Thermal and quantum fluctuations of the electromagnetic near field of atoms and macroscopic bodies play a key role in quantum electrodynamics (QED), as in the Lamb shift. They lead, e.g., to atomic level shifts, dispersion interactions (Van der Waals-Casimir-Polder interactions), and state broadening (Purcell effect) because the field is subject to boundary conditions. Such effects can be observed with high precision on the mesoscopic scale which can be accessed in micro-electro-mechanical systems (MEMS) and solid-state-based magnetic microtraps for cold atoms (‘atom chips’). A quantum field theory of atoms (molecules) and photons is adapted to nonequilibrium situations. Atoms and photons are described as fully quantized while macroscopic bodies can be included in terms of classical reflection amplitudes, similar to the scattering approach of cavity QED. The formalism is applied to the study of nonequilibrium two-body potentials. We then investigate the impact of the material properties of metals on the electromagnetic surface noise, with applications to atomic trapping in atom-chip setups and quantum computing, and on the magnetic dipole contribution to the Van der Waals-Casimir-Polder potential in and out of thermal equilibrium. In both cases, the particular properties of superconductors are of high interest. Surface-mode contributions, which dominate the near-field fluctuations, are discussed in the context of the (partial) dynamic atomic dressing after a rapid change of a system parameter and in the Casimir interaction between two conducting plates, where nonequilibrium configurations can give rise to repulsion. / Thermische und Quantenfluktuationen des elektromagnetischen Nahfelds von Atomen und makroskopischen Körpern spielen eine Schlüsselrolle in der Quantenelektrodynamik (QED), wie etwa beim Lamb-Shift. Sie führen z.B. zur Verschiebung atomarer Energieniveaus, Dispersionswechselwirkungen (Van der Waals-Casimir-Polder-Wechselwirkungen) und Zustandsverbreiterungen (Purcell-Effekt), da das Feld Randbedingungen unterliegt. Mikroelektromechanische Systeme (MEMS) und festkörperbasierte magnetische Fallen für kalte Atome (‘Atom-Chips’) ermöglichen den Zugang zu mesoskopischen Skalen, auf denen solche Effekte mit hoher Genauigkeit beobachtet werden können. Eine Quantenfeldtheorie für Atome (Moleküle) und Photonen wird an Nichtgleichgewichtssituationen angepasst. Atome und Photonen werden durch vollständig quantisierte Felder beschrieben, während die Beschreibung makroskopischer Körper, ähnlich wie im Streuformalismus (scattering approach) der Resonator-QED, durch klassische Streuamplituden erfolgt. In diesem Formalismus wird das Nichtgleich- gewichts-Zweiteilchenpotential diskutiert. Anschließend wird der Einfluss der Materialeigenschaften von normalen Metallen auf das elektromagnetische Oberflächenrauschen, das für magnetische Fallen für kalte Atome auf Atom-Chips und für Quantencomputer-Anwendungen von Bedeutung ist, sowie auf den Beitrag des magnetischen Dipolmoments zum Van der Waals-Casimir-Polder-Potential im thermisch- en Gleichgewicht und in Nichtgleichgewichtssituationen untersucht. In beiden Fällen sind die speziellen Eigenschaften von Supraleitern von besonderem Interesse. Beiträge von Oberflächenmoden, die die Feldfluktuationen im Nahfeld dominieren, werden im Kontext des (partiellen) dynamischen Dressing nach einer raschen Änderung eines Systemparameters sowie für die Casimir-Wechselwirkung zweier metallischer Platten diskutiert, zwischen denen in Nichtgleichgewichtssituationen Abstoßung auftreten kann.

Varactors form an important part of many communication circuits. They are utilized in oscillators, tunable matching networks, tunable filters and phase-shifters. This thesis deals with the design, analysis, characterization and applications of a novel MEMS varactor. Lower actuation voltage and higher dynamic range are the two important issues widely addressed in the study of MEMS varactors. The pull-in instability, due to which only 33% of the gap between plates could be covered smoothly, greatly reduces useful dynamic range of MEMS varactors. We propose a torsional MEMS varactor that exploits “displacement amplification” whereby pull-in is overcome and wide dynamic range is achieved. The torsion beam in the device undergoes torsion as well as bending. Behavior of the device has been analyzed through torque and force balance. Based on the torque balance and the force balance expressions, theoretical limits of torsion angle and bending for stable operation have been derived. Torsional MEMS varactors and its variants are fabricated through a commercial fabrication process (polyMUMPS) and extensive characterization has been carried out. Capacitance-voltage characteristics show a maximum dynamic range of 1:16 with parasitic capacitance subtracted out from the capacitance values. A bidirectional torsional varactor, in which the top AC plate moves not only towards bottom plate but also away from bottom plate, is also tested. The bottom AC plate is isolated from low resistivity substrate with a thin nitride layer. This gives rise to large parasitic capacitances at higher frequencies. So to avoid this, a varactor with both AC plates suspended in air is designed and fabricated. A dynamic range of 1:8 including parasitic capacitances has been achieved. Self-actuation is studied on fabricated structures and a torsional varactor that overcomes self-actuation has been proposed. Hysteresis behavior of the torsional varactor is analyzed for different AC signals across the varactor plates. Effects of residual stress on C-V characteristics are studied and advantages and disadvantages of residual stress on device performance are discussed. The torsional varactors have been cycled between Cmax and Cmin for 36 hours continuously without any failure. High-frequency characteristics of torsional varactors are analyzed through measurements on one-port and two port configurations. Measurements are done on polyMUMPS devices to study the capacitance variation with voltage, quality factor (Q) and capacitance variation with frequency. Effects of substrate are de-embedded from the device and characteristics of device are studied. An analog phase shifter based on torsional varactor proposed and analyzed through HFSS simulations. Very high tuning range can be achieved with a LC-VCO based on torsional varactors. A LC VCO with the torsional varactor as a capacitor in LC tank is designed. The torsional varactor and IC are fabricated separately and are integrated through wire bonding. Bond-wires are used as inductors.

New methodologies and concepts for developing compact and energy efficient automotive exhaust systems have been studied. This originates in the growing concern for global warming, to which road transportation is a major contributor. The focus has been on commercial vehicles—most often powered by diesel engines—for which the emission legislation has been dramatically increased over the last decade. The emissions of particulates and nitrogen oxides have been successfully reduced by the introduction of filters and catalytic converters, but the fuel consumption, which basically determines the emissions of carbon dioxides, has not been improved accordingly. The potential reduction of fuel consumption by optimising the exhaust after-treatment system (assuming fixed after-treatment components) of a typical heavy-duty commercial vehicle is ~4%, which would have a significant impact on both the environment and the overall economy of the vehicle. First, methodologies to efficiently model complex flow duct networks such as exhaust systems are investigated. The well-established linear multiport approach is extended to include flow-acoustic interaction effects. This introduces an effective way of quantifying amplification and attenuation of incident sound, and, perhaps more importantly, the possibility of predicting nonlinear phenomena such as self-sustained oscillations—whistling—using linear models. The methodology is demonstrated on T-junctions, which is a configuration well known to be prone to self-sustained oscillations for grazing flow past the side branch orifice. It is shown, and validated experimentally, that the existence and frequency of self-sustained oscillations can be predicted using linear theory. Further, the aeroacoustics of T-junctions are studied. A test rig for the full determination of the scattering matrix defining the linear three-port representing the T-junction is developed, allowing for any combination of grazing-bias flow. It is shown that the constructive flow-acoustic coupling not only varies with the flow configuration but also with the incidence of the acoustic disturbance. Configurations where flow from the side branch joins the grazing flow are still prone to whistling, while flow bleeding off from the main branch effectively cancels any constructive flow-acoustic coupling. Two silencer concepts are evaluated: first the classic Herschel-Quincke tube and second a novel modified flow reversal silencer. The Herschel-Quincke tube is capable of providing effective attenuation with very low pressure loss penalty. The attenuation conditions are derived and their sensitivity to mean flow explained. Two implementations have been modelled using the multiport methodology and then validated experimentally. The first configuration, where the nodal points are composed of T-junctions, proves to be an example where internal reflections in the system can provide sufficient feedback for self-sustained oscillation. Again, this is predicted accurately by the linear theory. The second implementation, with nodal points made from Y-junctions, was designed to allow for equal flow distribution between the two parallel ducts, thus allowing for the demonstration of the passive properties of the system. Experimental results presented for these two configurations correlate well with the derived theory. The second silencer concept studied consists of a flow reversal chamber that is converted to a resonator by acoustically short-circuiting the inlet and outlet ducts. The eigenfrequency of the resonator is easily shifted by varying the geometry of the short circuit, thus making the proposed concept ideal for implementation as a semi-active device. Again the concept is modelled using the multiport approach and validated experimentally. It is shown to provide significant attenuation over a wide frequency range with a very compact design, while adding little or no pressure loss to the system. / QC 20110208

This thesis treats the development of packaging and integration methods for the cost-efficient encapsulation and packaging of microelectromechanical (MEMS) devices. The packaging of MEMS devices is often more costly than the device itself, partly because the packaging can be crucial for the performance of the device. For devices which contain liquids or needs to be enclosed in a vacuum, the packaging can account for up to 80% of the total cost of the device. The first part of this thesis presents the integration scheme for an optical dye thin film NO2-gas sensor, designed using cost-efficient implementations of wafer-scale methods. This work includes design and fabrication of photonic subcomponents in addition to the main effort of integration and packaging of the dye-film. A specific proof of concept target was for NO2 monitoring in a car tunnel. The second part of this thesis deals with the wafer-scale packaging methods developed for the sensing device. The developed packaging method, based on low-temperature plastic deformation of gold sealing structures, is further demonstrated as a generic method for other hermetic liquid and vacuum packaging applications. In the developed packaging methods, the mechanically squeezed gold sealing material is both electroplated microstruc- tures and wire bonded stud bumps. The electroplated rings act like a more hermetic version of rubber sealing rings while compressed in conjunction with a cavity forming wafer bonding process. The stud bump sealing processes is on the other hand applied on completed cavities with narrow access ports, to seal either a vacuum or liquid inside the cavities at room temperature. Additionally, the resulting hermeticity of primarily the vacuum sealing methods is thoroughly investigated. Two of the sealing methods presented require permanent mechanical fixation in order to complete the packaging process. Two solutions to this problem are presented in this thesis. First, a more traditional wafer bonding method using tin-soldering is demonstrated. Second, a novel full-wafer epoxy underfill-process using a microfluidic distribution network is demonstrated using a room temperature process. / <p>QC 20130325</p>

Recent advances in molecular biology and nanotechnology have enabled scientists to study biological systems at molecular and atomic scales. This level of sophistication demands for new technologies to emerge for providing the necessary sensing tools and equipment. Recent studies have shown that terahertz technology can provide revolutionary sensing techniques for organic and non-organic materials with unprecedented accuracy and sensitivity. This is due to the fact that most of the macromolecules have vibrational and/or rotational resonance signatures in terahertz range. To further increase the sensitivity, terahertz radiation is generated and interacted with the bio-sample on a miniaturized test site or the so-called biochip. From the view point of generation and manipulation of terahertz radiation, the biochip is designed based on the same rules as in high frequency electronic chips or integrated circuits (IC). By increasing the frequency toward terahertz range, the conventional IC design methodologies and analysis tools fail to perform accurately. Therefore, development of new design methodologies and analysis tools is of paramount importance for future terahertz integrated circuits (TIC) in general and terahertz biochips in particular. In this thesis, several advancements are made in design methodology, analysis tool and architecture of terahertz and millimeter-wave integrated circuits when used as a biochip. A global and geometry independent approach for design and analysis of the travelling-wave terahertz photomixer sources, as the core component in a TIC, is discussed in details. Three solvers based on photonic, semiconductor and electromagnetic theories are developed and combined as a unified analysis tool. Using the developed terahertz photomixer source, a resonance-based biochip structure is proposed, and its operation principle, based on resonance perturbation method, is explained. A planar metallic resonator acting as a sample holder and transducer is designed, and its performance in terms of sensitivity and selectivity is studied through simulations. The concept of surface impedance for electromagnetic modeling of DNA self-assembled monolayer on a metal surface is proposed, and its effectiveness is discussed based on the available data in the literature. To overcome the loss challenge, Whispering Gallery Mode (WGM) dielectric resonators with high Q factor are studied as an alternative for metallic resonator. The metallic loss becomes very high at terahertz frequencies, and as a result of that planar metallic resonators do not exhibit high Q factor. Reduced Q factor results in a low sensitivity for any sensor using such resonators. Theoretical models for axially and radially layered dielectric resonators acting on WGM are presented, and the analytical results are compared with the measured data. Excitation of WGM through dielectric waveguide is proposed, and the critical coupling condition is explained through analytical formulation. The possibility of selecting one resonance among many for sensing application is also studied both theoretically and experimentally. A high sensitivity sensor based on WGM resonance in mm-wave and terahertz is proposed, and its sensitivity is studied in details. The performance of the proposed sensor is tested for sensing drug tablets and also liquid droplets through various measurements in mm-wave range. The comprehensive sensitivity analysis shows the ability of the proposed sensor to detect small changes in the order of 10−4 in the sample dielectric constant. The results of various experiments carried out on drug tablets are reported to demonstrate the potential multifunctional capabilities of the sensor in moisture sensing, counterfeit drug detection, and contamination screening. The measurement and simulation results obtained in mm-wave hold promise for WGM to be used for sensing biological solutions in terahertz range with very high sensitivity.

Recent advances in molecular biology and nanotechnology have enabled scientists to study biological systems at molecular and atomic scales. This level of sophistication demands for new technologies to emerge for providing the necessary sensing tools and equipment. Recent studies have shown that terahertz technology can provide revolutionary sensing techniques for organic and non-organic materials with unprecedented accuracy and sensitivity. This is due to the fact that most of the macromolecules have vibrational and/or rotational resonance signatures in terahertz range. To further increase the sensitivity, terahertz radiation is generated and interacted with the bio-sample on a miniaturized test site or the so-called biochip. From the view point of generation and manipulation of terahertz radiation, the biochip is designed based on the same rules as in high frequency electronic chips or integrated circuits (IC). By increasing the frequency toward terahertz range, the conventional IC design methodologies and analysis tools fail to perform accurately. Therefore, development of new design methodologies and analysis tools is of paramount importance for future terahertz integrated circuits (TIC) in general and terahertz biochips in particular. In this thesis, several advancements are made in design methodology, analysis tool and architecture of terahertz and millimeter-wave integrated circuits when used as a biochip. A global and geometry independent approach for design and analysis of the travelling-wave terahertz photomixer sources, as the core component in a TIC, is discussed in details. Three solvers based on photonic, semiconductor and electromagnetic theories are developed and combined as a unified analysis tool. Using the developed terahertz photomixer source, a resonance-based biochip structure is proposed, and its operation principle, based on resonance perturbation method, is explained. A planar metallic resonator acting as a sample holder and transducer is designed, and its performance in terms of sensitivity and selectivity is studied through simulations. The concept of surface impedance for electromagnetic modeling of DNA self-assembled monolayer on a metal surface is proposed, and its effectiveness is discussed based on the available data in the literature. To overcome the loss challenge, Whispering Gallery Mode (WGM) dielectric resonators with high Q factor are studied as an alternative for metallic resonator. The metallic loss becomes very high at terahertz frequencies, and as a result of that planar metallic resonators do not exhibit high Q factor. Reduced Q factor results in a low sensitivity for any sensor using such resonators. Theoretical models for axially and radially layered dielectric resonators acting on WGM are presented, and the analytical results are compared with the measured data. Excitation of WGM through dielectric waveguide is proposed, and the critical coupling condition is explained through analytical formulation. The possibility of selecting one resonance among many for sensing application is also studied both theoretically and experimentally. A high sensitivity sensor based on WGM resonance in mm-wave and terahertz is proposed, and its sensitivity is studied in details. The performance of the proposed sensor is tested for sensing drug tablets and also liquid droplets through various measurements in mm-wave range. The comprehensive sensitivity analysis shows the ability of the proposed sensor to detect small changes in the order of 10−4 in the sample dielectric constant. The results of various experiments carried out on drug tablets are reported to demonstrate the potential multifunctional capabilities of the sensor in moisture sensing, counterfeit drug detection, and contamination screening. The measurement and simulation results obtained in mm-wave hold promise for WGM to be used for sensing biological solutions in terahertz range with very high sensitivity.

Silicon alternatives to quartz crystal based oscillators to electronic system clocking are explored. A study of clocking requirements reveals widely different specifications for different applications. Traditional CMOS oscillator-based solutions are optimized for low-cost fully integrated micro-controller clock applications. The frequency variability of these clock generators is studied and techniques to compensate for this variability are proposed. The efficacy of these techniques in reducing variability is proven theoretically and experimentally. MEMS-resonator based oscillators, due to their exceptional quality factors, are identified as suitable integrated replacements to quartz based oscillators for higher accuracy applications such as data converter clocks. The frequency variation in these oscillators is identified and techniques to minimize the same are proposed and demonstrated. The sources of short-term variation (phase noise) in these oscillators are discussed and an inclusive theory of phase noise is developed. Techniques to improve phase noise are proposed. Findings from this research indicate that MEMS resonator based oscillators, may in future, outperform quartz based solutions in certain applications such as voltage controlled oscillators. The implications of these findings and potential directions for future research are identified.

Inter-chip input-output (I/O) communication bandwidth demand, which rapidly scaled with integrated circuit scaling, has leveraged equalization techniques to operate reliably on band-limited channels at additional power and area complexity. High-bandwidth inter-chip optical interconnect architectures have the potential to address this increasing I/O bandwidth. Considering future tera-scale systems, power dissipation of the high-speed I/O link becomes a significant concern. This work presents a design flow for the power optimization and comparison of high-speed electrical and optical links at a given data rate and channel type in 90 nm and 45 nm CMOS technologies. The electrical I/O design framework combines statistical link analysis techniques, which are used to determine the link margins at a given bit-error rate (BER), with circuit power estimates based on normalized transistor parameters extracted with a constant current density methodology to predict the power-optimum equalization architecture, circuit style, and transmit swing at a given data rate and process node for three different channels. The transmitter output swing is scaled to operate the link at optimal power efficiency. Under consideration for optical links are a near-term architecture consisting of discrete vertical-cavity surface-emitting lasers (VCSEL) with p-i-n photodetectors (PD) and three long-term integrated photonic architectures that use waveguide metal-semiconductor-metal (MSM) photodetectors and either electro-absorption modulator (EAM), ring resonator modulator (RRM), or Mach-Zehnder modulator (MZM) sources. The normalized transistor parameters are applied to jointly optimize the transmitter and receiver circuitry to minimize total optical link power dissipation for a specified data rate and process technology at a given BER. Analysis results shows that low loss channel characteristics and minimal circuit complexity, together with scaling of transmitter output swing, allows electrical links to achieve excellent power efficiency at high data rates. While the high-loss channel is primarily limited by severe frequency dependent losses to 12 Gb/s, the critical timing path of the first tap of the decision feedback equalizer (DFE) limits the operation of low-loss channels above 20 Gb/s. Among the optical links, the VCSEL-based link is limited by its bandwidth and maximum power levels to a data rate of 24 Gb/s whereas EAM and RRM are both attractive integrated photonic technologies capable of scaling data rates past 30 Gb/s achieving excellent power efficiency in the 45 nm node and are primarily limited by coupling and device insertion losses. While MZM offers robust operation due to its wide optical bandwidth, significant improvements in power efficiency must be achieved to become applicable for high density applications.

Metamaterials attracted significant attention in recent years due to their potential to create novel devices that exhibit specific electromagnetic properties. In this thesis, we investigated transmission and propagation properties of novel metamaterial structures. Electromagnetic properties of metamaterials are characterized and the resonance mechanism of Split Ring Resonator (SRR) structure is investigated. Furthermore, a recent lefthanded metamaterial structure for microwave regime called Fishnet-type metamaterial is studied. We demonstrated the left-handed transmission and negative phase velocity in Fishnet Structures. Finally, we proposed and successfully demonstrated novel approaches that utilize the resonant behavior of SRR structures to enhance the transmission of electromagnetic waves through sub-wavelength apertures at microwave frequency regime. We investigated the transmission enhancement of electromagnetic waves through a sub-wavelength aperture by placing SRR structures in front of the aperture and also by changing the aperture shape as SRR-shaped apertures. The incident electromagnetic wave is effectively coupled to the sub-wavelength aperture causing a strong localization of electromagnetic field in the sub-wavelength aperture. Localized electromagnetic wave gives rise to enhanced transmission from a single sub-wavelength aperture. The proposed structures are designed, simulated, fabricated and measured. The simulations and experimental results are in good agreement and shows significant enhancement of electromagnetic wave transmission through sub-wavelength apertures by utilizing proposed novel structures. Radius (r) of the sub-wavelength aperture is approximately twenty times smaller than the incident wavelength (r/&amp / #955 / ~0.05). This is the smallest aperture size to wavelength ratio in the contemporary literature according to our knowledge.

This dissertation is focused on the design, fabrication, and characterization of novel metamaterials in microwave and terahertz regions with the following outcomes: A planar &micro / -negative metamaterial structure, called double-sided SRR (DSRR), is proposed in the first part of this study. DSRR combines the features of a conventional split ring resonator (SRR) and a broadside-coupled SRR (BC-SRR) to obtain much better miniaturization at microwave frequencies for a given physical cell size. In addition to DSRR, double-sided multiple SRR (DMSRR), double-sided spiral resonator (DSR), and double-sided U-spiral resonator (DUSR) have been shown to provide smaller electrical sizes than their single-sided versions under magnetic excitation. In the second part of this dissertation, a novel multi-band tunable metamaterial topology, called micro-split SRR (MSSRR), is proposed. In addition to that, a novel magnetic resonator structure named single loop resonator (SLR) is suggested to provide two separate magnetic resonance frequencies in addition to an electric resonance in microwave region. In the third part, two different frequency tunable metamaterial topologies called BC-SRR and gap-to-gap SRR are designed, fabricated and characterized at terahertz frequencies with electrical excitation for the first time. In those designs, frequency tuning based on variations in near field coupling is obtained by in-plane horizontal or vertical displacements of the two SRR layers. The values of frequency shifts obtained for these tunable metamaterial structures are reported to be the highest values obtained in literature so far. Finally, in the last part of this dissertation, novel double-sided metamaterial based sensor topologies are suggested and their feasibility studies are presented.