Rozprawy doktorskie na temat „Whispering gallery modes (WGMs)”

La quantification de biomarqueurs spécifiques est un outil de diagnostic important. Les tests immunologiques standards tels que ELISA nécessitent de nombreuses étapes de lavage et une amplification du signal, en particulier à faible concentration. D'autre part, le transfert d'énergie résonant de type Förster (FRET) a été utilisé pour concevoir des tests biologiques homogènes en une seule étape qui ne nécessitent aucune étape de lavage, où le biomarqueur permet la formation d'un complexe "sandwich" impliquant des anticorps marqués par le donneur et d'autres marqués par l'accepteur. Le FRET du donneur vers l'accepteur fournit alors une signature optique de la formation du complexe, et donc du biomarqueur d'intérêt. Cependant, le FRET, qui est très sensible à la distance donneur-accepteur, ne se produit à un taux significatif que lorsque la distance donneur-accepteur est inférieure à 10 nm; la grande taille de nombreux complexes biologiques limite l'efficacité du transfert d'énergie, empêchant une détection sensible. Je propose ici une nouvelle modalité de transfert d'énergie qui utilise des microcavités optiques en solution. Ensuite, je décris un schéma de biodétection pour détecter un oligonucléotide biomarqueur de cancer en solution.À cette fin, j'ai conçu des structures de microcavité dans lesquelles des nanocristaux fluorescents sont placées à l'intérieur de microsphères diélectriques pour permettre un couplage fort de leur émission de fluorescence avec les modes de résonance de la cavité, appelés modes de galerie (WGM). J'ai étudié les propriétés structurelles et optiques de ces microcavités optiques. J'ai également caractérisé le transfert d'énergie entre ces modes et des nanoparticules acceptrices chargées de colorants présentes dans le champ évanescent, à quelques dizaines de nm au-dessus de la surface des microsphères. J’ai développé un modèle analytique pour caractériser les mécanismes de transfert d'énergie médié par les WGM (WGET). De plus, une comparaison entre WGET et FRET a révélé la supériorité du WGET dans le contexte de la construction de capteurs en termes de sensibilité et de portée de détection. Dans la dernière partie de la thèse, j’ai développé une stratégie pour fonctionnaliser ces microcavités optiques et leur permettre d'interagir avec des analytes cibles tels que l'ADN, l'ARN et les protéines avec une bonne spécificité. Cette stratégie a ensuite été adaptée pour fixer des sondes de capture d'ADN sur les microcavités activées par WGM. En utilisant les microsphères fixées à l'ADN comme donneur optique en combinaison avec des nanoparticules de colorants fonctionnalisées par un ADN complémentaire comme accepteurs optiques, un test de biodétection a été démontré avec succès pour détecter en solution un biomarqueur de cancer appelé survivine. Ce test a démontré une bonne sensibilité envers la cible, et s'est également avéré très spécifique. Le schéma de détection a été démontré dans un microscope confocal, au niveau de microsphères individuelles, puis transposé avec succès dans un instrument beaucoup plus simple tel qu'un spectrofluoromètre qui mesure la fluorescence de l'ensemble de la solution; la signature de la formation d'un complexe sandwich a été détectée efficacement.En conclusion, j'ai démontré que le transfert d'énergie assisté par microcavité présente plusieurs avantages par rapport aux tests FRET ordinaires. Un véritable test de biodétection basé sur le principe du WGET a également été conçu avec succès pour détecter des biomarqueurs du cancer avec une sensibilité et une spécificité élevées. Cette étude ouvre donc de nombreuses possibilités pour concevoir des tests plus performants et plus précis pour détecter diverses entités biologiques
Quantification of specific biomarkers is an important diagnostic tool. Standard immunoassays such as ELISA require extensive washing steps and signal amplification, in particular when the biomarker of interest is only present at very low concentrations. On the other hand, non-radiative Förster resonance energy transfer (FRET) has been used to design one-step homogenous bioassays which do not require any washing steps, where the biomarker enables the formation of a sandwich complex involving donor-labeled and acceptor-labeled antibodies. FRET from the donor to the acceptor then provides an optical signature of the complex formation, hence of the biomarker of interest. However, FRET which is highly sensitive to the donor-acceptor distance, only occurs in a significant rate when the distance between the donor and acceptor is less than 10 nanometers; thus the large size of many biological complexes limits the efficiency of energy transfer, preventing sensitive detection. Here I propose a novel energy transfer modality that uses solution-phase optical microcavities to enhance energy transfer. Following that, I describe a bio-sensing scheme designed to detect a cancer biomarker DNA in solution.To this aim, I have designed microcavity structures in which fluorescent colloidal quantum dots are located inside dielectric polymer microspheres to enable strong coupling of their fluorescence emission with the cavity resonance modes or whispering gallery modes (WGMs) of the microspheres. A detailed study was carried out to comprehend the structural and optical properties of these optical microcavities. I also characterized the energy transfer between these modes and acceptor dye-loaded nanoparticles present in the evanescent field, within a few tens of nanometers above the microsphere surface. An analytical model was constructed to provide insights into the WGM mediated energy transfer (WGET) mechanisms. Moreover, a comparison between WGET and FRET revealed the superiority of WGET in the context of building sensors with improved sensitivity and longer range of detection. In the last part of the thesis, a strategy is discussed in detail to provide biological functionalities to these optical microcavities which would enable them to interact with target analytes such as DNA, RNA, and proteins with high specificity, and moreover to reduce non-specific interactions. This strategy then was adapted to attach DNA capture probes onto the WGM enabled microcavities. Using the DNA attached microspheres as optical donor in combination with probe-DNA functionalized dye nanoparticles as optical acceptors, a biosensing assay has been successfully demonstrated to detect a cancer biomarker DNA called survivin in the solution phase. This assay did not only show good sensitivity towards the target, but also it has proven to be highly specific. The detection scheme has been demonstrated in a sophisticated confocal microscope at the single microsphere level, then successfully translated to a much simpler spectrofluorometer that measures fluorescence from the whole sample solution; the signature of the sandwich complex formation was also effectively detected.In conclusion, I demonstrated that microcavity-assisted energy transfer has several advantages over regular FRET assays. A real bio-sensing assay based on the WGET principle has also been successfully designed to detect cancer biomarkers with high sensitivity and specificity. This study thus opens up many possibilities to design high-performing and more accurate assays to detect varieties of biological entities

Anisotropic chalcogenide microsphere is introduced for coupling theoretical analyzing and coupling experiment. Whispering Gallery Modes (WGMs) of isotropic microsphere is introduced and the TE & TM WGMs dispersion relationship is derived from electromagnetic vector equations in the spherical coordinate. The Maxwell equations can be solved in 2D model for the 3D model of axisymmetric or Rotational symmetry isotropic microsphere. First 4 TE&TM WGMs are simulated in 2D model using finite-element weak method. The binding capability, mode volume V and quality factor Q depend on the refractive index and size of the microsphere. Plane wavefront light wave is assumed to propagate inside the microsphere; coupling coefficient is determined by WGMs numbers and the distance between the microsphere and the micro-taper. Coupling related Q factor is analyzed; TE & TM nonlinear microsphere coupling is introduced with Matlab simulation. Chalcogenide coupling experiments for transmission, reflection and drop-port function are conducted. The light waves for coupling are broadband incoherent light source and narrowband tunable laser. Broadband light gave sensitive results while the coherent laser gave easy coupling capability.The chalcogenide microsphere was used as a feedback element of an amplifying medium. Comparing with silica microsphere, chalcogenide microsphere?s response is more unstable due to free carriers perturbation and thermal activity.
Cette thèse présente une analyse théorique et expérimentale du couplage des microsphères anisotropes en verre de chalcogénure. Les modes de galerie résonants (WGMS) de microsphères isotrope sont aussi présentés et la relation de dispersion TE et TM des WGMS est dérivée à partir des équations vectorielles électromagnétiques en coordonnées sphériques. Les équations de Maxwell peuvent être résolues en 2D pour la résolution en 3D de microsphères axisymétriques ou a symétrie rotationnelle isotrope. Les quatre premiers WGMS TE et TM sont simulés dans le modèle 2D en utilisant la méthode des éléments finis. La capacité de liaison, le volume modal V et facteur de qualité Q dépendent de l'indice de réfraction et de la taille de la microsphère. On décompose une onde lumineuse en multiples fronts d'onde plan à l'intérieur de la microsphère; le coefficient de couplage entre une microsphère et un microfil est déterminé par le nombre de WGMS et la distance entre la microsphère et microfil. Le facteur de qualité Q est analysé; le couplage TE & TM de microsphères non linéaire est introduit à partir de simulations Matlab. Des expériences de couplage pour la transmission, la réflexion et le port à fonction «drop» sont conduites. Les ondes lumineuses pour le couplage proviennent d'une source de lumière à large bande incohérent et d'une source laser étroite accordable à bande étroite. La lumière à large bande a donné des résultats à haute sensibilité tandis que le laser cohérent facilite la mesure de couplage.En dernier lieu, les microsphères de chalcogénure ont été utilisées comme élément de rétroaction pour un milieu amplificateur. En comparaison avec des microsphères de silice, les microsphères de chalcogénure génèrent une réponse qui est plus instable due à la perturbation par les porteurs libres et l'activité thermique.

Thesis (Ph. D.)--University of Oregon, 2006.
Typescript. Includes vita and abstract. Includes bibliographical references (leaves 204-213). Also available for download via the World Wide Web; free to University of Oregon users.

For cavity quantum electrodynamics systems (cavity-QED) to play a role in quantum information processing applications and in quantum networks, they must be robust and scalable in addition to having a suitable method for the generation, processing and storage of quantum bits. One solution is to develop a composite system that couples a nitrogen vacancy (NV) center in diamond to a whispering gallery mode supported by a fused silica microsphere. Such a system is motivated by the optical and electron-spin properties of the NV center. The NV center is the leading spin-qubit and exhibits atomic like linewidths at cryogenic temperatures and has spin coherence times greater than milliseconds at room temperature. These long coherence times, coupled with nanosecond scale spin readout and manipulation times, allow for millions of quantum operations to be processed. Silica whispering gallery resonators are the only class of microresonators with quality factor high enough to reach the strong coupling regime, which is necessary for some quantum information processing applications. Integrating these two components into a system that could position a diamond nanopillar near the surface of a deformed-double stemmed microsphere system, with nanometer precision, at 10 K was a major achievement of this research. Cavity resonances in deformed microspheres can be excited with a free-space coupling technique which simplifies their integration into cryogenic environments. In these intentionally deformed resonators, an enhanced evanescent field decay length was observed at specific locations along the ray orbit. The double-stem arrangement enables the cavity resonance to be tuned over 450 GHz, with sub-10 MHz resolution, at 10 K. These two features, the enhanced decay length and broad range tuning with high resolution, are indispensible tools for cavity-QED studies with silica microspheres. Diamond nanopillars were fabricated from single crystal diamond with diameters as small as 140 nm in order to maintain a high quality factor. Studies were conducted on NV centers in nanopillars and bulk diamond to determine their suitability for cavity-QED applications. In an attempt to increase the light-matter interaction between NV centers and whispering gallery modes, diamond substrates were optically characterized that were irradiated with nitrogen ions.

This thesis presents the development of a refractometric sensor based on quantum dot-embedded polystyrene microspheres. The technique uses optical resonances within a microsphere, known as Whispering-Gallery Modes (WGMs), which produce narrow spectral peaks. The basic theory of WGMs is reviewed and specifically discussed for biosensing application. The spectral shifts of WGM peaks are sensitive to changes in the local refractive index. In the experiments, two-photon excited luminescence from the quantum dots couples into several WGMs within the microresonator. By optimizing the detection area, the spectral visibility of the WGMs is improved. The spectral shifts are measured as the surrounding index of refraction changes. The experimental sensitivity is about five times greater than that predicted by Mie theory. The sensor element is based on commercially available dielectric microspheres with a diameter about 10 μm. Thus, the technique is more economic and suitable for sensing applications, compared to microspheres of 100 μm in size which can only be made in the laboratory.

Optical resonators, which confine light by resonant recirculation, serve as the basis for a wide variety of optical components. Though they appear in many geometric forms, the most effective of optical resonators show axial symmetry in at least one dimension. A popular variation that finds broad application is the dielectric sphere. Acclaimed for their high quality (Q) factor and small modal volume, spheres owe credit of these attractive features to their support of whispering gallery mode (WGM) resonances. The sensitivity of a resonance's frequency and Q to strain, temperature, and other parameters of the surrounding medium can be the basis for ultracompact modulators and sensors. Physically, WGMs are special optical modes which can be understood as light rays that orbit the equator of the sphere guided by total internal reflection. Like a smooth stone can be skipped along the surface of a pond, light can be confined to the inside of a sphere by successive reflections. To best excite WGMs, the source light should initially trace a line tangent to the sphere's circumference. But incorporating a tiny sphere with such nanometric tolerances into a practical sensor structure has its challenges and the prospects for microsphere applications have suffered because of the plight of this problem. The work in this dissertation details the fabrication and function of three new "press fit" spherical resonators. These etched fiber micro-devices were developed to meet the demand for a robust, self-integrated means of coupling light between an optical fiber and WGMs in a microsphere resonator. The etching processes have been tuned to enable secure storage of a microsphere while also providing efficient excitation and interrogation of WGMs. Furthermore, the methods have been designed to be staightforward, quick, and repeatable. Using standard etchants on common polarization-maintaining fiber with readily purchased microspheres, the press fit resonators demonstrated here can be batch-fabricated and assembled. The press fit spherical resonator offers an alignment-free and conveniently pigtailed WGM coupler that has great potential for bio-science sensing applications and studies of resonant bispheres.
Ph. D.

Deux méthodes d'analyses électromagnétiques des Whispering Gallery (W. G) modes des R. D. Sont présentées dans ce mémoire. Une méthode approximative analytique et la méthode des éléments finis permettent de connaître avec précision la fréquence de fonctionnement et la cartographie du champ électromagnétique d'une structure microonde. Ces résultats couplés à une analyse électrique des dispositifs à résonateurs diélectriques ont permis la réalisation de filtres directifs et d'un combineur de puissance utilisant les W. G. Modes des résonateurs diélectriques.

L'objectif de ce travail a ete l'analyse, la conception, la realisation et le test d'oscillateurs et de combineurs de puissance pouvant fonctionner dans la bande millimetrique 90-100 ghz. L'absence d'analyseur de reseau dans cette bande de frequence, nous a tout d'abord conduit a la mise au point d'un banc de mesure manuel des caracteristiques des dispositifs millimetriques. Puis, les oscillateurs et les combineurs de puissance etant constitues par l'association d'un circuit actif et d'un circuit passif, nous nous sommes plus particulierement interesses a l'analyse de ces derniers. C'est ainsi qu'utilisant la methode numerique des elements finis, ont pu etre successivement definis les parametres electromagnetiques (frequence de resonance, repartition du champ) et electriques (schema equivalent) des circuits associant des lignes de transmission microstrip et des r. D. Excites sur leurs whispering gallery modes. Les modeles mis au point ont ensuite ete valides experimentalement a 100 ghz lors de la realisation et du test d'un oscillateur millimetrique a diode gunn delivrant 5 mw, et d'un combineur de puissance permettant d'additionner la puissance de sortie de trois sources independantes

Os micro-ressonadores que suportam whispering gallery modes têm atraído a atenção da comunidade científica devido a sua grande capacidade de confinar a luz, propriedade que faz dessas estruturas plataformas ideais para o desenvolvimento de pesquisa fundamental como interação da radiação com a matéria e óptica não linear. Além disso, suas características como operação em frequências do visível e de telecomunicações, facilidade de integração e alta sensitividade os tornam extremamente flexíveis para aplicações que vão desde filtros ópticos até sensores. Neste trabalho, demonstramos a fabricação de tais micro-ressonadores via fotopolimerização por absorção de dois fótons (FA2F). Esta técnica apresenta uma série de vantagens para a confecção de micro-dispositivos, sendo elas a capacidade de resolução inferior ao limite de difração, a flexibilidade de formas e ainda, a possibilidade de incorporar compostos de interesse à matriz polimérica a fim de introduzir novas funcionalidades ao material que compõe a estrutura final. Ademais, diferentes polímeros podem ser utilizados para a fabricação das microestruturas, tornando a técnica viável para uma vasta gama de aplicações. As microestruturas poliméricas que fabricamos são micro-cilindros ocos de boa integridade estrutural com 45 μm de diâmetro externo e 100 nm de rugosidade de superfície, o que as torna potencialmente aplicáveis como micro-ressonadores para frequências de operação típicas de telecomunicações. A fim de acoplar luz nessas estruturas, em colaboração com a Universidade de Valência, na Espanha, montamos um aparato de acoplamento. Neste aparato, a luz proveniente de uma fonte de luz centrada em 1540 nm é acoplada nos micro-ressonadores via campo evanescente por meio do uso de uma fibra óptica estirada de 1.5 μm de diâmetro. A potência transmitida é guiada para um analisador de espectro óptico, onde é possível identificar os modos ressonantes, representados como picos de atenuação com free spectral range em torno de 9.8 nm. Ao término desse projeto, um aparato similar foi montado no Grupo de Fotônica do IFSC/USP, a partir do qual pudemos medir os modos ressonantes tanto de fibras ópticas estiradas quanto dos micro-cilindros poliméricos. A finesse dos micro-ressonadores poliméricos caracterizados varia de 2.51 a 4.35, sendo da mesma ordem de grandeza do valor reportado na literatura para ressonadores de alta performance fabricados por FA2F a partir da mesma formulação de resina polimérica que utilizamos.
Whispering gallery modes microresonators have been attracting increasing interest due to their ability to strongly confine light within small dielectric volumes. This property is quite useful for basic research involving light-matter interaction and nonlinear optics, but their applications go beyond that. The ease of fabrication, on-chip integration and operation at telecommunication frequencies make them suitable for a variety of practical applications, including photonic filters and sensing. In the current work, we demonstrate the fabrication of such resonators via two-photon polymerization. Using this technique, complex 3D structures with submicrometer feature size can be produced. Besides, the flexibility of geometry and the possibility of incorporating a variety of additional materials, such as organic compounds make it a powerful tool for the fabrication of microresonators. The microstructures we have fabricated are 45 μm outer diameter hollow microcylinders, with good structural integrity and sidewall roughness estimated in 100 nm, which make their application as microresonators feasible in the near infrared wavelength regime. In order to couple light within these microresonators, an experimental setup was built at University of Valencia to implement the coupling. In this setup, light from a 1540 nm-centered broadband source was coupled into the fabricated microresonators via evanescent field using a 1.5 μm waist tapered fiber. The transmitted light was then guided to an optical spectral analyzer, where it was possible to measure resonances, represented as attenuation peaks, with free spectral range of about 9.8 nm. Afterwards, a similar experimental setup was assembled in the Photonics group at IFSC/USP, where we could observe resonances of both tapered optical fibers and the polymeric microresonators fabricated by means of two-photon polymerization. The finesse of the polymeric microresonators was estimated in 4.35, being in the same order of the finesse reported in the literature for high performance microring resonators fabricated using the same polymeric resin.

Ce travail de thèse a consisté à mettre en place toute une filière de fabrication de microtores en silice sur silicium (étapes de lithographie et de gravure en salle blanche pour la réalisation de microdisques, installation d'un banc optique permettant la transformation du résonateur en microtore par un procédé de recuit laser CO2), à installer un banc optique permettant de mesurer la largeur spectrale de leurs résonances optiques à 1.55 µm et enfin, à explorer l'intégration d'émetteurs de lumière composés d'éléments de la colonne IV comme du silicium et du germanium, dans ces cavités. Des microtores supportant des résonances de facteur de qualité Q proche de 10^8 à 1.55 µm ont été fabriqués. Ces réalisations sont très proches de l'état de l'art et valident à la fois la fabrication des cavités et le banc optique permettant les mesures spectrales des modes de galerie (WGM). Grâce à un contrôle fin des différentes étapes de fabrication, de nouveaux résonateurs ont également été réalisés, des microsphères de silice sur puce de petits rayons (entre 5 et 14 µm). Une étude détaillée de ces résonateurs est présentée. Des Q proches de 10^8 ont également été mesurés. Des cavités WGM comportant une couche de nanoclusters de silicium dans une matrice de silice avec des ions erbium (SiOx : Er) sont étudiées en photoluminescence. Un couplage des ces émetteurs à des WGM est observé à température ambiante dans le visible et dans l'infrarouge. Un travail de couplage du germanium aux WGM a commencé et semble prometteur
This work consisted in developing a fabrication process of silica microtoroids on a silicon chip (steps of lithography and etching in clean room for the realization of microdisks, set up of an optical bench to form a microtoroid with a reflow treatment of a silica microdisk by a CO2-laser), setting up an optical bench to measure the linewidth of their optical resonances at 1.55 µm and finally, exploring light emitters integration in these cavities such as silicon and germanium. Very high quality-factors (Q) close to 10^8 at 1.55µm have been measured on microtoroids. These realizations are very close to the State of the art and validate both the fabrication of these cavities and the optical bench to measure the linewidth of their Whispering Gallery Modes (WGM). With a precise control of the fabrication steps, new resonators have also been fabricated, silica microspheres on a chip with small radii (5 < r < 14µm). An in-depth study of these last ones is presented. Q-factors close to 10^8 have also been measured on microspheres. WGM cavities with a SiOx: Er layer (silicon nanoclusters in silica with erbium ions) are studied by photoluminescence. Coupling of these light emitters to WGM is observed in visible and near infrared at room temperature. A work of coupling of germanium to WGM began and seems promising

In this thesis we show several modelling tools which are used to study nonlinear photonic band-gap structures and microcavities. First of all a nonlinear CMT and BPM were implemented to test the propagation of spatial solitons in a periodic device, composed by an array of parallel straight waveguides. In addition to noteworthy theoretical considerations, active functionalities are possible by exploiting these nonlinear regimes. Another algorithm was developed for the three-dimensional modelling of photonic cavities with cylindrical symmetry, such as microdisks. This method is validated by comparison with FDTD. We also show the opportunity to confine a field in a region of low refractive index lying in the centre of a silicon microdisk. High Q-factor and small mode volumes are achieved. Finally the characterization of microdisks in SOI with Q-factor larger than 50000 is presented

[Truncated abstract] This thesis is split into two parts. In part one; A 50 K dual mode oscillator, the aim of the project was to build a 50 K precision oscillator with frequency stability on the order of 1014 from 1 to 100 seconds. A dual-mode temperature compensation technique was used that relied on a turning point in the frequency-temperature relationship of the difference frequency between two orthogonal whispering gallery modes in a single sapphire crystal. A cylindrical sapphire loaded copper cavity resonator was designed, modelled and built with a turning point in the difference frequency between an E-mode and H-mode pair at approximately 52.5 K . . . The frequencies and Q-factors of whispering spherical modes in the 3-12 GHz range in the fused silica resonator are measured at 6, 77 and 300 K and the Q-factor is used to determine the loss tangent at these temperatures. The frequency and Q-factor temperature dependence of the TM2,1,2 whispering gallery mode at 5.18 GHZ is used to characterise the loss tangent and relative permittivity of the fused silica from 4-300 K. Below 22 K the frequency-temperature dependence of the resonator was found to be consistent with the combined effects of the thermal properties of the dielectric and the influence of an unknown paramagnetic impurity, with a spin resonance frequency at about 138 ± 31 GHz. Below 8 K the loss tangent exhibited a 9th order power law temperature dependence, which may be explained by Raman scattering of Phonons from the paramagnetic impurity ions. A spherical Bragg reflector resonator made from multiple concentric dielectric layers loaded in a spherical cavity that enables confinement of field in the centre of the resonator is described. A set of simultaneous equations is derived that allow the calculation of the required dimensions and resonance frequency for such a resonator and the solution is confirmed using finite element analysis. A spherical Bragg reflector resonator is constructed using Teflon and free-space as the dielectric materials. A Q-factor of 22,000 at 13.87 GHz was measured and found to compare well with the design values.

I advanced the understanding of particle morphology and its implications for the behavior and effects of atmospheric aerosol particles. I have developed new experimental methods for the Aerosol Optical Tweezers (AOT) system and expanded the AOT’s application into studying realistic secondary organic aerosol (SOA) particle phases. The AOT is a highly accurate system developed to study individual particles in real-time for prolonged periods of time. While previous AOT studies have focused on binary or ternary chemical systems, I have investigated complex SOA, and how they interact with other chemical phases, and the surrounding gas-phase. This work has led to new insights into liquid-liquid phase separation and the resulting particle morphology, the surface tension, solubility, and volatility of SOA, and diffusion coefficients of SOA phases. I designed a new aerosol optical tweezers chamber for delivering a uniformly mixed aerosol flow to the trapped droplet’s position. I used this chamber to determine the phase-separation morphology and resulting properties of complex mixed droplets. A series of experiments using simple compounds are presented to establish my ability to use the cavity enhanced Raman spectra to distinguish between homogenous single-phase, and phase-separated core-shell or partially-engulfed morphologies. I have developed a new algorithm for the analysis of whispering gallery modes (WGMs) present in the cavity enhanced Raman spectra retrieved from droplets trapped in the AOT. My algorithm improves the computational scaling when analyzing core-shell droplets (i.e. phase-separated or biphasic droplets) in the AOT, making it computationally practical to analyze spectra collected over many hours at a few Hz. I then demonstrate for the first time the capture and analysis of SOA on a droplet suspended in an AOT. I examined three initial chemical systems of aqueous NaCl, aqueous glycerol, and squalane at ~ 75% relative humidity. For each system I added α-pinene SOA – generated directly in the AOT chamber – to the trapped droplet. The resulting morphology was always observed to be a core of the initial droplet surrounded by a shell of the added SOA. By combining my AOT observations of particle morphology with results from SOA smog chamber experiments, I conclude that the α-pinene SOA shell creates no major diffusion limitations for water, glycerol, and squalane under humid conditions. My AOT experiments highlight the prominence of phase-separated core-shell morphologies for secondary organic aerosols interacting with a range of other chemical phases. The unique analytical capabilities of the aerosol optical tweezers provide a new approach for advancing the understanding of the chemical and physical evolution of complex atmospheric particulate matter, and the important environmental impacts of aerosols on atmospheric chemistry, air quality, human health, and climate change.

xi, 125 p. : ill. (some col.) A print copy of this thesis is available through the UO Libraries. Search the library catalog for the location and call number.
This dissertation presents experimental and theoretical studies of radiation pressure cooling in silica optomechanical microresonators where whispering gallery modes (WGMs) are coupled to thermal mechanical vibrations. In an optomechanical system, circulating optical fields couple to mechanical vibrations via radiation pressure, inducing Stokes and anti-Stokes scattering of photons. In analogy to laser cooling of trapped ions, the mechanical motion can in principle be cooled to its ground state via the anti-Stokes process in the resolved-sideband limit, in which the cavity photon lifetime far exceeds the mechanical oscillation period. Our optomechanical system is a slightly deformed silica microsphere (with a diameter 25-30 μm ), featuring extremely high Q -factors for both optical ( Q o ∼ 10 8 ) and mechanical ( Q m ∼ 10 4 ) systems. Exploiting the unique property of directional evanescent escape in the deformed resonator, we have developed a free-space configuration for the excitation of WGMs and for the interferometric detection of mechanical displacement, for which the part of input laser that is not coupled into the microsphere serves as a local oscillator. Measurement sensitivity better than 5 × 10 -18 m /[Special characters omitted.] has been achieved. The three optically active mechanical modes observed in the displacement power spectrum are well described by finite element analysis. Both radiation pressure cooling and parametric instabilities have been observed in our experiments. The dependence of the mechanical resonator frequency and linewidth on the detuning as well as the intensity of the input laser show excellent agreement with theoretical calculations with no adjustable parameters. The free-space excitation technique has enabled us to combine resolved sideband cooling with cryogenic cooling. At a cryogenic temperature of 1.4 K, the sideband cooling leads to an effective temperature as low as 210 m K for a 110 MHz mechanical oscillator, corresponding to an average phonon occupation of 37, which is one of the three lowest phonon occupations achieved thus far for optomechanical systems. The cooling process is limited by ultrasonic attenuation in fused silica, which should diminish when bath temperature is further lowered, with a 3 He cryostat, to a few hundred millikelvin. Our experimental studies thus indicate that we are tantalizingly close to realizing the ground-state cooling for the exploration of quantum effects in an otherwise macroscopic mechanical system.
Committee in charge: Michael Raymer, Chairperson, Physics; Jens Noeckel, Member, Physics; Hailin Wang, Member, Physics; Paul Csonka, Member, Physics; Jeffrey Cina, Outside Member, Chemistry

Orientador: Newton Cesário Frateschi
Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin
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Resumo: Esta tese de doutorado apresenta resultados experimentais do crescimento de pontos quânticos de InAs diretamente sobre InGaAsP de baixa energia de bandgap (?g=1420 nm), cujo desenvolvimento visa a obtenção de um meio ativo com emissão na banda C (1520¿1570 nm) para a fabricação de ressonadores de microdisco. Baseado em resultados de fotoluminescência e microscopia de força atômica, o fenômeno da inter-difusão de elementos na interface InAs/InGaAsP é proposto e calculado, indicando a presença de Gálio e Fósforo na composição dos pontos quânticos. O ganho óptico de pontos quânticos de InAs crescidos sobre InGaAsP é também calculado com base nos resultados obtidos na análise de inter-difusão. Subseqüentemente, a teoria dos modos ressonantes no microdisco, particularmente os modos chamados whispering gallery modes (WGMs), é desenvolvida com o intuito de auxiliar os cálculos de fator de qualidade, fator de confinamento e corrente de limiar. Uma estrutura multicamada (diodo PIN) com região ativa baseada em pontos quânticos do sistema InAs/InGaAsP foi crescida por epitaxia de feixe químico (CBE) para a fabricação de ressonadores de microdisco. A fabricação dos microdiscos é feita por litografia óptica, corrosão por plasma de íons e ataque químico seletivo de InP. Feixe de íons focalizados (FIB) foi usado para substituir o ataque por plasma para diminuir a rugosidade das paredes dos discos. Os ressonadores de microdiscos são caracterizados elétrica e opticamente e os resultados são confrontados com base nos resultados teóricos apresentados ao longo da tese. Com base nos resultados das caracterizações eletro/ópticas dos ressonadores, correções como a inclusão de perdas ópticas da rugosidade da borda e aquecimento local foram acrescidas ao modelo teórico, resultando em boa concordância com os resultados experimentais. Por fim, apresentamos o desenvolvimento de dispositivos híbridos a partir de polímeros orgânicos depositados diretamente sobre microdiscos de InGaAs com o objetivo de integrar meio ativo orgânico com ressonadores inorgânicos para aplicações em optoeletrônica. Estes resultados foram obtidos durante o programa de doutorado com estágio no exterior no Laboratório Nacional de Nanotecnologia (NNL) vinculado à Università del Salento (Lecce/Itália)
Abstract:This doctorate¿s thesis presents the growth of InAs quantum dots directly on high bandgap InGaAsP (?g=1420 nm) barriers to be used as the active region of microdisk resonators with emission in the C-band (1520¿1570 nm). Based on photoluminescence and atomic force microscopy experiments, the occurrence of inter-diffusion on the InAs/InGaAsP interface is calculated, suggesting the presence of Gallium and Phosphorus in the quantum dots (QDs) composition. Based also on the inter-diffusion results, the optical gain of the InAs QDs is calculated. Subsequently, microdisk resonator whispering gallery modes (WGMs) are calculated and employed to predicting the cavity quality and confinement factors, as well as the threshold current. A PIN diode with an active region based on InAs QDs was grown by Chemical Beam Epitaxy (CBE) for the fabrication of current injected microdisk resonators. Microdisk fabrication process is performed using photolithography, reactive ion etching and InP selective wet-etching. Focused ion beam is used to replace the plasma etching in order to reduce the roughness of the disk¿s edge. Microdisks resonators are characterized electrically and optically and the measurements are analyzed based on the theoretical results presented along this thesis. Based on these measurements, optical losses caused by disk¿s edge roughness and local heating are added to our simulation tool, resulting in better agreement with the experimental results. Finally, we present the development of hybrid resonators using organic polymer deposited directly on inorganic microdisks integrating an organic active medium with inorganic resonators for optoelectronic applications. These results were obtained during our work at the National Nanotechnology Laboratory (NNL) and the University of Salento (Lecce/Italy)
Doutorado
Física da Matéria Condensada
Doutor em Física

Ces travaux de thèses portent sur l’étude de la dynamique du laser à mode de galerie dans le but de réaliser une source micro-onde en utilisant un laser à mode de galerie doublement monomode. Nous montrons ici les résultats expérimentaux sur le bruit relatif d’intensité (RIN) d’un laser à mode de galerie en verre ZBLALiP dopé aux ions Er3+. Outre l’aspect performances d’utilisation du laser, le spectre de RIN donne un certain nombre d’informations sur la dynamique du laser (temps de vie des photons, taux de pompage effectif, sources de bruit, ...).Les très forts facteur de qualités de ces résonateurs ainsi que leurs propriétés de confinement spatial amène un couplage non-linéaire etre les photons et les atomes du milieu amplificateur, faisant apparaitre dans le spectre de RIN des harmoniques de la fréquence de relaxation du laser. Le modèle harmonique développé permet d’estimer le volume de mode du mode de galerie en régime laser, quantité difficilement estimable dans ce régime d’émission. D’autre part, les mesures de RIN réalisées sur un verre industriel IOG-1 codopé Yb3+/Er3+ montrent la signature d’un couplage modal, induit par la diffusion Rayleigh, où les deux modes couplés fonctionnent au dessus du seuil laser. La dynamique de ce laser est également étudié et les comportements obtenus sont mis en parallèle avec les études réalisées sur le gyro-Laser à l’état solide
This thesis presents the studies of whispering gallery mode laser dynamics in order to realize a micro-wave source using simultaneous oscillations in a unique whispering gallery mode micro-laser. We show experimental results on the relative intensity noise (RIN) of a Whispering Gallery Mode Laser in ZBLALiP glass doped with Er3+ ions. Besides the pure laser specifications, the RIN spectrum gives informations about the dynamics inside the cavity, such as photon lifetime, effective pumping rate and noise sources. Moreover, we have shown that a single-mode emission comes with the presence of multiple harmonics of the relaxation frequency. The theoretical model taking account the non-linear coupling between photons and atoms allows us to determine the mode volume of the whispering gallery mode in laser regime, which is quite difficult to evaluate in this regime. On the other hand, we have studied the laser dynamics in an industrial IOG-1 glass codoped with Yb3+/Er3+ ions where the signature of a modal coupling, induced by Rayleigh scattering, lies in the RIN spectrum. In this particular case, the two coupled modes operate above threshold. The observed behavior is compared with thoses of a solid state gyro-laser

This thesis presents an investigation of the dynamic properties of wide range of interfacial systems, from colloidal particles in solution, through the realm of aerosols and onto studies of molecular adsorption at an interface. The primary experimental technique utilized is optical tweezers. An exploration of the history of the use of radiation pressure to manipulate matter is presented, followed by an introduction to how optical tweezers work. Some of the more advanced methods of tweezing are discussed, with an emphasis on the use of spatial light modulators (SLMs) to realise dynamic holographic optical tweezers (DHOTs), an example of which has been constructed within our laboratory using off-the-shelf optical components, and combined with a spectrometer to facilitate high resolution spectroscopic studies of microscopic systems. The spectroscopic analysis of microparticles is greatly enhanced by optical feedback generated when the wavelength of light utilized is an integer number of wavelengths around the circumference of the microsphere. Enhanced signal occurs at these wavelengths, termed whispering gallery modes (WGMs). The absolute position of these resonances depends strongly upon the shape, size and refractive index of the particle, and is predicted by Mie theory. A discussion of the concepts behind Mie theory, as well as how to use an experimental WGM spectrum to deduce the size and composition of a microparticle, is provided. This technique is then put to use in a detailed study on the properties of single aerosols, comprised of sodium chloride solution, and generated using a handheld medical nebulizer. Studies have been carried out on both evaporating and growing droplets trapped with a Gaussian beam; in the latter case, periods of size stability are observed, owing to resonant absorption of radiation at the trapping laser wavelength. The SLM can be used to change the trapping laser to a Laguerre-Gaussian (LG) mode, and an investigation of how this affects the dynamics of the droplet is presented. It is found that the use of LG modes with $ellgeq10$ produced Raman spectra with significantly more intense WGMs, and also suppressed droplet evaporation. Through observations made with fluorescent polystyrene microspheres, it is argued that the LG modes are more efficient at coupling into WGMs of the droplets. Leading on from these experiments on salt water droplets, experiments have been conducted using ionic liquids (ILs). These fluids have many fascinating properties and potential applications. The optical trapping of droplets comprised of aqueous solutions of the ionic liquid ethylammonium nitrate (EAN) and water has been demonstrated for the first time. These droplets are analysed spectroscopically by illuminating them with the output from a broadband LED; WGMs that are observed in the backscattered light are used to determine their size and composition. The response of the droplets to conditions of varying relative humidity has also been investigated. In order to characterise the relative humidity experienced by both the salt water and IL droplets, the concentration of water vapour within the trapping cells has been measured using diode laser absorption spectroscopy. The spatially modulated laser beam is then utilized in a different fashion; instead of optically tweezing a sample, a low numerical aperture objective lens is utilized to focus the laser onto the surface of a gold coated microscope slide. When a colloidal sample is placed on this surface, the thermal gradients cause the particles to form two dimensional crystals. The SLM is utilized to form multiple nucleation sites, and the dynamics of the crystals are directly observed in real time using video microscopy. It is found that grain rotation-induced grain coalescence (GRIGC) occurs, with the rotation of both crystals before coalescence. Control over the grain size is achieved by altering the separation of the laser spots, and shows that the time scale for grain boundary annealing in our system is in good agreement with theoretical expressions formulated for nanocrystal growth. Finally, as a complimentary technique to the microparticle spectroscopy previously discussed, a bulk interface is probed by using evanescent wave broadband cavity enhanced absorption spectroscopy (EW-BBCEAS) specifically to study the adsorption of cytochrome c (cyt c) to a fused silica surface. Visible radiation from a supercontinuum source is coupled into an optical cavity consisting of a pair of broadband high reflectivity mirrors, and a total internal reflection (TIR) event at the prism/water interface. Aqueous solutions of cyt c are placed onto the TIR footprint on the prism surface and the subsequent protein adsorption is probed by the resulting evanescent wave. The time integrated cavity output is directed into a spectrometer, where it is dispersed and analysed. The broadband nature of the source allows observation of a wide spectral range (ca 250 nm in the visible). The system is calibrated by measuring the absorption spectra of dyes of a known absorbance. Absorption spectra of cyt c are obtained for both S and P polarized radiation, allowing information about the orientation of the adsorbed protein to be extracted.

Les microrésonateurs à mode de galerie passifs à base de cristal ou de verre fabriqués par la méthode de fusion possèdent un facteur de qualité limité à quelques 10E8. Ceci est généralement dû à la contamination de la surface du résonateur lors de sa fusion. Dans ces travaux, nous proposons de contourner cette limitation en utilisant des microrésonateurs actifs pour compenser les pertes. Afin de caractériser les microrésonateurs actifs de très haut facteur de qualité ainsi obtenu, nous nous appuyons sur la méthode CRDM (Cavity Ring Down Measurement). Cette méthode interférométrique est d'une part bien adaptée à la caractérisation de résonateurs de très haut facteur de qualité et d'autre part elle permet de remonter de manière univoque aux facteurs de qualité intrinsèque Qo et extrinsèque Qe du résonateur. Dans un régime de compensation de pertes, nous avons pu atteindre tous les régimes de couplage et obtenus des facteurs de qualité intrinsèques excédant les 10E10. En régime d'amplification sélective, nous avons démontré expérimentalement que l'on pouvait obtenir des gains élevés allant jusqu'à 33 dB et des retards de groupe excédant 2,3 µs dans ces microrésonateurs actifs. Ces microrésonateurs de très haut facteur de qualité et de très haute finesse peuvent présenter un couplage modal se manifestant par un doublet de résonances. Une confrontation théorie/expérience avec la méthode CRDM permet de mesurer un écart très faible entre les doublets. Par ailleurs, ces microrésonateurs présentant un fort confinement spatial et une forte surtension, sont propices à l'observation d'effets non-linéaires. Une modélisation intégrant l'effet thermique et l'effet Kerr a été réalisée. Une confrontation théorie/expérience nous a permis d'estimer la puissance réellement injectée dans le mode ainsi qu'à estimer le volume du mode.

La présente thèse est consacrée à l’étude des peignes optiques de Kerr dans les résonateurs àmodes de galerie, au sein desquels la lumière peut être excitée par pompage externe. L’effet Kerrexistant dans ces résonateurs engendre des modes latéraux équidistants (dans le domaine spectral)de part et d’autre du mode excité, c’est à dire un peigne de fréquence. Cette thèse est diviséeen trois chapitres. Le premier est dédié à l’introduction de la génération de ces peignes et leurapplications. Le deuxième chapitre présente l’analyse de l’équation de Lugiato-Lefever, décrivantde manière analytique le système, et conduit à la construction de deux diagrammes de bifurcationpour les dispersions normale et anomale. Ils sont tracés en fonction des deux seuls paramètresexpérimentalement contrôlables une fois le résonateur fabriqué : la puissance du laser et sondécalage de fréquence. Ces diagrammes indiquent les plages de paramètres pour lesquels une,deux, ou trois solutions existent ainsi que leur stabilité. Les simulations numériques renseignentle type exact de solution associée à chaque aire (notamment les solitons brillants et sombres, lesbreathers, les peignes optiques de Kerr de premier et deuxième ordre, et un régime chaotique) ; cesdiagrammes indiquent donc les paramètres du laser à choisir afin de générer la solution souhaitée.Le troisième chapitre est dédié aux peignes de Kerr optique secondaires, lignes additionnelles dansle domaine spectral générées entre les lignes du peigne principal. Ils apparaissent en dispersionanormale, lorsque la quantité de photon pompe excède un seuil dit de second ordre, qui a étédéterminé numériquement
This thesis is dedicated to the study of the Kerr optical frequency combs in whispering gallery moderesonators, where the light can be excited by the extern pump. Due to the Kerr effect existing in theseresonators, the quasi-equidistant lines in the spectral domain are generated around the excited mode,that is the frequency comb. This thesis is devided in three chapters. The first one is dedicated to theintroduction of the Kerr comb generation and their applications.The second one presents the analysisof the Lugiato-Lefever equation used for the analytical study of the system, leading to the constructionof two bifurcation diagrams for the normal and anomalous dispersions. They are plotted for twoparameters, which can be controlled during experiments once the resonator has been fabricated,which are the pump power of the laser and its frequency detuning. These diagrams show the areas ofthe parameters for which one, two, or three solutions exist and their stability. The additional numericalsimulations show the exact type of the solution in each area (such as the bright and dark solitons,the breathers, the primary and secondary Kerr combs and chaotical regimes), finally these diagramsshow the parameters of the laser needed to be choosen for the generation of the desired solution.The third chapter is dedicated to the secondary Kerr combs, which are the additional lines generatedbetween the lines of the primary comb. They appear in the anomalous dispersion regime, when thequantity of the pump photons crosses the second-order threshold, which has been found numerically

University of Technology Sydney. Faculty of Science.
Zinc oxide (ZnO) is a large bandgap (3.37 eV at room temperature) semiconductor and is a good candidate for short wavelength photonic devices such as laser diodes. A large exciton binding energy (60 meV) at room temperature in addition to the advantages of being able to grow various nanostructure forms have made ZnO suitable for a wide range of applications in optoelectronic devices. Driven by the rapid advance of nanophotonics, it is necessary to develop single photon sources (SPSs) and optical resonators in new class of materials. In particular, SPSs are required for a wide range of applications in quantum information science, quantum cryptography, and quantum communications. ZnO has been investigated for classical light emitting applications such as energy efficient light emitting diodes (LEDs) and ultraviolet (UV) lasers. Significantly ZnO has recently been identified as a promising candidate for quantum photonic technologies. Thus in this thesis the optical properties of ZnO micro- and nano-structures were investigated for ZnO nanophotonic technologies, specifically their applications in single photon emission and optical resonators. Firstly, the formation of radiative point defects in ZnO nanoparticles and their photophysical properties were investigated. In particular, using correlative photoluminescence (PL), cathodoluminescence (CL), electron paramagnetic resonance (EPR), and x-ray absorption near edge spectroscopy (XANES) it is shown that green luminescence (GL) at 2.48 eV and an EPR line at g = 2.00 belong to a surface oxygen vacancy (V⁺o,s) center, while a second green emission at 2.28 eV is associated with zinc vacancy (VZn) centers. It is established that these point defects exhibit nanosecond lifetimes when excited by above bandgap or sub-bandgap (405 nm and 532 nm excitation wavelength) excitation. These results demonstrate that point defects in ZnO nanostructures can be engineered for nanophotonic technologies. ZnO nanoparticles were consequently studied for the investigation of room temperature single photon emission from defect centers in ZnO nanoparticles. Under the optical excitation with 532 nm green laser, the emitters exhibit bright broadband fluorescence in the red spectral range centered at 640 nm. The red fluorescence from SPSs in ZnO defect center is almost fully linearly polarized with high signal-to-noise ratio. The studied emitters showed continuous blinking; however, it was confirmed that bleaching can be suppressed using a polymethyl methacrylate (PMMA) coating. Furthermore, passivation by hydrogen treatment increase the density of single photon emitters by a factor of three. ZnO/Si heterojunctions were fabricated and used to investigate electrically driven light emission from localized defects in ZnO nanostructures at room temperature. It is shown that excellent rectifying behaviors were observed with the threshold voltages at ~ 18 V and ~ 7 V for ZnO nanoparticles and thin film-based devices, respectively. Both devices exhibit electroluminescence (EL) in the red spectral region ranging from ~ 500 nm to 800 nm when 40 V and 15 V were applied to ZnO nanoparticles/Si and ZnO thin film/Si, respectively. The emission is bright and stable for more than 30 minutes, providing an important prerequisite for practical devices. Finally, ZnO optical resonators were fabricated and investigated to enhance the visible light emission. Hexagonal ZnO microdisks with diameter ranging from 3 μm to 15 μm were grown by a carbothermal reduction method. Optical characterization of ZnO microdisks was performed using low temperature (80 K) CL imaging and spectroscopy. The green emission is found to be locally distributed near the hexagonal boundary of the ZnO microdisks. High resolution CL spectra of the ZnO microdisks reveal whispering gallery modes (WGMs) emission. Two different sizes (5 μm and 9 μm) of the ZnO microdisks were simulated to analyze the nature of light confinement in terms of geometrical optics. Respective analysis of the mode spacing and the mode resonances are used to show that the ZnO microdisks support the propagation of WGMs. The results show that the experimentally observed WGMs are in excellent agreement with the predicted theoretical positions calculated using a plane wave model. This work could provide the means for ZnO microdisk devices operating in the green spectral range.

New methods of biological analyte sensing are needed for development of miniature biosensors that are highly sensitive and require minimal sample preparation. One novel technique employs optical resonances known as Whispering Gallery Modes (WGMs). These modes arise from total internal reflection of light at the internal surface of a high index microsphere within a low index medium and produce an evanescent field that extends into the surrounding medium. The WGMs produce multiple narrow spectral peaks that shift position with variations in the local index of refraction sampled by the evanescent tail of the WGMs. To excite these WGMs, we embed quantum dots (QDs) in the periphery of polystyrene microspheres to serve as local light sources. By coupling emission from the QDs to the WGMs, the sensors can be excited and interrogated remotely and, by monitoring the shift of multiple resonance modes, may provide higher sensitivity and accuracy compared with similar techniques. The high refractometric sensitivity of the WGMs offers potential for trace detection of molecules adsorbed onto or bound to the microsphere sensor elements. The sensitivity of these sensors is demonstrated by monitoring the wavelength shift of multiple resonant modes as bulk index of refraction is changed. The potential for targeted biosensing is explored through addition of a protein that adsorbs to the microsphere surface, thrombin. Microsensor response in all cases demonstrated increased sensitivity over theoretical predictions. Models based on Mie theory and continuity of the radial functions across the sphere-media interface were used to model the location, Q-factor, and sensitivity of the WGMs in microspheres by considering the embedded QDs as a high index outer layer. This model was used, along with estimates of the QD-layer index and penetration depth, to relate the locations and sensitivities of the modes to our experimental results with strong agreement between the two. In all, these microspheres demonstrate feasibility for use as remote microsensors with sensitivities rivaling current techniques.

碩士
國立成功大學
機械工程學系碩博士班
101
Sonic crystals (phononic crystals) are periodic elastic composite materials. Such artificial crystals can exhibit acoustic or elastic band gaps in which sound and vibration are all forbidden in any direction, giving rise to prospective applications such as elastic/acoustic filters and noise/vibration isolations. One particularly interesting aspect of sonic crystals is the possibility of creating crystal defects to confine the elastic/acoustic waves in localized modes. Because of locally breaking the periodicity of the structure, the defect modes can be created within the band gaps, which are strongly localized around the local defect. The point defect is created by removing a single rod from the middle of the perfect periodic structure. There exist the defect bands in the absoulate band gap. The acoustic wave can propagate through the sonic crystal, since the defect band acts as a pass band in the band gap. The point defect can also act as the resonant cavity. At the frequency of the defect band, which is the resonant frequency, the acoustic waves should be localized in the resonant cavity and the pressures in the cavity are enhanced. Sonic WGM has not been analyzed in phononic crystal previously. In this paper, we study the WGM which formed by removing several cylinders away from phononic crystal with PWE method and analyze the pressure in the defect to confirm acoustic WGM resonance. The advantages of the of WGM resonance in this large-size cavity are the pressure and sensitivity are higher than the single defect resonance . Considering if we want to use the device as the sensor, it is important to insert a waveguide besides the cavity. So we also inserted a waveguide and investigate coupling between cavity and waveguide.

碩士
國立臺灣大學
光電工程學研究所
103
We have successfully fabricated optically active microdisk resonators with Si nanocrystals grown by plasma enhanced chemical vapor deposition (PECVD) and the post-annealing process. The room-temperature photoluminescence from single microdisk shows the characteristic modal structure of whispering-gallery modes in the wavelength between 600nm and1000nm. We fabricated Si-nanocrystal-embedded microdisk resonators by two different lithography processes. We use standard lithography to fabricate the microdisk resonators with diameters of 10μm and 20μm and electron-beam lithography for 4-μm, 6-μm, 8-μm and 10-μm-diameter disks. The quality factors of 8μm and 10μm disks can reach 1200 and 2400 respectively. We also fabricated thicker 10-μm-diameter disks to increase the confinement of the disk. We can also use Si-nc/SiO2 superlattice as the active layer in the microdisk resonators and the WGMs were observed clearly Finally, we discussed the relation between pump power and output power. We observed the saturation of the excitable nanocrystals at low pump power and the linewidth broadening with pump power increasing due to the excited carrier absorption (ECA).

博士
國立交通大學
光電工程系所
97
Whispering-gallery (WG) mode with high quality (Q) factor and multi-directional resonance is very suitable for serving as the active laser sources and passive devices with specific functionalities in photonic integrated circuits (PICs). In this dissertation, we design, fabricate, and characterize various photonic crystal (PhC) based micro- and nano-cavities with high Q WG modes. The possible applications are also investigated and discussed. In the beginning of this dissertation, we introduce the related research resources for researches on two-dimensional PhC cavity devices, including numerical simulation methods, nano-fabrication processes, and measurement systems. At first, we propose a nanocavity design with WG mode based on 8-fold quasi-PhC (QPhC). Various WG modal properties are addressed both in experiments and simulations, including single mode lasing actions, side mode reduction mechanism, compact device size, and so on. Besides, we also investigate a novel circular-PhC (CPhC) lattice structure with isotropic photonic band gap effect and characterize the designed CPhC microcavity with high Q WG mode. By using 12-fold QPhC lattice structure with high symmetry, we design a microcavity with high Q WG mode. WG mode lasing actions and the strong mode dependence on microcavity boundary are confirmed. Due to the WG mode field distribution, we insert a nano-post beneath the microcavity to serve as the current injection pathway and heat sink in electrically-driven structure. By fabricating microcavities with different nano-post sizes, we investigate the WG modal loss behaviors and heat sink improvement due to nano-post both in experiments and simulations. For the purpose of integration in PhC-based PICs, we project the 12-fold microcavity boundary on a PhC microcavity and enhance a high Q WG mode in it. Due to the presence of WG mode, we investigate the uniform coupling properties of different waveguide-cavity geometries. In applications, we propose a double-layered structure based on above PhC microcavity and investigate its possibility in serving as an optical stress sensor. In the end, we propose a nanocavity design with lowest order WG mode based on square PhC lattice. This WG mode can be with very small mode volume and large nano-post tolerance beneath the nanocavity at the same time.

Optical whispering-gallery mode (WGM) cavities, which exhibit extraordinary spatial and temporal confinement of light, are one of the leading transducers for examining molecular recognition at low particle counts. With the advent of hybrid photonic-plasmonic and increasingly sophisticated forms of these resonators, the importance of supporting numerical methods has correspondingly become evident. In response, we adopt a full-vector finite difference approximation in order to solve for WGM's in terms of their field distributions, resonant wavelengths, and quality factors in the context of naturally discontinuous permittivity structure. A segmented Taylor series and alignment/rotation operator are utilized at such singularities in conjunction with arbitrarily spaced grid points. Simulations for microtoroids, with and without dielectric nanobeads, and plasmonic microdisks are demonstrated for short computation times and shown to be in agreement with data in the literature. Constricted surface plasmon polariton (SPP) WGM's are also featured within this document. The module of this thesis is devised as a keystone for composite WGM models that may guide experiments in the field.
Graduate

碩士
國立中央大學
光電科學研究所
95
Microsphere resonators have attracted a lot of interest in recent years, due to ultra high quality factor and small modal volume. Numerous methods for coupling energy into the whispering gallery modes of a microsphere have been demonstrated, however most of them are limited by either low coupling efficiency or mechanical instability. In this thesis, an etch-eroded fiber coupler was investigated, and better coupling efficiency and acceptable stability was obtained. The orders of the WGMs and the quality factors can be determined by analyzing optical transmission spectra and fitting to the theoretical resonant wavelengths. Furthermore, it shows that the smaller the radius of the fiber; the higher the coupling efficiency. In this thesis, the highest coupling efficiency is obtained 42.07％, and the quality factor is ~ 25000.

碩士
國立中央大學
光電科學研究所
95
A simple method for the excitation of fundamental whispering-gallery modes in a BK7 glass microsphere by a side-polished fiber half-block coupler is demonstrated. The coupler is made of the single-mode fiber (Corning SMF-28) which has an effective refractive index of 1.4682 @1550nm. The radius and refractive index of the microsphere equal to 150± 1.5 um and 1.500065 @1550 nm, respectively. The resonant modes are identified from the transmission spectrum, which indicates that the quality factor of 17000, free spectral range of 1.7 nm and coupling efficiency of 10% are obtained.

碩士
國立臺灣大學
光電工程學研究所
103
Single-crystal silicon-cored fibers were made by using a combined techniques of powder-in-tube and vertical-drawing. Much cheaper polycrystalline silicon powders substituting expensive single-crystal silicon powders or seed rods were packed into a fused silica tube. By optimizing the drawing parameters, meter-long silicon-cored fibers were obtained with ultralow transmission losses because the entire lengths of silicon cores were single crystalline. The Si-cored fibers were drawn with resultant silica cladding and Si core diameters being in the range of 100-300 microns and 10-30 microns, respectively. We also demonstrated a fiber drawing system for fabricating Si cored tapered fiber. A fiber drawing system equipped with oxy-hydrogen flame and transition stage was used. According to the previously accumulated knowledge in fabrication of silica microfiber, we successfully fabricated Si cored tapered fibers with diameter of 2.6 microns in the waist section from an original Si-cored fiber with diameter of 20 microns. Silicon microsphere resonators which exhibited high quality factor (Q) whispering-gallery-modes (WGMs) could be rapidly fabricated from Si-cored fibers using CO2 laser reformation. WGMs were excited by using the tapered silica fiber coupling technique, and a record resonant Q as high as 4 x 10^5 was obtained. The shift of resonant wavelength caused by thermo-optic effect of Si material was also observed.

Thesis (M.S.)--University of Wisconsin--Madison, 1994.
Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 74-75).

碩士
國立清華大學
化學系
105
Light can be totally internally reflected inside a sphere made of dielectric material with refractive index higher than the environment. At specific wavelengths, standing waves are established, forming the photonic whispering-gallery modes (WGMs). On the interface of air and gold, surface plasmons (SPs) can be excited by photons if the momentum matching condition is fulfilled. When the spherical WGM resonator is placed on the gold substrate, the evanescent near fields of the WGMs can interact with the gold substrate. Depending on the polarization and the orbiting orientation of the WGMs, the interaction can result in spectral shift and intensity variation. The influence of the gold substrate on the WGM is of fundamental interest and practical importance when the sphere is to be connected to metallic electrodes for photoelectric effects. In this thesis, we investigate the influence of single-crystalline gold substrate on the WGMs of self-assembled semiconducting fluorescent π-conjugated polymer microspheres. In particular, we focus on the effects on WGM peak intensity and spectral shift. For peak intensity, we found that all peaks and the broadband fluorescence background in the emission spectrum are enhanced by the gold substrate. However, the intensity of transverse magnetic (TM) WGMs is usually lower than the corresponding transverse electric (TE) modes. This is found to stem from the WGM-to-SP coupling of the TM modes via Otto configuration. As for the spectral shift, we have observed that gold substrate results in blue shift of TE modes and red shift of TM modes. While for ITO substrate, both TE and TM show red shift. With theoretical and numerical analysis, we attribute the red and blue shift of the TM and TE mode to the negative and positive Goos-Hänchen shift on the gold substrate, respectively. The negative and positive Goos-Hänchen shifts correspond to effective enlargement and shrinkage of the sphere circumference and thus the red-shifted and blue-shifted peak positions, respectively. Typically, the assignment of TE and TM modes relies on theoretical analysis. This study shows that by identifying the metal surface plasmon coupling effect and the Goos-Hänchen shifts, the assignment of TE and TM mode can also be done experimentally. Finally, the influence of the graphene substrate on the whispering gallery mode is discussed. Graphene is known to be an efficient quencher and the quenching effect depends on the dipole orientation with respect to the graphene surface. Dipoles parallel to the graphene plane are quenched much more effectively than those perpendicular to the surface. Therefore, it is interesting to know if graphene substrate has different quenching effects on the TE and TM modes. The preliminary results show that there is no observable difference. This might be due to the fact that the coupling of WGMs to graphene substrate is different from that of dipole sources to graphene. The details of the influence of graphene on WGMs require further experimental and theoretical works.

Near-membrane and trans-membrane proteins and their interactions with the extracellular matrix (ECM) can yield valuable information about cell dynamics. However, advances in the field of nanoscale cellular processes have been hindered, in part, due to limits imposed by current technology. In this work, a novel evanescent field (EF) imaging technique is designed, modeled, created and tested for near-field imaging in the apical surface of cells. This technique and Förster resonance energy transfer (FRET) were used to investigate interactions between integrins on the cell surface and the ECM protein, fibronectin. The goal was to monitor changes in the integrin density at the cell surface as a function of clustering after binding to fibronectin on the microsphere surface. For the EF technique, quantum dot (QD)-embedded polystyrene microspheres were used to couple light into whispering gallery modes (WGMs) inside the microspheres; the resulting EF at the surface of the microsphere was used as a near-field excitation source with ~50 nm axial resolution for exciting fluorescently-labeled integrins. For FRET measurements (~10 nm axial resolution), QDs (donors) were coated on the surface of microspheres and energy transfer to red fluorescent protein (RFP)-integrin constructs (acceptors) studied. In both techniques, the QD-modified microspheres were mounted on atomic force microscope (AFM) cantilevers, functionalized with fibronectin, and brought into contact with fluorescently-labeled HeLa or vascular smooth muscle (VSM) cells. The results obtained from both methods show the clustering and activity of the integrins and are in good agreement with each other. Amsterdam discrete dipole approximation (ADDA) was used to study the effects of inhomogeneous surrounding refractive index on the quality factor and position of the WGMs due to the attachment of a microsphere to an AFM cantilever. WGMs of various QD-embedded microspheres mounted on AFM cantilevers were experimentally measured and shown to be consistent with the model.

abstract: This dissertation aims to study and understand relevant issues related to the electronic, spin and valley transport in two-dimensional Dirac systems for different given physical settings. In summary, four key findings are achieved. First, studying persistent currents in confined chaotic Dirac fermion systems with a ring geometry and an applied Aharonov-Bohm flux, unusual whispering-gallery modes with edge-dependent currents and spin polarization are identified. They can survive for highly asymmetric rings that host fully developed classical chaos. By sustaining robust persistent currents, these modes can be utilized to form a robust relativistic quantum two-level system. Second, the quantized topological edge states in confined massive Dirac fermion systems exhibiting a remarkable reverse Stark effect in response to an applied electric field, and an electrically or optically controllable spin switching behavior are uncovered. Third, novel wave scattering and transport in Dirac-like pseudospin-1 systems are reported. (a), for small scatterer size, a surprising revival resonant scattering with a peculiar boundary trapping by forming unusual vortices is uncovered. Intriguingly, it can persist in arbitrarily weak scatterer strength regime, which underlies a superscattering behavior beyond the conventional scenario. (b), for larger size, a perfect caustic phenomenon arises as a manifestation of the super-Klein tunneling effect. (c), in the far-field, an unexpected isotropic transport emerges at low energies. Fourth, a geometric valley Hall effect (gVHE) originated from fractional singular Berry flux is revealed. It is shown that gVHE possesses a nonlinear dependence on the Berry flux with asymmetrical resonance features and can be considerably enhanced by electrically controllable resonant valley skew scattering. With the gVHE, efficient valley filtering can arise and these phenomena are robust against thermal fluctuations and disorder averaging.
Dissertation/Thesis
Doctoral Dissertation Electrical Engineering 2017