Research On The Regulation And Application Of Light Field In Metallic Nanostructures

Surface plasmons(SPs)are collective oscillations of free electrons on surfaces of metal,which can localize the light field on the surface of metallic nanostructures and regulate the light field at the nanoscale,thus having many novel optical properties.It is well known that the characteristics of SPs resonance in metallic nanostructures can be controlled by adjusting their materials,shapes and structural sizes,which has an important application prospect in the nanophotonics.In this thesis,we first briefly introduce the development background,basic principles,optical properties,and cutting-edge applications of SPs.Then,by designing novel metallic nanostructures,a highly sensitive refractive index sensor and an ultra-narrow linewidth enhancement effect in singlelayer graphene were achieved.At the end of the thesis,we innovatively propose two types of SPs based metamaterials.The research of the thesis includes the following two aspects:1.Proposing a new method to enhance the sensing performance of three-dimensional metamaterials using optical microcavities.The metamaterials we designed are mainly composed of metallic vertical split-ring resonator resonators(VSRRs)and Fabry-Pérot optical cavity.We found a hybrid MSPs resonance mode with narrow linewidths due to the strong coupling of the MP resonance in the VSRRs and an optical cavity mode in the Fabry-Pérot cavity.Due to the high sensitivity of the hybrid MSPs resonance mode to changes in the refractive index of the surrounding dielectric environment,the metamaterials have very high sensing sensitivity(S=620 nm/RIU,S *=47.9/RIU)and quality factor(FOM=52.4,FOM *=1088.6),and found important applications in the field of label free biosensors.2.A new method is proposed to utilize the diffraction coupling effect of metallic nanoparticles to achieve ultra-narrow linewidth and high optical absorption efficiency of monolayer graphene.A monolayer graphene is sandwiched between a silica substrate and a periodic array of silver nanodisks covered by a silica superstrate.We found that both broadband and narrowband absorption effects of monolayer graphene can be achieved within the visible light wavelength range.The broadband absorption peak is attributed to the exaction of localized surface plasmons(LSPs)resonance in a single silver nanodisk,and the narrowband absorption peak originates from the diffraction coupling of LSPs resonance in the periodic array of silver nanodisks.By changing the period of the array,the Full Width at Half Maximum(FWHM)of the broadband absorption peak can change from 100 nm to 50 nm.Correspondingly,the FWHM of the narrowband absorption peak is tuned from approximately 6.4 nm to only 0.25 nm,realizing an extremely narrow absorption linewidth.These characteristics have important application prospects in graphene-based optoelectronic devices,such as photodetectors,photovoltaics,light-emitting devices,and filters.