Study On Novel Device Function And Optical Effect Based On The Surface Plasmon Polaritons

Surface Plasmon Polaritons (SPPs), as an important part of nano-optics, are elec-tromagnetic waves coupled to collective oscillations of electron plasma at the interface between a metal and a dielectric. Large field confinement and enhancement of SPPs endow them the ability to manipulate light in the nano-scale, which have great appli-cations in improving energy utilization and realizing integrated all-optical circuits. As one of the hottest topics in recent years, large amounts of new functional devices and properties based on SPPs have been theoretically proposed or experimentally demon-strated. In this dissertation, we first use the finite difference time domain (FDTD) and the finite element method (FEM) to provide a vivid description of the dispersion rela-tion and the coupling process of SPPs. Then, we make original designs for all-optical switches and field enhancement. Our key works and results are shown as follows:(1) The SPPs dispersion curves lie to the right of the light line of the dielectric. Excitation by light beams is not possible unless special techniques for phase-matching are employed such as evanescent waves or grating. With the help of FEM, we can directly depict the exact processes of lens coupling, grating coupling, dipole coupling and end-fire coupling, which enables us to visualize the conception of SPPs.(2) There are two main drawbacks that limit the practical applications of traditional all-optical devices:large scale and relatively high operational light intensity. We form Bragg gratings by periodically changing the width of the dielectric inside the nano-scaled MIM waveguide. An all-optical bistable switch is constructed by the Bragg grating resonator filled with Kerr medium. The transmission, threshold and bistability loop are studied by FDTD.(3) We present a bistable device consisting of a MIM Bragg grating resonator with a Kerr medium sandwiched between two dielectric slab waveguides. Light could be guided for a long distance in the dielectric waveguide and then be coupled and enhanced in the MIM Bragg resonator. With the help of an air-gap coupler, the coupling efficiency is up to90%. Moreover, a transfer matrix method based on the impedance theory is developed to study the transmission and reflection spectra as well as the bistability loop of such a switch. Our method is fast and accurate, as confirmed by FDTD.(4) Plasmonic Tamm states inside MIM waveguide are proposed. A transfer ma-trix method based on impedance is adopted to study and optimize the states. With participation of the plasmonic Tamm states, fields could be enhanced twice:the first enhancement is due to the coupling between a normal dielectric waveguide and a nano-scaled plasmonic waveguide and the second one is due to the strong localization and field enhancement of Tamm states. As shown in our2D configuration,|E|2could be enhanced by three orders of magnitude.