Mode Analysis And Transmission Line Theory In Deep Subwavelength Metal-dielectric Composite Waveguides

All-optical signal processing system requires advanced nano-photonics devices.Signal processing technique based on new electromagnetic medium and metamaterialshave been applied to the area of renewable energy resources and environmentalmonitoring. As a kind of special electromagnetic wave propagating along the interfaceof metal-dielectric (MD) interface, surface plasmons link the localied and propagatingoptical fields, therefore play an important role in deep subwavelength waveguides.New artifical electromagnetic medium composited by periodical arrangment ofmetal and dielectric materials in the wavelength scale with extraordinary opticalproperties can be widely used in all-optical communication and integrated optics.Meanwhile, the deep subwavelength waveguide structures of noble metal and dielectricmaterials play important role in optical communication and sensor technologies.This thesis analyzes the dispersion and effective refractive index of MD and MDMthree-layer waveguides with analytical and finite-difference time-domain (FDTD)method.. It is found that both symmetric and anti-symmetric modes or plasmonic modeand photonic mode exist in the MDM waveguide. There are only plasmonic modes forthe symmetric mode in the deep subwavelength range. MDM waveguide supportingsymmetric photonic mode does not belong to deep subwavelength range. Theanti-symmetric mode changes from plasmonic mode to be a photonic mode as thedielectric layer thickness increases. Then, we identify the cut-off conditions and criticalconditions of the four possible modes, and get the phase diagrams for the modes in thespace of different waveguide parameters and optical frequency.Then, we analyze the effective impedance of the MDM waveguide in the PECapproximation and compare it to the Yablonovitch effective circuit model. We present ageneral expression according to the field distribution. The different effective impedancemethod, and the numerical results get by FEM method prove that the theoretical resultsare more exact. The transmission line theory is then used to analysis the MDMtransmission properties. The transmittance are calculated with the this method andcompare faborabley with those obtained by FDTD and FEM simulations.The mode diagram and the transmission line theory in this dissertation may providean important guidiance in the design of the deep subwavelength MDM waveguidedevices, and are significant basises in the design and optimization of the next generationall-optical integrated system.