Research On Lightwave Adjustment Method Of Arrayed Nanotip Metasurface

Metasurface is a kind of functional surface-type lightwave control structure constructed by densely arranging special subwavelength units over the surface,and can be used to regulate incident lightwave parameters including the phase,the amplitude,the polarization,and the power flux.So far,the deviced metasurfaces demonstrate several characters such as the very small thickness,strong lightfield manipulation and other diverse functions,so as to exhibit fine application prospects in the fields of industrial inspection and light wave regulation and imaging detection.As illuminating the metasurface,the surface wave can be excited at the medium interface such as the typical metal-dielectric interface and also the surface charge distribution morphology and density changed dynamically,and further the incident lightwave modulated and transformed.In this dissertation,the lightwave reflection and transmission behaviors are adjusted based on the illumination excitation and directional constraint regulation of the surface waves over the nanotip metasurfaces constructed.In order to improve the lightwave control ability of the nanotip metasurfaces,a new kind of metasurface formed by coupling nanotip with nanopillar has been developed so as to further improve lightwave control efficiency according to the near-field coupling enhancement of multiple surface plasmons.For realizing dynamic regulation,a vertical nanotip metasurface based on Schottky barrier is developed.To exciting and manipulating intensive lightwave,a low-energy magnetic control metasurface is proposed.Based on the current micro-nano-technology,the research involving the modeling,simulation,fabrication,testing and evaluation of the nano-tip metasurfaces,have been carried out,which could provide a theoretical basis for nano-tip metasurface light wave control.The main work of the thesis is as follows:Firstly,both models about the charge aggregation and the surface wave converging aggregation over the nanotips of the metasurface are established.The charge distribution characteristics over the planar nanotip and the propagation behavior of the surface wave over the tip-typed micro-nano-structure are discussed and analyzed.The high capacity containing of the electron at the apex of the nanotip is demonstrated quantitatively.The finite-difference time-domain method is used to simulate and analyze the characteristics of the near-field light field distribution of a typical nanotip.The near-field light signal test and analysis are carried out by scanning near-field optical microscopy measurement.The researches show the effectiveness of the nanotip metasurface in achieving near-field lightwave convergence and enhancement and ultra-diffraction limit focusing.Subsequently,the regulation mechanism of the lightwave transmission and near-field focusing by modulating the metasurface morphology and parameters is carried out.The nanotip-nanopillar-coupled metasurface(NNCM)is designed,and its surface charge distribution characteristics and further the transmission enhancement owing to dipole radiation are analyzed according to the dipole model.By adjusting the structural parameters,the charge distribution over the NNCM(metal-dielectric interface)can be adjusted so as to realize an effective control of the spectral peak wavelength and height of the transmission lightwave.A light modulation film architecture based on the Schottky barrier coupled with the vertical nanotip metasurface is developed.At the interfaces between the gold film and the silicon vertical nanotip and also the aluminum foil and the silicon substrate,a dual-cascade Schottky barrier can be effectively formed.By electrically adjusting the height of the Schottky barrier,the charge distribution density on the surface of the nanotip can be associated controlled,so as to realize the regulation of the infrared transmittance of the metasurface.At present,under the control of an applied voltage of 0～4.4 V,an effective regulation of the infrared transmittance in a range of 21%～48% has been achieved,and the infrared radiation characteristics of the metasurface can also be effectively modulated by the voltage signal applied.Finally,the lightwave adjustment method based on the magnetic nanotip metasurface composed of a silicon substrate and a structured magnetic film for performing lightwave controlling,is carried out.Through the magnetic planar nanotip metasurface,the incident lightwave can be highly confined in an arrayed magnetic nanotips,so as to achieve a near-field lightwave enhancement and focusing and significantly reducing infrared reflectivity.In a wide wavelength range of 3～15 μm,the infrared reflectivity of the developed magnetic nanotip metasurface is as low as about 20%,which already realizes a highly efficient absorption of incident infrared lightwaves.By adjusting the structural morphology and parameters of the magnetic nanotip metasurface,it can be expected that a near-field lightwave confined effect of the magnetic nanotip will play a significant role in regulating the infrared reflection.