesis includes the following two aspects:1.We proposed metamaterials composed of a array of Split Ring Resonators(SRRs),a thin dielectric layer and a thick metal film,which has high sensitivity refractive index sensing performance in the near-infrared light band.The study found that when surface plasmon polaritons(SPPs)are introduced into metamaterials,MSPR in metal U-rings are strongly coupled to SPPs,resulting in two ultra-narrow linewidth hybrid MSPR patterns with full width at half maximum as narrow as 2.5 nm.Compared with the MSPR,the magnetic field strength in the metal U-ring not only greatly enhanced,but also produced an inverse crossing phenomenon similar to the rabbinic cleavage in atomic physics.In addition,since this hybrid MSPR mode is extremely sensitive to changes in the refractive index of the surrounding dielectric environment,this metamaterial has a very high sensing sensitivity(S=912 nm/RIU,S* = 95.64/RIU)and figure of merit(FOM=364.8,FOM*=160740.34),which has important application prospects in the field of biomedical sensing.2.We proposed graphene/metamaterials composites structure composed of periodic silver cross particle array,single-layer graphene,silica spacer layer and silver substrate.The study found that at the communication wavelength of 1550 nm,the maximum light absorption of single-layer graphene can reach 77%,and the full width at half maximum can reach 160 nm.Due to the local properties of MSPR,this broadband high absorption of single-layer graphene is not sensitive to the angle of incident light and the polarization of light.When the incidence angle of p-polarized and s-polarized light increases to 60°,its absorption maximum,absorption bandwidth,and resonance position hardly change.By applying an external bias voltage to change the Fermi energy of the graphene,the absorption of a single layer of graphene can be fully modulated to a modulation depth of up to100%.In addition,the absorption of single-layer graphene has a sudden change near the transition between electronic bands,showing electro-optical switching characteristics.This research has potential applications in graphene-based optoelectronic devices such as photodetectors and modulators.