Surface Plasmon Transmission And Control In Metal-insulator-metal Waveguides

Surface plasmons (SPs) are a special kind of electromagnetic field, which arestrongly confined to the interface of metal and dielectric materials. Recently, plasmonwaveguides have attracted considerable attention due to their ability of allowing forwaveguiding in subwavelength scale. A variety of metallic structures have been pro-posed as waveguides which can be applied to photonic integrated circuits. Among them,metal-insulator-metal (MIM) plasmon waveguides are considered to have unique advan-tages. Compared with other waveguides, it is more compact and easier to be integratedinto optical circuits. On the basis of these reasons, we investigated the transmission char-acteristics of surface plasmons in metal-insulator-metal waveguide and proposed severalplasmonic elements based on metallic waveguide to realize plasmon control in nano-scale.The major achievements made in this thesis are summarized as follows:The enhancement characteristics of the local field in the surface plasmon nanocavi-ties are investigated numerically. The cavity is constructed by placing a defect structure inthe thickness-modulated MIM waveguide Bragg gratings. The characteristic impedancebased transfer matrix method is used to calculate the transmission spectra and the reso-nant wavelength of the cavities with various geometric parameters. The finite-differencetime-domain (FDTD) method is used to obtain the field pattern of the resonant mode andvalidate the results of the transfer matrix method. The calculation and simulation resultsreveal the existence of resonant wavelength shift and intensity variation with geometricparameters, such as the modulation period of the gratings, the length and the width of thedefect structure. Both numerical analysis and theoretical interpretation on these phenom-ena are given in details.Plasmonic re?ectors based on serial stub structure in MIM waveguide are studied.A general theory of periodic stub structure using transmission line model is developed.The transmission characteristics, e.g., periodicity and symmetry of the spectra, are closelyrelated to the ratio of structure period to stub length. Investigation reveals that the trans-mission valleys of the spectra could be divided into two categories, which is quite differentfrom conventional Bragg re?ectors. FDTD method is also used to validate our analysisresults. The concept of antire?ection coating in the theory of multilayer films is introducedto the two-dimensional MIM structures to realize total transmission of optical energy atthe waveguide discontinuities. The antireflection structure consists of a resonant cavitywhich is constructed by changing the insulator width of the waveguide. FDTD method isused to achieve the optimal design directly. A T-splitter with zero re?ection is proposed,utilizing a cavity structure in the input waveguide. A transformer with enhanced transmis-sion between different waveguides is presented for further validating the efficiency andgenerality of these cavity based antire?ection structures. The simulation results show thatsuch a structure can realize a perfect antire?ection function.A compact add-drop coupler with square ring resonator (SRR) in MIM plasmonwaveguide is studied. It is shown that there exist both traveling-wave and standing-waveresonant modes in the resonator due to the in?uence of the four corners in the square ring.Based on SRR, a new type of two-dimensional plasmonic L-shaped bend is proposed.The compact geometry and high add-drop efficiency of the proposed structure enable therealization of flexible flow control at waveguide junctions, e.g. T-splitter and X-crossintersections, in nano scale. The optical field propagation patterns in the gap waveguidejunctions equipped with SRRs are investigated by FDTD method.