The Study Of Multi-layer Nanostructures Based On Surface Plasmon Polaritons

Surface plasmons are special electromagnetic wave,appearing on the interface of metal and medium,under certain conditions with light incidence on the metal surface.It propagates along the interface between metal and medium in the horizontal direction and decreases exponentially in the direction perpendicular to the interface.The surface plasmons have local characteristics.Different from general electromagnetic waves,they can generate many new physical phenomena,for example,the transmission enhancement characteristic with light incidence on a metal film with subwavelength periodic array holes.The local enhancement characteristics of surface plasmons can break through the diffraction limits which constrain the development of traditional optical devices,and provide possibilities for the development and integration of more precise optical devices.This is the reason why surface plasmons have attracted much attention.Due to the characteristic,surface plasmons have great application prospects in nano-level photonic devices,data acquisition and storage devices and new nano-materials.This article mainly discusses"the nanosystem composed of gold grating and three waveguides","metal cap/media/metal grating"and"the dielectricSiO₂/plasma/vacuum"three multilayer structure,aiming at delving into surface plasmons on the properties and working mechanism.The studies provide theoretical basis for the application with electromagnetic wave for the three structures.This paper is divided into five parts:In the first chapter,the physical significance of surface plasmons is described,and the basic properties,development and application of surface plasmons are introduced.In the second chapter,the finite-difference time-domain method,which is the research method adopted in this paper,is introduced in detail,including the difference equation of the finite-difference time-domain method,numerical stability condition and error,calculation region setting,type and setting of excitation source and boundary condition,etc.In chapter 3,We investigate the optical properties of nanosystems based on metal gratings and multilayer structures.The results show that when the line width is between 0.75 and 1.5,an ultra-narrow electromagnetic induction transparent peak is obtained in the visible and near-infrared regions,which is formed by the destructive interference between the Fabry-Perot resonance?FPR?and waveguide modes?WGM?.When the grating period P increases,the transparent peak of electromagnetic induction redshifts with the waveguide mode?WGM?.The transparent peak of electromagnetic induction remains the same for different slit widths.The thickness of the fluoropolymer layer determines the coupling between the fabry-perot resonance?FPR?and the waveguide mode?WGM?,which affects the electromagnetic induced transparent line width.As the thickness of the ZnO-SiO₂ layer gradually increases,electromagnetic transparency is repeated emergence due to the presence of more advanced TM modes.With the change of n₁,both the fabry-perot resonance?FPR?and waveguide mode?WGM?have red shift,so the electromagnetic induction transmission peak appears at the longer wavelength.Because the fluoropolymerlayer substrate is far away from the grating,n₃ can only affect the waveguide mode?WGM?,so the red-shifted waveguide mode and the unchanged fabry-perot resonance?FPR?form the Fano lineshape.Both normal and oblique incidence numerical simulation results are consistent with the theoretical calculation results.Our work provides another method for realizing ultra-narrow electromagnetic induction transparencyIn the chapter 4,the physical mechanism of enhanced light transmission is briefly introduced.The enhanced light transmission of metal cap/dielectric ball/metal grating structure is studied.Results show that compared with continuous metal film structure and metal grating structure,the light transmission of the structure has obvious enhancement.The metal grating and metal cap structure inspired localized surface plasmons with different resonant modes,producing fano coupling resonance.Our study reveals different resonance modes of localizd surface plasmons can producee Fano resonance.In the chapter 5,the surface plasmons functions of dielectric SiO₂/plasma/vacuum structures at GHz frequencies are studied.The results show that for the excitation of TM polarization wave,the surface plasmons exist at the interface between plasma and vacuum,under GHz frequency.At this time,even if?<?_p,the plasma thickness is greater than skin depth,the incident wave can still penetrate the plasma layer.However,for TE polarized waves,no surface plasmons are generated.At the same time,the thickness and collision frequency of the plasma layer were studied,and the optimal value ofd?_p is between 0.15-0.55 and the optimal value of?38??_p is between1?10^-3-1?10^-2.Although?,_p is negative,there is no surface plasmons peak.By studying three typical plasma frequencies,it is determined that the generation of surface plasmons is universal to any plasma frequency.