Precious Resonance Study Of Noble Metal Nanostructures

Localized plasmon resonances of the metallic nanostruetures have been investigated extensively due to their unusual optical properties. Among them involves a whole lot, such as unidirectional plasmonic coupling?plasmon focus?plasmonic waveguides and interference?surface enhanced Raman scattering (SERS) and so on. Particularly, When incident electromagnetic waves interact with the nanostructures, different plasmon modes of the nanostructures can be excited and the coupling between these modes can produce new modes, optical phase transitions, or plasmonic energy transfer. So these have been investigated extensively, such as Fano resonances, which result from the coupling between the dark modes and the bright modes aroused great interest due to their promising applications in the field of multi-wavelength surface enhanced spectroscopy, photovoltaic devices, light trapping, and biochemical sensing. Therefore, many nanostructures have been designed such as the ring-disk nanocavities? disk-ring plasmonic nanostructures with double symmetry breaking?nanoellipsoid/ring plasmonic cavities.Taking the fact that most of the current researches Fano line shapes can't be effective regulated, and the application of magnetic Fano resonances can't be investigated extensively. We design the novel nanoellipsoid/ring plasmonic cavities and double split-hole disk nanostructure, and systematically investigated their optical property. The thesis is divided into two parts. In part one, the optical property of nanoellipsoid/ring plasmonic cavities, is designed and studied. In part two, the optical property of double split-hole disk, is designed and studied.Part one:the optical property of nanoellipsoid/ring plasmonic cavities.Surface plasmon resonances of an ellipsoid-ring nanostructure with spatial symmetry breaking have been investigated theoretically. In this plasmonic system, the multiple Fano resonances are enhanced and can be tuned effectively by rotating the nanoellipsoid in the cavity of the ring. It is demonstrated that such multiple Fano resonances result from the plasmon coupling between the bright mode of the nanoellipsoid and the dark mode of the nanoring. The dark octupolar and the bright octupolar Fano resonances can be excited by modifying the geometrical parameters of the nanostructure. The asymmetry also allows the generation of strong electric field enhancements in this nanostructure which can be applied in the surface-enhanced spectroscopy.Part two:the optical property of double split-hole disk.The plasmon resonances and magnetic field enhancement in double split-hole disk are investigated by using finite element method. The multipolar modes and the magnetic Fano resonances of the double split-hole disk can be tuned by modifying the structure parameters. The oscillate direction of the closed current in the right and the left split hole can be tuned, achieving the bright and dark magnetic modes of this system. These new emergent phenomena in this nanostructure have potential applications in the propagation of low-loss magnetic plasmons and advanced devices based on magnetic Fano resonances.