Rozprawy doktorskie na temat „Hyperbolic metamaterial”

Des propriétés optiques inédites sont prédites si des nanorésonateurs optiques sont organisés dans un matériau, ce qui peut être réalisé par l’auto-assemblage de nanoparticules plasmoniques synthétisées chimiquement. Dans ce travail de doctorat, nous utilisons des structures ordonnées de copolymères à blocs pour organiser des nanoparticules plasmoniques. Nous étudions le lien entre la structure des nanocomposites en films minces, et en particulier la nature, la densité et l’organisation des nanoparticules, et leurs propriétés optiques. Pour cela, nous avons tout d’abord produit des phases lamellaires de copolymères diblocs poly(styrène)-block-poly(2-vinylpyridine) (PS-b-P2VP) en films minces d’épaisseur (100nm-700nm) et de période lamellaire (17nm-70nm) contrôlées, et dont l’alignement et l’homogénéité sont optimisés. Nous avons développé une synthèse in situ, au sein de ces films lamellaires, qui permet de produire de façon contrôlée et reproductible, des nanoparticules plasmoniques de diamètre 7-10nm sélectivement dans les domaines P2VP. Nous avons montré que la taille et la forme des particules d’or formées in situ peuvent être modifiées en jouant sur le solvant et le réducteur chimique mis en jeu. Nous avons étudié en détail la structure des nanocomposites formulés, ce qui est en particulier nécessaire à la bonne exploitation des données d’ellipsométrie spectroscopique afin de déterminer les réponses optiques. La structure des échantillons a été étudiée par différentes méthodes de microscopie (électronique en transmission ou à balayage, à force atomique), ainsi que de la diffusion des rayons X. Nous avons utilisé une microbalance à Quartz pour étudier la quantité d’or introduite dans les matrices lamellaires de manière « cinétique » au fil de son augmentation progressive. La quantité d’or atteint des valeurs de 40 % en volume. Les propriétés optiques des films nanocomposites sont déterminées par ellipsométrie spectroscopique à angle variable et analysées à l’aide de modèles de milieux effectifs. Les films sont homogènes et anisotropes uniaxes, et on peut définir leur tenseur de permittivité diélectrique avec une composante ordinaire εo (parallèle au substrat) et une composante extraordinaire εe (perpendiculaire au substrat). L’analyse permet de montrer que les deux composantes εo and εe présentent une résonance proche de la longueur d’onde =540nm, avec une amplitude très supérieure pour εo. Lorsque la quantité d’or dans la structure lamellaire est suffisante, εo devient négatif au voisinage de la résonance et le matériau atteint le régime appelé hyperbolique, ce qui constitue un jalon essentiel pour le développement de matériaux pour des applications en imagerie hyper-résolue
Novel optical properties in the visible range are foreseen when organizing nanoresonators, which can be performed by the self-assembly of plasmonic nanoparticles prepared by wet chemistry. In this project, we use templating block copolymers structures to organize plasmonic particles. Our goal is to relate the structure of the prepared nanocomposites thin films, and in particular the nature, density and spatial organization of the nanoparticles, with their optical index.For this purpose, we first fabricate lamellar superlattices of diblock copolymers (poly(styrene)-block-poly(2-vinylpyridine) of controlled thickness (100nm-700nm), controlled lamellar period size(17 nm-70 nm) and optimized alignment and homogeneity. Following the fabrication of the multilayer templates, an in situ and reproducible synthesis of metallic nanoparticles was developed in order to generate nanocomposites selectively inside the P2VP layers. The size of Au nanoparticles can be well controlled around 7-10 nm. We also found that the reduction process could influence the shape (sphere, triangle or cylinder) and size by using different solvents or reducing agents. Because the extraction of accurate optical responses from the spectroscopic ellipsometry data, which will come in the last part, critically relies on the precise knowledge of the sample structure. We have used several experimental techniques to access a precise description of the produced materials. In particular, we used a Quartz Crystal Microbalance as a measurement tool to ‘kinetically’ study the volume fraction of Au loading. We find that the amount of gold in the composite layers can be varied up to typically 40 volume%. The optical properties of the nanocomposite films are determined by variable angle spectroscopic ellipsometry and analyzed by appropriately developed effective medium models. The films are structurally uniaxial and homogeneous, and we can define their dielectric permittivity tensor with the ordinary (parallel to the substrate) and extraordinary (normal to the substrate) components. The analysis of the lamellar structures allows the extraction of the components εo and εe, both presenting a resonance close to =540nm, with a significantly stronger amplitude for εo. When the gold load is high enough and the couplings between particles are strong enough, the values of εo become negative close to the resonance, and the material reaches the so-called hyperbolic regime, which constitutes a step towards applications in hyper-resolution imaging

Hyperbolic metamaterials, due to their extraordinary optical properties, have gained much attention in the scientific community, in particular for imaging to create sub-wavelength imaging devices. A special class of hyperbolic metamaterials are the wire media (WM), comprised of a sub-wavelength array of metal wires. From radio to terahertz (THz) frequencies, WM possess a nearly flat dispersion relation that allows them to support high spatial frequency propagating waves, and can be used to beat the diffraction limit. With WM, two practical imaging devices have been demonstrated at microwave and THz frequencies: endoscope (straight WM) and hyperlens. However, their performance is highly dependent on frequency, and at some frequencies is limited by the unwanted imaging artefacts, and thus require effective methods to correct them. Moreover, most previous designs of magnifying hyperlenses rely on either curved or tapered geometry, making fabrication difficult, especially in large volumes. In this thesis, we numerically study these unwanted artefacts, and introduce post-processing methods to remove them, so that the WM can be used as a broad-band imaging device. In addition, for the first time we fabricate a magnifying WM prism hyperlens at THz frequencies that does not rely on the tapering process, making fabrication easier. We experimentally characterize the transmission properties of the prism hyperlens using THz time-domain spectroscopy that allows us to resolve sub-wavelength information with a two-fold magnified image. Finally, on the basis of analytical approaches, we study the far-field propagation with the prism hyperlens, and also discuss when reconstruction of sub-wavelength objects in the far-field is possible.

Hyperbolic Metamaterials (HMMs) are engineered structures capable of supporting lightmatter interactions that are not normally observed in naturally occuring material systems. These unusual responses are enabled by an enhancement of the photonic density of states (PDOS) in the material. The PDOS enhancement is a result of deliberately introduced anisotropy via a permittivity sign-change in HMM structures which increases the number and frequency spread of possible wave vectors that propagate in the material. Subwavelength structural features allow effective medium theories to be invoked to construct the k-space isofrequency quadratic curves that, for HMMs, result in the k-space isofrequency contour transitioning from being a bounded surface to an unbounded one. Since the PDOS is the integral of the differential volume between k-space contours, unbounded manifolds lead to the implication of an infinite or otherwise drastically enhanced PDOS. Since stored heat can be thought of as a set of non-radiative electromagnetic modes, in this dissertation we demonstrate that HMMs provide an ideal platform to attempt to modify the thermal/IR emissivity of a material. We also show that HMMs provide a platform for broadband plasmonic sensing. The advent of commercial two photon polymerization tools has enabled the rapid production of nano- and microstructures which can be used as scaffolds for directive infrared scatterers. We describe how such directive components can be used to address thermal management needs in vacuum environments in order to maximize radiative thermal transfer. In this context, the fundamental limitations of enhanced spon- taneous emission due to conjugate impedance matched scatterers are also explored. The HMM/conjugate scatterer system’s performance is strongly correlated with the dielectric function of the negative permittivity component of the HMM. In order to fully understand the significance of these engineered materials, we examine in detail the electromagnetic response of one ternary material system, aluminium-doped zinc oxide (AZO), whose tuneable plasma frequency makes it ideal for HMM and thermal transfer applications. This study draws upon first principle calculations from the open literature utilizing a Hubbard-U corrected model for the non-local interaction of charge carriers in AZO crystalline systems. We present the first complete dielectric function of industrially produced AZO samples from DC to 30,000 cm ^–1 and conclude with an assessment of this material’s suitability fo the applications described.

Wire media (WM) are hyperbolic metamaterials consisting of subwavelength arrays of metal wires. Their hyperbolic dispersion properties allow them to support modes with highly subwavelength variations, which have been used to create subwavelength imaging devices. These devices have had great early success, with the two primary realizations, the WM metamaterial hyperlens and the resonant metalens, being experimentally demonstrated at terahertz and microwave frequencies respectively. However at terahertz frequencies and above, undesirable effects begin to limit the performance of these devices, and we require new techniques to maintain the viability of these devices. In this thesis, we study these subwavelength modes in both conventional and novel WM structures, using a strategy which combines the physical intuition gained from analytical treatments with the accuracy of fully numerical models. This strategy is implemented to test the limitations of approximations used in deriving analytical models of WM slabs, and the regimes in which effective medium treatments are valid. We use these models to understand the behavior found in novel WM geometries, and propose ways of utilizing these geometries to improve the performance of WM subwavelength imaging devices. While performing this analysis we also uncover interesting behavior unrelated to subwavelength imaging, and suggest alternative applications and research for these novel WM devices. In addition to our theoretical work, we also fabricated a 1D WM resonant metalens and performed an experiment to characterize this lens at terahertz frequencies. This experiment provides a greater understanding of the practical issues confronted at these frequencies, and presents an opportunity to connect our theoretical work with real life measurements. We use the insights gained through this thesis to create a strategy for optimising the performance of this lens, and propose a design with an improved response at terahertz frequencies.

The goal of this project is to study novel nanoscale excitation volumes, sensitive enoughto study individual chromophores and go on to study new and exciting self assemblyapproaches to this problem. Small excitation volumes may be engineered using light con-finement inside apertures in metal films. These apertures enhance fluorescence emissionrates, quantum yields, decrease fluorescence quenching, enable higher signal-to-noiseratios and allow higher concentration single chromophore fluorescence, to be studied byrestricting this excitation volume. Excitation volumes are reported on using the chro-mophore's fluorescence by utilising fluorescence correlation spectroscopy, which monitorsfluctuations in fluorescence intensity. From the correlation in time, we can find the res-idence time, the number of chromophores, the volume in which they are diffusing andtherefore the fluorescence emission efficiency. Fluorescence properties are a probe ofthe local environment, a particularly powerful tool due to the high brightness (quantumyield) fluorescent dyes and sensitive photo-detection equipment both of which are readilyavailable, (such as avalanche photodiodes and photomultiplier tubes). Novel materialscombining the properties of conducting and non-conducting materials at scales muchsmaller than the incident wavelength are known as meta-materials. These allow combi-nations of properties not usually possible in natural materials at optical frequencies. Theproperties reported so far include; negative refraction, negative phase velocity, fluorescenceemission enhancement, lensing and therefore light confinement has also been proposed tobe possible. Instead of expensive and slow lithography methods many of these materialsmay be fabricated with self assembly techniques, which are truly nanoscopic and otherwiseinaccessible with even the most sophisticated equipment. It was found that nanoscaled volumes from ZMW and HMMs based on NW arrays wereall inefficient at enhancing fluorescence. The primary cause was the reduced fluorescencelifetime reducing the fluorescence efficiency, which runs contrary to some commentatorsin the literature. NW based lensing was found to possible in the blue region of the opticalspectrum in a HMM, without the background fluorescence normally associated with a PAAtemplate. This was achieved using a pseudo-ordered array of relatively large nanowireswith a period just smaller than lambda / 2 which minimised losses. Nanowires in the traditionalregime lambda / 10 produced significant scattering and lead to diffraction, such that they werewholly unsuitable for an optical lensing application.

In the past few years, intensive research efforts have been devoted to studying new approaches to controlling the photon emission of quantum emitters (QEs), especially for telecommunication applications. These approaches rely on tailoring the QE\'s radiation, usually assessed via well-known figures-of-merit such as lifetime (τ) and quantum efficiency (η). Controlling the QE\'s photon emission is important because the faster its photons are emitted, the greater is the number of times it returns to the excited state per second. Therefore, it is crucial to create additional decay channels to reduce τ, which necessarily requires increasing the Purcell factor (P). One of the most promising approaches to increase P involves a new class of metamaterials, known as hyperbolic metamaterials (HMM). This class of materials exhibits pronounced anisotropy, with the parallel and perpendicular permittivity tensor elements (with respect to the anisotropy axis) presenting opposite signs, resulting in an open hyperboloidal isofrequency surface (IS). This unusual IS shape leads to the most outstanding feature of HMMs, namely, the existence of photonic modes with wavenumber (k) much larger than those in free-space (k0), known as high-k modes. By engineering these modes, it is possible to manipulate the HMM photonic density of states (PDoS), thus controlling the QE\'s radiation parameters. The simplest approach to designing HMM is by means of a planar stack of alternating thin metal and dielectric layers. However, the finite thickness of these layers induces spatial dispersion, making the extraction of effective parameters (homogenization) of these media a challenging task. In this context, we propose in this thesis a new constitutive parameter retrieval approach that takes spatial dispersion into account for all electromagnetic parameters of the medium. We demonstrate that the real part of the dispersion curve flattens out (correspondingly with a large imaginary part) because of the absence of propagating modes inside the metamaterial. This flat region is strongly dependent on the layer thicknesses and is a direct manifestation of spatial dispersion. Moreover, we demonstrate that the QE\'s lifetime calculation is overestimated if this effect is not taken into account in the homogenization procedure, which is detrimental for telecommunication applications. Moreover, we demonstrate how to enhance P by a factor greater than 100 with the use of HMMs. However, most of the QE dissipated power couples into the HMM as high-k modes (which do not propagate in free-space). Therefore, the energy is thermally dissipated inside the HMM with a consequent reduction of η . Some authors have resorted to nano-patterned HMMs (NPHM) to convert the high-k modes into free-space modes (k≤k0) aiming at increasing η. However, much of the NPHMs designs still rely on computationally costly three dimensional (3D) numerical simulations. Thus, we also propose in this thesis a new semi-analytical method to model, both in two- and three-dimensions (2D and 3D, respectively), the radiation emission of QEs interacting with nano-patterned structures. The low computational cost of this method makes it attractive for mapping P and η as function of the QE and NPHM relative position. This mapping is a helpful tool to understand the decay behavior of the whole system since QEs are arbitrarily distributed and oriented inside the NPHM. The analytically calculated decay curve allows the systems effective quantum efficiency (ηeff) and Purcell factor (Peff) to be directly obtained assuming multiple arbitrarily distributed electromagnetic sources. In this sense, we propose here a new procedure to optimize the NPHM geometrical parameters to maximize ηeff while achieving the desired Peff. We apply the proposed model to an NPHM composed of nine Ag/SiO2 layers, with the polymer host layer embedded with Rhodamine 6G, to maximize ηeff for a specified tenfold increase of Peff. This procedure allowed ηeff to be increased by 69% and 170% for one- and two-dimensional nano-patterning, respectively. Moreover, the time required to build the P and η maps (used in the calculation of the decay behavior) is reduced by approximately 96% when compared to those numerically calculated via FDTD. This procedure paves the way to the realization of new high-speed and efficient light sources for telecommunication applications.
Nos últimos anos, intensivo esforço tem sido devotado para o estudo de novas método para o controla da missão de fótons de emissores quânticos (EQs), especialmente para aplicações em telecomunicações. Estes métodos dependem da adaptação da radiação dos EQs, geralmente avaliadas por meio das bem conhecidas figuras de mérito, como o tempo de meia vida (τ) e a eficiência quântica (η). O controle da emissão de fótons é importante pois quanto mais rápido os fótons são emitidos, maior é o número de vezes que o EQ retorna ao seu estado excitado por segundo. Portanto, é crucial criar canais de decaimento adicionais para reduzir τ, o que necessariamente requer o aumento do fator de Purcell (P). Uma das abordagens mais promissoras para aumentar P envolve uma nova classe de metamateriais, conhecida como metamateriais hiperbólicos (MHs). Esta classe de materiais apresenta pronunciada anisotropia, onde os elementos paralelo e perpendicular do tensor de permissividade (em relação ao eixo de anisotropia) apresentam sinais opostos, resultando em uma superfície de isofrequência (SI) hiperboloidal aberta (IS). Essa forma incomum de SI leva à característica mais marcante dos MHs, a existência de modos fotônicos com número de onda (k) muito maior do que aqueles no espaço livre (k0), conhecidos como modos alto-k. Ao manipular esses modos, é possível manipular a densidade de estados fotônicos (DES) dos MHs, controlando assim os parâmetros de radiação do QE. A abordagem mais simples para a criação de MHs é por meio de uma pilha plana de camadas metálicas e dielétricas alternadas. Entretanto, a espessura finita dessas camadas induz a dispersão espacial, tornando a extração de parâmetros efetivos (homogeneização) destes meios uma tarefa desafiadora. Neste contexto, propomos nesta tese uma nova abordagem de recuperação de parâmetros constitutivos a dispersão espacial de todos os parâmetros eletromagnéticos do meio é levada em consideração. Nós demonstramos que a parte real da curva de dispersão se aplaina (correspondentemente com uma grande parte imaginária) devido à ausência de modos propagantes dentro do metamaterial. Esta região plana é fortemente dependente das espessuras das camadas e é uma manifestação direta da dispersão espacial Além disso, nós mostramos que se a dispersão espacial não for corretamente considerada no processo de homogeneização, o tempo de meia vida do EQ pode ser superestimado, o que é prejudicial para aplicações de telecomunicações. Além disso, demonstramos como melhorar P por um fator maior que 100 com o uso de MHs. a maior parte da potência dissipada pelos EQs são acopladas nos MHs como modos de alto-k (que não se propagam no espaço livre). Portanto, a energia é dissipada termicamente no interior do MH, resultando em uma redução de η. Alguns autores recorreram a MHs nano-estruturados (MHNE) para converter os modos alto-k em modos de espaço livre (k≤k0) visando o aumento de η. No entanto, muitos dos projetos do NPHM ainda dependem de simulações numéricas tridimensionais (3D) computacionalmente dispendiosas. Assim, também propomos nesta tese um novo método semi-analítico para modelar, tanto em duas como em três dimensões (2D e 3D, respectivamente), a emissão de radiação de EQs interagindo com estruturas nano-estruturadas. O baixo custo computacional deste método faz com que seja atrativo para o mapeamento de P e η em função da posição relativa do EQ e do MHNE. Esse mapeamento é uma ferramenta útil para entender o comportamento de decaimento de todo o sistema, já que os EQs são arbitrariamente distribuídos e orientados dentro do MHNE. A curva de decaimento calculada analiticamente permite que a eficiência quântica efetiva do sistema (ηeff) e o fator de Purcell (Peff) sejam obtidos diretamente, assumindo múltiplas fontes eletromagnéticas arbitrariamente distribuídas. Neste sentido, propomos aqui um novo procedimento para otimizar os parâmetros geométricos do MHNE visando a maximização de ηeff enquanto Peff é aumentado à um valor desejado. Aplicamos o modelo proposto a um MHNE composto por nove camadas de Ag/SiO2, com a camada de polímero embutida com Rodamina 6G, visando maximizar ηeff para um aumento de dez vezes de Peff. Este procedimento permitiu que o ηeff fosse incrementado em 69% e 170% para nano-estruturas uni e bidimensionais, respectivamente. Além disso, o tempo necessário para construir os mapas P e η (utilizados no cálculo da curva de decaimento) é reduzido em aproximadamente 96% quando comparado com os calculados numericamente via FDTD. Este procedimento abre caminho para o desenvolvimento de novas fontes de luz de alta velocidade e eficiência para aplicações de telecomunicações.

Le contrôle des ondes électromagnétiques joue un rôle fondamental dans les technologies photoniques actuelles. De nos jours, on assiste à une demande croissante de composants agiles capable d'absorber efficacement les ondes électromagnétiques dans divers gamme de fréquences. Habituellement, ces absorbeurs s'appuient sur les résonances plasmoniques qui apparaissent dans les métaux nobles dans la gamme visible. Cependant, l'extension des propriétés plasmoniques aux spectres infrarouge et THz nécessite des matériaux adéquats ayant un comportement métallique à ces fréquences. Dans ce travail, nous étudions numériquement et expérimentalement les structures métal-isolant-métal (MIM) réalisées à partir de semi-conducteur hautement dopé Si: InAsSb qui a un comportement métallique dans la gamme infrarouge. Dans la deuxième partie, nous avons amélioré l'efficacité des résonateurs MIM en utilisant des métamatériaux hyperboliques qui miniaturisent les résonateurs. Dans la dernière partie, nous proposons un design universel ultra-mince qui permet de dépasser les contraintes associées au choix des matériaux et permettant la réalisation d'un absorbeur fonctionnant sur une gamme spectrale allant de l'infrarouge aux micro-onde
The control of light absorbance plays a fundamental role in today's photonic technologies. And the urge to design and develop flexible structures that can absorb electromagnetic waves is very growing these days. Usually, these absorbers relies on plasmonic resonances that arise in noble metals in the visible range. However, the extension of the plasmonic properties to the infrared and THz spectra requires adequate materials that have a metallic behavior at these frequencies. In this work, we study numerically and experimentally the metal-insulator-metal (MIM) structures realized from highly doped semiconductor Si:InAsSb that has a metallic behavior in the infrared range. In the second, part we improved the efficiency of the MIM resonators by using hyperbolic metamaterials that also miniaturize the resonators. In the last part, we propose an ultra-thin universal design that overcomes the material barrier so that the total absorption can be achieved for different spectral ranges without changing the material

De nos jours, les plasmas sont principalement utilisés à des fins industrielles. L'un des exemples les plus fréquemment cités d'utilisation industrielle est la production d'énergie électrique via des réacteurs nucléaires à fusion. Pour contenir le plasma correctement à l'intérieur du réacteur, un champ magnétique est imposé en arrière-plan, et la densité et la température du plasma doivent être précisément contrôlées. Cela est effectué en envoyant des ondes électromagnétiques à des fréquences et dans des directions spécifiques en fonction des caractéristiques du plasma.La première partie de cette thèse de doctorat est consacrée à l'étude du modèle du plasma avec un fort champ magnétique en arrière-plan, ce qui correspond à un métamatériau hyperbolique. L'objectif est d'étendre les résultats existant en 2D au cas 3D et de dériver une condition de radiation. Nous introduisons une séparation des champs électriques et magnétiques ressemblant à la décomposition TE et TM habituelle, puis nous présentons quelques résultats sur les deux problèmes résultants. Les résultats sont dans un état très partiel et constituent un brouillon approximatif sur le sujet.La deuxième partie étudie l'EDP dégénérée associée aux ondes résonantes « lower-hybrid » dans le plasma. Le problème aux limites associé est bien posé dans un cadre variationnel « naturel ». Cependant, ce cadre n'inclut pas le comportement singulier présenté par les solutions physiques obtenues via le principe d'absorption limite. Ce comportement singulier est important du point de vue physique car il induit le chauffage du plasma mentionné précédemment. Un des résultats clés de cette deuxième partie est la définition d'une notion de saut à travers l'interface à l'intérieur du domaine, ce qui permet de caractériser la décomposition de la solution d'absorption limite en parties régulière et singulière
Nowadays, plasmas are mainly used for industrial purpose. One of the most frequently cited examples of industrial use is electric energy production via fusion nuclear reactors. Then, in order to contain plasma properly inside the reactor, a background magnetic field is imposed, and the density and temperature of the plasma must be precisely controlled. This is done by sending electromagnetic waves at specific frequencies and directions depending on the characteristics of the plasma.The first part of this PhD thesis consists in the study of the model of plasma in a strong background magnetic field, which corresponds to a hyperbolic metamaterial. The objective is to extend the existing results in 2D to the 3D-case and to derive a radiation condition. We introduce a splitting of the electric and magnetic fields resembling the usual TE and TM decomposition, then, it gives some results on the two resulting problems. The results are in a very partial state, and constitute a rough draft on the subject.The second part consists in the study of the degenerate PDE associated to the lower-hybrid resonant waves in plasma. The associated boundary-value problem is well-posed within a ``natural'' variational framework. However, this framework does not include the singular behavior presented by the physical solutions obtained via the limiting absorption principle. Notice that this singular behavior is important from the physical point of view since it induces the plasma heating mentioned before. One of the key results of this second part is the definition of a notion of weak jump through the interface inside the domain, which allows to characterize the decomposition of the limiting absorption solution into a regular and a singular parts

碩士
國立交通大學
電子工程學系 電子研究所
104
A new structure for a nearly-perfect hyperbolic meta-material(HMM) absorber is proposed, and initial experimental verification is provided. To date, HMM PMAs are realized using tapered stacks that can provide adiabatic waveguiding over a wide spectral range. Nevertheless, the tapered nature can prevent its usage for large-area applications such as the emitters in thermophotovoltaics (TPV). The design proposed here has decent wavelength scalability and can be used from optical black holes to microwave perfect absorbers. The physics behind the HMM straight-sidewall cavity is the broadband highly confined resonance. While, in most of the cases, the broadband quasi-guided modes are weekly confined in nature, the HMM cavity can provide broadband resonances but still maintain reasonably strong oscillation strength for high absorption. This is because the photonic density of state (PDOS) is boosted dramatically by the hyperbolic dispersion of the straight-sidewall Al/SiO2 stacks.

碩士
國立臺灣海洋大學
光電科學研究所
107
Silver nanoparticles on hyperbolic metamaterial (HMM) fabricated by thermal deposition and sputter system respectively have been studied. Surface morphology and uniformity of the structure were observed by Atomic Force Microscope (AFM) and Scanning Electron Microscope (SEM). The light absorption band of the structure was measured by spectrometer. The influences of different SiO2 thickness between silver nanoparticles and hyperbolic metamaterial on Surface Enhanced Raman Spectroscopy (SERS) have been investigated. Afterwards, the samples were sputtered different thickness of SiO2 followed by thermal deposited Alq3 and DCJTB, respectively. The increasing intensity of Photoluminescence (PL) and the significantly decreased life time of Time-Resolved Photoluminescence (TRPL) were observed.

碩士
國立臺灣海洋大學
光電科學研究所
103
The main goal of this thesis is to explore the hyperbolic metamaterial multi-layer structure for fluorescence enhancementof CdSe / ZnS quantum dots (CdSe / ZnS Core-Shell Quantum Dot) and fluorescent dye(DCJTB).We put different nanoparticles:silver nanoparticles/nanostars on multi-layers substrate to probe the influence of nanoparticles on the photoluminescence and time-resolved photoluminescence of quantum dots and DCJTB. We used D.C.sputter to manufacture the Si-Ag multi-layers and we found that quantum dots on multi-layers,the PL intensity of quantum dotson multi-layersis enhanced approximately 3.051 times than that on glass substrate. After spreading silver nanoparticles on multi-layers,the PL intensity of quantum dotsis enhanced approximately 5.029 times and the PL intensity of quantum dotsis enhanced 6.129times with thenanostar on multi-layers. We use COMSOL to simulate and choose single layer’s thickness to control the absorptionof substrate.We then use thermal evaporation to deposit DCJTB on multi-layers substrate.We found that the PL intensity of dyeon multi-layers is 4.007 times than that on glass substrate. After adding silver nanoparticles on multi-layers,the PL intensity of dye is enhanced approximately 5.634 times.Finally, we put nanostar on the substrate,PL intensity of dyeis enhanced 7.675times and its lifetime shrinks 42.2%

碩士
國立臺灣海洋大學
光電科學研究所
105
In this paper, Fourier ion beam (FIB)、magnetron sputtering (Magnetron Sputter) are used to make the multilayered multilayer structure, and the antenna is strengthened by FIB etching to improve the field enhancement and directionality. We firstly usedScanning electron microscope (SEM) ,respectively to observe the surface roughness , thickness and the uniformityof the substrates.Ensure the width between the nano antenna. Secondly ,we used Photoluminescence to measure the light of absorption wave in the structure. For investigating the influences of photoluminescence (PL) and time-resolved photoluminescence (TRPL),we deposited the fluorescent dye "DCJTB" on the different thickness of hyperbolic meta-material . We observed that the PL intensity ofnano-antenna on HMM sample which deposited 75 nm DCJTB was increased about 17 times, and the lifetime could be shortened about 46% comparing with deposited 75nm DCJTB on Silicon. We demonstrated that the localized surface plasma of nano-antenna on HMM samples could enhance the resonance vibration strength of fluorescent molecules. Therefore, when the PL intensity is increased, the lifetime is shortened at the same time.

碩士
國立清華大學
光電工程研究所
106
We present an analytical description of the modes property for a dipole emitter when put above a gold nanorods hyperbolic metamaterials slab. In the long wavelength region, we simplify the hyperbolic metamaterials as an effective anisotropic medium and show that the optimized purcell factor originates from the imaginary part of the TM mode reflection coefficients, which is not only determined by bulk hyperbolic dispersion but also the selective slab thickness due to the Fabry-Perot resonance. We characterize the plane wave propagation inside the HMM slab as ‘critical coupling mode’ and ‘resonating mode’ and explain the dipole field enhancement in a view of angular expansion. Factors of HMM slab thickness, the metal fill ratio, metal loss and quenching effect are taken into discussion. Using the rigorous coupled wave analysis with the optimized geometry, we deliberately design a silicon bullseye grating and demonstrate more than 12 folds farfield radiation enhancement. This numerical method is not only suitable for nanorods HMM material but also for multilayer HMM material and other anisotropic medium, serving as an efficient tool for the design of high speed incoherent optical source devices.

碩士
國立臺灣海洋大學
光電科學研究所
105
In this study, we fabricated and characterized a large area of periodic germanium nanostructures on hyperbolic metamaterial (HMM) substrate by using nanosphere lithography (NSL) and then decorated the substrate with nano silver particles and star-shaped gold/sliver nanoparticles. At first, we used scanning electron microscope (SEM) to observe the surface of the substrates and measured the absorption spectrum of the structure to investigated the Surface Enhanced Raman Spectroscopy (SERS) with silver nanoparticles and star-shaped gold/sliver nanoparticles on different thickness of hyperbolic metamaterial (HMM). In the NIR Raman experiment, we used 4-aminothiophenol (4-ATP) to investigate the behaviors of different samples. We fabricated 3 different structures, star-shaped gold/sliver nanoparticles、Ge nanorod and silver particles on Ge HMM with four different thickness. Experimental results showed that Raman signal from HMM with 150nm in thickness had the strongest Raman signal due to the absorption peak near 1064nm.

碩士
國立臺灣海洋大學
光電科學研究所
106
The annealed silver nanoparticles have been grown on hyperbolic metamaterial (HMM) by Multi-targets co-sputter system and Thermal coater, afterwards, surface morphology of the sample has been observed by Atomic Force Microscope (AFM) and then structural integrity and film uniformity of the sample have been investigated by Scanning Electron Microscope (SEM). In addition, the light absorption band of the structure is confirmed by spectrometer, and the influences of the silver particle sizes by different annealing temperatures to the Surface Enhanced Raman Spectroscopy (SERS) have been investigated. Photoluminescence (PL) and time-resolved photoluminescence (TRPL) have been measured after the thermal deposition of fluorescent dye on sample. The results show that annealed silver particles with fluorescent dye Alq3 on HMM can enhance the PL intensity by 12.23 times and reduce the PL life time by 32%, compared with fluorescent dye Alq3 on silicon substrate. Here we prove that surface plasmon resonance between hyperbolic metamaterial and silver nanoparticles can effectively increase the oscillatory intensity of the fluorescent molecules, the PL intensity and shorten the PL lifetime.

碩士
國立臺灣海洋大學
光電科學研究所
103
In this thesis, wemainly used centrifugal method to arrange gold,silver, and unique star-shaped gold nanoparticles on silver-aluminum oxide substrate and Ge-Ag hyperbolic metamaterial substrate to fabricate the SERS substrate. Then, we employed these substrates to measure the Raman spectrum of molecules with different excitation wavelengths, including 532nm and 1064nm, to observe the effect of different metal nanoparticles generated in different excitation wavelength. And we used COMSOL multiphysics software to simulate SERS substrate’s absorborption and distribution of electric field intensity when the nanoparticles were aggregated. We found that the absorption spectrum peak of nanoparticle will be red-shifted and enhanced as nanoparticle aggregation occurs. When the laser excited at 532nm, we found that the Raman intensity of molecules adsorbed on silver nanoparticles over ALD substrates is greater than that adsorbed on silver nanoparticles over HMM substrate. That is due to coupling occurs when the substrate’s absorborption is very close to silver nanoparticle’s absorborption. On the other hand, star-shaped nanoparticle’s signal intensity is greater than gold nanoparticles under 1064nm Raman spectrum, that is because of the absorption spectrum peak of star-shaped nanoparticles at 974nm,which are very close to the laser wavelength, the surface plasma phenomena would be more stronger. Finally, we counted the number density of nanoparticles by using image J software and calculate the Raman spectra contributed from each nanoparticle. We found that the star-shaped nanoparticle’s signal intensity is greater than gold and silver nanoparticles under 1064nm Raman spectrum in the same density. On the ALD substrate, the Raman intensity of molecules adsorbed on mstar-shaped nanoparticles enhanced approximately 5.48 times than that adsorbed on gold nanoparticles under 1064nm Raman spectrum in the same density; the Raman intensity of molecules adsorbed on siliver nanoparticles enhanced approximately 1.49 times than that adsorbed on gold nanoparticles under 1064nm Raman spectrum in the same density. On the HMM substrate, the Raman intensity of molecules adsorbed on star-shaped nanoparticles enhanced approximately 7.17 times than that adsorbed on gold nanoparticles under 1064nm Raman spectrum in the same density; the Raman intensity of molecules adsorbed on siliver nanoparticles enhanced approximately 1.22 times than that adsorbed on gold nanoparticles under 1064nm Raman spectrum in the same density.

碩士
國立臺灣海洋大學
光電科學研究所
105
Abstract In this paper, we used focus-ion-beam (FIB) to mill gold antenna with concentric rings and magnetron sputter to fabricate the metamaterial with hyperbolic property. We then used these nano-structures to enhance the field strength and the directionality of nano-antenna. In the experiment, we firstly used the scanning electron microscope (SEM) to observe the surface of the structure, thickness of the film, integrity, uniformity, different sizes of the circles on hyperbolic metamaterial (HMM ) substrates, and coupling gap between two antenna. We also measured the absorption wavelength of the structure, and examined the characteristics of the samples by Raman spectroscopy to explore the effects of different concentric ring diameters for Surface Enhanced Raman Spectroscopy (SERS). The experimental data show that the 4-aminothiophenol (4-ATP) coated on the hyperbolic metamaterial substrate after milling the concentric rings antenna had an enhanced effect for the Raman signals of coated molecules. By combining hyperbolic metamaterial and gold/silver star-shaped nanoparticles, the Raman signal of 4-ATP can be enhanced up to 7.61 times as compared with that from bare HMM. Keyword: Surface Enhanced Raman Spectroscopy, Hyperbolic Metamaterial.

There is much current interest in coupling emitters, such as fluorescing dye molecules and semiconductor quantum dots to plasmonic systems. Controlling the electromagnetic interactions between quantum emitters and the plasmonic system in the weak, intermediate, and strong coupling regimes has focused on an intense research effort in recent years. The weak and intermediate coupling regimes are associated with enhancement of the emission and absorption rates of nearby resonant emitters, while the strong coupling regime allows for coherent energy transfer between emitters and plasmonic system. Interest in this topic is motivated by the ability of plasmonic system to confine light to sub diffraction-limited mode volumes, which can drive coherence effects in collective quantum emitter systems, leading to applications in coherent light generation, photochemistry, quantum information processing, and quantum photonic fluids. In the first part of my thesis, I will discuss the experimental and theoretical study of room-temperature tunable coupling of single-photon emitting colloidal quantum dots(CQDs) to localised and delocalised modes in plasmonic nanocavity arrays using second-order photon correlation and time-resolved photoluminescence measurement. We will also discuss experimental evidence of indirect excitation of remote CQDs mediated by both the modes in the plasmonic arrays and propose a model to explain these observations. The second part of my thesis focuses on room temperature strong coupling between excitons in CQD assembly and surface lattice resonances in Plasmonic lattices and the emergence of the additional polaritonic peak in photoluminescence spectra of strongly coupled CQD-plasmonic lattice hybrid templates. In the third work, we will discuss the experimental and theoretical study of long-range optical energy propagation due to strongly coupled CQD-plasmonic lattice devices.The last part of my thesis focuses on the observation of photonic spin momentum locking in achiral CQD coupled to a special class of plasmonic metamaterial with hyperbolic isofrequency, known as hyperbolic metamaterial(HMM). We provide a theoretical explanation for the emergence of spin momentum locking through rigorous modeling based on photon Green’s function where pseudo spin of light arises from coupling of CQDs to evanescent modes of HMM.

碩士
國立臺灣海洋大學
光電科學研究所
104
In this study,we fabricated and characterized the substrates of silver nanorod array on hyperbolic metamaterial (HMM) by using thermal evaporation combined with oblique angle deposition (OAD),nanosphere lithography (NSL) and reactive-ion etching (RIE). At first, we used atomic force microscope (AFM) and scanning electron microscope (SEM),respectively, to observe the surface of the substrates and then measured theabsorptionspectra of the structure,and examined the characteristics ofthe substrates by Surface Enhanced Raman Spectroscopy (SERS). Finally, we deposited fluorescent dye "DCJTB" on the substrate and investigated its optical propoerties by using photoluminescence (PL) and time-resolved photoluminescence (TRPL). We observed that the PL intensity and lifetime of DCJTB75 nmin thickness deposited on silver nanorodsover HMM substrate was increased about 20.7times and could be shortened about 59%, respectively,as compared with those DCJTB deposted on bare silicon. We demonstrated that the localized surface plasmon of silver nanorodsover HMM substrates could enhance the resonance vibration strength of fluorescent molecules. Therefore, the PL intensity is increased and the lifetime is shortened at the same time.

碩士
國立臺灣大學
應用力學研究所
104
Conventional dielectric waveguides, such as optical fiber, cannot operate at the nanoscale due to the diffraction limit that light cannot be guided within the subwavelength structures. Plasmonic waveguides (PWs), guiding surface plasmon-polaritons (SPPs)––a form of surface waves which have smaller effective wavelength at the same frequency, make light can propagate in subwavelength dimensions and have been used in photonic integrated circuits. However, the propagation length of SPPs in PWs are limited due to the losses of metal. Hybrid plasmonic waveguides (HPWs) combine the advantages of the dielectric waveguides and the PWs, which have a balanced performance between high confinement and long-range propagation. On the other hand, anisotropic material has been used to control the optical momentum of waves in different directions. In this study, we propose and analyze a new design of cylindrical PWs based on strongly anisotropic media––hyperbolic metamaterial, that is, cylindrical PWs cladded by hyperbolic metamaterials or metal–dielectric–hyperbolic (MDH) cylindrical waveguides. This new type of waveguides has similar function as the HPWs with high field confinement and the long propagation length. 　　We analytically solve the basic properties of the MDH cylindrical waveguides: First, we derive the dispersion equation of three-layer anisotropic cylindrical waveguides based on Maxwell’s equations. Second, the propagation constant, propagation length, mode area and the figure of merit (FOM) of the transverse magnetic modes are obtained from the dispersion relation. Through observing the trend of the FOM, we found the MDH cylindrical waveguides have high field confinement which approximates to the isotropic metal–dielectric–metal (MDM) cylindrical waveguides. Nevertheless, the propagation losses will be sharply reduced, which leads to the longer propagation length. For example, for the case of Ag–ZnO–hyperbolic cylindrical waveguides with the size around 400 nm at wavelength, it perform both extremely small mode area that approximates to the Ag–ZnO–Ag cylindrical waveguides and better propagation length which is almost twice longer than that of the MDM cases.

碩士
國立清華大學
光電工程研究所
104
Chiral structures exhibit strong interactions with circularly polarized light, and have been demonstrated to show many polarization dependent properties, such as circular dichroism. In this study, we use a complete and incomplete dielectric helix array as a model system to examine the interactions of circularly polarized light with helical structures. A dielectric helix array produces the circular polarization band gaps having not only the same handedness with the structure but also the opposite handedness. The gap with the opposite handedness results from additional chiral motifs induced by the adjacent helices. Dual polarization band gaps can thus be tailored by varying the geometrical parameters, and circular-polarization dependent properties can be manipulated for optoelectronic devices and applications. Hyperbolic metamaterial (HMM) has attracted considerable attention owing to several exotic optical properties. One of these is the enhanced spontaneous emission, resulting from the hyperbolic dispersion of HMM. However, the out-coupling of light from HMMs is difficult due to the evanescent character of the high-k modes at the surface. In this study, the optical properties of nanowire HMMs with the enhanced structure are characterized. The results show the loss in the system is reduced, and the high-k modes of HMM is coupled out by virtue of the enhanced structure. The radiative enhancement can reach the value of 7.2 in the infrared region. The resonances inside the nanowire HMM are also analyzed to examine the mechanism of the enhancement of light. The analysis results are important toward engineering highly-efficient photonic devices based on HMMs.

Hui, Ka Shing = 梯度的各向異性超材料的廣角度的古斯-漢欣位移 / 許嘉誠.
Thesis (M.Phil.)--Chinese University of Hong Kong, 2013.
Includes bibliographical references (leaves 78-82).
Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web.
Abstracts also in Chinese.
Hui, Ka Shing = Ti du de ge xiang yi xing chao cai liao de guang jiao du de Gusi-han xin wei yi / Xu Jiacheng.

碩士
國立交通大學
光電工程研究所
105
Recently, increasing attentions are paid to the two-dimensional materials especially TMDCs due to its direct band gap light emission. It was view as a next generation semiconductor materials which would apply to the optoelectronic device. However, challenging of TMDCs was that they suffered weak quantum yield. Therefore, in this study, we demonstrated the spontaneous emmission enhancement of MoS2 on the planar hyperbolic metamaterials (P- HMMs). In the first part, we designed the planar P-HMM at the PL wavelength of MoS2 which have the better mode coupling in the vertical direction compared to multilayers HMMs. Moreover, its anisotropic property make the PL of MoS2 led to in-plane confinement and resonance. Therefore, the strong coupling between structure and two-dimensional materials and spontaneous emission enhancement was observed in both experiment and simulation. In the second part, we started to curved the planar 1-D HMM into the concentric planar HMM (CPHMM) because we expected the better resonance in the ring cavity. On one hand, because the concentric structure could support the Whisper Gallery Mode (WGM) resonance compared to one dimensional resonance, the higher spontaneous emission enhancement of MoS2 with CP-HMM was observed than enhancement with P-HMM. On the other hand, by the photoluminescence mapping analysis, the highest happened at the inner edge of CP-HMM than other position of CP-HMM. It meant the energy concentration at the inner edge which led to the stronger mode coupling to the two-dimensional materials led to the higher enhancement. The similar results was also confirmed by the simulation results by Finite Element Method. Therefore, it showed the possibility to develop the ultrasmall light source combing subwavelength cavity and atomic thick two-dimensional materials.

碩士
國立清華大學
材料科學工程學系
105
The optical responses of one dimensional hyperbolic metamaterials (1DHMMs) are usually determined by effective medium theory based on the long wavelength approximation. However, the long wavelength approximation shows significant deviation when the wavelength of the incident light is comparable with the unit cell of HMMs. Therefore, plasmonic band theory have been suggested to analyze the 1DHMMs recently and the existence of the interface state has been proposed. The requirement for the existence of the interface state is determined by the admittance matching condition. Furthermore, the interface state formation in the plasmonic band gap can be related to the properties of the plasmonic band in terms of the wave admittance, so called “bulk-interface correspondence”. In this work, we experimentally identify the existence of the interface state of 1DHMM by the Kretschmann and the Otto configurations. By varying the metallic filling ratio in the 1DHMMs, we successfully demonstrate the disappearance and reappearance of the interface state which indicates the optical topological phase transition of 1DHMMs.

Over the past several decades our understanding and meticulous characterization of the transient and spatial properties of materials evolved rapidly. The results present an exciting field for discovery, and craft materials to control and reshape light that we are just beginning to fathom. State-of-the-art nano-deposition processes, for example, can be utilized to build stratified waveguides made of thin dielectric layers, which put together result in a material with effective abnormal dispersion. Moreover, materials once deemed well known are revealing astonishing properties, v.gr. chalcogenide glasses undergo an atomic reconfiguration when illuminated with electrons or photons, this ensues in a temporal modification of its permittivity and permeability which could be used to build new Photonic Integrated Circuits.. This work revolves around the characterization and model of heterogeneous and time-varying materials and their applications, revisits Maxwell's equations in the context of nonlinear space- and time-varying media, and based on it introduces a numerical scheme that can be used to model waves in this kind of media. Finally some interesting applications for light confinement and beam transformations are shown.