Les structures à cristaux photoniques bidimentionnels ont permis la fabrication d'une large variété de composants nanophotoniques. En particulier, dans les PC parfaits, la densité locale d'états optiques se trouve exacerbée au niveau des points de symétrie du diagramme de bande. Près de ces points, où la vitesse de groupe tend vers zéro, la faible courbure de bande courbure de bande donne lieu à des modes stationnaires, dits de lumière "lente" (ou modes de Bloch lents). Les propriétés de la lumière lente en font de bons candidats pour améliorer l'effet Purcell, pour produire des effets non-linéaires ou pour concevoir des lasers à faible seuil. Parmi ces modes, les modes de Bloch lent émettant dans la direction verticale, c'est à dire situé au niveau du point Γ de la zone de Brillouin, sont particulièrement intéressants pour intégrer des architectures 2D avec de l'optique en espace libre. En particulier, certains de ces modes ont permis la réalisation d'émission laser dans la 3e direction avec des propriétés de polarisation particulières. D'autres applications prometteuses concernent le désordre : en introduisant un désordre aléatoire mais contrôlé dans la structure photonique, il est possible d'induire une transition entre le mode de Bloch lent de la structure ordonnée vers un mode localisé par le désordre, de type localisation d'Anderson dans une structure faiblement désordonnée.Dans cette thèse, les modes de Bloch lents ont été étudiés et caractérisés en Microscopie optique en champ proche. Nous nous sommes concentrés sur les modes en Gamma de la structure graphite. Le SNOM a permis de visualiser la composante évanescente du mode avec une résolution spatiale inférieure à la limite de diffraction. Dans ce travail, nous avons montré que le champ lointain et de l'image en champ proche du mode à la surface du cristal photonique sont différentes et que seules les mesures en champ proche permettent de rendre compte du mode réel à l'intérieur de la membrane de cristal photonique, en accord avec prédiction théorique. L'importance du choix de la sonde (silice, pointe métallisée, Nano-antenne) pour l'étude des structures à cristaux photoniques a également été démontrée. Outre la mesure d'intensité du champ électromagnétique, la polarisation du champ électrique a été mesurée à l'échelle nanométrique pour la première fois par l'aide d'une antenne à ouverture papillon. Ces résultats permettent d'identifier sans équivoque des modes avec les simulations 3D-FDTD.Dans ce travail est également rapporté la première observation de la localisation de la lumière dans deux types de lasers aléatoires à base de cristaux photoniques bidimensionnels. Le caractère aléatoire est introduit soit en déplaçant les positions des motifs du cristal (trous d'air), soit en faisant varier de façon aléatoire le diamètre des trous. Pour la première fois nous avons observé directement par SNOM la localisation de la lumière dans le cristal désordonné. Cela nous a permis d'observer la transition de morphologie du mode de Bloch lent entre le cristal ordonné et le cristal désordonné. / 2D-Photonic crystal (PC) structures have enabled the fabrication of a wide variety of nanophotonic components. In perfect PCs, the exploitation of the enhanced local density of states at critical points of the band diagram has attracted considerable attention. Near these points, where the group velocity vanished, low curvature flat bands give rise to delocalized and stationary optical slow Bloch modes (or slow light modes). Properties of slow light make them good candidates to enhance Purcell or various non-linear effects or to design low-threshold lasers. Among these modes, slow Bloch modes (SBMs) emitting in the vertical direction, i.e. located at the Γ- point of the Brillouin zone are particularly interesting for integrating 2D PC architectures with free space optics. In particular, some SBMs proved to be suitable for achieving strong vertical emission with peculiar polarization properties. Other promising applications concern disorder: by introducing a controlled randomness into the PC structure, it is possible to induce a transition from slow Bloch mode (in ordered PC) to Anderson’s localization (in disordered PC) as a function of disorder degree. In this PhD dissertation, Slow Bloch modes have been studied and characterized by the means of Near-field Scanning Optical microscopy (NSOM). We particularly focused on Slow Bloch laser mode at Γ- point of a honeycomb 2DPC. This NSOM technique enables to visualize the evanescent component of the mode with a spatial resolution below the diffraction limit. In this work, we showed that the far-field and the near-field image of the mode at the 2D-PC surface are different and that near-field results yield a better insight in the real mode structure inside the PC slab in agreement with theoretical prediction. The importance of the probe selection (bare silica, metallized tip and bow-tie aperture nanoantenna) for studying III-V photonic crystal structures was also demonstrated. Besides intensity measurement of the electromagnetic field, the polarization of the electric field has been measured at the nanoscale for the first time by using a bow-tie nano-antenna probe. These results enable the unambiguous identification of the modes with the 3D-FDTD simulations.In this work is also reported the first observation of two-dimensional localization of light in two types of 2D random photonic crystal lasers, where Slow Bloch Mode (SBM) is scattered by artificial structural randomness in triangular PCs. The structural randomness is introduced whether by nanometer displacements in the positions of lattice elements (air holes), whether by variation of the hole diameters. The direct near-field imaging of the lasing mode by use of NSOM for the first time, allowed us to observe the transition of the extended planar SBM to be Anderson localized.

Doctor of Philosophy / Department of Physics / Kristan L. Corwin / This research has focused on the development, demonstration, and characterization of a new type of laser based on optically-pumped gases contained within hollow optical fibers. These novel lasers are appealing for a variety of applications including frequency metrology in the mid-infrared, free-space communications and imaging, and defense applications. Furthermore, because of the hollow core fibers used, this technology may provide the means to surpass the theoretical limits of output power available from high power solid-core fiber laser systems. Gas-filled hollow-core fiber lasers based on population inversion from acetylene ([superscript]12C[subscript]2H[subscript]2) and hydrogen cyanide (HCN) gas contained within the core of a kagome-structured hollow-core photonic crystal fiber have now been demonstrated. The gases are optically pumped via first order rotational-vibrational overtones near 1.5 μm using 1-ns duration pulses from a home-built optical parametric amplifier. Narrow-band laser emission peaks in the 3-μm region corresponding to the ΔJ = ±1 dipole allowed rotational transitions between the pumped vibrational overtone modes and the fundamental C-H stretching modes have been observed in both molecules. High gain resulting from tight confinement of the pump and laser light together with the active gas permits these lasers to operate in a single pass configuration, without the use of any external resonator structure. Studies of the generated mid-infrared pulse energy, threshold energy, and slope efficiency as functions of the launched pump pulse energy and gas pressure have been performed and show an optimum condition where the maximum laser pulse energy is achieved for a given fiber length. The laser pulse shape and the laser-to-pump pulse delay have been observed to change with varying pump pulse energy and gas pressure, resulting from the necessary population inversion being created in the gases at a specific fiber length dependent on the launched pulse energy. Work is on going to demonstrate the first continuous wave version of the laser which may be used to produce a single coherent output from many mutually incoherent pump sources.

This thesis aims at revealing the fundamental guiding and coupling properties of nonreciprocal electromagnetic surface waves on magneto-optical or gyromagnetic media and designing novel applications based on the properties. We introduce the background in the first chapter. We then describe the concept of nonreciprocity and the main calculation method in the second chapter. In the third chapter, we show that one-way waves can be sustained at the edge of a gyromagnetic photonic crystal slab under an external magnetic field. We also investigate the coupling between two parallel one-way waveguides. We reveal the condition for effective co-directional and contra-directional coupling. We also notice that the contra-directional coupling is related to the concept of a “trapped rainbow”. In the fourth chapter, we address the concept of a “trapped rainbow”. It aims at trapping different frequency components of the electromagnetic wave packet at different positions in space permanently. In previous structures, the entire incident wave is reflected due to the strong contra-directional coupling between forward and backward modes. To overcome this difficulty, we show that utilizing nonreciprocal waveguides under a tapered external magnetic field can achieve a truly “trapped rainbow” effect at microwave frequencies. We observe hot spots and relatively long duration times around critical positions through simulations and find that such a trapping effect is robust against disorders. Lastly, in the fifth chapter, we study the one-way waves in a surface magnetoplasmon cavity. We find that the external magnetic field can separate the clockwise and anti-clockwise cavity modes into two totally different frequency ranges. This offers us more choices, both in the frequency ranges and in the one-way directions, for realizing one-way components. We also show the waveguide-cavity coupling by designing a circulator, which establishes the foundation for potential applications. / <p>QC 20160816</p><p></p>

The void spaces in colloidal crystals (opals, three-dimensional (3D) close-packed arrays of silica nanospheres) and their replicas are used as templates in the fabrication of new nanostructured materials. 3D ordered nanomeshes and nanosphere arrays are readily obtained by chemical and/or electrochemical methods. Using silica opal templates, metals or polymers are infiltrated into the interstices between the silica nanospheres. Subsequent dissolution of the opals with HF solution produces open 3D mesh structures. Metal (such as Ni, Co, Fe, Pd, Au, Ag, and Cu) and conductive polymer (such as polyaniline) meshes are obtained by electrochemical deposition approach, while the nonconductive polymer (such as poly(methyl methacrylate) (PMMA)) meshes are synthesized by chemical polymerization method. Some new types of meshes are fabricated by the conversion of metal meshes and polymer meshes. NiO meshes are formed by oxidizing Ni meshes in the air. The NiO meshes exhibit higher volume occupation fraction than Ni meshes and the nanocrystalline sizes of NiO particles can be adjusted by the oxidation temperature. Due to the mechanical flexibility of polymer meshes, the compression of PMMA meshes produces deformed PMMA meshes which contain oblate pores. These meshes can be again served as templates to prepare new types of colloidal crystals (nanosphere arrays) and specific nanocomposites. By the use of poorly conductive NiO mesh or PMMA mesh arrays as templates, 3D periodic metal nanosphere arrays, such as those of Ni, Co, Au and Pd, are readily fabricated by the electrodeposition method. Metal/NiO or Metal/PMMA composites can also be obtained if the templates are left intact. The magnetic behavior of metal (such as Ni and Co) meshes and sphere arrays has been investigated. These nanoscale arrays show significantly enhanced coercivities compared with bulk metals, due to the size effect of the nanometer dimensions of the components in meshes and sphere arrays. Angle-dependent magnetic properties of Ni and Co sphere array membranes exhibit out-of-plane anisotropy.

Quarter-wave retarders (QWR) that employ total internal reflection (TIR) and interference of light in a transparent thin-film coating at the base of a prism are presented. Explicit equations that guide the optimal design are provided. The optimal refractive index and normalized thickness of QWR coatings on glass and ZnS prisms are determined as functions of the internal angle of incidence from 45o to 75o. An achromatic QWR that uses an Si3N4- coated N-BK10-Schott glass prism is also presented with retardance error of 3o over the 400-600 nm wavelength range. An iterative procedure for the design of a polarizing beam splitter (PBS) that uses a form-birefringent, subwavelength-structured, one-dimensional photonic-crystal layer (SWS 1-D PCL) embedded in a high-index cubical prism is presented. The PBS is based on index matching and total transmission for the p polarization and total internal reflection for the s polarization at the prism-PCL interface at a 45o angle of incidence. A high extinction ratio in reflection ( 50 dB) over the 4-12 μm IR spectral range is achieved using a SWS 1-D PCL of ZnTe embedded in a ZnS cube within an external field of view (FOV) of ±6.6o and in the presence of grating filling factor errors of up to ±10%. Comparable results, but with a wider field of view, are also obtained with a Ge PCL embedded in a Si prism. A design for visible spectrum (553–713 nm) PBS SWS 1-D PCL of ZnTe embedded in a ZnS cube is also presented. The PBS shows a FOV of ±7o. A circular polarizing beam splitter (CPBS) with equal throughput for p and s polarization using SWS 1-D PCL embedded in a high-index cubical prism is introduced. A dual QWR in transmission and reflection with 50–50% CPBS is designed using the PCL. Such a CPBS shows large deviation from the design point as a result of small changes in the design parameters; e.g. a change of 10% in the filling factor results in 12o shift from the 90o phase shift between p and s polarizations, which limits the practical utility of the device.

High-order wavefront correction is not only beneficial for high-contrast imaging, but also spectroscopy. The size of a spectrograph can be decoupled from the size of the telescope aperture by moving to the diffraction limit which has strong implications for ELT based instrument design. Here we present the construction and characterization of an extremely efficient single-mode fiber feed behind an extreme adaptive optics system (SCExAO). We show that this feed can indeed be utilized to great success by photonic-based spectrographs. We present metrics to quantify the system performance and some preliminary spectra delivered by the compact spectrograph.

O presente trabalho tem como objetivo estudar a produção e caracterização de filmes finos do tipo GeO2-Bi2O3 (BGO) produzidos por sputtering-RF com e sem nanopartículas (NPs) semicondutoras, dopados e codopados com íons de Er3+ ou Er3+/Yb3+ para a produção de amplificadores ópticos. A produção de guias de onda do tipo pedestal baseados nos filmes BGO foi realizada a partir de litografia óptica seguida por processo de corrosão por plasma e deposição física a vapor. A incorporação dos íons de terras-raras (TRs) foi verificada a partir dos espectros de emissão. Análises de espectroscopia e microscopia foram indispensáveis para otimizar os parâmetros dos processos para a construção dos guias de onda. Foi observado aumento significativo da luminescência do Er3+ (região do visível e do infravermelho), em filmes finos codopados com Er3+/Yb3+ na presença de nanopartículas de Si. As perdas por propagação mínimas observadas foram de ~1,75 dB/cm para os guias pedestal em 1068 nm. Para os guias dopados com Er3+ foi observado aumento significativo do ganho na presença de NPs de silício (1,8 dB/cm). O ganho óptico nos guias de onda amplificadores codopados com Er3+/Yb3+ e dopados com Er3+ com e sem NPs de silício também foi medido. Ganho de ~8dB/cm em 1542 nm, sob excitação em 980 nm, foi observado para os guias pedestal codopados com Er3+/Yb3+ (Er = 4,64.1019 átomos/cm3, Yb = 3,60.1020 átomos/cm3) com largura de 80 µm; para os guias codopados com concentração superior de Er3+/Yb3+ (Er = 1,34.1021 átomos/cm3, Yb = 3,90.1021 átomos/cm3) e com NPs de Si, foi observado aumento do ganho óptico de 50% para guia com largura de 100 µm. Os resultados apresentados demonstram que guias de onda baseados em germanatos, com ou sem NPs semicondutoras, são promissores para aplicações em dispositivos fotônicos. / This work aims to study the production and characterization of GeO2-Bi2O3 (BGO) thin films produced by RF-sputtering with and without semiconductor nanoparticles (NPs),doped and codoped with Er3+ or Er3+/Yb3+ ions for the production of optical amplifiers. The pedestal type waveguide production based on BGO thin film was done trough optical lithography followed by reactive ion etching and physical vapor deposition processes. The incorporation of the rare-earth ions was verified from the emission spectra. Spectroscopy and microscopy analysis were indispensable to optimize the processes parameters for the waveguide fabrication. It was observed minimum propagation losses of ~1,75 dB/cm, at 1068 nm for the pedestal type waveguides. Optical gain was also measured in the Er3+/Yb3+ codoped waveguides with and without Si nanoparticles. Optical gain of 8 dB/cm, at 1542 nm, under 980nm pumping were obtained for 80 µm width Er3+/Yb3+ codoped waveguides (Er = 4,64.1019 atoms/cm3, Yb = 3,60.1020 atoms/cm3). For waveguides doped with higher concentration of Er3+/Yb3+ (Er = 1,34.1021 átomos/cm3, Yb = 3,90.1021 átomos/cm3) and containing silicon nanoparticles, it was observed 50% enhancement of the optical gain for 100 µm width waveguides. For the Er3+ doped waveguides, it was observed significant gain enhancement in the presence of silicon nanoparticles (1.8 dB/cm). The present results demonstrate that germanate waveguides, with or without semiconductor NPs are promising for applications in photonic devices.

Os metais nobres são admirados desde as culturas mais antigas por sua capacidade de refletir a luz. Com os desenvolvimentos na área da nanotecnologia se pode entender um pouco mais sobre a interação entre a luz e estes metais. Devido a esta interação foi criada a Plasmônica e a partir dela começaram os estudos acerca dos plasmons de superfície (SP). Estes estudos vêm gerando inúmeros desenvolvimentos nas pesquisas de gravação magneto-ótica, microscopia, detectores moleculares biológicos entre outras. Como os SPs são ondas evanescentes, eles precisam ser observados em campo próximo. Com o intuito de observar e compreender a propagação destes SPs foi utilizado um microscópio ótico de varredura em campo próximo (SNOM). Para isto, o SNOM foi adaptado para operar em modo de transmissão. A sonda do SNOM serviu de coletora de luz para que a partir de imagens óticas em amostras de Ag e Au pudéssemos caracterizar a propagação destes SPs na superfície do material e também a sua dependência com a distância de detecção. Os resultados mostraram que a propagação do SP é maior que 70m e a intensidade do SP na superfície do metal depende fortemente da rugosidade da amostra e de possíveis defeitos. Foi possível ainda estimar a que distância a partir da superfície da amostra, em que o SP decai para 1/e. Este resultado está de acordo com o esperado teoricamente, que prevê para a distância de propagação do SP, o valor de 420nm. Através do SP ainda foi possível analisar defeitos existentes na amostra. E pelas imagens topográficas do SNOM também foi possível observar os grãos de Ag e Au da amostra. Em posse destes resultados pudemos concluir que o SNOM é uma ótima ferramenta para a análise dos plasmons de superfície. / The noble metals are largely admired since ancient cultures because of its capability to reflect light. With the development of nanotechnology it is possible now to understand the interaction between these metals and light. Due to this strong interaction, the Plasmonic area was created and the studies on Surface Plasmons(SP) started. These studies are responsible for important new developments in magneto-optical recording, new optical microscopy apparatus, molecular biological sensors, among others. As SPs are evanescent waves, they need to be observed in near-field optics. For the observation and study of the propagation of these SPs a scanning near-field optical microscope (SNOM) was used. The SNOMs probe was used in collection mode so that we could characterize the propagation of SPs in the material surface and the dependence with the distance of detection in air, for thin films of Ag and Au. The results showed that the propagation of the SP inside the metallic film is beyon 70m. And the SPs intensity in the metal surface is strongly dependent on the roughness of the sample. It was also possible to estimate the distance from the samples surface the SP decay to 1/e. Our measurements agree to the theoretical calculation of 420nm for this distance. The SP made it possible to analyze existing defects on the sample. Furthermore, with the SNOM topographical images it was also possible to observe the grains of the policrystalline Ag and Au samples. From these results we could conclude that the SNOM is a very useful tool for the analysis of surface plasmons in thin films.

Photonic crystal fibres (PCFs) are special fibres with air holes which run along the whole fibre length. These holes not only determine the fibres' unique properties, but also provide a new degree of freedom for fibre modications. In this thesis, we focus on hole control in PCFs from two perspectives: during their fabrication and after they have been made. We found for the first time that the direct information of viscosity was not necessary for description of the fibre drawing process. This conclusion matched our experimental results without recourse to any adjustable fitting parameters. By post-processing of PCFs, which modifies the cladding and core structure and shape, we have achieved a series of novel devices for both linear and nonlinear applications. We have demonstrated fibre devices with cores resembling Young's double slits that have good performance in terms of compatibility and intensity enhancement for a specific application in fibre optic spectrometers. The bulk of this thesis reports on higher-order modes and their nonlinear applications. We achieved all-fibre, low loss and broadband mode converters in highly nonlinear PCFs (HNPCFs) which converted the fundamental mode (LP01) to a higher-order mode (LP02), which can then be converted back if necessary. This higher-order mode has been used for supercontinuum (SC) generation and four wave mixing (FWM) at wavelengths unobtainable for the fundamental mode. This is achieved by utilising the profound dispersion properties of the higher-order mode. We also demonstrated another kind of mode conversion: from the fundamental mode to a Bessel-like beam or its Fourier transform version, an annular beam. Three different methods were implemented experimentally to achieve this non-diffractive, self-healing beam.

A modelagem numérica de cristais fotônicos tridimensionais é o objeto de estudo deste trabalho. Especificamente, o método das diferenças finitas no domínio do tempo (FDTD) é utilizado para a modelagem de um cristal FCC (face-centered-cubic) formado por opalas de látex imersas em ar. Por meio de uma análise comparativa com o cristal formado por opalas inversas (opalas de ar incrustadas em uma matriz dielétrica com alto índice de refração), é mostrado que o baixo contraste de índice de refração do cristal de látex é característica preponderante para a inexistência de uma banda proibida completa. No entanto, podem ser observadas bandas fotônicas proibidas ao longo de algumas direções de propagação, como é evidenciado através da investigação da difração de Bragg relativa à família de planos cristalinos (111). Sempre que possível os resultados numéricos são comparados com os dados experimentais disponíveis. / The numerical modeling of tridimensional photonic crystals is the object of study in this work. Especifically, the finite difference time domain method (FDTD) is used for the modeling of a FCC (face-centered-cubic) crystal composed by latex opals immersed in air. Through a comparative analysis to a crystal composed by inverse opals (close-packed air opals in a dielectric matrix with high refractive index), it is shown that the low contrast of the latex crystal is the crucial characteristic to prevent the rising of a complete photonic band gap. However, photonic band gaps can be observed for certain directions of propagation, as it is demonstrated by the investigation of Bragg diffraction related to the (111) crystalline planes. Wherever possible, the numerical results are compared to available experimental data.