Partial enclosures are commonly used to reduce machinery noise. However, it is well known in industry that enclosures sometimes amplify the sound at low frequencies due to strong acoustic resonances compromising the performance. These noise issues are preventable if predicted prior to prototyping and production. Though boundary and finite element approaches can be used to accurately predict partial enclosure insertion loss, modifications to the model require time for remeshing and solving. In this work, partial enclosure performance at low frequencies is simulated using a plane wave transfer matrix approach. Models can be constructed and the effect of design modifications can be predicted rapidly. Results are compared to finite element analysis and measurement with good agreement. The approach is then used to design and place resonators into a sample enclosure. Improvements in enclosure performance are predicted using plane wave simulation, compared with acoustic finite element analysis, and then validated via measurement.

The explosive development of the telecom industry and in particular wireless and mobile communications in recent years has lead to a rapid development of new component and fabrication technologies to continually satisfy the mutually exclusive requirements for better performance and miniaturization on the one hand and low cost on the other. A fundamental element in radio communications is time and frequency control, which in turn is achieved by high performance electro-acoustic components made on piezoelectric single crystalline substrates. The latter, however, reach their practical limits in terms of performance and cost as the frequency of operation reaches the microwave range. Thus, the thin film electro-acoustic technology, which uses thin piezoelectric films instead, has been recently developed to alleviate these deficiencies. This thesis explores and addresses a number of issues related to thin film synthesis on the one hand as well as component design and fabrication on other. Specifically, the growth of highly c-axis textured AlN thin films has been studied and optimized for achieving high device performance. Perhaps, one of the biggest achievements of the work is the development of a unique process for the deposition of AlN films with a mean c-axis tilt, which is of vital importance for the fabrication of resonators operating in contact with liquids, i.e. biochemical sensors. This opens the way for the development of a whole range of sensors and bio-analytical tools. Further, high frequency Lamb wave resonators have been designed, fabricated and evaluated. Performance enhancement of FBAR devices is also addressed, e.g. spurious mode suppression, temperature compensation, etc. It has been demonstrated, that even without temperature compensation, shear mode resonators operating in a liquid still exhibit an excellent performance in terms of Q (200) and coupling (~1.8%) at 1.2 GHz, resulting in a mass resolution better than 2 ng cm-2 in water, which excels that of today’s quartz sensors.

QC 20100618

This thesis treats the development of an integrated optical sensor array. The sensors are slot-waveguide ring resonators, integrated with on-chip surface grating couplers and light splitters, for alignment tolerant, real-time, refractive index sensing, and label-free biosensing. The work includes: the design of components and system layouts, the development of fabrication methods, the fabrication of sensor chips, the characterization of the chips, and the development of physical system models for accurate extraction of resonance wavelengths in measured spectra. The main scientific achievements include: The evaluation of a novel type of nano-structured optical waveguide for biochemical sensing. The realization of an array of such slot-waveguide sensors, integrated with microfluidic sample handling, for multiplex assays. The first study of the thermal behavior of slot-waveguide sensors and the discovery of unique temperature compensation capabilities. From an application perspective, the use of alignment tolerant surface gratings to couple light into the optical chip enables quick replacement of cartridges in the read-out instrument. Furthermore, the fabrication sequence avoids polishing of individual chips, and thus ensures that the cost benefits of silicon batch micro-fabrication can be leveraged in mass production. The high sensitivity of the slot waveguide resonators, combined with on-chip referencing and physical modeling, yields low limits of detection. The obtained volume refractive index detection limit of 5 × 10−6 refractive index units (RIU), and the surface mass density detection limit of 0.9 pg/mm2, shows that performance comparable to that of commercial non-integrated surface plasmon resonance sensors, made from bulk optical components, canbe achieved in a compact cartridge. / Qc20100715 / SABIO

Electroabsorption is the physical phenomenon by which the absorption of light in a medium can be controlled by applying an electric field. The Quantum–Confined Stark Effect, which makes the absorption band–edge in quantum wells very field–dependent, together with the strong absorption peak provided by excitons, are the physical foundations for the success of electroabsorption modulators based on quantum well structures in telecommunication networks. This thesis describes the design and fabrication of surface–normal electroabsorption modulation devices. The techniques needed to understand the design and fabrication of surface–normal multiple quantum well optical modulators are introduced, as are the various characterisation techniques used during and after the fabrication. Devices for several types of applications have been designed, fabricated, characterised and in some cases integrated into optical systems: – Two–dimensional arrays of 128´128 pixel amplitude modulators grown on GaAs substrates have been fabricated and characterised. Speeds of up to 11700 frames per second were demonstrated, limited by the output electronics of the computer interface. – Large–area modulators grown on GaAs substrates for free–space optical communication were developed, with an active area of 2cm2 and a modulation speed of several megahertz. Contrast ratios up to 5:1 on full modulator areas were measured. Problems limiting the yield and modulation speed of such devices have been studied, and solutions to overcome them have been demonstrated. – Large–area devices grown on InP substrates for free–space optical communication have been developed. Contrast ratios of up to 2:1 for transmissive types have been demonstrated. – Devices consisting of two rows of pixels, grown on GaAs substrates, with an active area of 22mm´5mm, divided into 64 or 128 pixels per row have been developed. These amplitude modulation devices were designed for optical signal processing applications. – One variant of these optical signal processing devices was also characterised as a ternary, binary amplitude and binary phase modulator array. – The use of GaAs multiple quantum well optical modulators in a free–space optical retro–communication system has been studied. An opto–mechanical design for a modulating retro–reflector is described, allowing a large field of view in one direction using reflecting, resonant–cavity modulators for high contrast ratios. / QC 20100802

Dielectric resonators offer high-Q (low loss) characteristics which make them ideal for filters with narrow bandwidth and low insertion loss specifications. They are mainly used in satellite and wireless system applications. Such applications desire the highest performance filters with the lowest amount of size and mass, which has been the main motivation for size reduction techniques invented over the past three decades for these filters. In addition with the emergence of different communication system technologies, several bands are now required to be supported by a single front-end, calling for emergence and development of dual-band and multi-band filters. To date few work has been done in the area of dual-band dielectric resonator filters. Dielectric resonators filters are important components in many communication systems, when a group of such filters are brought together to perform multiplexing of RF channels. These multiplexer systems tend to be fairly complex and bulky in design, and there is strong desire to reduce their size and mass to the maximum extent possible. Novel quadruple-mode, dual-mode, and dual-band filters as well multiplexers are presented in this thesis. The first ever quadruple-mode dielectric resonator filter using the simple cylinder structure is reported in this work. A cylindrical dielectric resonator sized appropriately in terms of its diameter and height is shown to operate as a quadruple-mode resonator, which is achieved by having two mode pairs of the structure resonate at the same frequency. Single-cavity, quad-mode filters and higher order 4n-pole filters are realizable using this quad-mode cylindrical resonator, offering significant size reduction for dielectric resonator filter applications. The structure of the quad-mode cylinder is then simplified by cutting lengthwise along the central axis of the cylinder, to produce a half-cut cylinder suitable for operation in a dual-mode regime. Novel dual-mode, 2n-pole filters are realizable using this half-cut cylinder, by making the two resonances equal in frequency. The dual-mode half-cut filter is shown to be a strong contender for replacing existing dual-mode filters used in satellite and wireless applications, as it offers superior size and mass characteristics. By making the resonances unequal in frequency, novel dual-band filters and multiplexers are further realizable, by carrying separate frequency bands on different resonant modes of the structure. The first true orthogonal mode dual-band dielectric resonator is presented in this work, using the half-cut structure. Multiplexers are also derived from these dual-band resonators, which greatly reduce size and mass of many-channel multiplexers at the system level, as each two channels are overloaded in one physical branch. Full control of center frequencies of resonances, input and inter-resonator couplings are achievable, allowing realization of microwave filters with different bandwidth, frequency, and return loss specifications, as well as advanced filtering functions with prescribed transmission zeros. Spurious performance of the half-cut cylinder can also be improved by cutting one or more through-way slots between opposite surfaces of the resonator. Size and mass reduction achieved by using the full and half-cut resonators described in this thesis, provide various levels of size reduction in microwave systems, both device and system level.

Dielectric resonators offer high-Q (low loss) characteristics which make them ideal for filters with narrow bandwidth and low insertion loss specifications. They are mainly used in satellite and wireless system applications. Such applications desire the highest performance filters with the lowest amount of size and mass, which has been the main motivation for size reduction techniques invented over the past three decades for these filters. In addition with the emergence of different communication system technologies, several bands are now required to be supported by a single front-end, calling for emergence and development of dual-band and multi-band filters. To date few work has been done in the area of dual-band dielectric resonator filters. Dielectric resonators filters are important components in many communication systems, when a group of such filters are brought together to perform multiplexing of RF channels. These multiplexer systems tend to be fairly complex and bulky in design, and there is strong desire to reduce their size and mass to the maximum extent possible. Novel quadruple-mode, dual-mode, and dual-band filters as well multiplexers are presented in this thesis. The first ever quadruple-mode dielectric resonator filter using the simple cylinder structure is reported in this work. A cylindrical dielectric resonator sized appropriately in terms of its diameter and height is shown to operate as a quadruple-mode resonator, which is achieved by having two mode pairs of the structure resonate at the same frequency. Single-cavity, quad-mode filters and higher order 4n-pole filters are realizable using this quad-mode cylindrical resonator, offering significant size reduction for dielectric resonator filter applications. The structure of the quad-mode cylinder is then simplified by cutting lengthwise along the central axis of the cylinder, to produce a half-cut cylinder suitable for operation in a dual-mode regime. Novel dual-mode, 2n-pole filters are realizable using this half-cut cylinder, by making the two resonances equal in frequency. The dual-mode half-cut filter is shown to be a strong contender for replacing existing dual-mode filters used in satellite and wireless applications, as it offers superior size and mass characteristics. By making the resonances unequal in frequency, novel dual-band filters and multiplexers are further realizable, by carrying separate frequency bands on different resonant modes of the structure. The first true orthogonal mode dual-band dielectric resonator is presented in this work, using the half-cut structure. Multiplexers are also derived from these dual-band resonators, which greatly reduce size and mass of many-channel multiplexers at the system level, as each two channels are overloaded in one physical branch. Full control of center frequencies of resonances, input and inter-resonator couplings are achievable, allowing realization of microwave filters with different bandwidth, frequency, and return loss specifications, as well as advanced filtering functions with prescribed transmission zeros. Spurious performance of the half-cut cylinder can also be improved by cutting one or more through-way slots between opposite surfaces of the resonator. Size and mass reduction achieved by using the full and half-cut resonators described in this thesis, provide various levels of size reduction in microwave systems, both device and system level.

The main topic of this thesis is the performance improvement of microresonators as mass-sensitive biochemical sensors in a liquid environment. Resonant microstructures fabricated on silicon substrates with CMOS-compatible micromachining techniques are mainly investigated. Two particular approaches have been chosen to improve the resolution of resonant chemical/biochemical sensors. The first approach is based on designing a microresonator with high Q-factor in air and in liquid, thus, improving its frequency resolution. The second approach is based on minimizing the frequency drift of microresonators by compensating for temperature-induced frequency variations. A disk-shape resonant microstructure vibrating in a rotational in-plane mode has been designed, fabricated and extensively characterized both in air and in water. The designed resonators have typical resonance frequencies between 300 and 1,000kHz and feature on-chip electrothermal excitation elements and a piezoresistive Wheatstone-bridge for vibration detection. By shearing the surrounding fluid instead of compressing it, damping is reduced and quality factors up to 5800 in air and 94 in water have been achieved. Short-term frequency stabilities obtained from Allan-variance measurements with 1-sec gate time are as low as 1.1 10-8 in air and 2.3 10-6 in water. The performance of the designed resonator as a biological sensor in liquid environment has been demonstrated experimentally using the specific binding of anti-beta-galactosidase antibody to beta-galactosidase enzyme covalently immobilized on the resonator surface. An analytical model of the disk resonator, represented by a simple harmonic oscillator, has been derived and compared with experimental results. The resonance frequency and the Q-factor of the disk resonator are determined from analytical expressions for the rotational spring constant, rotational moment of inertia, and energy loss by viscous damping. The developed analytical models show a good agreement with FEM simulation and experimental results and facilitate the geometrical optimization of the disk-type resonators. Finally, a new strategy to compensate for temperature-induced frequency drifts of resonant microstructures has been developed based on a controlled stiffness modulation by an electronic feedback loop. The developed method is experimentally verified by compensating for temperature-induced frequency fluctuations of a microresonator. In principle, the proposed method is applicable to all resonant microstructures featuring excitation and detection elements.

Split ring resonator (SRR) is a metamaterial structure which displays negative permeability values over a relatively small bandwidth around its magnetic resonance frequency. Unit SRR cells and arrays have been used in various novel applications including the design of miniaturized microwave devices and antennas. When the SRR arrays are combined with the arrays of conducting wires, left handed materials can be constructed with the unusual property of having negative valued effective refractive indices. In this thesis, unit cells and arrays of single-ring multiple-split type SRR structures are numerically analyzed by using Ansoft&rsquo / s HFSS software that is based on the finite elements method (FEM). Some of these structures are constructed over low-loss dielectric substrates and their complex scattering parameters are measured to verify the numerical simulation results. The major purpose of this study has been to establish equivalent circuit models to estimate the behavior of SRR structures in a simple and computationally efficient manner. For this purpose, individual single ring SRR cells with multiple splits are modeled by appropriate two-port RLC resonant circuits paying special attention to conductor and dielectric loss effects. Results obtained from these models are compared with the results of HFSS simulations which use either PEC/PMC (perfect electric conductor/perfect magnetic conductor) type or perfectly matched layer (PML) type boundary conditions. Interactions between the elements of SRR arrays such as the mutual inductance and capacitance effects as well as additional dielectric losses are also modeled by proper two-port equivalent circuits to describe the overall array behavior and to compute the associated transmission spectrum by simple MATLAB codes. Results of numerical HFSS simulations, equivalent circuit model computations and measurements are shown to be in good agreement.

This thesis reports design and implementation of a MEMS based gravimetric resonator for cytometry applications. There are mainly two objectives of this thesis / to enable in-flow analysis and to perform closed loop operation that does not require any additional processing or equipment. A novel MEMS based resonator with in-flow capabilities is proposed for detection of agents inside micro channels. High resolution of mass detection inside micro channels is planned to be succeeded with lateral motion in the micro channel floor. The idea embedding lateral resonators emerges from decreasing squeeze film damping during the motion of the resonator. Lateral motion is supported by hydrophobic parylene coating to decrease the damping. Theory and design of the gravimetric resonators are explained and the fabrication flow is constructed and performed successfully by combining SOI, SOG and polymer micro fabrication techniques. Problems during the fabrication are overcome and optimized flow is presented. The devices have a foot print area of 1.5 x 0.5 cm2 which is mainly composed of reservoirs for fluidic connections. Ten types of devices are designed according to their mass sensitivities and compliances. Trade offs between frequency, injected current, and compliance are analyzed successfully by taking also the performance parameters of the interface electronics in to account. Test results reveal that single latex bead with 3 &micro / m diameter and 14.127 pg mass can be sensed successfully and mass sensitivity is measured to be 5.91 fg/Hz for this type of device.