Study About Surface Plasmons Polaritions Through A Metal Slit Surrounded By Sub-wavelength Structures

At present, without the limitation of the conventional optical resolution, near-field optics has been become one of the hot issue researches. Near-field optics studies the optical phenomena within one wavelength near the surface. The light wave in near field contains the radiation field and the evanescent wave. Since the evanescent wave contains the information of the sub-wavelength structure surface, the measurement of subtle information can be obtained by the detection of the evanescent wave. The most significant characteristic of evanescent wave is the electric field decays quickly with the increasing of the propagation distance away from the surface. Therefore, the detection of the evanescent wave should be done in the near-field. An sub-wavelength holes or granule near the surface of the structures can scatter effectively the evanescent wave, and make it propagate into the far field. The surface plasmons polaritions is actually a surface electromagnetic wave which exists in the surface of the dielectric and the metal. It behaves the characteristic of the evanescent wave.In this paper, according to the two-dimensional finite difference time domain (FTDT) method for the perfect metal and metal, we calculate the transmission distribution of the single slit surrounded by the sub-wavelength structure by the Fortran programmer, where TM mode is chosen as incident wave which impinges on the sub-wavelength structure. Changing the shape and the number of the sub-wavelength structure which near the surface of the film, we first analyzed the influence of the sub-wavelength structure on the distribution of transmission field, and then analyzed the influence of the number of the grooves on transmission when a light impinges on the sub-wavelength slit surrounded by surface grooves. Finally, according to the Drude model, we modify the traditional finite difference time domain, and calculate the transmission field suitable for Ag.The whole paper is divided into six chapters.The first chapter introduces the research background of the subject, a brief overview of the surface plasmons polaritions in the near-field optical, as well as the basic theory of high transmission and the development of the status.In chapter 2, we introduce 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. In chapter 3, according to the finite difference time domain (FTDT) method, the calculation programmer for the distribution of electric field when a TM plane irradiate on a sub-wavelength perfect metal slit. Then we discussed the influence of the shape and the number of the sub-wavelength structures near the surface on the distribution of electric field.In chapter 4, we design the calculation programmer for the transmission of the sub-wavelength slit surrounded by grooves in perfect metal film. In the paper, we analyzed the influence of the geometrical parameters of grooves on the input surface on transmission, including the number of the grooves, the width of the grooves and the depth of the grooves etc. we hold the view that the influence of the grooves on transmission because the grooves actually change the storage and re-release of energy at corresponding position, and them collect more energy for transmission.In chapter 5, according to the Drude model, we wok out the finite difference time domain equations suitable for metal. We calculate the distribution of electric field and the transmission when a TM plane wave irradiate on a sub-wavelength Ag slit surrounded by grooves on the input surface.In chapter 6, we give a summary of this paper, and put forward the following work.