The development and fabrication of silicon-based phononic band gap crystals has been gaining interest since phononic band gap crystals have implications in fundamental science and display the potential for application in engineering by providing a relatively new platform for the realization of sensors and signal processing elements. The seminal study of phononic band gap phenomenon for classical elastic wave localization in structures with periodicity in two- or three-physical dimensions occurred in the early 1990’s. Micro-integration of silicon devices that leverage this phenomenon followed from the mid-2000’s until the present. The reported micro-integration relies on exotic piezoelectric transduction, phononic band gap crystals that are etched into semi-infinite or finite-thickness slabs which support surface or slab waves, phononic band gap crystals of numerous lattice constants in dimension and phononic band gap crystal truncation by homogeneous mediums or piezoelectric transducers. The thesis reports, to the best of the author's knowledge, for the first time, the theory, design methodology and experiment of an electrostatically actuated silicon-plate phononic band gap quasi-crystal architecture, which may serve as a platform for the development of a new generation of silicon-integrated sensors, signal processing elements and improved mechanical systems. Electrostatic actuation mitigates the utilization of piezoelectric transducers and provides action at a distance type forces so that the phononic band gap quasi-crystal edges may be free standing for potentially reduced anchor and substrate mode loss and improved energy confinement compared with traditional surface and slab wave phononic band gap crystals. The proposed phononic band gap quasi-crystal architecture is physically scaled for fabrication as MEMS in a silicon-on-insulator process. Reasonable experimental verification of the model of the electrostatically actuated phononic band gap quasi-crystal architecture is obtained through extensive dynamic harmonic analysis and mode shape topography measurements utilizing optical non-destructive laser-Doppler velocimetry. We have utilized our devices to obtain fundamental information regarding novel transduction mechanisms and behavioral characteristics of the phononic band gap quasi-crystal architecture. Applicability of the phononic band gap quasi-crystal architecture to physical temperature sensors is demonstrated experimentally. Vibration stabilized resonators are demonstrated numerically.

In this study, impulse response of a multipurpose hall, namely METU Northern Cyprus Campus Auditorium (NCCA) is analyzed and the acoustical quality of the auditorium is evaluated. Suggestions to increase the acoustical satisfaction has been made and to overcome the probability of bass-rise caused by the noise of HVAC systems, a proposal has been made to control low frequency sounds by introducing the volume resonators for the specified frequency. For the study, Odeon, which is used effectively in computer based acoustical simulation studies, is used for the analysis part. In the analysis, a 3D drawing of the hall has been produced by the help of the exact dimensions derived from the original submission of the project by the permission of the authorities.

The need for miniaturized frequency-selective components in electronic systems is clear. The questions are whether and how micro-electro-mechanical systems (MEMS) can satisfy the need. This dissertation aims to address these questions from a scientific perspective. Silicon is the focus of this work, as it can benefit from scaling of the semiconductor industry. Silicon also offers many technical advantages. The characteristics of silicon resonators from 32 kHz to 1 GHz are described. The temperature stability and phase noise of a 6-MHz temperature-compensated oscillator and a 100-MHz temperature-controlled oscillator are reported. Silicon resonator design and characterization, with a focus on quality factor, linearity, and the electrical equivalent circuit, are included. Electrical tuning, electromechanical coupling, finite element modeling, and unexpected findings of these resonators are also described. A manufacturability technique employing batch process compensation is demonstrated. Results indicate that silicon is an excellent material for micromechanical resonators. The aim of this research is to explore the fundamental limitations, provide a foundation for future work, and also paint a clearer picture on how micromechanical resonators can complement alternative technologies.

Thesis (MScEng)--University of Stellenbosch, 2002. / ENGLISH ABSTRACT: Keywords: Coupled resonator filters, Co-axial line resonators, Basic Coupling Design, Co-axial resonator filter The study of the basic dynamics of filters, with the emphasis on coupled resonator filters, is presented. Special attention is paid to the synthesis of doubly terminated coupling matrices using the Darlington method. Due to restrictions placed on the filter by the equivalent circuit used, a coupling matrix reduction is applied to the resulting coupling matrix. An investigation is performed on A/2 co-axial line resonators, with the emphasis on rectangular co-axial line resonators with a round center conductor. The basic definition of the coupling coefficient is revisited and it is calculated using the method based on Bethe's theory and Cohn's experimental work. A 4th-order co-axial resonator filter operating at 3 GHz is designed using the theory outlined in this thesis. The measured response is in good agreement with the theory in terms of the center frequency, but disagree in terms of the coupling coefficient, bandwidth and Q-factor. The reasons for this, as well as suggestions for improving the accuracy of the parameters mentioned, are given. / AFRIKAANSE OPSOMMING: Sleutelwoorde: Gekoppelde resoneerder filters, Ko-aksiale lyn resoneerders, Basiese Koppeling Ontwerp, Ko-aksiale resoneerder filter Die studie van die basies dinamika van filters, met die klem op gekoppelde resoneerder filters, is voorgelê. Spesiale aandag is gegee aan die sintese van dubbelbelaste koppel matrikse met die gebruik van die Darlington metode. As gevolg van die beperkings wat op die filter geplaas word deur die gebruik van die ekwivalent stroombaan, word 'n koppel matriks vermindering gebruik. 'n Ondersoek is gedoen op A/2 ko-aksiale lyn resoneerders, met die klem op reghoekige ko-aksiale lyn resoneerders met 'n ronde binnegeleier. Die basiese definisie van die koppel koëffisiënt is hersien en dit is bereken met die gebruik van die metode wat baseer is op Bethe se teorie en Cohn se experimentele werk. 'n 4de-orde ko-aksiale resoneerder filter wat opereer by 3 GHz is ontwerp met die gebruik van die teorie wat in hierdie tesis gaskets word. Die gemete weergawe is in goeie ooreenkoms met die teorie in terme van die senter frekwensie, maar verskil in terme van die koppel koëffisiënt, bandwydte en Q-faktor. Die rede hiervoor, as ook voorstelle vir die verbetering van die akkuraatheid van die parameters wat genoem is, IS gegee.

Nanomechanical resonators (NR) are cantilevers or doubly clamped nanowires (NW) which vibrate at their resonance frequency. These nanowires with picogram-level mass and frequencies of the order of MHz can resolve added mass in the attogram (10-18 g) range, enabling detection of a few molecules of cancer biomarkers based on the shift in resonance frequency. Such biomarker detection can help in the early stage detection of cancer and also aid in monitoring the treatment procedure in a more advanced stage. Optical transduction is one of the methods to measure the resonance frequency of the cantilever. However, there is a dependence of measured resonance frequency on the polarization of light and the laser power coupled as thermal energy into the cantilever during the measurement. This thesis presents a numerical model of the nanocantilever and shows the variation in resonance frequency and amplitude due to varied amounts of energy absorption by the NW from the laser during resonance measurements. This thesis answers questions on the effects of laser heating by calculating the temperature distribution in the NW, which changes the Young’s modulus and stiffness, causing a resonance downshift. It also shows the variation of resonance amplitude, affecting signal strength in measurements, by considering the effects of structural damping. In this work, a numerical model of the nanowire was analyzed to determine the temperature rise of the NW due to laser heating. The maximum temperature was calculated to be about 500 K with 1 mW of laser power absorbed in Silicon NWs and it is shown that the nanowire tip would reach its melting point for about 2.6 mW of laser power absorbed by it. The resonance shift due to attained temperature of the NW was calculated. The frequency is predicted to decrease by 24 kHz for a 11.6 MHz resonator, when 2mW of laser power is absorbed. However, the frequency shift is mode-dependent and is larger for higher modes. The variation in vibration amplitude around the resonance peaks is calculated based on the effects of structural damping. This can be used to decide on the suspension height of the NW above the substrate, before fabrication. This calculation also provides a method to study the variation in material damping due to temperature. Finally, a semi-analytical method for calculating the frequency of a cantilever beam with varying Young’s modulus is derived to examine the validity of the results calculated above. An effective Young’s modulus value for the laser heated NW is given, which serves as a correction factor for the resonance shift. The derivation is then extended to calculate the resonance shift with an addition of a mass to the beam of varying Young’s modulus. / Graduate / 2019-12-13

O Bi5Ti3FeO15 foi sintetizado pelo mÃtodo de ReaÃÃo no Estado SÃlido (RES) e posteriormente adicionado de V2O5 (PentÃxido de VanÃdio) objetivando melhorar suas propriedades dielÃtricas. Para as anÃlises estruturais foram utilizadas as seguintes tÃcnicas: DifraÃÃo de Raios-X (DRX), Microscopia EletrÃnica de Varredura (MEV), Espectroscopia de DispersÃo de Energia de Raios-X (EDS), Espectroscopia Raman e Infravermelho (IV). Para o estudo das propriedades dielÃtricas do material em radiofrequÃncia e em microondas, foram empregadas, respectivamente, a Espectroscopia de ImpedÃncia (EI) e o mÃtodo de Hakki e Coleman. A tÃcnica de DRX foi utilizada para identificar a fase BFT pura, bem como as duas novas fases originadas a partir da adiÃÃo de V2O5: Bi4V1.5Fe0.5O10.5 e Bi2Ti2O7. As alteraÃÃes na morfologia dos grÃos e a resposta dielÃtrica foram atribuÃdas à presenÃa destas fases secundÃrias. Em radiofrequÃncia verificou-se que a adiÃÃo de V2O5 aumentou a permissividade dielÃtrica e reduziu os valores de tangente de perda, resultados semelhantes aos obtidos em microondas. Ressonadores DielÃtricos foram fabricados como um protÃtipo para antena monopolo. Os valores de frequÃncia de funcionamento da antena variaram entre 2,4 GHz e 3,1 GHz. Jà os valores de coeficiente de temperatura da frequÃncia ressonante (f) variaram de -330 a -192 ppm/ÂC. Assim sendo, a cerÃmica BFT adicionada de V2O5, pode ser utilizada em dispositivos de microondas, como telefones mÃveis, por exemplo. / The Bi5Ti3FeO15 (BFT) was synthesized by the solid state reaction method (SLR) and then added by V2O5 (vanadium pentoxide) to improve its dielectric properties. For the structural analyses the following technics were used: X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), Raman and infrared spectroscopy. For the dielectric propeties of the material at radiofrequency and microwave ranges, impedance spectroscopy (IS) and the Hakki-Coleman methods were used respectively. The XRD technique was used to identify the BFT phase as well as the two new ones (Bi4V1.5Fe0.5O10.5 and Bi2Ti2O7). Changes in the grain morphology and the dielectric response were assigned due to the presence of these secondary phases. The V2O5 addition increased the dielectric permittivity and reduced the loss tangent values at radiofrequency range; similar results were obtained at microwave. The Dielectric resonators (DR) were fabricated as a prototype for monopole antenna. The antenna operating frequency (2.4 - 3.1 GHz) and temperature coefficient of resonance frequency (τf) (from -330 to -192 ppm/ÂC) changed as a function of V2O5 concentration in the DR. Thus, BFT ceramics added by V2O5 are good candidates to be used for microwave devices as cell mobile phones, for example.

Orientador: Newton Cesário Frateschi / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin / Made available in DSpace on 2018-08-15T03:39:57Z (GMT). No. of bitstreams: 1 SilvaFilho_Adenirda_D.pdf: 7071967 bytes, checksum: 323c5d4f6939473d571146b5d6531fda (MD5) Previous issue date: 2010 / Resumo: Este trabalho apresenta o uso de cavidades ressonantes baseadas em geometrias de bilhares caóticos construídas em meios semicondutores opticamente ativos, visando seu aproveitamento ao sensoriamento. Apesar do comportamento clássico caótico do estádio, a descrição quântica, no limite semiclássico, mostra inesperados acúmulos de densidade de probabilidade sobre muitas trajetórias periódicas fechadas, chamadas cicatrizes. A literatura mostra que o espaço físico das trajetórias relacionadas a cada cicatriz pode ser obtido pela soma da densidade de probabilidade de auto-estados na vizinhança de cada cicatriz. Classicamente, as trajetórias ligadas a cada auto-estado possuem órbitas muito próximas devido a sua instabilidade, e quando misturadas, definem uma órbita de largura não nula. No domínio óptico, isomórfico ao problema quântico descrito acima, as trajetórias vêm de um tratamento de traçado de raios e os auto-estados são os modos eletromagnéticos estacionários. Particularmente, no caso da cavidade dielétrica, o sistema é aberto, uma vez que a luz pode ser transmitida para fora do ressonador. Desta forma, há grande mistura dos modos e uma seleção maior daqueles que podem sobreviver por terem trajetórias com ângulos internos de incidência maiores que o ângulo crítico para reflexão total interna. Em uma trajetória fechada e curta, modos estacionários são definidos e essas trajetórias têm maior probabilidade de serem observadas, em relação a outras possíveis. Quando o ressonador é constituído por um meio ativo opticamente, este confinamento realiza a realimentação óptica do sistema, cujo ganho óptico permite o estabelecimento estável e coerente de tais trajetórias. Estes resultados inspiraram a realização deste trabalho, cuja grande motivação foi investigar o processo de seleção modal e aplicá-lo em dispositivos práticos para sensoriamento em pequenos volumes. Experimentalmente foi desenvolvida uma técnica híbrida de fabricação utilizando um sistema de íons focalizados (FIB) juntamente com técnicas de microfabricação convencionais para a produção de cavidades estádio com meio ativo de poços quânticos de InGaAsP. Finalmente, foram obtidos resultados da emissão espectral com grande concordância com a previsão teórica baseada numa abordagem matemática simples de soma incoerente de cicatrizes. A seleção modal foi demonstrada com a alteração da excentricidade e com a inserção de furos sobre as trajetórias. A aplicação ao sensoriamento foi explorada tanto pela observação do espectro de emissão quanto pela detecção de fotocorrente por estádios emissor e detector integrados. Variações de até 80% de fotocorrente e alterações significativas do espectro foram observadas para detecção de isopropanol e água. Estes resultados mostram possibilidades de sensoriamento prático utilizando os estádios / Abstract: This work presents the development of resonant cavities based on chaotic billiard geometries built with semiconductor active optical medium for sensing applications. In spite of the classically chaotic behavior of the stadium, the quantum description of the problem in the semi-classical limit shows unexpected accumulations of the density of probability on closed periodic paths called scars. The literature shows that the physical space of the paths related to a given scar can be obtained by adding several eigen-states neighboring each scar. Classically, the paths connected to each eigen-state have very close orbits due to their instability which, when mixed, define a non-zero width orbit. In the optical domain, isomorphic to the quantum problem described above, the paths are a result of the ray treatment and the eigen-modes are the stationary electromagnetic modes. Particularly, in the case of a dielectric cavity, the system is open for light can escape the resonator. Therefore, there is a great mixture of modes and a strong selection of modes with paths with incidence angle below the critical angle. In a closed and short path, stationary modes are defined and those paths have larger probability of observation. When the resonator has an optically active medium, the confinement provides optical feedback to the system which with optical gain allows the establishment of coherent and stable scars. These results inspired this work where the process of modal selection was investigated and applied for sensing in small volumes. Experimentally, a hybrid fabrication approach based on Focused Ion Beam (FIB) and conventional micro-fabrication techniques was used to produce stadium optical cavities with InGaAsP quantum well active region. Finally, we obtained the spectral emission of the devices with good agreement with our simulation based on a simple mathematical approach employing the incoherent summation of the scars. The modal selection with the modification of the eccentricity of the cavity and with the insertion of holes along the scars was demonstrated. The application to sensing was explored by the observation of the emission spectrum as well as by measured photo-current on detection between stadia emitter and detector integrated. Photo-current variations of up to 80% and significant changes of the emission spectrum were observed for isopropanol and water detection. These results show possibilities of practical sensing by stadiums / Doutorado / Física / Doutor em Ciências

A operação dinamicamente estável com zonas conjuntas foi obtida para um ressonador laser contendo dois bastões de Nd:YAG com módulos laser comerciais. O ressonador não polarizado gerou 115 W de potência no modo transversal fundamental TEM00. Quando polarizado por lâmina de Brewster atingiu 100,5W de potência de saída com 91% de polarização. Quando o ressonador foi polarizado com um polarizador de filme fino, obteve-se melhora na qualidade de feixe e um aumento na polarização, com o valor de M2 sendo 1,56 e 1,84 nas direções x e y respectivamente com 95,4% de polarização. A potência de saída foi, ao nosso conhecimento, a mais alta obtida para lasers polarizados operando no modo fundamental e usando módulos lasers comerciais de Nd:YAG bombeados lateralmente por diodos sem nenhuma preparação especial. / Dynamically stable operation with joined stability zones of a linearly polarized resonator is shown for a laser containing two diode side-pumped Nd:YAG rods with commercial laser modules. The unpolarised resonator provided 115 W of TEM00 output. When polarized by a Brewster plate, it reached 100.5 W of output power with 91% polarization. When the resonator was polarized by a thin film polarizer, an increase in beam quality was obtained with M2 values of 1.56 and 1.84 in the x and y directions, respectively with 95.4% polarization. The output power achieved is, to our knowledge, the highest reported for polarized, fundamental-mode lasers using commercial, diode side-pumped Nd:YAG modules without any special preparation.

No description available.

With the advent of micro and nano electromechanical systems (MEMS/NEMS), there has been rapid development in the design and fabrication of sensitive resonant sensors. Sensitivity of such devices depends on the resonant frequency and the quality factor (Q). The Q of these devices are dependent on process induced prestress in the structural geometry, interaction with the external environment, and the encapsulation method. For high frequency sensors operating in air and under encapsulation condition, the Q is dominated by structural and fluid-structure interaction losses. In this thesis, we set out to study the dominant energy dissipative mechanisms that are constituent of the experimentally observed loss (Q-factor) in two specific test geometries—uncapped and capped circular MEMS drumhead resonators. Considering the importance of various factors, we consider four important problems pertaining to the uncapped as well as capped resonators. In the first problem, the most important factors perhaps are the acoustic radiation losses emanating from the annular plate, and the effect of added mass effect on the natural frequencies of the annular plate. The second problem is to investigate the dominant contribution of squeeze film losses and acoustic radiation losses with respect to various natural frequencies of the annular plate. The third problem is to consider the effect of prestress on the natural frequencies of the annular plate and its associated fluid-structure interaction losses (quality factors due to squeeze film damping and acoustic radiation losses). The fourth problem is to study the dominant fluid-structure interaction losses and structural losses that are constituent of experimentally measured Q-factors of the encapsulated annular plate (conceptual representation of MEMS device under packaged conditions). In the first problem, we study the mode dependent acoustic radiation losses in an uncapped drumhead microresonator which is represented by a annular circular plate fixed at its outer edge, suspended over a fixed substrate. There are two main effects which are associated with such systems due to the fluid-structure interaction. First is the “added mass effect,” which reduces the effective resonance frequency of the structure. The second is the acoustic radiation loss from the top side of the resonator, that affects the quality factor of the vibrating structure. In deriving the analytical solution, we first obtain the exact mode shapes of the structure ignoring any effect of the surrounding fluid (air) on the mode shape. Subsequently, we use these mode shapes to study the effect of the surrounding fluid on the associated natural frequencies and the Q-factor. The effect of “added mass” on the frequencies of the structure is found to be negligible. However, the acoustic radiation losses found to be significant. Additionally, we found that the variation in Qac over the first few modes (< 40 MHz) is marked with a local maximum and a minimum. Beyond this range, Qac increases monotonically over the higher frequency modes. It is also found that such kind of variation can be described using different acoustics parameters. Finally, comparing the acoustics radiation loss based quality factor with the experimental results for the uncapped drumhead resonator, the acoustic damping dominates only at higher modes. Therefore, our second problem forms the basis of finding other fluid-related damping. In the second problem, we explore the fluid losses due to squeeze film damping in the uncapped drumhead micro resonator. In this case, the squeeze film loss is due to the flow of the fluid film between the bottom surface of the annular plate and the fixed substrate. Based on the literature survey, it is found that the squeeze film damping reduces with increase in the air-gap thickness and the operating frequencies respectively. However, the squeeze film effect can not be ignored at lower frequencies. In order to investigate the contribution of squeeze film damping in uncapped resonator, we determine squeeze-film damping based quality factor Qsq corresponding to different modes of the resonators using FEM based software, ANSYS. On comparing Qsq with the experiments, we found that Qsq matches well with the experiments corresponding to the lower modes. Therefore, it is found that Qsq dominates at low frequencies (< 20 MHz) and Qac plays significant role at high frequencies (> 40 MHz). Both types of damping should be considered while modeling the fluid damping in uncapped resonator. In the next study, we discuss the effects of prestress on the resonant frequencies and quality factor. In the third study, we discuss the applicability of thin-plate theory with prestress and membrane theory in computing the frequencies and quality factor due to acoustic and squeeze film losses in the uncapped drumhead resonator. In the first two studies, although the quality factor due to acoustic losses and the squeeze film captures the correct trend of the experimental results, there is a mismatch between the experimental and theoretical frequencies computed with added mass effect. In order to improve the computation of frequencies corresponding to measured modes, we first used membrane theory to predict the frequencies, and finally we quantify that there exists discrepancy between computed and the corresponding experimental frequencies with error of about 8–55%. Since, both the membrane as well as thin plate theory without prestress do not correctly model the frequencies, we used the thin plate theory with prestress. For a prestress level of 96 MPa, we found the match between the computed frequencies and the corresponding quality factors with the measured values. However, we also found that there exists strong dependence of prestress on the acoustic radiation loss, with decrease in the acoustic loss based quality factors with increase in the prestress level. In the subsequent problem, we focus on the computation of losses in capped drumhead resonator which leads to a design possibility of improving the quality factor by containing the acoustic radiation losses. In the fourth problem, we study the structural and fluid-structure interaction losses which are dominant constituent of net Q-factor observed in experiments due to encapsulation of uncapped drumhead resonator. Essentially, the geometry of the capped resonator constitutes upper and lower cavities subjected to fluid-structure interaction losses on both sides of the annular plate. The dominant fluid-structure interaction loss is found to be due to squeezing action acting simultaneously in the upper and lower cavities. However, as we go to the higher modes, squeeze film damping become very small and the damping due to structure related losses such as clamping and thermoelastic losses becomes significant. We found the thermoelastic damping to be the dominant source of structural damping at higher resonant modes, whereas, the clamping losses are found to be relatively smaller. Finally, on comparing the net quality factor with the experimental results, we observed that the squeeze film losses are dominant at lower frequencies, and thermoelastic losses dominate at the higher frequencies. However, there remains some discrepancy between theoretical and experimental Q-factors particularly over higher frequency range. Such discrepancy may be due to some unaccounted factors which may be explored to improve the modeling of damping in capped resonators. The emphasis of this work has been towards developing a comprehensive understanding of different dominant dissipative mechanisms, classified into the fluid-structure interaction and the structural losses, that are constituent of the Q-factor at various resonant modes of uncapped and capped drumhead resonators.