Coupling Effects Of Light And Surface Plasmons In Metal Microstructures And Its Manipulation

Since the concept of surface plasmons was proposed, owning to its unique optical property and great potential for application, surface plasmons were extensively studied by many scientists. Recently, with the development of micro- and nano-fabrication technologies and theoretical study, we are witnessing a dramatic growth in both the number and scope of plasmonic applications. Plasmonics has become one of the frontier of physics. Surface plamons plays an important role in many phenomena, including extraordinary optical transmission(EOT), localized field enhancement, negative refraction, super resolution, magnetic resonances, slow light, nano-laser, et al. plasmonics have a broad application prospect in data store, metal waveguide, subwavelength imaging, solar battery bio-sensor and negative refraction materials.Extraordinary optical transmission was first reported by T. W. Ebbesen in 1998, it showed that orders of magnitude more light than Bethe’s prediction could be transmitted through the holes., This has since stimulated much fundamental research and promoted subwavelength apertures as a core element of new optical devices. Now it is generally accepted that the enhanced transmission is origin from Arrayed structure provides extra momentum for converting incident light to SPs. Surface-wave-activated holes in metal films are finding many potential applications in wavelength filtering, surface plasmon source, subwavelength focusing, surface plasmon enhancing nonlinear effects. This thesis focuses on fabrication, characterization and potential application of subwavelength hole array on metal film.Firstly, we have studied both experimentally and theoretically the transmission of light through a thin silver film with an isolated subwavelength hole, the hole chain and the hole array with different geometries, respectively. It is shown that that when the light illuminates an isolated subwavelength hole, localized surface plasmons (LSPs) are excited and contribute to transmission of the hole; while the light illuminates the hole chain and array, both LSPs and propagating surface plasmons (PSPs) are excited, and their contributions to the transmission of holes strongly depend on the geometry of the hole chain and array, and also on the polarization of incident light.Secondly, we demonstrate that electromagnetic waves passing through the subwavelength apertures on a silver film interfere with each other in the airgap behind the apertures. Depending on the width of the airgap, either constructive or destructive interference occurs. It is shown that constructive interference enhances the extraordinary optical transmission and evidently improves the quality factor, whereas destructive interference weakens the extraordinary optical transmission.Thirdly, by introduce a period grooves to the metal surface, the band structure of surface plasmon was changed, we the combination of sub-wavelength hole arrays and grooves can be used to inhibiting particular peak in transmission spectrum. These numerical calculations have been verified partly by experiments, and further experimental work is continuing. The result broadens our knowledge about the behavior of SPP on periodic surface microstructure, and it may provide ideas to design novel adjustable optical filter. Fourthly, we study the fluorescence enhancement effect in sub-wavelength metal hole array. It is found the strong filed concentration effect in the metal microstructure can help speed up the transition rate of the electron of dye molecule. And it was also observed the shape of the emission spectra is chaned when the dye was put on the surface of structured metal film. To sum up, we have studied the coupling effects of light and surface plasmons in metal microstructures and its manipulation. The findings provide scientific basics for developing new electromagnetic materials as well as opening new perspective in manipulating the electromagnetic waves.