Research On Propagation Properties Of Two Kinds Of Surface Plasmonic Waveguides

Along with the continual improvement of the level of information in modern society, requiring the communication systems dealing with vast amounts of data at ever increasing speed. Due to the fundamental limitations imposed on the existing electronic technologies, modern signal processing systems have to recur to integrated optics to cope with the increasing challenges. Conventional media integrated optical devices have bottleneck in aspects of the miniaturization and integration due to the existence of the diffraction limit. In recent years, a new idea is found to be beating the diffraction limit. There exist a kind of electromagnetic modes that supported by metal-dielectric interfaces, and its lateral dimension is always shorter than the wavelength, exhibiting thereby subwavelength confinement. So it breaks through the diffraction limit fundamentally. These modes, in which optical fields are coupled to electron oscillations, are usually called surface plasmons (SPs). Now, people begin to investigate the use of SPs to realize subwavelength optical devices, thereinto the surface plasmonic waveguides (SPWs) have been an increase of interest. The SPWs are the foundation to achieve the optical circuit. The design, facture and application have great significance for integrated optical components to miniaturization and highly density.In this dissertation, the concept of surface plasmon, surface plasmon polaritons and surface plasmonic waveguides are expounded firstly and the finite difference frequency domain (FDFD) method is introduced simply. Then we propose two kinds of new SPWs structures, the propagation properties of the waveguides have been studied by using the full vector FDFD.The main contents include as follows:(1) The first kind of SPW with double elliptical metallic nanorods is designed. Then dependence of the distribution of energy flux density, effective index and propagation length of the fundamental mode on the geometrical parameters and working wavelengths are analyzed. Results show that the energy flux density mainly distribute in the middle area which is formed by the two elliptical metallic nanorods and the closer to the arc edge the stronger modal energy flux density. Since the effective index and propagation length can be adjusted by the geometrical and electromagnetic parameters, this kind of surface plasmonic waveguide can be applied to the field of photonic components in the integrated optical circuits and sensors.(2) Another kind of our proposed SPW with three circular air cores is investigated. The dependence of the distribution of energy flux density, effective index, propagation length and mode area of the fundamental mode on the geometrical parameters and working wavelengths are analyzed. Then with the same parameters, we take our SPW with three circular air cores compared with the existing similar waveguides structures. Finally, the possibility to overcome the large propagation loss by using the gain medium as core material is investigated. Results show that the energy flux density distribute mainly in two wedged corners which are formed by three circular air cores, and the closer to the corners the stronger modal energy flux density. And with the same parameters, the proposed SPW in this paper has better propagation properties. When the core material has been changed from air to the gain medium with higher dielectric constant, confinement is expected to increase, and the propagation length can be extended obviously with the help of the gain dielectric medium. These studies will provide some theoretical basis for the future practical application of optical communication and optical devices.