Broad Single-band And Narrow Multi-band Of Metallic Nanostructures Induced By Surface Plasmons

Since the 20 th century, much attention has been focused on the plasmonic nanostructure fields since subwavelength surface plasmon this new science is established. Compared with traditional optical devices, nanostructures not only are suitable for integration, but also can break through the optical diffraction limit since the sizes of these nanostructures are very small. Generally, the nanostructures show fancy potential applications in the solar cells, sensors, filters, and optical couplers.In the thesis, we firstly introduced the definition of surface plasmons and then analyzed the novel optical properties of the nanostructures based on the theory of surface plasmon resonances. Furthermore, three new nanostructures including metal film with a nanohole array, two-layered nanostructures consisting of a metal nanocube array and a nanohole array, and complex nanostructures combined by the metal film with a three-layered metal-dielectric-metal cylinder array were designed and simulated via the finite-difference time-domain method. By combining the related theories of localized surface plasmons and surface plasmon polaritons, based on the transmission/reflection properties, electric field intensity distribution patterns, we studied the novel optical phenomena of these nanostructures and obtained perfect optical transmission properties with a broadband or narrow multiple bands and the relationship of these optical properties with the structural parameters, and further investigated the physical mechanisms of the plasmon resonance modes in these metallic nanostructures.In the second chapter, we theoretically design a new-type metallic nanostructure with nanocubic holes in the metal film. The theoretical results show that a perfect super-width transmission from the ultraviolet to the middle infrared with the transmission value reaching up to 99% is achieved based on the effective medium theory. The perfect super-broadband transparency can be efficiently tailored by varying the size of the holes, the lattice period of the hole array, and the materials filled in the holes. This kind of plasmonic nanostructure presents wide applications in new-type metallic transparent electrodes and solar cells.In the third chapter, we a new double-layer nanostructure consisting of nanocubes and nanoholes arranged into hexagonal arrays is designed and studied. Here, double greatly enhanced optical transmission peaks with narrow bandwidths in the visible and near-infrared regions are achieved via strong plasmon resonance coupling effects of the nanohole and nanocube arrays. The transmission values for these two peaks are larger than 80%. The double spectral enhanced optical transmission behaviors can be efficiently tailored by varying the widths, periods and heights of nanocubes and cubic nanoholes. By combining the electric field energy distribution patterns of corresponding plasmonic resonance modes, we further analyzed their physical mechanisms. The kind of nanostructures with narrow double-bands can be widely used in optical filters and sensors.In the forth chapter, the optical properties of a novel nanostructure composed of a continuous thin silver(Ag) film and a hexagonal array of three-layered silver-silica-silver nanocylinders are studied. Three obvious transmission bands in the visible and near-infrared regions are achieved resulting from the excitation of localized surface plasmons of the nanoparticles and surfaced plasmon polaritions on the underlying continuous Ag film, and their cooperative effects. The optical properties can be efficiently tuned by varying several parameters, such as the width of the outer and inner nanocylinders, the period of the nanoparticle array, the height of the underlying Ag film and the dielectric constants filled in the middle layer between outer and inner nanocylinders. These contribute to the study on the multi-band optical filters and multiplexing sensors.In the fifth chapter, we design and study a novel designed nanostructure consisting of a hexagonal array of aligned vertically three-layered metal-dielectric-metal nanodisk and a silver film. The novel nanostructure exhibits three obvious optical transmission bands due to the excitation of subradiant, superradiant plasmon modes and Fano resonance. The superradiant mode is a dipolar mode symmetrically coupled, shown enhanced and broad band in transmission spectrum. Meanwhile, the subradiant mode, which cannot be directly excited by incident light in the small nanostructures due to the dipole limit, is obtained through an overall reduction of the total dipole moment of the hybridized mode resulting from anti-symmetric coupling of the dipole moments of the Ag nanodisk pairs. Furthermore, symmetry-breaking introduced by changing the size, position of one disk can introduce asymmetric Fano resonance that the superradiant mode, the low energy bonding resonance couples to the higher order subradiant mode. SPPs of the underlying Ag film also play a significant role in the three plasmon modes via coupling with LSPs of nanodisk pairs. As a result, the nanostructure exhibits good tunability of the optical properties by modifying the sizes of each disk layer, the thickness of the underlying metal film and the dielectric constants of the middle layer. Particularly, subradiant mode and Fano resonance show substantial reductions in line width. These results demonstrate the nanostructure with great advantages in optical sensing and plasmonic filters.In the conclusion, the proposed nanostructures with broadband or multi-bandwidth will play a significant role in the optical applications, such as: the solar cell, sensor, filter, and optical coupler.