abstract: Dual-wavelength laser sources have various existing and potential applications in wavelength division multiplexing, differential techniques in spectroscopy for chemical sensing, multiple-wavelength interferometry, terahertz-wave generation, microelectromechanical systems, and microfluidic lab-on-chip systems. In the drive for ever smaller and increasingly mobile electronic devices, dual-wavelength coherent light output from a single semiconductor laser diode would enable further advances and deployment of these technologies. The output of conventional laser diodes is however limited to a single wavelength band with a few subsequent lasing modes depending on the device design. This thesis investigates a novel semiconductor laser device design with a single cavity waveguide capable of dual-wavelength laser output with large spectral separation. The novel dual-wavelength semiconductor laser diode uses two shorter- and longer-wavelength active regions that have separate electron and hole quasi-Fermi energy levels and carrier distributions. The shorter-wavelength active region is based on electrical injection as in conventional laser diodes, and the longer-wavelength active region is then pumped optically by the internal optical field of the shorter-wavelength laser mode, resulting in stable dual-wavelength laser emission at two different wavelengths quite far apart. Different designs of the device are studied using a theoretical model developed in this work to describe the internal optical pumping scheme. The carrier transport and separation of the quasi-Fermi distributions are then modeled using a software package that solves Poisson's equation and the continuity equations to simulate semiconductor devices. Three different designs are grown using molecular beam epitaxy, and broad-area-contact laser diodes are processed using conventional methods. The modeling and experimental results of the first generation design indicate that the optical confinement factor of the longer-wavelength active region is a critical element in realizing dual-wavelength laser output. The modeling predicts lower laser thresholds for the second and third generation designs; however, the experimental results of the second and third generation devices confirm challenges related to the epitaxial growth of the structures in eventually demonstrating dual-wavelength laser output. / Dissertation/Thesis / Ph.D. Electrical Engineering 2011

abstract: In 2022, integrated circuit interconnects will approach 10 nm and the diffusion barrier layers needed to ensure long lasting devices will be at 1 nm. This dimension means the interconnect will be dominated by the interface and it has been shown the interface is currently eroding device performance. The standard interconnect system has three layers - a Copper metal core, a Tantalum Adhesion layer and a Tantalum Nitride Diffusion Barrier Layer. An alternate interconnect schema is a Tantalum Nitride barrier layer and Silver as a metal. The adhesion layer is removed from the system along with changing to an alternate, low resistivity metal. First principles are used to assess the interface of the Silver and Tantalum Nitride. Several stoichiometric 1:1 Tantalum Nitride polymorphs are assessed and it is found that the Fe2P crystal structure is actually the most stable crystal structure which is at odds with the published phase diagram for ambient crystal structure. The surface stability of Fe2P-TaN is assessed and the absorption enthalpy of Silver adatoms is calculated. Finally, the thermodynamic stability of the TaN-Ag interconnect system is assessed. / Dissertation/Thesis / Ph.D. Materials Science and Engineering 2012

Inserir conteúdos de Física Quântica no Ensino Médio torna-se um desafio para os professores, tanto por uma possível falta de preparo como pela falta de incentivo. Apesar da existência de materiais didáticos disponíveis, raramente os professores sentem-se preparados para abordar tais conteúdos em sala de aula. Além disso, o atual currículo do Ensino Médio bem como o programa ENEM, não estimulam ao ensino do assunto aqui referido. No entanto, em função da importância da abordagem da Física Quântica, e também frente à propagação de versões místicas e de representações sociais, é preciso continuar tentando contribuir para que essa inserção venha a ocorrer futuramente. Nesse sentido, foi elaborada uma unidade de ensino sobre tópicos de Física Quântica com a intenção de estimular o interesse e a curiosidade do aluno. Como referencial teórico foi utilizada a teoria de aprendizagem de David Ausubel, buscando desenvolver uma aprendizagem significativa dos conteúdos selecionados da Física Quântica a partir de conhecimentos prévios existentes na estrutura cognitiva dos alunos. A proposta foi elaborada seguindo os passos das Unidades de Ensino Potencialmente Significativas – UEPS (MOREIRA, 2011) onde, num primeiro momento foi feito o levantamento dos conhecimentos prévios dos alunos, em seguida foi apresentado o conteúdo de uma forma mais geral e, a partir daí, cada assunto foi abordado de forma mais específica, visando à diferenciação progressiva e à reconciliação integradora. Os conceitos abordados foram quantização, incerteza, estado e superposição de estados, apresentados de acordo com os passos da UEPS. A implementação do trabalho foi realizada em quatro turmas de 3ª série do Ensino Médio da E. E. E. M. Carlos Antonio Kluwe, em Bagé, RS, durante os meses de outubro, novembro e dezembro de 2011. As quatro turmas, denominadas A, B, C e D, foram divididas em dois grupos. O primeiro grupo, formado pelas turmas A e B iniciou as atividades em 10 de outubro de 2011 e o segundo grupo, formado pelas turmas C e D iniciou as atividades em 31 de outubro. Dentre as atividades desenvolvidas são analisados de forma qualitativa os mapas mentais e mapas conceituais elaborados em duplas, bem como a comparação entre eles, e são mostrados os trabalhos livres confeccionados pelos alunos e o jornal de cada turma Ainda são apresentados alguns comentários de estudantes sobre seu desenvolvimento na compreensão dos conceitos abordados na proposta. A análise feita a partir dos resultados obtidos forneceu indícios de aprendizagem significativa, que é o objetivo de uma UEPS. São apresentados também alguns comentários que indicam a boa receptividade da proposta, que encoraja novas aplicações. / It has become a challenge to high school teachers to include contents of quantum physics in the school curriculum not only for the lack of due preparation but for the scarcity of incentive. In spite of available educational resources, teachers seldom feel ready to approach such contents in the classroom. Furthermore, the present high school curriculum as well as the National High School Exam (ENEM) do not seem to encourage the teaching of quantum physics. Nevertheless, because of the relevance of quantum physics and the dissemination of its mystical versions with their social representations, it is necessary to continue attempting at contributing to make this insertion possible in the near future. In this sense, a teaching unit on topics of quantum physics was developed with the purpose of motivating the students ’ interest and curiosity. David Ausubel’s theory of meaningful learning was used a its theoretical framework, so as to facilitate the occurrence of meaningful learning of the chosen contents of quantum physics based on the students’ prior knowledge about the subject. The proposal was developed in agreement with the steps of the Potentially Meaningful Teaching Units – PMTU (Moreira, 2011), according to which the first step was to make a survey of the students’ prior knowledge followed by a general presentation of the contents. From there on, each topic received a more specific/extensive treatment aiming at progressive differentiation and integrative reconciliation. The concepts involved in this study were quantization, uncertainty, state, and superposition of states and they were presented according to the PMTU’s steps. Implementation of this proposal occurred in four different classes of the 3rd year of high school at the State School E.M. Carlos Antonio Kluwe, Bagé, RS, Brazil, from October to December of 2011. These four classes, named A, B, C, and D, were divided into two groups. The first one, formed by classes A and B, started their activities on the October 10, 2011, while the second group, classes C and D, started them on October 31, 2011. The activities performed by the students, such as mind maps and concept maps drawn in pairs, as well as their comparison were qualitatively analysed. There are also shown free-choice works the students produced, as well as the newspaper that each of the classes put together. In addition, some of the students’ comments on their own development regarding the concepts approached in this proposal are presented. The analysis based on obtained results suggested evidence of the occurrence of meaningful learning, which is the aim of a PMTU. Furthermore, some comments that might indicate a fair receptivity to the proposal are also set forth since they seem to encourage new implementations of this proposal.

Apresenta-se um estudo preliminar a respeito das possíveis representações sociais da Física Quântica entre estudantes de diferentes grupos sociais. Após levantamento prévio sobre associações possíveis para a expressão "Física Quântica", foi elaborado um questionário composto por um teste de associação escrita de conceitos (TAEC) e um teste de associação numérica de conceitos (TANC). Responderam ao questionário 494 pessoas, divididas em três grupos: graduandos no curso de Física, estudantes de outros cursos superiores e alunos de Ensino Médio. As respostas aos questionários foram analisadas utilizando estatística multidimensional, o que permitiu a obtenção de diagramas que refletem a estrutura conceitual compartilhada pelos grupos sociais investigados. À luz dos referenciais teóricos da aprendizagem significativa e das representações sociais, foi possível verificar a existência ou não destas representações, que podem atuar como subsunçores para o ensino de Física, juntamente com outras ideias que compõem a ecologia representacional mental do aprendiz. Algumas dessas ideias podem ter sofrido a influência de meios de divulgação, como mídia, livros e filmes. Esses meios auxiliam na propagação de conceitos científicos - ou quase científicos - influenciam o conhecimento das pessoas, por isso se faz necessário investigar qual o significado atribuído a tais conceitos na elaboração de representações sociais. Os resultados indicam a existência de representações sociais compartilhadas entre sujeitos de alguns grupos investigados, permitindo sua identificação e caracterização. Foram encontrados indícios da influência dos meios de divulgação nas representações sociais dos alunos de Ensino Médio, que devem ser mais bem estudados em trabalhos futuros. / A preliminary study regarding possible social representations of quantum physics among students from different social groups is described. Based on an initial survey on word associations to the expression "quantum physics" a questionnaire was constructed including a test of written concept associations (WCA) and a test of numerical concept association (NCA). This questionnaire was answered by 494 students, divided into three groups: physics undergraduate students, high school students, and undergraduate students from subjects other than physics. Data was analysed using the multidimensional scaling technique which provided spatial diagrams that reflect the conceptual structure shared by the investigated social groups. In the theoretical framework of the meaningful learning and social representations theories it was possible to gather evidences of the existence or not of social representations which may act as subsumers in the learning of physics together with other representations that constitute the mental representational ecology of the learners. Some of these representations might be an effect of information provided by books, movies and other media. This media disseminate information regarding scientific - or almost scientific concepts - and influence people's knowledge. Given that previous knowledge is the main variable influencing the acquisition of knew knowledge it is important to investigate the social representations resulting from this dissemination of information. Research findings suggest the existence of social representations about quantum physics shared by some of the subjects and groups studied. Specially in the case of high school students some evidence was obtained about the existence of social representations that should be more explored in future studies.

A simulação de cores corresponde à essência do processo de síntese de imagens realistas. Em se tratando de minerais, a presença de uma dada impureza, ou uma variação de sua concentração, pode fazer com que alguns materiais sofram alterações dramáticas em suas cores. Por exemplo, enquanto o quartzo puro é transparente, a ametista é um tipo violeta de quartzo, cuja cor é determinada pela presença de traços de ferro. A quantidade de ferro define o matiz percebido. A cor apresentada por um mineral pode ser determinada com base no seu espectro de absorção. No entanto, a definição de todas as variações possíveis é impraticável e, portanto, tal informação está disponível apenas para um subconjunto dos minerais existentes. Esta dissertação apresenta uma proposta para estimar a cor de ágatas, bem como para simular as cores de ágatas sintéticas (inexistentes). A abordagem utilizada baseia-se nos fundamentos da teoria quântica, e parte de uma descrição da molécula de sílica que se deseja simular. À esta, pode-se adicionar quantidades diferentes de impurezas e alterar o número de átomos incluídos na simulação. O resultado obtido é o espectro de absorção do mineral, que pode então ser utilizado para determinar a cor da ágata com a composição desejada. Embora uma simulação detalhada de todo o processo seja uma tarefa computacionalmente extremamente cara, esta dissertação apresenta alguns resultados que corroboram com a correção da solução proposta. Também é apresentada uma técnica independente que pode ser utilizada para definir um volume de ágata com base em uma imagem 2D. / Color simulation is the essence of realistic image synthesis. In the case of minerals, the presence of a given impurity, or a variation of its concentration, can cause some materials to experience dramatic changes in color. For instance, while pure quartz is transparent, amethyst is a violet type of quartz, whose color is determined by the presence of traces of iron. The amount of iron defines the perceived hue. The color presented by a mineral can be determined based on its absorption spectrum. However, defining all possible variations is impractical and, therefore, such information is available only for a subset of the existing minerals. This thesis presents an approach for simulating the colors of existent agates, as well as for predicting the colors for (non-existent) synthetic ones. The approach is based on the fundamentals of quantum theory, and starts with the description of the silica molecule one wants to simulate. One can add different amounts of impurities, and alter the number of atoms included in the simulation. The obtained result is the absorption spectra of the mineral, which can then be used for determining the color of the agate with the desired composition. Although a detailed simulation of the entire process is extremely computationally-expensive, the thesis presents some results that corroborate the correctness of the proposed solution. It also introduces a standalone technique for defining agate volumes based on 2D images of agates.

Cette thèse est consacrée à l'étude mathématique et numérique du modèle de Hartree-Fock-Bogoliubov (HFB) pour les systèmes quantiques attractifs, qui est abondamment utilisé en physique nucléaire. Après avoir présenté le modèle et ses principales caractéristiques, nous expliquons comment le discrétiser et nous montrons des résultats de convergence. Nous examinons tout particulièrement l'algorithme de point fixe (parfois appelé Roothaan) et montrons qu'il converge ou alors oscille entre deux états dont aucun n'est solution du problème. Ceci généralise au cadre HFB des résultats de Cancès et Le Bris pour le modèle plus simple de Hartree-Fock dans le cas répulsif. Suivant ces mêmes auteurs, nous proposons un algorithme basé sur la contrainte relachée et pour lequel la convergence est garantie. Dans dernière partie de la thèse, nous illustrons le comportement de ces algorithmes par des simulations numériques pour plusieurs modèles. Dans un premier temps nous considérons un système purement gravitationnel où les particules interagissent avec le potentiel de Newton. Nos simulations montrent que la matrice d'appariement est toujours non nulle, un fait qui n'a pas encore pu être démontré rigoureusement. Nous étudions ensuite un modèle très simplifié pour la description de protons et neutrons dans le noyau atomique. / This work is devoted to the theoretical and numerical study of Hartree-Fock-Bogoliubov (HFB) theory for attractive quantum systems, which is one of the main methods in nuclear physics. We first present the model and its main properties, and then explain how to discretize it. We prove some convergence results, in particular for the simple fixed point algorithm (sometimes called Roothaan). We show that it converges, or oscillates between two states, none of them being a solution. This generalizes to the HFB case previous results of Cancès and Le Bris for the simpler Hartree-Fock model in the repulsive case. Following these authors, we also propose a relaxed constraint algorithm for which convergence is guaranteed. In the last part of the thesis, we illustrate the behavior of these algorithms by some numerical experiments. We first consider a system where the particles only interact through the Newton potential. Our numerical results show that the pairing matrix never vanishes, a fact that has not yet been proved rigorously. We then study a very simplified model for protons and neutrons in a nucleus.

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

xiv, 195 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. / We explore the reconstruction of B-state vibrational wave packets in I 2 from simulated two-color nonlinear wave packet interferometry data. As a simplification of earlier proposals, we make use of different vibrational energy ranges in the B-state--rather than different electronic potential surfaces--for the short-pulse preparation and propagation of both target and reference wave packets. Numerical results from noisy interferograms indicate that experimental reconstruction should be possible with high fidelity (>0.99). Time-resolved coherent nonlinear optical experiments on small molecules in low-temperature host crystals are exposing valuable information on quantum mechanical dynamics in condensed media. We make use of generic features of these systems to frame two simple, comprehensive theories that will enable the efficient calculation of their ultrafast spectroscopic signals and support their interpretation in terms of the underlying chemical dynamics. Both treatments rely on the identification of normal coordinates to unambiguously partition the well-structured guest-host complex into a system and a bath and expand the overall wave function as a sum of product states between fully anharmonic vibrational basis states for the system and approximate Gaussian wave packets for the bath degrees of freedom. The theories exploit the fact that ultrafast experiments typically drive large-amplitude motion in a few intramolecular degrees of freedom of higher frequency than the crystal phonons, while these intramolecular vibrations indirectly induce smaller-amplitude--but still perhaps coherent--motion among the lattice modes. The equations of motion for the time-dependent parameters of the bath wave packets are fairly compact in a fixed vibrational basis/Gaussian bath (FVB/GB) approach. An alternative adiabatic vibrational basis/Gaussian bath (AVB/GB) treatment leads to more complicated equations of motion involving adiabatic and nonadiabatic vector potentials. Numerical tests of the FVB/GB are presented. We consider two bilinearly coupled harmonic oscillators with varying coupling strengths and initial conditions and show that the mixed quantum/semiclassical theory compares favorably with the exact results. Linear absorption spectra and wave-packet interferometry signals calculated using the theory are presented. This dissertation includes previously published coauthored material. / Committee in charge: David Herrick, Chairperson, Chemistry; Jeffrey Cina, Advisor, Chemistry; Thomas Dyke, Member, Chemistry Michael Kellman, Member, Chemistry; Hailin Wang, Outside Member, Physics

xvi, 218 p. : ill. (some col.) / Our theoretical studies involve the control of electronic energy transfer in molecular dimers through the preparation of specific vibrational coherences prior to electronic excitation. Our control strategy is based upon the fact that, following impulsive electronic excitation, nuclear motion acts to change the instantaneous energy difference between site-excited electronic states and thereby influences short-time electronic excitation transfer (EET). By inducing coherent intramolecular vibration in one of the chromophores prior to short-pulse electronic excitation, we exert external control over electronic dynamics. As a means to monitor this coherent control over EET, we propose using multidimensional wave-packet interferometry (md-WPI). Two pairs of polarized phase-related femtosecond pulses following the control pulse would generate superpositions of coherent nuclear wave packets in optically accessible electronic states. Interference contributions to the time- and frequency-integrated fluorescence signal due to overlaps among the superposed wave packets provide amplitude-level information on the nuclear and electronic dynamics. We test both the control strategy and its spectroscopic investigation by calculating pump-probe difference signals for various combinations of pulse polarizations. That signal is the limiting case of the control-influenced md-WPI signal in which the two pulses in the pump pulse-pair coincide, as do the two pulses in the probe pulse-pair. We present calculated pump-probe difference signals for a variety of systems including a simplified model of the covalent dimer dithia-anthracenophane (DTA) in which we treat only the weakly Franck-Condon active ν 12 anthracene vibration at 385 cm -1 . We further present calculated nl-WPI difference signals for an oriented DTA complex, which reveal amplitude-level dynamical information about the interaction of nuclear motion and electronic energy transfer. We also present pump-probe difference signals from a model system in which a CF 3 group, whose torsional angle is strongly Franck-Condon active, has been added to the anthracene monomers which make up DTA. We make use of electronic structure calculations to find the torsional potential of the monomer, from which we calculate the spectroscopic signals of the dimer. We show that a significant measure of control over short-time EET is achievable in this system. This dissertation includes previously published coauthored material. / Commitee in charge: Dr. Michael E. Kellman, Chair; Dr. Jeffrey A. Cina, Advisor; Dr. David R. Herrick; Dr. Andrew H. Marcus; Dr. Daniel A. Steck

xiii, 164 p. : ill. (some col.) / We explore the frequency translation of single-photon states of light and the creation of photon pairs by four-wave mixing in optical fiber. Frequency translation refers to changing the central frequency of a field, while photon pair creation refers to the creation of two individual photons at the same time. We demonstrate these effects in third-order nonlinear optical fiber. While both phenomena have previously been shown by three-wave mixing in second-order nonlinear media, there are compelling reasons to develop these tasks in third-order media. Most importantly, frequency translation in third-order material allows for the practical implementation of both small and large frequency shifts, while second-order material only practically allows for large shifts. Photon creation in third-order media often permits more flexible phase-matching conditions, allowing for the creation of a wider variety of quantum states than is often possible in second-order media. In our theoretical study of photon pair creation, we focus on the spectral correlations of the photon pairs. We pay particular attention to the creation of quantum states of high purity, where the photons are not spectrally correlated with one another. High purity photons are a requisite resource for several different quantum information processing applications, such as linear-optical quantum computing. We find that states with high purity can be realized with a minimal amount of spectral filtering. Experimentally, we study photon frequency translation in photonic crystal fiber. The central wavelength of the input photons was translated from 683 nm to 659 nm. We perform second-order intensity correlation measurements on both channels to demonstrate their quantum nature. This resulted in values of 0.21 ± 0.02 and 0.19 ± 0.05 for the 683-nm and 659-nm channels, respectively, demonstrating that those fields were dominated by their single-photon component. The efficiency at which the process occurred was 29 percent. Theoretically, we develop a Green function formalism to describe the translation process and develop a computational model to calculate the solution to the governing equations. Also, in a related experiment, we demonstrate classical frequency translation from 851 nm to 641 nm, a record translation in both wavelength and frequency, at an efficiency of 0.2 percent in a birefringent fiber. / Committee in charge: Dr. Daniel Steck, Chair; Dr. Michael Raymer, Advisor; Dr. Steven van Enk, Inside Member; Dr. Raghuveer Parthasarathy, Inside Member; Dr. Andrew Marcus, Outside Member