The Study Of Highly Sensitive Refractive Index Biosensors Based On Metamaterials

The study on high-sensitivity refractive index biosensors based on metamaterials have been the focus of current research.In this thesis,by studying the regulation of magnetic resonance in metamaterials and the enhancement effect of magnetic resonance in three-dimensional optical metamaterials,we have obtained high-performance biosensors,which can find important applications in the field of unlabeled biomedicine.In this thesis,we firstly introduced the basic properties and characteristics of surface plasmons and their related applications in biosensors and surface plasmon lasers.Then through further exploration in this field,the basic knowledge of metamaterials and the characteristics and related applications of magnetic surface plasmons were introduced.Finally,we have designed two novel biosensors based on metamaterials.The content of this thesis mainly includes the following two aspects:1.We have designed the metamaterials that can support the strong magnetic plasmon resonance.The metamaterials consist of a periodic array of two closely aligned metal nanodisk pairs placed on a metal substrate.In essence,the strong magnetic resonance in our designed metamaterials arised from a kind of antisymmetric resonance mode,which is formed by the near field plasmon hybridization of the silver nanodisk pairs.When this strong magnetic resonance is excited,the metamaterials can simultaneously possess a large magnetic field enhancement,an ultra-narrow spectral line width and nearly perfect light absorption characteristics,which have potential applications in high-performance refractive index sensors.Our theoretical research shows that this metamaterials have very high sensing sensitivity?S=991 nm/RIU,S*=47/RIU?and figure of merit?FOM=124,FOM*=17702?.Therefore,they have important application prospects in the field of unlabeled biosensors.In addition,the metamaterials can also support huge magnetic field enhancement,and has potential applications in magnetic nonlinearity and spontaneous emission of magnetic dipoles.2.We innovatively introduced the propagated SPPs into three-dimensional?3D?metamaterials to enhance the magnetic fields,and explored their biosensors.Our designed 3D metamaterials consist of a periodic array of vertical U-shaped split-ring resonators?VSRRs?,a Si O₂ spacer,and an Ag substrate.We found that by placing the 3D metamaterials on the silver substrate separated by the silica spacer layer,MP resonance in the silver VSRRs can be strongly coupled with SPPs propagating on the surface of the silver substrate,thus forming a narrow-band hybrid MP mode with great magnetic field enhancement.In addition,we found that for this strong coupling to happen,the magnetic field direction of the SPPs propagating on the silver substrate must be parallel to the direction of the magnetic moment induced in the silver VSRRs.More importantly,because this narrow-band hybrid MP mode is extremely sensitive to the surrounding dielectric environment,the sensing sensitivity and FOM of our designed 3D metamaterials can reach as high as 700nm/RIU and 170 nm,respectively,which are much higher than other plasmonic sensors reported in the literature.These results indicate that our designed 3D metamaterials have potential applications in the field of unlabeled biomedical sensing.