Optical Properties And Optical Manipulation Of Coupled Modes In Micro/Nano-Metallic Structures

The excitation of surface plasmon polaritons (SPP) in metallic nanostructure represents a feasible and practical approach for manipulating the photons at the subwavelength scale. Of particular interesting is the coupling of SPP, which can not only be used to facilitate the spectral tunability and tailor the optical response of the structure, but also offer many exotic optical properties. The optical properties and optical manipulation of coupled modes in micro/nano-metallic structures are studied in this thesis: The roles played by waveguide mode in SPP assisted extraordinary transmission are investigated, within one and two dimensional periodic array; The enhanced optical bistability with coupled modes are studied in the metallic-nonlinear dielectric composite structure; The coupling process between the GPP mode and MP mode, supported by a metallic-dielectric multilayer structure, and the manipulation of dispersion are numerically investigated; The controllable mechanism of plasmonic induced transparency window is investigated in bright-dark-bright plasmon resonators. A plasmonic EIT-like switching is designed.The main research works and conclusions are as following:1. It is clearly demonstrated that the roles played by waveguide mode in SPP assisted extraordinary transmission within one and two dimensional periodic array. Based on the surface impedance boundary condition (SIBC) and mode expansion method, the transmission process of light through subwavelength metallic slit array is investigated analytically. The results show that the wavelength of transmission peak is determined by Fabry-Perot factor related to waveguide mode and the additional phase introduced by the interaction between surface plasmon and other diffractive orders. In a periodic double-hole array, the transmission characteristics of structure and the waveguide property are investigated using FDFD and 3D-FDTD. It is shown that the evanescent waveguide mode enhances the coupling of SPP excited on the different metal and dielectric interface, which contributes to the split of transmission peaks. When the waveguide mode is completely suppressed, the enhanced transmission results from the tunneling effect of SPP and the transmission spectrum exhibits a single peak.2. The influences of 3-rd nonlinear effect on excitation and coupling of SPP are numerically investigated, assisted with the dispersion relation of SPP in the composite metal and nonlinear dielectric structure. In the nonlinear dielectric–metal grating with sinusoidal profile–nonlinear dielectric (ND-M-ND) structure, the transmission spectrum exhibits the asymmetric profile (Fano profile) due to the resonance of long range surface plasmon polariton (LRSPP) and short range surface plasmon polariton (SRSPP). We investigated the influence of nonlinear effect on the transmission profile and the optical bistability, demonstrated the dependence of threshold intensity of bistability on the thickness of metal film. The results show that the structure can achieve better optical bistability effect with nonlinear refractive index change n2Iin ~10-3. In the metal-nonlinear dielectric multilayer structure, the properties of bulk plasmon polariton (BPP) resulting from the coupling of gap plasmon polariton (GPP) and the enhanced optical nonlinearity based the high localization of BPP mode are studied. The results show that a bistability threshold of 6.9MW/cm2 can be obtained with excitation of BPP0 mode, which is much lower than the results based on the large local field enhancement at band edge of metal-dielectric photonic band gap structure[Phys. Rev. Lett. 99,127402 (2007)].3. We study the coupling between two highly localized plasmon modes: gap plasmon polariton (GPP) mode and magnetic polariton (MP) mode, supported by a metallic-dielectric multilayer structure. The coupling behavior and energy splitting of modes is analyzed using polariton model and FDFD method. The results demonstrated that the odd and even order MP modes exhibit the different mode selection during the coupling with GPP mode, due to the opposite field symmetry. These hybrid modes lead to the unique dispersion characteristics and the remarkable spectral-directional absorption property of structure.4. The plasmonic induced transparency phenomenon in a structure consisted of two-bright and one-dark plasmon resonators is investigated. It is found that the transparency window of structure can be adjusted based on the interference effect of dark plasmon mode. We design a plasmonic EIT-like switching using the bright-dark-bright plasmon resonators. The structure has two opposite excitation states, i.e. in phase and out of phase modes, due to the different spatial arrangement of bright plasmon resonators. Under in-phase mode excitation, the constructive interference of dark plasmon mode can be achieved. The amplitudes of transparency window can be strengthened, and reach the maximum at 135 degree polarization. Under out-of phase mode excitation, the transmission dips become deeper due to the destructive interference of dark plasmon mode, and reach the minimum at 45 degree polarization. A structure composed of multiple coupled bright-dark plasmon resonators is designed. Based on the different energy coupling behavior under in or out of phase mode excitation, the field localization behavior in dark plasmon resonators can be controlled by the incident light polarization.Highlights of the dissertation are as following:1. By virtue of the unique optical behavior of coupled modes, the mode coupling behavior and nonlinear optical properties are studied in a nonlinear dielectric-metal film-nonlinear dielectric structure and a metallic-nonlinear dielectric multilayer structure. The optical bistability with low pump threshold and high contrast is achieved.2. The coupling behavior between GPP mode and MP mode , supported by a metallic-dielectric multilayer structure, is numerically investigated. The hybrid modes result in the unique dispersion characteristics and the remarkable spectral-directional absorption property of structure.3. Based on the interference effect of dark plasmon mode, the controllable mechanism of plasmonic induced transparency is proposed and numerically proven. A plasmonic EIT-like switching is designed by using a bright-dark-bright plasmon resonators. The transparency window and field localization in the structure can be efficiently adjusted by incident light polarization.