<p>The objective of this thesis is to evaluate a generic process for fabrication and characterization of the Superconductive coplanar waveguide (CPW) resonators. Superconductive CPW resonators with various lengths and shapes are designed to investigate their electrical and magnetic properties as well as resonance properties and sensitivities. In the first part of thesis, two different models are introduced in order to estimate the nonlinear kinetic inductance of a superconducting CPW resonator. The first model is based on Bean critical-state model and the second one is based on current dependence of London penetration depth. The existence of a shift in resonant frequency  of Superconductive CPW resonator caused by a non-linear kinetic inductance is also shown experimentally. Simulations were carried out to estimate the nonlinear kinetic inductance due to the self- induced magnetic field penetration.</p><p>The rest of the thesis is concerned with development of very smooth Aluminum (Al) thin films with RMS (Root Mean Square) roughness 1~nm and CAD (Computer Aid Design) of superconductive CPW resonators. Experimental investigation of a generic fabrication technique for superconductive CPW resonator is carried out. Many resonators are fabricated with different design parameters, such as centerline or gap width, film thickness and gap capacitors length. The fabrication process is described in detail. Electron Beam Lithography is used to fabricate Nb and Al CPW resonators which are coupled to outer conductors via gap capacitors. We have fabricated GHz frequency CPW resonators with quality factors, Q up 5X10^5.</p>

La détection optofluidique à champ évanescent, tout particulièrement la biodétection sans marqueur par microrésonateurs optiques, est une technologie émergente faisant l’objet d’une recherche intensive. Dans ce contexte, nous montrons que les microanneaux polymères sont d’excellents transducteurs. Ceci est dû en partie à la facilité et au faible coût de leur fabrication et de leur intégration, mais aussi à leur robustesse. Une méthode rapide, répétable et peu coûteuse a été mise au point pour fabriquer de tels composants, avec de longues durées de vie et des performances représentant l’état de l’art actuel. Un deuxième avantage est l’extrême sensibilité moléculaire en surface. La preuve en est l’obtention d’un signal détectable avec seulement 500 molécules de 5-TAMRA-cadavérine (5-TC, M = 515 g/mol) adsorbées, et ce après un simple traitement UV/ozone. Cependant, les performances des anneaux polymères ne deviennent apparentes qu’une fois le composant couplé à une instrumentation de haute précision. A cet effet, un instrument de mesure fut construit pour mesurer en temps-réel de très faibles variations des résonances optiques en régime optofluidique. Ceci a permit l’observation d’une cinétique d’absorption/désorption de 5-TC sur son antigène. Néanmoins, une réelle détection spécifique ne peut être atteinte qu’avec un instrument multiplexé en transducteurs. Une telle configuration est possible, mais n’a pas encore été développée. Par contre, l’instrument de mesure réalisé peut être utilisé tel quel pour des applications très diverses, de la mesure de coefficients de diffusion à l’étude d’effets thermiques locaux. / Optofluidic evanescent field sensing, especially microresonator-based label-free biochemical sensing, is an emerging technology under intensive study. In this context, we demonstrate that polymeric microring resonators are excellent transducers. It is partly due to the simplicity and cost-efficiency of their fabrication and integration, and also to their robustness: a fast, repeatable and low-cost method was developed to fabricate devices with long lifetimes and state-of-the-art performances. A second advantage is the extreme sensitivity achievable to grafted molecules: a detectable signal was obtained with only a few hundreds of 5-TAMRA-cadaverine (5-TC) molecules, relatively small as compared to nucleic acids, antibodies and other biomolecules. The surface immobilization of 5-TC molecules was achieved after a simple and reproducible UV/ozone procedure for surface preparation. However, the qualities of polymer microring resonators only become apparent when coupled to high-precision instrumentation. In that respect, a measuring instrument was built to detect minute and real-time variations of the optical resonances, and thus in an optofluidic regime. The detection of absorption and desorption of 5-TC molecules on a surface functionalized with its antibody was achieved. However, truly specific responses of the instrument would only be achieved in a multiplexed configuration. Such configuration is achievable, but has yet to be developed. Meanwhile, the measuring instrument, as is, can be used for a wide variety of applications, from the measurement of dispersion coefficients to the study of local thermal effects.

Le résonateur étudié s'insère dans un projet industriel porté par NXP Semiconductors. L'objectif est la réalisation d'un résonateur MEMS RF intégrable en vue de remplacer le quartz dans certaines applications. La compatibilité du procédé de fabrication avec les technologies utilisées par la société et le faible coût de production représentent les principaux enjeux du projet. Le résonateur TFEAR (Thin Film Elongation Acoustic Resonator) est un barreau, constitué d'une superposition de couches minces de type Métal/AlN/Métal. Les propriétés piézoélectriques du nitrure d'aluminium (AlN) sont ainsi exploitées : l'application d'un champ électrique alternatif, parallèle à l'épaisseur du barreau, entraîne une propagation d'ondes acoustiques suivant sa longueur. Les dimensions des résonateurs fabriqués correspondent à des fréquences de résonance comprises entre 10MHz et 50MHz. Cette thèse s'intéresse la modélisation et à la caractérisation électrique du résonateur TFEAR. Les modèles théoriques sont développés par simulations numériques 3D et par calculs analytiques 1D. Le comportement électrique du TFEAR est décrit par un schéma équivalent, dont les éléments sont exprimés en fonction des paramètres physiques et des pertes des matériaux le constituant. Un facteur de qualité de 2250 sur un TFEAR résonant à 25,79MHz et dont la résistance motionnelle est de 2,1 kOhms a été relevé. Ces mesures ont été complétées par la caractérisation des paramètres physiques de la couche piézoélectrique. Par exemple, des valeurs de coefficient piézoélectrique d33f atteignant 2,6 pm/V ont été relevées (pour un maximum théorique de 3,93 pm/V) / The studied resonator is part of an industrial project carried by NXP Semiconductors. The objective is the realization of a integrable RF MEMS resonator in order to replace quartz in some applications. The compatibility of the manufacturing process with the technologies used by the company and low cost production represent the main challenges of the project. The resonator TFEAR (Thin Film Elongation Acoustic Resonator) is a bar, consisting of a superposition of thin film type Metal/AlN/metal. The piezoelectric properties of aluminum nitride (AlN) are exploited : the application of an alternating electric field, parallel to the thickness of the bar, resulting in propagation of acoustic waves along its length. The sizes of the manufactured resonators correspond to resonant frequencies between 10MHz to 50 MHz. This thesis focuses on modeling and electrical characterization of the TFEAR resonator. The models are developed by 3D numerical simulations and by 1D analytical calculations. The electrical behavior of TFEAR is described by an equivalent circuit which elements are expressed in terms of physical parameters and losses of the constituent materials. A quality factor of 2250 on a 25.79MHz resonant TFEAR which motional resistance is 2.1 kOhms has been noticed. These measurements were completed by the characterization of the physical parameters of the piezoelectric layer. For example, piezoelectric coefficient d33;f values were recorded up to 2.6 pm/V (for a theoretical maximum of 3.93pm/V)

Gegenstand der vorliegenden Arbeit waren II-VI-Halbleiter basierende Mikroresonatoren. Die Ziele der Arbeit bestanden dabei hauptsächlich in: 1. Untersuchung nichtlinearer Emission und starker Exziton-Photon-Kopplung bei eindimensionalem photonischem Einschluß auch bei hohen Leistungsdichten und Temperaturen 2. Erzeugung dreidimensionalen photonischen Einschlusses 3. Untersuchung nichtlinearer Emission in photonischen Punkten 4. Nachweis starker Kopplungseffekte in photonischen Punkten / Topic of this work were II-VI-semiconductor based microcavities. The main goals were: 1. study of nonlinear emission and strong exciton photon coupling in structures with one-dimensional photonic connement, even at elevated excitation power densities and temperatures 2. preparation of three-dimensional photonic confinement 3. study of nonlinear emission from photonic dots 4. proof of strong coupling in photonic dots

Exotic aspects of quantum mechanics, such as quantum entanglement, can be exploited to solve computational problems that are impractical to solve with conventional computers. With the realization of robust solid-state qubits, such as Nitrogen Vacancy (NV) centers in diamond, an outstanding challenge is to develop experimental approaches that can control the interactions between individual qubits. This dissertation develops a diamond-based experimental system that exploits acoustic waves or mechanical vibrations to mediate interactions between spin qubits. This spin-mechanical system features three essential elements: robust qubits, high quality-factor diamond nanomechanical resonator, and strong spin- mechanical coupling, thus enabling a new and promising platform for pursuing solid- state quantum computer. For the spin-mechanical system, NV centers are created near the surface of a bulk diamond through nitrogen ion implantation followed by stepwise high temperature annealing. We successfully suppress environmental fluctuations and achieve NV centers with stable and spectrally narrow (< 50 MHz) fluorescence at low temperature, which is crucial for the spin-mechanical system. Diamond nanomechanical resonators with a fundamental frequency near 1 GHz have been successfully fabricated with a diamond-on-insulator approach. The resonators are suspended from a silicon substrate and are supported with long and thin tethers, decoupling the mechanical modes from the surrounding environment. Diamond nanofabrication is still in its infancy. Numerous fabrication problems occurring during etching, mask transfer, and wafer bonding have been painstakingly resolved. Strong spin-mechanical coupling is demonstrated via the strain coupling of the NV excited-states. The spin-mechanical coupling takes place through a 𝚲-type three- level system, where two ground-spin-states couple to an excited-state through a phonon-assisted as well as a direct dipole optical transition. Both coherent population trapping and optically-driven spin transitions have been realized. The coherent population trapping demonstrates the coupling between an acoustic wave and an electron spin coherence through a dark state, thus avoiding the short lifetime of the excited state. The optically-driven spin transitions can enable the quantum control of both spin and mechanical degrees of freedom. This dissertation includes previously published co-authored material.

Thesis advisor: Krzysztof Kempa / The resonant modes of a sequence of periodically spaced microstrip resonators is studied. The system is analyzed as transmission line with periodic capacitive gaps, as a waveguide with apertures via normal mode expansion, and through a derivation of the static fields in the gap between two microstrip resonators via conformal mapping. FDTD simulations are also performed to numerically calculate the resonant modes of the sequence and also its absorption spectrum when it contains a lossy dielectric. It is found, as expected, that when the gap size is large, the microstrip resonators are uncoupled and there resonant modes are unperturbed. As the gap size narrows, the resonators become strongly coupled, and changing boundary conditions perturb the resonant modes upwards in frequency. Moreover, an additional resonant mode is observed that does not correspond to any uncoupled mode. / Thesis (BS) — Boston College, 2011. / Submitted to: Boston College. College of Arts and Sciences. / Discipline: College Honors Program. / Discipline: Physics Honors Program. / Discipline: Physics.

The purpose of this dissertation is to provide a theoretical model to design RF coils using multiconductor transmission line (MTL) structures for MRI applications. In this research, an MTL structure is represented as a multiport network using its port admittance matrix. Resonant conditions and closed-form solutions for different port resonant modes are calculated by solving the eigenvalue problem of port admittance matrix using block matrix algebra. A mathematical proof to show that the solution of the characteristic equation of the port admittance matrix is equivalent to solving the source side input impedance is presented. The proof is derived by writing the transmission chain parameter matrix of an MTL structure, and mathematically manipulating the chain parameter matrix to produce a solution to the characteristic equation of the port admittance matrix. A port admittance matrix can be formulated to take one of the forms depending on the type of MTL structure: a circulant matrix, or a circulant block matrix (CB), or a block circulant circulant block matrix (BCCB). A circulant matrix can be diagonalized by a simple Fourier matrix, and a BCCB matrix can be diagonalized by using matrices formed from Kronecker products of Fourier matrices. For a CB matrix, instead of diagonalizing to compute the eigenvalues, a powerful technique called “reduced dimension method� can be used. In the reduced dimension method, the eigenvalues of a circulant block matrix are computed as a set of the eigenvalues of matrices of reduced dimension. The required reduced dimension matrices are created using a combination of the polynomial representor of a circulant matrix and a permutation matrix. A detailed mathematical formulation of the reduced dimension method is presented in this thesis. With the application of the reduced dimension method for a 2n+1 MTL structure, the computation of eigenvalues for a 4n X 4n port admittance matrix is simplified to the computation of eigenvalues of 2n matrices of size 2 X 2. In addition to reduced computations, the model also facilitates analytical formulations for coil resonant conditions. To demonstrate the effectiveness of the proposed methods (2n port model and reduced dimension method), a two-step approach was adopted. First, a standard published RF coil was analyzed using the proposed models. The obtained resonant conditions are then compared with the published values and are verified by full-wave numerical simulations. Second, two new dual tuned coils, a surface coil design using the 2n port model, and a volume coil design using the reduced dimensions method are proposed, constructed, and bench tested. Their validation was carried out by employing 3D EM simulations as well as undertaking MR imaging on clinical scanners. Imaging experiments were conducted on phantoms, and the investigations indicate that the RF coils achieve good performance characteristics and a high signal-to-noise ratio in the regions of interest.

MEMS (Microelectromechanical Systems) acoustic sensors are a promising platform for Point-of-Care biosensing. In particular, piezoelectrically driven acoustic sensors can provide fast results with high sensitivity, can be miniaturized and mass produced, and have the potential to be fully integrated with sample handling and electronics in handheld devices. Furthermore, they can be designed as multiplexed arrays to detect multiple biomarkers of interest in parallel. In order to develop a microfabricated biosensing platform, a specific and high affinity biodetection platform must be optimized, and the microfabricated sensors must be designed to have high sensitivity and maintain good performance in a liquid environment. A biomolecular sensing system that uses high affinity peptide aptamers and a passivation layer has been optimized for the detection of proteins of interest using the quartz crystal microbalance with dissipation monitoring (QCM-D). The resulting system is highly specific to target proteins, differentiating between target IgG molecules and other closely related IgG subclasses, even in complex environments such as serum. Piezoelectrically actuated MEMS resonators are designed to operate in flexural microplate modes, with several modes shown to be ideally suited for fluid based biosensing due to improved performance in the liquid environment. The increase in quality factor of these MEMS microplate devices in liquid, as compared to air, is further investigated through the analytical and finite element modeling of MEMS fluid damping mechanisms, with a focus on acoustic radiation losses for circular microplate devices. It is found that the impedance mismatch at the air-water interface of a droplet is a key contributor to reduced acoustic radiation losses and thus improved device performance in water. Microplate acoustic sensors operating in flexural plate wave and microplate flexural modes are then integrated with a fluidic cell to facilitate protein sensing from fluid samples. Flexural plate wave devices are used to measure protein mass adsorbed to the sensor surface and initial results toward microplate flexural mode protein sensing are presented. Finally, challenges and areas of future research are discussed to outline the path towards finalization of a sensing platform taking advantage of the combination of the sensitive MEMS acoustic sensor capable of operating in a liquid environment and the specific and high affinity biomolecular detection system. Together, these form the potential basis of a novel Point-of-Care platform for simple and rapid monitoring of protein levels in complex samples.

Zinc oxide is a very versatile material that can be used in many microsystems and MEMS applications. ZnO thin film has been utilized in a wide variety of MEMS devices because of its unique piezoelectric, optical, and electrical properties. In particular, piezoelectric property of ZnO can be used in numerous applications from resonators and filters to mass sensors and micro-actuators (e.g., micro-valve and micro-pump). Because of its versatility, this research was focused on analyzing some key properties of ZnO thin film achieved by two different deposition techniques, Pulsed Laser Deposition (PLD) and Sputtering. Multiple experiments were conducted in order to identify the best conditions for the growth of ZnO thin film. Under the optimum conditions, the ZnO thin films will provide the best piezoelectric performance in devices such as microcantilevers. In order to find the best deposition conditions in both PLD and Sputtering multiple depositions have been done and then analyzed using the XRD, AFM, FTIR, nanoindenter, and ellipsometer. For the PLD the best conditions were found to be at 200°C with a partial pressure of O2 of 100 millitorr. For the sputtering system the best film formed when the substrate temperature was kept at 400°C along with RF power of 250 Watts, and a flow rate of 25% O2 and 75% Ar. Both experiments were similar in the fact that both a certain amount of O2 in the chamber and an elevated temperature are needed to facilitate the formation of ZnO crystal structure.

Dem Einsatz niederdimensionaler Nanostrukturen als optisch aktives Medium wird enormes Potential vorausgesagt sowohl in den klassischen optoelektronischen Bauteilen (wie z.B. Halbleiterlasern) als auch in optischen Bauteilen der näachsten Generation (z.B. Einzelphotonenquellen oder Quellen verschränkter Photonenpaare). Dennoch konnten sich quantenpunktbasierte Halbleiterlaser, abgesehen von einigen wenigen Ausnahmen (QDLaser inc.), im industriellen Maßstab bisher nicht gegen Bauelemente mit höherdimensionalen Quantenfilmen als optisch aktivem Element durchsetzen. Deshalb scheint der Einsatz von Quantenpunkten (QPen) in nichtklassischen Lichtquellen gegenwärtig vielversprechender. Um jedoch solche Bauteile bis zur letztendlichen Marktreife zu bringen, müssen neben der starken Unterdrückung von Multiphotonenemission noch wesentliche Grundvoraussetzungen erfüllt werden: In dieser Arbeit wurden grundlegende Studien durchgeführt, welche insbesondere dem Fortschritt und den Problemen der Effizienz, des elektrischen Betriebs und der Skalierbaren Herstellung der Photonenqullen dienen sollte. Zum Einen wurden hierfür elektrisch betriebene Einzelphotonenquellen basierend auf gekoppelten QP-Mikroresonatoren realisiert und de ren Bauteileffizienz gezielt optimiert, wobei konventionelle selbstorganisierte InAs-QPe als aktives Medium eingesetzt wurden. Für die skalierbare Integration einzelner QPe in Mikroresonatoren wurde des Weiteren das gesteuerte QP-Wachstum auf vorstrukturierten Substraten optimiert und auf diese Art ortskontrollierte QPe in Bauteile integriert. Für die Realisierung hocheffizienter, elektrisch gepumpter inzelphotonenquellen wurde zunächst das Wachstum von binären InAs-QPen im Stranski-Krastanov-Modus optimiert und deren optische Eigenschaften im Detail untersucht. Durch das Einbringen einer Schicht von Siliziumatomen nahe der QP-Schicht konnten die Emitter negativ geladen werden und der helle Trionenzustand der QPe als energetischer Eigenzustand des Systems zur effizienten Extraktion einzelner Photonen ausgenutzt werden. Durch die Integration dieser geladenen QPe in elektrisch kontaktierte, auf Braggspiegel basierte Mikrotürmchen konnten Einzelphotonenquellen realisiert werden, in denen gezielt Licht-Materie- Wechselwirkungseffekte zur Steigerung der Bauteileffizienz ausgenutzt wurden. Basierend auf theoretischen Überlegungen wurde die Schichtstruktur soweit optimiert, dass letztendlich experimentell eine elektrisch gepumpte Einzelphotonenquelle mit einer Photonenemissionsrate von 47 MHz sowie einer zuvor unerreichten Bauteileffizienz von 34 % im Regime der schwachen Licht-Materie-Kopplung demonstriert werden konnte. Da Effekte der Licht-Materie-Wechselwirkung zwischen QP und Resonator neben der spektralen Resonanz ebenfalls von der relativen Position von Resonator und QP zueinander abhängen, ist eine Kombination von positionierten QPen und Bauteilausrichtung nahezu unumg¨anglich für die skalierbare, deterministische Herstellung von Systemen aus perfekt angeordnetem Emitter und Resonator. Deshalb wurden bestehende Konzepte zum geordneten Wachstum von QPen weiterentwickelt: Hierbei wurde geordnetes InAs-QP-Wachstum mit Perioden realisiert, die vergleichbare Abmessungen wie optische Resonatoren aufweisen, also Nukleationsperioden zwischen 500 nm und 4 μm. Durch ein genaues Anpassen der Wachstums- und Prozessbedingungen konnte des Weiteren die Bildung von QP-Molekülen auf den Nukleationsplätzen nahezu unterdrückt beziehungsweise gesteuert werden. Durch eine systematische Optimierung der optischen Eigenschaften der QPe konnten Emitter mit Einzelquantenpunktlinienbreiten um 100 μeV realisiert werden, was eine Grundvoraussetzung zur Studie ausgeprägter Licht-Materie-Wechselwirkungseffekte in Mikroresonatoren darstellt. Letztendlich konnten durch die Integration derartiger QPe in optisch sowie elektrisch betriebene Mikroresonatoren erstmals Bauteile realisiert werden, welche einige der prinzipiellen, an eine Einzelphotonenquelle gestellten Anforderungen erfüllen. Insbesondere konnten deutliche Signaturen der schwachen Licht-Materie-Kopplung einzelner positionierter QPe in photonische Kristallresonatoren, Mikroscheibenresonatoren sowie Mikrotürmchenresonatoren festgestellt werden. Darüberhinaus konnte an einem spektral resonanten System aus einem positionierten QP und der Grundmode eines Mikrotürmchenresonators eindeutig Einzelphotonenemission unter optischer Anregung demonstriert werden. Ebenfalls konnten Mikrotürmchenresonatoren mit integrierten positionierten QPen erstmals elektrisch betrieben werden und somit die Grundvoraussetzung für eine der skalierbaren Herstellung effizienter Einzelphotonenquellen geschaffen werden. / Employing low dimensional nanostructures as active medium in classical optoelectronic devices (for instance semiconductor laser diodes) as well as optical devices of the next generation (such as single photon sources or sources of entangled photon pairs promises enormous potential. Yet, despite some exceptions (for example QDLasers inc.), quantum dot (QD)-based semiconductor lasers can hardly compete with devices exploiting higher dimensional gain material so far. Hence, using QDs as single photon emitters seems very promising. In order to achieve compatibility on the market, some urgent pre-requisites still need to be met in such devices besides the surpression of multiphoton emission: • Efficiency: Only a highly efficient single photon source can be reasonably employed in applications. • Electrical operation: In order to achieve a high integration density and for reasons of user friendlyness, the device needs to be driven electrically. • Scalability: The scalable fabrication of single photon sources is pre-requisite and one of the greatest technological challenges. • Temperature: Eventually, single photon sources will only be established in the wide field of secure data transmission if their operation at room temperature can be assured. In this work, basic studies were carried out especially devoted to the progress in the first three challenges. On the one hand, electrically driven single photon sources based on coupled QD-microcavities were realized and optimized by employing conventional self organized InAs QDs as active material. On the other hand, in order to facilitate a scalable integration of single QDs into microcavities, directed QD nucleation on pre-patterned substrate was optimized. These site-controlled QDs were at last integrated into resonator devices. In order to realize highly efficient, electrically driven single photon sources, at first the growth of binary Stranski-Krastanov InAs QDs was optimized and their emission properties were investigated in detail. By introducing Silicon atoms in the vicinity of the QD-layer, the emitters could be negatively charged. The resulting bright trion state of the QDs can subsequently be exploited as the energetic eigenstate of the system for the extraction of single photons. By integrating these charged QDs in contacted, Bragg-reflector based micropillars, single photon sources were realized exploiting light-matter coupling to enhance the device’s efficiency. Based on theoretical considerations, the grown layer sequence was optimized to an extent that eventually an electrically driven single photon source with an emission rate of 47 MHz and an unprecedented device efficiency of 34 % in the weak coupling regime could be demonstrated. Since the effects of light-matter coupling between QD and resonator rely on the QD’s position in the device, a combination of site-controlled QD-growth and device alignment is almost inevitable for a scalable, deterministic fabrication of perfectly aligned emittercavity systems. Therefore, existing concepts for ordered QD-growth were adapted and improved [KH07]: Ordered QD-growth on periods comparable to dimensions of optical resonators between 500 nm und 4 μm was realized. By carefully adjusting the growth and process conditions, formation of QD-molecules on nucleation sites could be controlled and supressed almost entirely. Carrying out a systematic optimization of the QD’s optical properties, emitters with single QD-linewidth around 100 μeV were realized. This is pre-requsite for the study of pronounced light-matter interaction in microcavities. Finally, the integration of such QDs in optically and electrically driven microresonators resulted in devices demonstrating some of the fundamental properties requested from a single photon source. Pronounced signatures of the weak light-matter coupling between a site-controlled QD in a photonic crystal cavity, a microdisk cavity and micropillar cavities were observed. Furthermore, single photon emission of a spectrally resonant system of sitecontrolled QD and micropillar cavity under pulsed optical excitation was unambigiously demonstrated. Beyond this, micropillar cavities with site-controlled QDs were electrically driven for the first time, which is pre-requisite for the scalable fabrication of efficient single photon sources.