Study Of Metallic Nanostructures-based Enhancement Of Localized Surface Plasmon Resonance In Ultra-broadband Electromagnetic Wave And Applications

With development of information technology, people can obtain and make use of more and more information.The traditional information retrieval technology is mainly based on extracting the far-field low frequency signal. On the other hand, the near field signal contains abundant information. Since the near field signal only exists within a wavelength from the surface of the object and decays exponentially. The near field signal acquisition is confronted with many obstacles. With the rapid development of manufacturing technology, nano-devices also gradually become one of the research hotspot. Near-field scanning optical microscope(NSOM), appeared at the end of last century, is a revolution in optics because it is a breakthrough of conventional diffraction limit. Dramatic progress has been made in near-field detection, nanoscale imaging devices, medicine, biology sensing and other fields due to the high resolution of the NSOM.Terahertz radiation(THz) with its unique characteristics occupies an important position in the electromagnetic spectrum. THz wave has many advantages such as rich substance spectral information, high penetration and low energy. In view of the advantages of the THz wave, it is the ideal illumination source for the applications of material detection, medical imaging and biological sensing. However, large amounts of materials present special properties when working in the THz, especially the metal, which leading to the THz gap. It is a real challenge to combine the THz waves with NSOM. We hope to realize the near-field detection with characteristics of low injury, high efficiency and high resolution.This paper mainly focuses on local surface plasmon enhancement of metal nanostructures in ultra-wideband electromagnetic wave. The theory of plasma, physical properties and excitation modes of the surface plasma are introduced in detail. Including the performance contrast between the traditional metal nanostructures, selection of metal probe model, FDTD algorithm simulation of the probe and the influence of various parameters on the work performance have been studied. Our target is that design a metal probe which can lead to local surface plasmon resonance within the ultra-wideband electromagnetic spectrum. Limited by nano manufacturing technology and THz wave source, only the computational numerical simulation of the performance of probes in the spectrum ranging from visible to the THZ wave has been studied. Considering the limit of the THz wave source, this paper proposes plasmonic lenses with concentric elliptical slits in the visible wave in order to explore the application of metallic nanostructures in electromagnetic wave.In conclusion, the metal probe can lead to local surface plasmon resonance in the ultra-wide band through the visible light to terahertz. The hot spot is much smaller than that of the diffraction limit. Three main parameters such as the angle of the cone, the height of the probe, the size of pinpoint have been analyzed. The results provide reference for the practical application of new probes. Regarding the application of metallic nanostructures in electromagnetic wave, the plasmonic lenses with concentric elliptical slits can realize good focusing region and ultra-elongated depth of focus. This phenomenon may has potential applications in optical nanoscopy.