The Characteristics Of Surface Plasmons And Their Functional Devices

Surface plasmon polaritons(SPPs) are electromagnetic modes which are induced by the coupling of the incident wave to collective oscillations of the conductor's electron plasma. These electromagnetic waves propagate at the interface between a conductor and a dielectric, and evanescently decay along the perpendicular direction. Surface plasmon polaritons can offer a new approach to break through the diffraction limit and to manipulate light in nano-scale. In recent years, the research on SPPs has been a surge, and many devices based on SPPs, such as filter, M-Z interferometer, splitter and laser, have been proposed. In this dissertation, a novel hybrid plasmonic waveguide and an active resonator based on SPPs are proposed and investigated. Now we show our key works as follow:(1) First, we introduce the research background, the development and characteristic parameters of SPPs.(2) Second, the dielectric function of the free electron gas is introduced, which is used to describe the optical response of metals. Then we introduce surface plasmon polaritons at a single interface and in multilayer system. The common techniques for SPPs excitation such as prism and grating coupling as well as end-fire coupling are also presented. At last, the chapter closes with a brief look at finite element method(FEM), since the simulation software Comsol which is used in this dissertation is based on FEM.(3) The third contribution of this work is the development of a novel hybrid plasmonic waveguide. The influences of waveguide parameters on the mode area and propagation distance are discussed theoretically by using “COMSOL Multiphysics”software which is based on finite element method. The simulation results show that the proposed waveguide can achieve light confinement in both horizontal and vertical directions. Meanwhile, ultra-long propagation distance which reach to centimeter magnitude can be obtained.(4) Finally, a plasmonic active resonator based on metal/insulator/metal(MIM)heterostructure is proposed. Firstly, we demonstrate that the MIM heterostructure with a side-coupled nanodisk resonator can act as a filter. Then we design a plasmonic active resonator based on two symmetric nanodisk resonators. The resonant wavelength can be tuned by changing the refractive index of the nanodisk resonator. And we find that the resonant wavelength exhibits a red-shift with the increase of refractive index. When these two nanodisks' refractive index are equal, a new resonant cavity, in which the gain material fills, will be formed between these two nanodisks. If the wave with resonant wavelength transmits into the waveguide, it will be restrict into the new cavity, and increases intensity through the gain material.We have demonstrated the losses can be compensated by the gain material, so the structure can be used as an active resonator.