M.Phil. (Energy Studies) / Non-destructive investigations of unusual natural polycrystalline diamond samples are reported. The samples originate from various international locations discovered in soils and sediments and may have been formed by di erent mechanisms which are the subject of debate. Analysis techniques include scanning electron microscopy, with energy dispersive spectroscopy and X-ray di raction. Sample composition, structure and surface stresses were investigated. The samples (two Egyptian nodules, two Brazillian carbonados, two Venetian ballas diamonds and a polycrystalline diamond compact sample consisting of a polycrystalline diamond layer sintered onto a Co-cemented tungsten carbide support) are cubic diamonds, with varying amounts of minority phases. In most cases the minority phases could not be identi ed unambiguously due to their low intensities and the overlap of Bragg peaks. The Egyptian nodule samples in particular showed a large presence of oxygen that could not be linked to speci c metal oxides. The Ballas samples had the lowest impurity content. Using a Rietveld based quanti cation analysis, the crystalline cubic diamond contents were determined respectively as 99 wt.%, 98 wt.% and 76 wt.% in the Ballas, Brazilian carbonado and Egyptian nodule samples. A signi cant result from this study is the substantial inhomogeneous peak broadening observed in the X-ray diffraction patterns of the Egyptian samples. This is indicative of the presence of nano-crystalline diamond grains in addition to substantial mechanical deformation with extensive accumulation of dislocations and crystalline defects. These observations are supportive of a recently proposed impact mechanism for their formation.

Orientador: Thiago Pedro Mayer Alegre / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin / Made available in DSpace on 2018-08-31T00:04:36Z (GMT). No. of bitstreams: 1 Benevides_RodrigodaSilva_M.pdf: 12114965 bytes, checksum: 9db892fbca5fe67d883b58515f6e1dc7 (MD5) Previous issue date: 2016 / Resumo: A área de optomecânica de cavidades passou por um grande desenvolvimento na última década. O crescente interesse nesta área foi impulsionado principalmente pela interessante conexão entre movimentos mecânicos e campos ópticos. Tal acoplamento é amplamente explorado em diversos experimentos, com escalas variando de interferômetros quilométricos a cavidades ópticas microestruturadas. O principal desafio em todos estes experimentos é criar um dispositivo optomecânico com um longo tempo de vida óptico e mecânico, ao mesmo tempo em que mantém um grande acoplamento. Neste contexto, as cavidades de cristal fotônico surgiram como fortes candidatas já que elas são capazes de confinar campo óptico em um volume modal muito reduzido e por um longo tempo de vida. No regime clássico, estes pequenos dispositivos, que podem oscilar mecanicamente com frequências de alguns poucos MHz até dezenas de GHz, permitem detectar forças, massas e deslocamentos muito pequenos. Elas também são usadas para produzir osciladores mecânicos de alta qualidade, que podem ser sincronizados por intermédio do campo óptico. No regime quântico, a optomecânica quântica de cavidades tem sido usada para ajudar na compreensão do fenômeno de decoerência em uma escala mesoscópica, criando estados não-clássicos fortemente acoplados entre campo óptico e movimento mecânico, intermediado pela interação optomecânica. Entretanto, até agora, foram realizados poucos estudos sobre a possibilidade de produção destes dispositivos em larga escala, um passo necessário para massivas aplicações tecnológicas e científicas destes dispositivos. Neste trabalho, descrevemos um estudo detalhado de cavidades optomecânicas baseadas em cristais fotônicos produzidos numa fábrica de dispositivos compatíveis com indústria CMOS. Nós demonstramos a viabilidade desta plataforma explorando três geometrias distintas de cristais fotônicos. Primeiramente, nós mostramos como atingir fatores de qualidade muito elevados usando uma geometria consistente com as limitações de fabricação. Nossos fatores de qualidade são os maiores já reportados usando cavidades de cristal fotônico fabricadas com litografia óptica. Em seguida, investigamos uma cavidade do tipo fenda, possibilitando a produção de alto acoplamento optomecânico usando um movimento mecânico planar. Por fim, desenhamos um escudo acústico, com dimensões variadas, para restringir o modo mecânico para dentro da região óptica. Essa estratégia foi usada de forma bem sucedida para produzir altos fatores de qualidade mecânicos e acoplamentos optomecânicos, permitindo a observação de resfriamento e amplificação de modos mecânicos à baixa temperatura / Abstract: The field of cavity optomechanics has experienced a rapid growth in last decade. The increasing interest in this area was mostly driven by the intricate interface between mechanical motion and the optical field. Such coupling is widely explored in a variety of experiments scaling from kilometer long interferometers to micrometer optical cavities. The challenge on all these experiments is to create an optomechanical device with long-living optical and mechanical resonances while keeping a large coupling rate. In this context photonic crystal cavities have emerged as a strong candidate since they are able to produce very small optical mode volume and long optical lifetime. In the classical regime, these tiny devices, which can mechanically oscillate from frequencies ranging from couple MHz up to tens of GHz, allows for highly sensitive small forces, masses, displacements and acceleration detectors. They are also used to produce high quality optically driven mechanical oscillators which can be synchronized via an optical field. In the quantum regime, cavity quantum optomechanics is being used to understand decoherence phenomena in a mesoscopic scale by creating nonclassical states between light and mechanical modes intermediated by optomechanical interaction. However up to now, few studies have been done concerning the possibility of large scale production of these devices, a necessary step towards massive technological and scientific application of these devices. In this work, we describe a detailed study of optomechanical cavities based upon photonic crystal cavities fabricated in a CMOS-compatible commercial foundry. We prove the feasibility of this platform exploring three photonic crystal designs. First, we show how to achieve ultra-high optical quality factors using a design resilient to the fabrication constrains. Our demonstrated quality factors are the largest ever reported using photonic crystal cavities manufactured by optical lithography. Secondly, we investigate a slot type optical cavity, able to produce very large optomechanical coupling using a simple in-plane motion. Finally, we design a trimmable acoustic shield to restrict the mechanical motion inside the optical region. Such strategy was successfully used to produce high mechanical quality factor and optomechanical coupling which enabled the observation of cooling and amplification of mechanical modes at low temperature / Mestrado / Física / Mestre em Física / 2014/12875-4 / 132737/2014-0 / FAPESP / CNPQ

Atteindre le régime de couplage fort entre des nanocavités et des systèmes atomiques est un élément clé dans l'information quantique. Durant ma thèse, j'ai designé et fabriqué des nanocavités à cristal photonique en GaInP pour le couplage fort autour de 800 nm, longueur d'onde typique des atomes du Rubidium (780 nm) et de Césium (852 nm), les plus utilisés dans le domaine, ainsi que de l'Argon (811 nm). L'objectif est de faire interagir ces atomes avec la partie évanescente du mode fondamental de la nanocavité. Pour cela, un facteur de qualité de l'ordre de 8.10^4 et un volume modal inférieur à 0,04 µm^3 est nécessaire.La nanocavité est l'élément clé d'une plateforme nanophotonique. Nos plateformes sont composées d'une nanocavité à cristal photonique résonant autour de 800 nm, d'un réseau-coupleur pour collecter la lumière issue d'une fibre optique et vice versa et de guides d'alimentation pour transporter la lumière du réseau-coupleur à la nanocavité. Plusieurs défis technologiques ont émergé. La nanocavité doit avoir un fort facteur de qualité et un faible volume modal, le réseau-coupleur doit collecter le maximum de lumière issue de la fibre, les guides d'alimentation doivent transporter la lumière sans perte et, enfin, un mécanisme pour coupler la lumière des guides d'alimentation dans la nanocavité devait être trouvé.J'ai simulé, designé, fabriqué et caractérisé les éléments de ma structure. J'ai obtenu des facteurs de qualité supérieurs à 10^7 en théorie, et de l'ordre de 2.10^4 expérimentalement, détenant ainsi le record pour les cavités en GaInP autour de la longueur d'onde de 800 nm pavant la voie à la réalisation des expériences de couplage fort. / Reaching the strong coupling between nanocavities and atomic systems is a key element for Quantum Information. During my PhD, I designed and fabricated photonic crystal nanocavities in Gallium Indium Phosphide (GaInP)for strong coupling around 800,nm, typical wavelength of atoms such as Rubidium (780,nm), Cesium (852 nm), the most used in this domain, and the Argon atoms (811 nm).The aim of my PhD thesis is to provide with a nanophotonic platform dedicated to strong coupling interaction. For this, nanocavities having optical resonances arounf 800 nm, with quality factors larger than 8.10^4 and mode volumes smaller than 0.04µm^3 are necessary.The nanocavity is a key element of nanophotonic plateform. Our platforms are composed of a photonic crystal nanocavityitself, a grating-coupler in order to collect light from a optic fiber and vice versa and feeding waveguides in order to transport the light from the grating-coupler to the cavity. An efficient nanophtonic platfom for a reaslitic implementation should have a nanocavity with a large Q-factor and small mode volume. The grating-coupler must efficiently collect the light from the optical fiber, and the feeding waveguides must transport the light without losses.I simulated, designed,fabricated and caracterized the elements of my structure. I obtained quality factors larger than 10^7 in theory, and about 2.10^4 experimentally, getting the record for the nanocavities in GaInP around the wavelength 800 nm, which make them close to realize experiments of strong coupling.

La réalisation d’un laser en optique intégrée sur niobate de lithium dopé erbium passe par la création d’une cavité Fabry-Pérot. Cette cavité peut être obtenue de manière classique en déposant des miroirs diélectriques multicouches aux extrémités du guide d’onde. Des problèmes de fiabilité de fabrications de ces miroirs peuvent être contournés en utilisant des réseaux de Bragg gravés à la surface du guide d’onde. Une autre approche, c’est un laser DFB bien connu, dans ce cas le cœur du guide à contraste d’indice, est structuré périodiquement par des réseaux de Bragg aussi gravés à la surface. Cette thèse présente une nouvelle configuration d’un cristal photonique (CP) 2D de forme originale LOM (pour Laterally Over-Modulated) pour remplacer les réseaux de Bragg gravés à la surface de guide d’onde de titane diffusé sur un substrat de niobate de lithium dopé erbium. Ce travail de thèse s'inscrit dans ce mouvement. Son but est la conception, la fabrication et la caractérisation de LOM, destinées à réaliser un laser émettant à λ = 1,55µm répondant aux exigences de l'intégration photonique. La structure LOM proposée vise en même temps : - Le renforcement de l’émission spontanée par effet Purcell dans un milieu amplificateur où le couplage, de la sur-modulation de l’indice optique CP1D (effet Bragg) et CP2D (BIP), replie les relations de dispersion et crée de fait des régions de faible vitesse de groupe. - Le remplacement de la configuration Fabry-Pérot nécessitant un dépôt de couche diélectrique par une structure DFB réalisable en une seule étape de fabrication, d’où le choix de la technologie FIB « Focused Ion Beam ». L’optimisation de LOM occupe une partie du travail. Des simulations numériques ont été menées en deux dimensions par un logiciel « RSoft », utilisant les techniques des ondes planes et FDTD, pour obtenir un meilleur rendement de transmission possible autour de 1.55µm. En accord avec les simulations, nous présentons la réalisation et la caractérisation de LOM dans un guide d’onde Er:Ti:LiNbO3 de coupe X propagation Z pompé à 980nm par une diode laser continue. Un gain d’amplification de 9 dB a été obtenu pour un LOM de 780 trous d’air de diamètre 290nm et de période 540nm constituant une surface de (22µm X 9µm). L’étape suivante consiste à améliorer le LOM pour arriver à créer un laser intégré. / Achieving an erbium doped lithium niobate integrated optical laser needs to create a classic Fabry-Perot cavity or a distributed feedback structure (DFB). The Fabry-Perot cavity can be obtained by a multilayer dielectric mirrors at the ends of the waveguide. In the DFB Structure the waveguide is structured periodically by a surface Bragg gratings. This thesis presents a new structure of a 2D photonic crystals (PC) form called LOM (Laterally Over- Modulated) to replace Bragg gratings. The objective of this thesis is the design, manufacture and characterisation of the LOM structure, intended to achieve a LiNbO3 integrated laser emitting at 1.55μm. The proposed LOM structure aims at the same time: - To enhance the spontaneous emission by Purcell effect in Er:LiNbO3 area where LOM structure allows fold dispersion relations and create regions of low group velocity. - To replace the Fabry-Pérot structure by a LOM requiring only one-step growth, where the choice of FIB "Focused Ion Beam" technology. Optimization of the LOM structure occupies part of the work. Numerical calculations were conducted by "RSoft" software, using plan-waves and FDTD techniques, for maximum transmission around 1.55μm. Finally, we present the achievement and the characterisation of our LOM structure in a x-cut and z-propagating Ti:Er:LiNbO3 waveguide using 980nm pump. A 9 dB gain was obtained for a LOM sample (22 μmX9 μm) formed by 780 air holes of diameter D=290 nm and period a=540 nm. The next step is to improve the LOM structure to create an integrated laser.

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第20090号 / 工博第4257号 / 新制||工||1659(附属図書館) / 33206 / 京都大学大学院工学研究科電子工学専攻 / (主査)教授 野田 進, 教授 藤田 静雄, 教授 川上 養一 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DGAM

This Licentiate presents the main results of theoretical study of light propagation in photonic structures, namely lasing disk microcavities and photonic crystals. In the first two papers (Paper I and Paper II) we present the developed novel scattering matrix technique dedicated to calculation of resonant states in 2D disk microcavities with the imperfect surface or/and inhomogeneous refractive index. The results demonstrate that the imperfect surface of a cavity has the strongest impact on the quality factor of lasing modes. The generalization of the scattering-matrix technique to the quantum-mecha- nical case has been made in Paper III. That generalization has allowed us to treat a realistic potential of quantum-corrals (which can be considered as nanoscale analogues of optical cavities) and to obtain a good agreement with experimental observations. Papers IV and V address the novel effective Green's function technique for studying propagation of light in photonic crystals. Using this technique we have analyzed characteristics of surface modes and proposed several novel surface-state-based devices for lasing/sensing, waveguiding and light feeding applications. / <p>Report code: LIU-TEK-LIC 2006:5</p>

Three-dimensional (3D) metal photonic crystals (MPCs) can exhibit interesting electromagnetic properties such as ultra-wide photonic or "plasmonic" band gaps, selectively tailored thermal emission, extrinsically modified absorption, and negative refractive index. Yet, optical-wavelength 3D MPCs remain relatively unexplored due to the challenges posed by their fabrication. This work explores the use of multi-photon direct laser writing (DLW) coupled with electroless metallization as a means for preparing MPCs. Multi-photon DLW was used to prepare polymeric photonic crystal (PC) templates having a targeted micron-scale structure and form. MPCs were then created by metallizing the polymeric PCs via wet-chemical electroless deposition. The electromagnetic properties of the polymeric PCs and the metallized structures were characterized using Fourier transform infrared spectroscopy. It is shown that metallization transforms the optical properties of the structures from those of conventional 3D dielectric PCs to those consistent with 3D MPCs that exhibit ultra-wide photonic band gaps. These data demonstrate that multi-photon DLW followed by electroless deposition provides a viable and highly flexible route to MPCs, opening a new path to metal photonic materials and devices.

The purpose of this thesis is to investigate a novel method to develop broadband microstrip (patch) antennas using substrates containing photonic crystals. Photonic crystals are a class of periodic dielectric, metallic, or composite structures that when introduced to an electromagnetic signal can exhibit a forbidden band of frequencies (or bandgap) in which the incident signal destructively interferes and thus is unable to propagate. It is proposed that such photonic crystals will reduce surface waves and prohibit the formation of substrate modes, which are commonly known inhibitors of patch antenna designs. By reducing or eliminating the effects of these electromagnetic inhibitors with photonic crystals, a broadband response can be obtained from inherently narrowband antennas. In addition, it is also proposed that the behavior of the photonic crystals will lead to a reduction in pattern sidelobes resulting in improvements in radiation pattern front-to-back ratio and overall antenna efficiency. This research is verified through analytical simulations and experimental investigations in the Virginia Tech anaechoic chamber. / Master of Science

Globally increasing levels of bandwidth and capacity requirements force the optical communications industry to produce new products that are faster, more powerful, and more efficient. In particular, optical-electronic-optical (O-E-O) conversions in Wavelength Division Multiplexing (WDM) mechanisms prevent higher data transfer speeds and create a serious bottleneck for optical communications. These O-E-O transitions are mostly encountered in the Wavelength converters of WDMs, and as a result, all-optical wavelength conversion methods have become extremely important. The main discussion in this thesis will concentrate on a specific all-optical wavelength conversion mechanism. In this mechanism, photonic crystal structures are integrated with moving MEMS/NEMS structures to create a state-of-the-art all-optical wavelength converter prototype. A wavelength conversion of 20% is achieved using this structure. Since the interaction of light with moving MEMS/NEMS structures plays an important role in the proposed wavelength conversion mechanism, modeling and simulation of electromagnetic waves becomes a very crucial step in the design process. Consequently, a subsection of this thesis will focus on a proposed enhancement to the finite-difference time-domain (FDTD) to model moving structures more efficiently and more realistically. This technique is named "Linear Dielectric Interpolation" and will be applied to more realistically and efficiently model the proposed photonic crystal MEMS/NEMS wavelength conversion mechanism.

Photonic crystals (PCs), consisting of a periodic pattern of variations in the material properties, are one of the platforms proposed as synthetic optical materials to meet the need for optical materials with desired properties. Recently, applications based on dispersive properties of the PCs have been proposed in which PCs are envisioned as optical materials with controllable dispersive properties. Unlike the conventional use of PCs to achieve localization, in these new applications propagation inside the photonic crystal is studied, and their dispersive properties are utilized. Among these applications, the possibility of demultiplexing light using the superprism effect is of particular interest. Possibility of integration and compactness are two main advantages of PC-based wavelength demultiplexers compared to other demultiplexing techniques, for applications including compact spectrometers (for sensing applications), demultiplexers (for communications), and spectral analysis (for information processing systems). I develop the necessary simulation tools to study the dispersive properties of photonic crystals. In particular, I will focus on superprism-based demultiplexing in PCs, and define a phenomenological model to describe different effects in these structures and to study important parameters and trends. A systematic method for the optimization and design of these structures is presented. Implementation of these structures is experimentally demonstrated using the devices fabricated in a planar SOI platform based on designed parameters. In the next step, different approaches to improve the performance of these devices (for better resolution and lower insertion loss) are studied, and extension of the concepts to other material platforms is discussed.