| The study of metallic nanostructures has become an important research direction in recent years due to their unique characteristics of localized surface plasmon resonance?LSPR?.Due to the coupling effects of LSPR,a localized enhancement of electric field?E-field?will be formed on or near the surface of the metal nanostructures when light is irradiated at a specific wavelength.At the same time,the light is limited to the subwavelength range,breaking the traditional diffraction limit.In this work,we perform a systematic study of metallic bowtie nanoantenna?BNA?and their varous applications.In particular,the unique triangular structure of BNA can produce effective plasmonic resonance coupling between the tips of the BNA arrays.By adjusting the material,geometric parameters,and dielectric environment of BNA structures,the LSPR characteristics of BNA can be effectively controlled,and a huge enhanced E-field can be generated in the nano-gap area.The strong capability of E-field enhancement makes BNA structure having potential applications in the fields of optical sensor,nano light source,photoelectric device,et al.In addition to the strong E-field enhancement,BNA structure also shows excellent performance compared to other nanostructure designs,such as excellent directivity,tunable broadband spectral response,efficient electro-optical drive and polarization control.Therefore,the intelligently designed plasmonic BNA structure can be widely used in the field of nanophotonics.In this thesis,the LSPR characteristics of metallic BNA array structures and their potential applications in surface enhanced Raman scattering?SERS?and refractive index based biosensors were studied using numerical simulations.The BNA array structures were fabricated by electron beam lithography?EBL?and a multilayer-film deposition system,and used in the study of SERS and perovskite photodetector?PD?in near infrared?NIR?region.The main themes of this thesis paper are as follows:1.Theoretical studies on LSPR characteristics of metal BNA array structures.The theoretical model of metallic BNA array structures with metal-insulator-metal?MIM?configuration was established.The characteristics of LSPR were calculated and analyzed using finite-difference time-domain?FDTD?simulations.By adjusting the geometry parameters of BNA array structure,such as size,height and period,the LSPR was continuously tunable from deep ultraviolet to NIR.At the same time,the relationship between the angle and polarization direction of the incident light and LSPR properties were studied.According to the LSPR properties of the BNA array structures,the application of LSPR in SERS was numerically calculated,and the enhancement factor?EF?related to the localized E-field was determined to be EF=1.33×108,which is due to the hot spot effect realized under a single wavelength.The application of LSPR in refractive index-based biosensor was also numerically calculated,which was shown to be capable of detecting the glycerin pure water mixture with concentration varying from 0%to 40%?Refractive index:from 1.333 to1.368?.The high detection sensitivity of 497 nm/RIU was achieved.2.The SERS study on the composite substrate that is composed of BNA array structures and Ag2S semiconductor quantum dots?QDs?.The BNA array structures based on Au,which had the enhancement effect of localized electromagnetic field in the NIR spectral region,was theoretically designed and experimentally fabricated.The designed BNA array structures has a broadband enhancement spectrum,which can realize the synchronous enhancement of excitation signal and Raman scattering signal in SERS detection.Ag2S semiconductor QDs with excellent infrared characteristics were synthesized by chemical synthesis method,and coated on the surface of BNA array uniformly to prepare BNA/Ag2S composite SERS substrate.Using 4-aminothiophenol?PATP?as probe molecules,the Raman spectrum of BNA/Ag2S/PATP system was measured,collected,and analyzed by Raman spectrometer.It was verified theoretically and experimentally that the synergistic effect of enhancement mechanism of the E-field enhancement and charge transfer of BNA/Ag2S composite substrate could enhance the SERS effect significantly in the NIR spectral region.Simultaneously,the polarization dependence of the BNA/Ag2S composite SERS substrate was studied,which verified the dependence of the SERS signal of the BNA/Ag2S composite substrate on the polarization direction of excitation source both theoretically and experimentally.3.The study on enhanced performance of perovskite photodetector?PD?by metallic BNA array structures in NIR region.The BNA array structure with huge E-field enhancement effect and broadband enhancement spectrum in the NIR spectral region were theoretically designed and experimentally fabricated.The perovskite polycrystalline films((Cs0.06FA0.79MA0.15)Pb(I0.85Br0.15)3)were spin-coated onto the surface of BNA array substrates by a one-step spin-coating method,which prepared the plasmonic functionalized perovskite PD based on BNA arrays substrate?BNA-PD?.The photoelectric performances of the BNA-PD under the laser illumination of 785,633,and 532 nm were measured and analyzed using semiconductor test systems comparing to normal perovskite PD based on Si/SiO2 substrate PD?Si/SiO2-PD?.The enhancement characteristics of BNA array structures to perovskite PD in the NIR spectral region were verified theoretically and experimentally.Comparing to the Si/SiO2-PD,the responsivity of BNA-PD was enhanced by 2962%,with a detectivity?D*?of 1012 and a high external quantum efficiency?EQE?of 188.8%,which were enhanced by30 times.The BNA-PD achieves the comparable photoelectric performance in NIR region with visible spectral region.At the same time,the optical response and stability of the BNA-PD were studied.The BNA-PD realized the highly boosted performance with excellent optical properties and stability from visible light to near-infrared spectrum. 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