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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
111

Surface plasmon resonance enhanced photophoresis in nano-metallic colloids. / CUHK electronic theses & dissertations collection / Surface plasmon resonance enhanced photophoresis in nano-metallic colloids.

January 2012 (has links)
表面等離子共振 (SPR) 是受激發的電子的總體振動,一般在金屬、電介質界面上發生。我們能以振盪的電場去激發SPR。由於表面等離子共振時會產生巨大的增強電場,這令他在近場光學與納米光學中有著廣泛的應用。例如:微流控芯片、等離子波導、隱形裝置等等。 / 在這論文中,我們會研究納米金屬體之間的作用力。基於以下原因,這在納米技術中是一個重要課題。第一,當了解到物體之間的作用力後,我們可以以此開發出把納米尺寸的物體移動與放置的方法,有助於用自下而上式的方法製作納米器件。第二,物體之間的作用力會改變器件中納米顆粒的位置,因而會影響器件的特性。 / 在一般情況下,納米尺寸的物體的作用力都可以略去不理的,因為作用力是與體積成正比。但是,當表面等離子共振發生時,相互作用力會急速地增強。這增強是由於金屬顆粒的電偶會急速地增強的原故。我們稱這現象為「表面等離子共振增強光泳」 (SPREP). / 這論文由三個主要部份組成。第一部份,我們研究一帶梯度的金屬納米球與一振盪及旋進電偶之間的相互作用。我們以第一原理進路去解決這問題,並作了長波長假設。我們的解析解能夠處理多極效應,這效應在外場不均勻時是不可忽略的。我們探討了作用力、力矩、電場分佈。更發現了,當金屬納米球的梯度很高時,電偶與金屬納米球之間與有一穩定的力平衡。這研究有助於開發新型的光學鑷子。 / 第二部份,我們探討兩個金屬納米球之間的 SPREP,我們介紹了不同的計算方法。Bergman-Milton譜表示以及多重鏡象法。 兩個金屬納米球之間也有著穩定的平衡, 這表示在一群納米球中,可能有著穩定結構。這穩定的平衡,是由於表面等離子共振的頻率與相互距離有關,這是一種多體效應。這研究有助於了解納米簇的結構形成。 / 最後,我們以離散偶極子近似法(DDA)研究多體問題,雖然DDA並不是精確解,但當顆粒之間相距不太接近時,這依然是一個良好的近似。當顆粒的數量太多時,我們以等效介質理論去著手,不再考慮每一顆粒各自的位置,而只考慮顆粒的濃度。 / Surface plasmon resonance (SPR) is the collective electrons excitations, which occurred at the metal-dielectric interfaces and can be induced by an oscillating electric field. Because of the large field enhancement, SPR has a wide range of applications in near field optics and nano-optics, such as biosensors, lab-ona- chip devices, plasmonic waveguides, and cloaking devices. / In this thesis, we study the interparticle forces between metallic nanosized objects. It is an important topic in nanotechnology for at least two reasons. Firstly, the study of the interparticle forces may provide methods to control the motion and position of nano-size objects, which can be used to fabricate artificial nano-structure by bottom up approach. Secondly, the force can change the arrangement of the particles in the nanodevices and hence affecting the property of the devices. / The interparticle forces of nano-sized dielectric particles are negligible, since the force is proportional to the volume of the objects. However, the interparticle forces of metallic particles will be greatly enhanced when SPR occurs, which is able to compensate the volume effect. This phenomenon is called surface plasmon resonance enhanced photophoresis (SPREP), which is one of the consequences of the rapid increase in the dipole moment in the particles. / This thesis is consisted of three main parts. In the first part, we study the SPREP between a graded metallic nanosphere and a point dipole which is undergo oscillation and precession. A first principle approach is applied to handle this problem. Our analytic solutions are able to capture the multipole effect, which cannot be neglected in highly non-uniform fields. We have analyzed three important physical quantities: the induced force, the induced torque, and the field distribution. Furthermore, we find that there is a binding between the nanoparticle and the dipole source, when the gradation of the graded particles is large enough. This study has a potential application in developing a novel kind optical tweezers. / In the second part, we study the SPREP between two metallic nanoparticles. The force spectra are calculated by two different methods: Bergman- Milton spectral representation and multiple image method. The binding between two nanoparticles is observed, which indicates a possible stable structure among the metallic clusters. The binding is caused by the excitation of collective plasmon modes, and the consequence that the resonance poles sℓ are the functions of separation distances. This study may provide a better understanding in the structure formation of colloidal clusters in nano-scales. / Finally, we consider a many-particle system by the discrete dipole approximation (DDA) and effective medium theory. Although, the DDA is not an exact formalism, it is a suitable approximation for considering finite number of particles, if the distances among particles are not too close. When the number of particles in the host solution is large, we can use the effective medium theory to handle the problem. Instead of considering all discrete particles individually, we will consider the interaction between a single particle and a new effective host solution, where the dielectric function of the effective host solution is determined by the concentration of nanoparticles in the host solution. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Chan, Kin Lok = 納米金屬顆粒中的表面等離子共振增強光泳 / 陳建樂. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2012. / Includes bibliographical references (leaves 90-94). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese. / Chan, Kin Lok = Na mi jin shu ke li zhong de biao mian deng li zi gong zhen zeng qiang guang yong / Chen Jianle. / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Nanoparticles and nanotechnology --- p.1 / Chapter 1.2 --- The history of nanoparticles and nano-optics --- p.1 / Chapter 1.3 --- Applications of nanoparticles --- p.2 / Chapter 1.3.1 --- Optical applications --- p.2 / Chapter 1.3.2 --- Biological and medical applications --- p.3 / Chapter 1.4 --- Electrokinetics of nanoparticles --- p.4 / Chapter 1.4.1 --- Review on recent work on electrokinetics --- p.5 / Chapter 1.5 --- Objectives of the thesis --- p.6 / Chapter 2 --- Basic Principles --- p.8 / Chapter 2.1 --- Drude model --- p.8 / Chapter 2.2 --- Complex dielectric function --- p.9 / Chapter 2.2.1 --- Electric field in an imperfect conductor --- p.10 / Chapter 2.3 --- Effective medium theory --- p.11 / Chapter 2.3.1 --- Maxwell-Garnett approximation --- p.12 / Chapter 2.3.2 --- Bruggeman approximation --- p.13 / Chapter 2.3.3 --- Bergman-Milton spectral representation (BMSR) --- p.13 / Chapter 2.3.4 --- Effective dielectric function of shelled sphere --- p.17 / Chapter 2.4 --- Surface plasmon resonance (SPR) --- p.18 / Chapter 2.5 --- Surface plasmon resonance enhanced photophoresis (SPREP) --- p.20 / Chapter 2.6 --- Justification of long wavelength limit --- p.23 / Chapter 3 --- Manipulation of Nanoparticles by a Single Dipole Source --- p.25 / Chapter 3.1 --- Introduction --- p.25 / Chapter 3.2 --- Formalism --- p.26 / Chapter 3.2.1 --- Electrostatic potential of a dipole --- p.27 / Chapter 3.2.2 --- Electrostatic potential of a dipole in terms of multipole expansion --- p.27 / Chapter 3.2.3 --- Laplace's equation of graded sphere --- p.30 / Chapter 3.2.4 --- Boundary value problem --- p.31 / Chapter 3.2.5 --- Force --- p.33 / Chapter 3.2.6 --- Torque --- p.35 / Chapter 3.3 --- Result and discussion --- p.36 / Chapter 3.3.1 --- Force --- p.38 / Chapter 3.3.2 --- Torque --- p.45 / Chapter 3.3.3 --- Electric field distribution --- p.46 / Chapter 3.4 --- Conclusion --- p.48 / Chapter 4 --- Interaction between Two Objects --- p.49 / Chapter 4.1 --- Introduction --- p.49 / Chapter 4.2 --- Interaction between two particles --- p.50 / Chapter 4.2.1 --- Dipole approximation --- p.50 / Chapter 4.2.2 --- Multiple images method --- p.52 / Chapter 4.2.3 --- Bergman-Milton spectral representation for collection of grains --- p.58 / Chapter 4.2.4 --- Equation of motion --- p.61 / Chapter 4.2.5 --- Result and discussion --- p.62 / Chapter 4.3 --- Particle near a conducting plane --- p.67 / Chapter 4.3.1 --- Dipole approximation --- p.67 / Chapter 4.3.2 --- Multiple image method --- p.69 / Chapter 4.3.3 --- Result and discussion --- p.70 / Chapter 5 --- Many-particle Systems --- p.72 / Chapter 5.1 --- Introduction --- p.72 / Chapter 5.2 --- Discrete dipole approximation --- p.72 / Chapter 5.2.1 --- 2-particle system --- p.73 / Chapter 5.2.2 --- 4-particle system --- p.74 / Chapter 5.2.3 --- Result and discussion --- p.75 / Chapter 6 --- Concentration Effect --- p.80 / Chapter 6.1 --- Introduction --- p.80 / Chapter 6.2 --- Formalism --- p.81 / Chapter 6.2.1 --- Result and discussion --- p.83 / Chapter 7 --- Summary --- p.88 / Bibliography --- p.90 / Chapter A --- Eigenfunctions, Eigenvalues, and Green's function --- p.95 / Chapter A.1 --- Isolated sphere --- p.95 / Chapter A.1.1 --- Eigenfunctions and eigenvalues --- p.96 / Chapter A.1.2 --- Green's function --- p.98 / Chapter A.2 --- Planar interface --- p.98 / Chapter A.2.1 --- Eigenfunctions and eigenvalues --- p.99 / Chapter A.2.2 --- Green's function --- p.100 / Chapter B --- Property of Spherical Harmonics and Associated Legendre Polynomials --- p.101 / Chapter B.1 --- Complex conjugate of Yℓm(Ω): --- p.102 / Chapter B.2 --- Differential Property --- p.102 / Chapter B.3 --- Limiting value --- p.102
112

Microspectroscopy of localised plasmons

Burnett, Mathew T. January 2009 (has links)
Working with nanoscale optics requires methods and equipment designed for the purpose. This thesis describes the development of techniques and a system for performing highly localised spectroscopy. The system consists of a nanonics multiview 2000 scanning near-field optical microscope, a grating spectrometer and a photonic crystal fibre supercontinuum light source. Discussion of the microscope includes its modes of operation and development of software to collect and analyse data. In order to demonstrate the setup, an example of localised spectroscopy is presented in the form of an investigation of hollow core photonic crystal fibre. Taking spectra of the components of the cladding of these fibres makes it possible to investigate the origins of bandgap guidance. A core focus of nanoscale optics is the interaction of light with metal structures. This field is called plasmonics. Fabrication of structures is presented and requires special facilities and processes. These processes are both time consuming and expensive, both factors that emphasise the need for prior modelling. Forward difference time domain modelling of a proposed structure comprising of a concentrically arranged ring and disk is explored using home written code and a commercial package called CST Microwave Studio. The investigation of this concentric design through modelling shows a very highly localised field enhancement which can be engineered to have a narrow spectral resonance in the near infrared. The interaction of the two components which govern this resonance is explained using a theory called plasmon hybridization. Once the optical behaviour of small metal objects is understood they can be used in other ways. An example of this is shown in Porous Silicon. As a material it provides an excellent template for formation of metal nano-particles. Embedded in a high surface area network of silicon these particles can be used as very effcient catalysts.
113

Surface plasmon polaritons (SPPs) mediated light extraction efficiency of light-emitting material from metallic nanohole array. / 表面等離子體激元改變納米金屬洞陣列上發光材料的光提取效率 / Surface plasmon polaritons (SPPs) mediated light extraction efficiency of light-emitting material from metallic nanohole array. / Biao mian deng li zi ti ji yuan gai bian na mi jin shu dong zhen lie shang fa guang cai liao de guang ti qu xiao lu

January 2012 (has links)
表面等離子體激元和熒光分子之間的電磁相互作用已因廣泛應用於量子運算中的量子信息處理和分子生物技術的分子檢測而得到相當大的關注。雖然通過把熒光分子放置在電漿系統旁來改善熒光分子的發光度和方向性已被廣泛接受,但是了解表面等離子體激元和熒光材料之間的相互作用的物理亦是很重要的。 / 在這篇論文中,我們將研究在二維納米銀洞陣列上有機染料帶方向性的發光特性。通過量度在每個角度的反射和熒光發光光譜,我們可以繪製出二維納米銀洞陣列所產生的電磁共振模式的色散關係及熒光材料發光度與方向的關係。此外,在陣列上以不同方向行走的表面等離子體激元的衰變壽命亦被找出。我們亦將反射率和熒光發光光譜進行比較,從而發現熒光發光的加強跟表面等離子體激元的光譜位置、衰變後傳播的方向、它的衰變壽命和它的耦合效率有十分密切的關係。為了解背後的物理,我們建立了一個理論模型去區分能量從有機染料轉移到表面等離子體激元的過程與表面等離子體激元衰變過程對表面等離子體激元改變熒光材料發光度的影響。因此,我們可以對能量從有機染料轉移到表面等離子體激元的過程與方向的關係進行定量分析。最後,我們的研究結果與由有限差分時域模擬計算所得的結果吻合。結論得出在二維納米銀洞陣列上所實現的表面等離子體激元増加有機染料光提取效率與三維空間中方向的關係是源於電漿帶隙的產生所引致的態密度重整及分配。 / The electromagnetic interaction between surface plasmon polaritons (SPPs) and fluorescent molecules has been capturing considerable attention for a wide variety of applications ranging from quantum information processing in quantum computing to molecule detection in biotechnology. Although it is widely accepted that the light emission efficiency and directionality are improved by placing the fluorescent molecules in close proximity to a plasmonic system, the understanding of the physics on how SPPs interact with the fluorescent materials is of importance. / In this thesis, the directional emission properties of LDS organic dyes supported on two-dimensional Ag nanohole array is studied. Angle-resolved reflectivity and photoluminescence spectroscopy have been employed to map out the dispersion relations of electromagnetic resonance modes arising from the array and the dependence of plasmonic emission on emission angle. In addition, the decay lifetimes of SPP modes in different propagation directions in array have been determined. By comparing the reflectivity and photoluminescence mappings, we find that the emission enhancement is strongly correlated with the spectral and angular positions of SPP modes together with their lifetimes and coupling efficiencies. To understand the underlying physics, we have developed an analytical model to differentiate the surface plasmon mediated emission (SPME) into energy transfer from LDS to SPPs and the radiative decay of surface plasmons. As a result, the directional dependence of the energy transfer process can then be analyzed quantitatively. Finally, our results are compared with the finite-difference-time-domain simulations with good agreement. It is concluded that the directional dependence of the surface plasmon mediated emission is attributed to the redistribution of the density of states in the periodic nanohole array due to the opening of the plasmonic gaps. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Chan, Kay Fung = 表面等離子體激元改變納米金屬洞陣列上發光材料的光提取效率 / 陳其鋒. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2012. / Includes bibliographical references (leaves 115-123). / Abstracts also in Chinese. / Chan, Kay Fung = Biao mian deng li zi ti ji yuan gai bian na mi jin shu dong zhen lie shang fa guang cai liao de guang ti qu xiao lu / Chen Qifeng. / Chapter Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Surface plasmon polaritons (SPPs) and surface plasmon mediated emission (SPME) --- p.2 / Chapter 1.2 --- Directional surface plasmon mediated emission (SPME) on metallic nanohole array --- p.5 / Chapter 1.3 --- Our analytical model of surface plasmon mediated emission --- p.8 / Chapter 1.3.1 --- Formalism of rate equations --- p.8 / Chapter 1.3.2 --- Determination of the directional dependence of the coupling efficiency from decay rates of the SPP and the fluorescent material --- p.11 / Chapter 1.4 --- Organization of the thesis --- p.12 / Chapter Chapter 2 --- Theory of surface plasmon polaritons --- p.14 / Chapter 2.1 --- The Maxwell’s equations and the boundary conditions for electromagnetic waves --- p.14 / Chapter 2.2 --- Dielectric constant of metal --- p.18 / Chapter 2.3 --- Master equation for electromagnetic waves, the Bloch form of SPPs and the dispersion relation of SPPs at the interface between dielectric and metal --- p.19 / Chapter 2.4 --- Excitation of surface plasmon polaritons by grating coupling --- p.27 / Chapter 2.5 --- Decay of surface plasmon polaritons --- p.29 / Chapter 2.5.1 --- Non-radiative decay --- p.29 / Chapter 2.5.2 --- Radiative decay --- p.31 / Chapter Chapter 3 --- Experimentation and Simulation --- p.37 / Chapter 3.1 --- Sample preparation --- p.37 / Chapter 3.1.1 --- Interference lithography [2.2, 3.7, 3.8] --- p.37 / Chapter 3.1.2 --- E-beam evaporation --- p.39 / Chapter 3.1.3 --- Spin coating of florescence material --- p.40 / Chapter 3.2 --- Measurements --- p.41 / Chapter 3.2.1 --- Angle-resolved specular reflection measurement [3.10] --- p.42 / Chapter 3.2.2 --- Angle-resolved photoluminescence (PL) spectroscopy [3.11] --- p.43 / Chapter 3.2.3 --- K-space (Fourier space) imaging [3.12, 3.13, 3.14] --- p.44 / Chapter 3.3 --- FDTD --- p.46 / Chapter 3.3.1 --- Theory of FDTD --- p.46 / Chapter 3.3.2 --- Simulation of the reflectivity of plane wave --- p.52 / Chapter 3.3.3 --- Simulation of the field pattern with a dipole source --- p.55 / Chapter 3.3.3.1 --- Near-to-far field projection --- p.59 / Chapter 3.3.3.2 --- Near field pattern in k-space --- p.60 / Chapter Chapter 4 --- Analysis --- p.62 / Chapter 4.1 --- Angle-resolved reflectivity measurement --- p.62 / Chapter 4.1.1 --- SPP mode identification --- p.62 / Chapter 4.1.2 --- Wavelength dependence of uncoupled SPPs decay rates --- p.65 / Chapter 4.1.3 --- Directional dependence of uncoupled SPPs decay rates --- p.71 / Chapter 4.2 --- Angle-resolved PL spectroscopy --- p.79 / Chapter 4.2.1 --- Comparison with the angle-resolved reflectivity --- p.79 / Chapter 4.2.2 --- Differentiation of the resonance and off-resonance positions on the PL mapping --- p.81 / Chapter 4.3 --- K-space imaging --- p.83 / Chapter 4.3.1 --- Reflectivity and the comparison with the phase - matching equation --- p.83 / Chapter 4.3.2 --- k-space imaging of the PL emission --- p.85 / Chapter 4.4 --- Directional dependence of the emission factor --- p.86 / Chapter 4.5 --- Directional dependence of the coupling rate of the LDS emission to the SPP mode --- p.94 / Chapter 4.6 --- Near field in k-space from the FDTD method --- p.97 / Chapter Chapter 5 --- Conclusions --- p.113 / Bibliography --- p.115
114

Excitation électrique locale de nanostructures plasmoniques par la pointe d'un microscope à effet tunnel / Local electrical excitation of plasmonic nanostructures with a scanning tunnelling microscope

Rogez, Benoit 16 December 2014 (has links)
Nous utilisons un microscope à effet tunnel (STM) associé à un microscope optique inversé pour l’excitation et la détection des plasmons de surface propagatifs et/ou localisés. L’excitation de ces plasmons est assurée par passage d’un courant tunnel inélastique entre la pointe du STM et la surface d’un film métallique mince (épaisseur de 50 nm) d’or ou d’argent déposé sur une lamelle de verre. Les fuites radiatives des plasmons de surface propagatifs et la lumière émise par les plasmons localisés dans le substrat de verre sont collectées par un microscope optique via un objectif à immersion. Il est alors possible de déterminer à la distribution spatiale et angulaire des émissions issues de ces plasmons de surface excités par STM, ainsi qu’à leur distribution en longueurs d’onde. Dans cette thèse, nous nous sommes intéressés au fonctionnement et à l’émission de lumière sous la pointe d’un microscope à effet tunnel fonctionnant à l’air. Nous montrons que la présence d’eau adsorbée au sein de la jonction tunnel, associée à la boucle d’asservissement du STM induit un mode de fonctionnement oscillant et périodique du STM sans lequel il serait difficile d’exciter les plasmons de surface. Ensuite, nous avons montré qu’il est possible de contrôler la directivité des plasmons de surface propagatifs excités par STM en excitant localement un nanofil d’or déposé sur le film d’or. L’étude détaillée de cette directivité nous a permis de démontrer que, contrairement au cas du nanofil d’or déposé sur verre, un nanofil d’or déposé sur film d’or ne se comporte pas comme un résonateur Fabry Pérot. Nous avons proposé un modèle simple dans lequel le nanofil est assimilé à un réseau linéaire d’antennes. Ce modèle permet de rendre compte des structurations spectrales et spatiales des plasmons de surface sur le film d’or résultant de l’ajout du nanofil d’or. Puis, nous avons étudié le couplage entre des nanofibres organiques fluorescentes (structures excitoniques) et les plasmons de surface propagatifs d’un film métallique d’or ou d’argent sur lequel ces nanofibres sont déposées. Nous avons ainsi montré que (i) la fluorescence de la nanofibre peut exciter des plasmons de surface à la surface du film d’or, (ii) la nanofibre organique agit comme un guide d’onde plasmonique et (iii) qu’il est possible d’injecter des plasmons de surface propagatifs du film excités par STM dans ces modes guidés par la nanofibre. D’autre part, en étudiant la figure d’interférences dans le plan de Fourier, nous avons pu confirmer que l’émission du dipôle sous la pointe STM et les plasmons de surface propagatifs excités par STM sont cohérents, donc issus du même événement tunnel. Enfin, nous discutons les effets du couplage entre des nanocristaux semiconducteurs (quantum dots) individuels et un monofeuillet de graphène. Nous montrons que la présence du graphène réduit d’un facteur ~10 la durée de vie de l’état excité des quantum dots déposés sur graphène par rapport aux quantum dots déposés sur verre. Pour les quantum dots déposés sur graphène, il résulte de cette réduction de la durée de vie de l’état excité, une baisse de l’intensité de fluorescence et une réduction du phénomène de scintillement avec un temps de résidence dans un état brillant globalement plus long que pour les quantum dots déposés sur verre. Les différents résultats obtenus au cours de cette thèse permettent de mieux comprendre l’excitation de plasmons de surface avec un microscope à effet tunnel, le couplage entre nanostructures plasmoniques et le couplage entre une structure plasmonique et une nanostructure excitonique. Ils ouvrent des perspectives intéressantes pour le développement de nanodispositifs hybrides plus complexes liants plasmons et excitons et contrôlés électriquement / We use a scanning tunnelling microscope (STM) to excite propagating and/or localised surface plasmons on a thin metallic film (50 nm thick) made of gold or silver deposited on a glass substrate. The leakage radiation of these STM-excited propagating surface plasmons, and the light emitted by localized plasmons into the glass substrate are collected by an inverted optical microscope equipped with an oil immersion objective. Using this setup, it is possible to image both the spatial and angular distribution of the light emitted into the glass substrate on a cooled-CCD. Sending this light to a spectrometer, it is also possible to obtain the wavelength distribution of these STM-excited plasmons. In this manuscript, we discuss the different operation modes of an STM in air. We show that the thin water layers adsorbed on both the STM tip and sample, along with the STM feedback loop, may give rise to an oscillatory mode of operation. Moreover, this mode turns out to be the most efficient one for plasmon excitation with a STM in air. We then show that, when the STM tip is used to locally excite plasmons on a gold nanowire deposited on a gold film, propagating surface plasmons may be preferentially launched along the nanowire axis. Precise understanding of this directivity allows us to demonstrate that, when deposited on a gold film, gold nanowires do not behave as Fabry-Perot resonators, but may be described quite accurately with a one dimensional antenna array model. With this model, it is thereby possible to explain the complex spatial and spectral characteristics of the STM-excited plasmons on the gold film after the addition of the nanowire. Next, we focus on the coupling between fluorescent organic nanofibres (excitonic nanostructures) and propagating surface plasmons on a metallic film (either gold or silver). We show that when the nanofibres are deposited on the metallic film, (i) their fluorescence can excite propagating surface plasmon, (ii) the nanofibre can act as a plasmonic waveguide, and (iii) it is possible to inject surface plasmons propagating onto the metallic film into the guided plasmonic modes of the nanofibre. Moreover, by studying Fourier space images, we confirmed that the vertical dipole localised under the STM tip and the STM-excited propagating surface plasmons are coherent. We finally study the coupling between individual semiconducting nanocrystals (quantum dots) and a graphene monolayer deposited on a glass substrate. We show that, when deposited on graphene, the fluorescence lifetime of the quantum dots is about 10 times shorter than for the quantum dots deposited on bare glass. This leads to a weaker fluorescence signal and reduced blinking behaviour with longer time spent into a bright state. These results improve our understanding of the STM excitation of surface plasmons. They also provide information on the coupling between plasmonic nanostructures and between plasmonic and excitonic entities. in particular, these results are a promising step toward the conception and the realisation of complex electrically driven hybrid plasmonic/excitonic nanodevices
115

Experimental and theoretical studies of the optical properties of periodic metallic nanostructures. / 週期性金屬鈉米結構光學特性的實驗和理論研究 / CUHK electronic theses & dissertations collection / Experimental and theoretical studies of the optical properties of periodic metallic nanostructures. / Zhou qi xing jin shu na mi jie gou guang xue te xing de shi yan he li lun yan jiu

January 2009 (has links)
By combining experiment and theory, we believe our study shed light on developing a new method for well investigating and controlling the different plasmonic modes and open their way for some great applications in biology, chemistry and photonics. / Finally, this thesis presents an approach to quantitatively evaluate the SP-mediated light emission. Based on this consideration, efforts are taken to find the temperature effect of SP on the light emission in semiconductor. On metal/ZnO system, a more realistic picture for the light emission is depicted by experimentally measuring the temperature-dependent photoluminescence and theoretically calculating the Purcell enhancement factor. The increasing plasmonic density of states with the lower temperature has been regarded as being responsible for the enhanced light emission. / Firstly, studies are performed on finding an in-depth understanding into the optical properties of two-dimensional (2D) metallic nano-cavity structure (grating). Structures are fabricated by interference lithography and thin film techniques. Grating geometries can be easily tuned by using these versatile techniques with high reproducibility and precision. Plasmonic dispersion in the 2D grating has been mapped out by angle-dependent reflectivity measurements. Two particular nanostructures, i.e., nano-bottle array and elliptical hole array, have been chosen to investigate the dependence of plasmonic properties on geometries change. Theories are also put forward to understand the origin and electromagnetic properties of the obtained plasmonic modes. / Surface plasmons (SP), the collective oscillations of the conduction electrons between the metal/dielectric interface, strongly influence the optical properties of metallic nanostructures and are of great interest for future photonic devices. Here, this thesis mainly focuses on the experimental and theoretical investigations on the optical properties of the metallic periodic nanostructures. / With an understanding into the different plasmonic properties of the metallic nanostructures, researches are then undertaken to explore how this associated electromagnetic field interacts with the molecules adsorbed onto a sample surface. The distinct and strong correlation between the plasmonic modes and surface enhanced Raman scattering (SERS) is verified on the one-dimensional silver grating. In particular, the detailed analysis of the enhancement factor from surface plasmons excitation and de-excitation process in SERS has been performed. On the other hand, the technique used to fabricate the controllable "hot spot" for enhancing Raman scattering has been introduced on the 2D metallic grating. Complemented by the theoretical simulation, the conditions for optimizing SERS enhancement effect are proposed. / Li, Jia = 週期性金屬鈉米結構光學特性的實驗和理論研究 / 李佳. / Adviser: Ong Hock Chun. / Source: Dissertation Abstracts International, Volume: 71-01, Section: B, page: 0388. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2009. / Includes bibliographical references (leaves 135-144). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. Ann Arbor, MI : ProQuest Information and Learning Company, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in English and Chinese. / Li, Jia = Zhou qi xing jin shu na mi jie gou guang xue te xing de shi yan he li lun yan jiu / Li Jia.
116

Comparison of SPR and Edge Tracking as a Measure of Binding Kinetics in Whole Cells

January 2018 (has links)
abstract: Most drugs work by binding to receptors on the cell surface. These receptors can then carry the message into the cell and have a wide array of results. However, studying how fast the binding is can be difficult. Current methods involve extracting the receptor and labeling them, but both these steps have issues. Previous works found that binding on the cell surface is accompanied with a small change in cell size, generally an increase. They have also developed an algorithm that can track these small changes without a label using a simple bright field microscope. Here, this relationship is further explored by comparing edge tracking results to a more widely used method, surface plasmon resonance. The kinetic constants found from the two methods are in agreement. No corrections or manipulations were needed to create agreement. The Bland-Altman plots shows that the error between the two methods is about 0.009 s-1. This is about the same error between cells, making it a non-dominant source of error. / Dissertation/Thesis / Masters Thesis Biochemistry 2018
117

Theoretical studies of two-dimensional periodic metallic nano-cavities. / 二維週期性金屬納米共振腔的理論研究 / Theoretical studies of two-dimensional periodic metallic nano-cavities. / Er wei zhou qi xing jin shu na mi gong zhen qiang de li lun yan jiu

January 2009 (has links)
Iu, Hei = 二維週期性金屬納米共振腔的理論研究 / 姚熙. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2009. / Includes bibliographical references (leaves 89-91). / Abstracts in English and Chinese. / Iu, Hei = Er wei zhou qi xing jin shu na mi gong zhen qiang de li lun yan jiu / Yao Xi. / Chapter 1 --- Introduction --- p.1 / Chapter 2 --- Introduction to Surface Plasmon Polaritons --- p.3 / Chapter 2.1 --- The Maxwell´ةs Equations --- p.3 / Chapter 2.2 --- Photonic crystals --- p.5 / Chapter 2.3 --- Modeling Metal --- p.9 / Chapter 2.4 --- Surface plasmon polarition --- p.12 / Chapter 3 --- Rectangular Cavity --- p.17 / Chapter 3.1 --- Basic simulation cell setup --- p.17 / Chapter 3.2 --- Method of mode identification --- p.18 / Chapter 3.2.1 --- Dispersion relation calculation --- p.18 / Chapter 3.2.2 --- Reflection spectra --- p.19 / Chapter 3.3 --- Results and discussions --- p.20 / Chapter 4 --- Nano-bottle cavity --- p.25 / Chapter 4.1 --- Cylindrical cavity --- p.25 / Chapter 4.1.1 --- Dispersion relations calculation --- p.25 / Chapter 4.1.2 --- Field pattern calculation --- p.29 / Chapter 4.2 --- Nano-bottle cavity --- p.46 / Chapter 4.2.1 --- The effect of the bottleneck on (0,1) mode --- p.47 / Chapter 4.2.2 --- The effect of aperture size on (0,1) mode --- p.58 / Chapter 4.2.3 --- The effect of the depth of cavities on (0,1) mode --- p.62 / Chapter 4.2.4 --- "The effect of aperture size on (-1,0) mode" --- p.63 / Chapter 4.3 --- Discussions --- p.64 / Chapter 4.4 --- Verified with experimental results --- p.68 / Chapter 5 --- Aspect ratio --- p.71 / Chapter 5.1 --- Simulation structure --- p.72 / Chapter 5.2 --- Aspect ratio S = 2 --- p.73 / Chapter 5.3 --- The effect of aspect ratio --- p.74 / Chapter 5.3.1 --- Orientation dependence of the resonant mode --- p.74 / Chapter 5.3.2 --- Excitation frequency of the resonant mode --- p.75 / Chapter 5.4 --- Field location and strength --- p.76 / Chapter 5.5 --- Discussions --- p.77 / Chapter 5.6 --- Comparison with experimental results --- p.79 / Chapter 6 --- Conclusions and future works --- p.83 / Chapter 6.1 --- A possible new mode excitation --- p.84 / Chapter 6.2 --- Cavities with aspect ratio under p-polarized light --- p.86 / Bibliography --- p.89 / Chapter A --- Computational Simulation --- p.92 / Chapter A.l --- Finite-Difference Time-Domain --- p.92 / Chapter A.2 --- Computational grid --- p.93 / Chapter A.3 --- Boundary Condition --- p.93 / Chapter A.4 --- Source --- p.94 / Chapter A.5 --- Field strength --- p.94
118

Theoretical and experimental investigations on surface plasmon cross coupling mediated emission from ZnO. / 表面等離子交叉耦合協助氧化鋅發射的理論和實驗研究 / Theoretical and experimental investigations on surface plasmon cross coupling mediated emission from ZnO. / Biao mian deng li zi jiao cha ou he xie zhu yang hua xin fa she de li lun he shi yan yan jiu

January 2007 (has links)
Lei, Dangyuan = 表面等離子交叉耦合協助氧化鋅發射的理論和實驗研究 / 雷黨願. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2007. / Includes bibliographical references (leaves 81-85). / Abstracts in English and Chinese. / Lei, Dangyuan = Biao mian deng li zi jiao cha ou he xie zhu yang hua xin fa she de li lun he shi yan yan jiu / Lei Dangyuan. / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Motivations --- p.1 / Chapter 1.2 --- Thesis outline --- p.3 / Chapter 2 --- Background and Proposition --- p.7 / Chapter 2.1 --- Surface plasmon mediated emission from semiconductor --- p.7 / Chapter 2.1.1 --- General mechanism --- p.7 / Chapter 2.1.2 --- Formulation of SP coupling --- p.10 / Chapter 2.1.2.1 --- Derivation of dispersion relation --- p.10 / Chapter 2.1.2.2 --- Plasmonic density of states (DOS) --- p.13 / Chapter 2.1.2.3 --- Field distribution in dielectric/metal/dielectric System --- p.13 / Chapter 2.1.2.4 --- Determination of Purcell factor (Fp) --- p.16 / Chapter 2.1.3 --- Emission enhancement from metal-capped ZnO --- p.17 / Chapter 2.2 --- Proposal for making high efficiency top-emitting LED --- p.22 / Chapter 3 --- Experimental Setup and Measurement System --- p.24 / Chapter 3.1 --- Sample preparation --- p.24 / Chapter 3.1.1 --- Radio frequency magnetron sputtering --- p.24 / Chapter 3.1.2 --- Spin-coating --- p.27 / Chapter 3.1.3 --- Rapid thermal annealing --- p.29 / Chapter 3.2 --- Optical characterizations --- p.29 / Chapter 3.2.1 --- Transmittance measurement --- p.29 / Chapter 3.2.2 --- Photoluminescence (PL) measurement --- p.31 / Chapter 3.2.3 --- EDX for composition measurement --- p.32 / Chapter 4 --- Theoretical Simulations and Experimental Results --- p.36 / Chapter 4.1 --- Tunable surface plasmon resonance by using metal alloys --- p.36 / Chapter 4.1.1 --- Dielectric constants calculation --- p.37 / Chapter 4.1.2 --- Dispersion relation of alloy/Si02 --- p.41 / Chapter 4.1.3 --- Plasmonic density of states and Purcell factor of alloy/semiconductor --- p.43 / Chapter 4.1.3.1 --- Air/AlxAg1-x/ZnO system --- p.43 / Chapter 4.1.3.2 --- Air/AlxAul-x/ZnTe --- p.46 / Chapter 4.1.3.3 --- Air/ AgxAul-x/CdSe system --- p.48 / Chapter 4.1.4 --- Experimental results of AlxAgl-x/ZnO --- p.52 / Chapter 4.1.5 --- Discussion and mini-conclusion --- p.56 / Chapter 4.2 --- Enhanced forward emission from metal-insulator-metal/ZnO by coupled surface plasmon --- p.57 / Chapter 4.2.1 --- Plasmon modes in metal-insulator-metal (MIM) --- p.57 / Chapter 4.2.2 --- Transmittance simulation of MIM and MIMIM --- p.63 / Chapter 4.2.3 --- Transmittance measurement of MIM --- p.68 / Chapter 4.2.4 --- Transmittance and photoluminescence of MIM/ZnO. --- p.73 / Chapter 4.2.5 --- Discussion and mini-conclusion --- p.78 / Chapter 5 --- Conclusions --- p.79 / Chapter 6 --- References --- p.81
119

Broadband nearly perfect absorption in plasmonic absorber based on multiple surface plasmon resonances / 在等離子吸收器中基於多重表面等離子元共振的寬頻近完全吸收 / CUHK electronic theses & dissertations collection / Broadband nearly perfect absorption in plasmonic absorber based on multiple surface plasmon resonances / Zai deng li zi xi shou qi zhong ji yu duo chong biao mian deng li zi yuan gong zhen de kuan pin jin wan quan xi shou

January 2014 (has links)
In complex plasmonic nanostructures, the multiple metal-dielectric interfaces support several elementary modes of surface plasmon polariton. Hybridized surface plasmon polariton (HSPP) is formed due to the evanescent coupling between surface plasmon polaritons on different interfaces. In our first work, we studied the properties of HSPP in a metal-dielectric-metal waveguide with periodically varying refractive index, using Hamiltonian optics approach. We investigated the feasibility of light manipulation inside this structure by extracting the allowed phase orbits using the proposed quantization condition. Besides, the time series of position and wavevector of HSPP are simulated by solving the Hamiltonian equations. The result revealed three distinct HSPP modes formed inside the waveguide: confinement, propagation and retardation. Lastly, we investigated the usage of the proposed structure as an optical filter. / Nearly perfect absorption (NPA) refers to a phenomenon that the reflection and transmission of incident electromagnetic waves on a system are being suppressed, thus the energy of waves is being trapped and dissipated in the system. In our second work, a design of broadband, wide angle of incidence and polarization-independent nearly perfect absorber is proposed based on multiple surface plasmon resonances. The absorptance is computed to confirm NPA for TM and TE modes. Besides, the absorptance depends also on the thickness of the composite layer and this dependence is explained by the hybridized surface plasmon (HSP) formed inside the absorber. Particularly for TE mode, the broadband HSP fast wave which coupled efficiently with the incident light, can only be generated for proper thickness of the composite layer, in contrast to the previous proposal of fast wave generation mechanism using metal/epsilon-near-zero structure to yield narrow-band NPA by S.Feng. The proposed absorber can be used to construct light harvesting devices because of its high efficient energy absorption. / 在複合的等離子納米結構中的多個金屬-電介質介面能支持數個表面等離子激元(surface plasmon polariton)的基礎模態。而雜交化表面等離子激元(hybridized surface plasmon polariton)就是不同表面上的表面等離子激元因衰減性耦合而形成的。在我們第一個工作中,我們以哈密頓光學(Hamiltonian optics)研究了在有週期性折射率變化的金屬-電介質-金屬波導中雜交化表面等離子激元的特性。我們以所提出的量化條件析取出容許的相位軌跡,從而探究在此結構中操縱光波的可行性。此外,雜交化表面等離子激元的位置和波向量隨時間的變化會通過解哈密頓方程計算出來。結果顯示在此波導中,雜交化表面等離子激元有三種不同的模態:密閉,傳播,延滯。最後,我們探討了此結構作為光學過濾器的應用。 / 近完全吸收(Nearly perfect absorption)是指射在一系統上的電磁波的反射和傳輸都被壓制,而波的能量則被困鎖和消耗在系統中的一個現象。在我們第二個工作中,我們提出了一個基於多重表面等離子元共振的寬頻、廣入射角、與偏振無關的近完全吸收器設計。我們計算了吸引率以確認在TE及TM模態下的近完全吸收。此外,吸引率亦與複合層的厚度有關,而此關係能以在吸收器形成的雜交化表面等離子解釋。特別是TE模態時,能有效地與入射光耦合的寬頻雜交化表面等離子快波(Broadband HSP fastwave)只能在合適的厚度才能產生,與S.Feng所提出以金屬/近零介電常數材料結構產生快波,從而達至窄頻近完全吸收不同。因為高效能的能量吸引,我們提出的吸收器能作建構光收集裝置之用。 / Lee, Sze Fung = 在等離子吸收器中基於多重表面等離子元共振的寬頻近完全吸收 / 李時鋒. / Thesis M.Phil. Chinese University of Hong Kong 2014. / Includes bibliographical references (leaves 58-62). / Abstracts also in Chinese. / Title from PDF title page (viewed on 24, October, 2016). / Lee, Sze Fung = Zai deng li zi xi shou qi zhong ji yu duo chong biao mian deng li zi yuan gong zhen de kuan pin jin wan quan xi shou / Li Shifeng. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only.
120

Localized Photoemission in Triangular Gold Antennas

Scheffler, Christopher M. 22 March 2019 (has links)
With the development of ultra-fast laser technology, several new imaging techniques have pushed optical resolution past the diffraction limit for traditional light-based optics. Advancements in lithography have enabled the straightforward creation of micron- and nanometer-sized optical devices. Exposing metal-dielectric structures to light can result in surface plasmon excitation and propagation along the transition interface, creating a surface plasmon polariton (SPP) response. Varying the materials or geometry of the structures, the plasmonic response can be tailored for a wide range of applications. Photoemission electron microscopy (PEEM) has been used to image excitations in micron-sized plasmonic devices. With PEEM, optical responses can be characterized in detail, aiding in the development of new types of plasmonic structures and their applications. We show here that in thin, triangular gold platelets SPPs can be excited and concentrated within specific regions of the material (thickness ~50 nm); resulting in localized photoemission in areas of high electric field intensity. In this regard, the platelets behave as receiver antennas by converting the incident light into localized excitations in specific regions of the gold platelets. The excited areas can be significantly smaller than the wavelength of the incident light (λ≤1µ). By varying the wavelength of the light, the brightness of the excited spots can be changed and by varying the polarization of the light, the brightness and position can be changed, effectively switching the photoemission on or off for a specific region within the triangular gold structure. In this work, the spatial distribution of surface plasmons and the imaging results from photoemission electron microscopy are reproduced in simulation using finite element analysis (FEA). In addition, we show that electromagnetic theory and simulation enable a detailed and quantitative analysis of the excited SPP modes, an explanation of the overall optical responses seen in PEEM images, and prediction of new results.

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