Enhaned Spps Effects Based On Multi-Layer Dieletric Films

Surface plasmon polaritons (SPPs) are generated by the interaction between photons and conduction electrons at the metal/dielectric interface. By taking its advantages of high intensity and sub-wavelength size, SPPs show great potential in the photonic components development for miniaturization and integration. Therefore, the physical mechanism and the applications of SPPs have been studied widely.In this paper, we mainly study the focusing characteristics of plasmonic metal-medium multilayer grating. Firstly, the basic principle and the corresponding feature length of SPPs are introduced. Meanwhile, a variety of novel effects produced by SPPs are explained. Secondly, several nano-metal grating structures which can control the focusing beam are listed, and the principle and operation mechanism are analyzed. Finally, by taking the multilayer film theory into account, a metal-medium multilayer grating is proposed in the paper. Through the simulation and analysis, it can be found that metal-medium multilayer grating can largely improve the focus features.The focal length can be varied from~2.6μm to5.82μm by adjusting the dielectric thickness, which demonstrates the performance of our proposed scheme is better than that of the method through changing surface groove distribution. The dielectric material properties have significantly influence on the focal effects, which is mainly caused by matching rules between the metal and medium dielectric constant. It is also found that the focal length increases linearly versus the number of metal-dielectric layers. The maximum depth of focus can reach26.38μm. Compared to the conventional mono-metal grating, the focusing properties of the proposed MDM structure are largely enhanced because of the multiple scattering and coupling of SPPs along the metal-dielectric multilayer films. This scheme may be helpful for designing the subwavelength optical devices, as well as facilitating the manufacturing processes.