Study On Metal-Dielectric Subwavelength Waveguide Structure

Surface Plasmon Polaritions (SPPs) is a kind of wave that propagates along the surface of conductor and a kind of excited state formed by the interactions between free electron and photon. We can use the interactions between SPPs and light field to control the propagation of light actively. The photonic devices are developed by SPPs and have the advantages of miniaturization, high-capacity and high integration etc. The photonic devices also provide new thinking for the development of latest types of photonic devices. The characteristics of novel type of nano metal-dielectric-metal waveguide devices are studied in this thesis which provides a theoretical basis in its practical applications.The main research work includes the following aspects:1. The mechanisms of surface plasma is described in this thesis. It particularly describes that how surface plasmon is stimulated and provides some thinking about the design of novel structure of light. According to metal Drude model, we calculate the Drude parameters of metal Ag corresponding to different bands which can provide the basis of the next numerical stimulations.2. On the basis of SPPs excitation, propagation and coupling rules, we firstly design a novel type of waveguide whose structure is metal-dielectric-metal and single-channel grating, and then stimulate it numerically by FDTD. Secondly, we contrast the result of the stimulation with single straight waveguide under the same external conditions. After doing this, we find that the use of grating to stimulate SPPs is feasible, and the capacity about filtering of single-channel grating waveguide is much better than straight waveguide.3. We demonstrate that grating can stimulate SPPs through the analysis about single-grating waveguide. In order to overcome the shortcoming that the trash rack in a single-channel waveguide will obstruct to propagate a surface plasmon wave, we optimize the single-channel grating waveguide and design a dual-channel grating waveguide with symmetric structure. It can stimulate and select some frequency by up channel. It can also radiate SPPs in the form of photon by down channel. This kind of structure can function as a filtering and its emitted light field intensity is very high. 4. Under different structural parameters, we analyze the relationship between the wavelength and the field intensity of output light and find the relationship between center wavelength and structural parameters corresponding to the maximum output intensity by FDTD. This result provide a reference for the development of new filter based on SPPs.