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The Optical Properties Of Surface Plasmon In Noble Metal Nanoarrys Nanosystem

Posted on:2012-02-14Degree:DoctorType:Dissertation
Country:ChinaCandidate:Z K ZhouFull Text:PDF
GTID:1228330344951881Subject:Optics
Abstract/Summary:PDF Full Text Request
Surface Plasmons (SPs) are collective electron oscillations that occur at the interface between metals and dielectrics. Depending on the geometry, optical waves can couple to these electron oscillations in the form of freely propagating electron density waves along metal surface or localized excitations. Based on the unique properties of plasmons, numbers of intriguing phenomena have been discovered, leading to numerous useful practical applications, which range from enhanced sening and spectroscopy for chemical identification and biodetecion at the single molecule level, light guiding and manipulation at the nanoscale, the design and fabrication of nanophotonics devices and metamaterials (such as negative-index metamaterials and invisible cloak), high resolution optical (multicolor) imaging below the diffraction limit and so on. Recently, the study of surface plasmon waves has become a subdiscipline of nanophotonics, concerning primarily with the generation, propagation, detection and properties of the plasmon waves, and this new subfield is named plasmonics.In the field of plasmonics, extensive research efforts have been devoted to utilizing elegantly fabricated metal nanostrctures to manipulate the propagation, intensity and polarization of light. Herein, we put our research emphasis on the SP properties of nanowire (or nanorod) array nanosystem nanostructure, duo to the fact that a stronger local field enhancement and smaller plasmon damping exist in the nanorods or nanowires arrays comparing with nanofilms or nanoparticles. The nanowire arrays are electrochemically grown in anodic aluminum oxide (AAO) templates, which are prepared by using a two-step anodization process. Our main achievements are as follows:(1) We use DDA and FDTD methods to theoretical study the interference of dark plamon modes of the Au nanorod array and bright plamon modes of the percolating Au film, and we observe significant enhancement of transimission and local fieds, which are caused by plasmonic Fano resonance. Then, following the theoretical instructions, we build our experiments on coupling discrete plamon modes of the Au nanorod array to low quality factor (low-Q continuum modes of the percolating Au film, and uncover striking optical phenomena from the nanorod-film hybrids nanosystem at plasminc Fano resonance, as reflected by the dramatically enhanced optical transmission of the percolating film and 2 orders of magnitude enhancement in the avalanche multiphoton luminescence (MPL) of the nanorod array. Our theoretical simulations qualitatively reproduce the experimental results. The simulation results and the experimental observations indicate the dominate enhancing mechanism is plasmonic Fano resonances. The nonlinear enhancement effect arising from the plasmonic Fano resonance in this nanorod-film hybrid system may bring about promising applications in the design of various plasmonic nanodevices, such as enhancing the sensitivity of surface enhanced Raman scattering (SERS) substrates, improving the efficiency of nanoantenna arrays, and building plasmonic lasers.(2) On theoretical studies, we investigate half-wave plasmon oscillations, resonate transmission, and subwavelength imaging behaviors of the Ag nanowire arrays with near-field point-source excitations. Our computational simulations reveal the plasmon-mediated radiative energy transfer across Ag nanowire arrays leads to a significantly greater energy transfer efficiency and distance. We have theoretically achieved a more than 100 folds enhancement of the electromagnetic field with the assistance of Ag nanowire array over a distance longer than 500 nm. Then we turn to experimental demonstrations of long-range excitation energy transfer between quantum dots (QDs) by using Ag nanowire arrays, and our measured radiative energy transfer efficiency between QDs reached about 70%. Our studies show that the silver nanowire array supported a long-range radiative excitation energy transfer with a high efficiency and a good directionality, which can give rise to several prospective applications in nanophotonics.(3) We first time fabricate Nd ions doped anodic aluminum oxide (Nd:AAO) templates, observed linear, subliner and superlinear photonluminescence (PL) from Nd:AAO membranes loaded with Ag nanowires, which were electrochemically deposited in the Nd:AAO templates. Also we investigate the excitation power dependences of emission polarization ratio and the spectral width of PL from Nd ions. The reported nonlinear amplifications of the PL intensity demonstrate the existence of strong interaction between randomly-dispersed Nd ions and the ordered-arrayed Ag nanowire in AAO templates.
Keywords/Search Tags:Surface plasmon, plasmonic Fano resonance, radiative energy transfer, plasmon hybrid, enhanced transmission, enhanced multiphoton photoluminescence
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