| Surface Plasmon polaritons(SPPs) is Electromagnetic waves constrained to the metal surface by the interaction between photons and free electrons, which can confine the light spread in subwavelength structure , overcome the diffraction limit and greatly reduced the size of photonic devices. SPPs have many prominent features such as near-field aggregation, transmission enhancement, ultra-high resolution imaging and so on. So SPPs is potential in optical waveguide devices, biosensors, super-resolution imaging and other related fields.Firstly, the researching background of SPPs and history of the development of SPPs are reviewed. We introduce FDTD numerical calculation method which is used to analyze SPPs mode field distribution and the basic theory of SPPs.Secondly, the theory of SPPs-excitation in Kretschmann structure is analyzed. According to the reflectivity formula, the effects of the parameters of the dielectric material, metal film thickness and shape of structure to SPPs excitation at different excitation angle is studied, and the impact of these parameters on the excitation wavelength and spectrum bandwidth of SPP excitation is summarized. Then we find the optimal parameters which can make spectrum bandwidth of SPP excitation narrow.Finally, on the base of theory of Kretschmann structure, the process of SPPs excited by triangular metal film is simulated with FDTD method. We found that there are two SPPs excitation mechanism in this excitation structure: near-field SPPs excitation mechanism and the Kretschmann structure SPPs excitation mechanism. A periodic triangular metal film is designed and the SPPs excitation process is analyzed in this structure. In this structure the ability of wavelength selection of Kretschmann Structure is fully used without the impact of the near field of SPPs excitation mechanism. We realized beam splitter in which light of wavelengths of 0.6526 m m, 0.6888 m m and 0.7293 m m can be separated. |
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