Enhancement Of Ultrafast Nanoscale Plasmon Field And Its Coherent Cotrol

The surface plasmon polariton (SPP) in the interface of metal and dielectric can break the diffraction limit of conventional optics, leading to the integration of light and electron on the same chip. This technology can be the foundation of ultra-fast computing generation. Surface plasmon resonance is able to enhance the radiation efficiency of fluorescence molecules and Raman scattering spectrum. Nowadays, the structures which are used to generate local surface plasmon are normally nanostar and bowtie antenna. Many advantages are involved in both of the structures:there are many branched tips in nanostar that could make nanostar supplying more resonance wavelength. For bowtie antenna, higher near-field electric enhancement is in the gap of bowtie antenna and higher fabricating accuracy can be achieved. However there are disadvantages in both of the structures. For bowtie antenna, as less branched tips that cause less resonance wavelength is involved; for nanostar, as the tips branched in three dimensions that cause less fabricating accuracy. We used the nanocross structure to study the near-field coupling. The nanocross owes the advantages of multi-tips and higher fabricating accuracy. While disadvantages are also involved:none core which acts as an electron reservoir in nanostar is owed by the nanocross, so under the condition of asymmetry structure, the coupling between each tips will be stronger.In this thesis, the effects to the extinction cross sections of the different length of arms and the reaction mechanisms between each arms are researched. We study the near-field control characters in different shapes by three-dimensional finite difference time domain method (FDTD) with FDTD solutions (Lumerical Inc. version8.6). The innovative results are as follow:(1) In asymmetry nanocross structure, the length of one arm increases will cause the extinction peak red-shift. The length of arm which direction is perpendicular to the polarization of the source changing will affect the resonance wavelength of the arm which direction is parallel to the polarization of the source, especially for the length of parallel arm and perpendicular arm is nearly the same.(2) The reason of perpendicular arm exciting is the different length of parallel arms and that cause the different resonance wavelength. For one of the parallel arm resonant, the opposite one can not offer enough opposite charges that will induce the perpendicular arm transfer the needed charges to the resonant arm and cause itself resonant.(3) We achieve the bowtie antenna near-field control by changing the relative phase delay between two sources with mutually orthogonal polarization. Only one triangle can not support the near-field control by changing the relative phase delay. (4) With two sources of mutually orthogonal polarization illuminate symmetry shuriken structure, coherent control can be achieved under the condition of each arm owes the electric components of the two sources.