| Surface Plasmon Polaritons (SPPs) was a very particular optic characteristic of metal structure within some nanometers, which could limit his transmission only in the near-field while his light intensity was perfect large. This particular characteristic allows photons device to be made in nanometer scale. Surface Plasmon Polaritons was a kind of elapse wave in the near-field; therefore plentiful fine information of metallic structure was taking with it. This allows us to control the transmission of the transmission Surface Plasmon Polaritons by alter the structure of the metal; also, it can be used in microscopy of near-field. Research of nanometer structure basing on Surface Plasmon Polaritons had been one of the fastest developing works, and a new science of SPPs came into being. Along with the developing of nano-science, the Plasmonics contains extensive matter, such as enlarge of surface light electric field,spectrum of enlarged surface light,enlarge of transmitted light,SPPs nanometer wave-guide,enlarge of the optic force,SPPs light catalyze,energy transfer of enlarged surface light,selective absorbing of light, and so on.Surface Plasmon Polaritons has expansive applying foreground in the Photonics,Optoelectronics,Micro-nano photonics,Biomedicine,Informatics, et. Moreover, the entire implement related SPPs were correlative with the transmission and the distributing of the Surface Plasmon Polaritons, so had to discover the transmission,the diffraction and distributing of the SPPs in more detail.This paper introduced two-dimensional metal dispersion finite difference time domain (FDTD)method , using Drude model to write a series of procedures to calculate the different distributing of the light and the transmittance when some of the parameter was varying. By changing the metal silver (Ag) film thickness, the width of the structure of nano-metal, grating period, we give the gray scale of the diffraction and the curve of transmission optical field. The paper discussed the function of the elapse wave and the SPPs in the Ag structure, and detailed analysis were giving to explain how the parameter of nano-slits impressed the diffraction and the transmission of SPPs. Since the SPPs is a new research domain, the aim of this paper lied in finding out some phenomenon of it to lay the ground work for the deeper and systemicer research.The whole paper was divided into five chapters. The content was layed out as follow:The first chapter introduced the research background of the subject briefly; also, an overview of the Surface Plasmon Polaritons at the near-field optical applications was give.In chapter 2, we give the finite difference time domain method (FDTD) and the characteristics of the basic principles discussed in FDTD method, as well as the stability of the numerical solution of time step and space step length relationship, give a finite difference time domain method currently used perfectly matched layer (PML) absorbing boundary conditions. Because of the negative refractive index properties of the metal, we imported a Drude dispersion model, and prepared a Dispersive FDTD program independently.Chapter 3 used the dispersion of the FDTD computational procedures to simulate the transmission through the nano-metal structure. By changing the metal silver (Ag) film thickness, the width of nano-metal structure, and the grating period, we research the transmission characteristics of the SPPs in the nano metallic structure. We tried to research the physics essence how the factors like SPPs lead the enhancing of the transmittance and how much it works on that.In chapter 4, on basis of the Finite-difference time-domain technique, the temporal transmission characteristics through a series of slits are developed. We give the curve of the transmittance when changing the thickness of Ag,the width of the slits and the space between slits, et. And then we analyzed the effect of SPPs to the optic characters in near-field and the transmission of energy.In chapter 5, we give a summary of this paper, and put forward the following work.
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