Design And Investigation Of Nano Optical Waveguide And Cavity

With the development of nano fabrication technology and integrated optical industry,it has been a significant research interests to control and manipulate light at nano scale.It is a hot topic in the international forefront of research to exploit smaller and better nano optical devices.Due to the unique charateristics,surface plasmon polaritons have attracted many reasearchers.In recent years,various nano optical elements based on surface plasmon polariton emerge endlessly.In this thesis,we design an ultrasmall surface plasmon polariton nanocavity,a hybrid dual wedge plasmonic waveguide,a wedge-like plasmonic waveguide,and all-dielectric waveguides with subwavelength mode confiment.We study the optical properties of these nano optical devices mentioned above using finite difference time domain method,finite element method,and discrete dipole approximation method.The main research works are summarized as follows:1.Writing the Matlab codes to calculate the propagation and scattering of electromagnetic field in multilayer media.We calculate the propagation and scattering of electromagnetic field in a three-layer medium using this Matlab program and overcome the problem of divergency when metal touches the perfect matched layer boundary.2.Based on the knowledge of surface plasmon polariton's properties,we design an ultrasmall surface plamon polarion nanocavity,study its optical properties by FDTD,DDA and FEM,calculate the Purcell factor,quality factor and mode volume,analyze the resonant modes of the surface plasmon poalriton nanocavity,investigate the influence of the optical constant of nanocavity material on the optical properties of the nanocatity,and research the effect when the silica substrate is included.3.On the sufficient knowledge of the state-of-the-art of all kinds of micro-nano optical waveguides,we design a hybrid dual wedge plasmonic waveguide,a wedge-like plasmonic waveguide,an all-dielectric nanowire waveguide,and an all-dielectric bowtie waveguide,research the optical properties of these waveguides by finite element method.Highlights of the dissertation are as follows:1.We design an ultrasmall surface plasmon polariton nanocavity.Compared with the ultrasmall plasmonic nanodisk resonators,the ultrasmall surface plasmon polariton nanocavity can achieve a smaller mode volume,a higher quality factor,and a larger Purcell factor.This is beneficial to the research on the enhancement of spontaneous emission.2.We design a hybrid dual wedge plasmonic waveguide.The hybrid dual wedge plasmonic waveguide can acquire both low-loss propagation and ultra-deep subwavelength mode confinement.Moreover,the hybrid dual wedge plasmonic waveguide has good tolerance to the practical fabrication errors.All of these will make the hybrid dual wedge plasmonic waveguide have various applications in high integrated optical circuits,optical trapping and nanolasers.3.Based on the orthogonal boundary conditions of Maxwell's equations,we design all-dielectric waveguides.The all-dielectric waveguides simultaneously realizes subwavelength mode confinement in two dimensions and theoretically lossless propagation,overcomes the obstacles of high attenuation of plasmonic waveguides and poor mode confinement of traditional dielectric waveguides.The all-dielectric waveguides pave a way for the design of nano optical devices in the furture.