The goal of the thesis is to fabricate the integrated asymmetric Mach-Zehnder Interferometer and Optical waveguide Ring Resonator with simple fabrication process. A 1.49

Recently, there are great demands for RF band pass filters with smaller size/volume, lighter weight, and higher performance for advanced mobile/wireless communication system. However, fabricated RF filters using traditional lumped element, dielectric resonators, or surface acoustic wave¡]SAW¡^filters have difficulties in on-chip integration, power handling capability, and temperature compensation. Alternatively, thin-film bulk acoustic wave resonator¡]FBAR¡^filters are very suitable devices for MMIC¡¦s since they can be fabricated on Si or GaAs substrates at a lower magnitude than lumped elements or dielectric resonators, plus they have a much lower insertion loss and higher power handling capabilities than surface acoustic wave devices and full integration with other CMOS RF IC circuitry for realizing a goal of system on chip¡]SOC¡^. In their simplest form, practical FBARs consist of a sputtered piezoelectric thin film sandwiched between top and bottom electrodes onto which an electric field is then applied. An FBAR must have two acoustically reflecting surfaces in order to trap energy and produce resonating characteristics. For this purpose, the thin film bulk acoustic resonator has to be isolated acoustically from the substrate. In view of this, in order to obtain a high Q factor and reduce spurious responses, this paper proposed the air gap type resonator using the sacrificial layer etching. The thickness of the AlN thin film used for piezoelectric thin film of Air-gap FBAR is 1um. Pt/Ti with 3000Å/300Å thickness is used as the top and bottom electrode. The device has a resonance frequency of 1.2GHz, and S11-paparameter of -25dB is also obtained.

Microwave dielectric resonators (DRs) are being widely used in microwave telecommunication devices owing to their excellent characteristics of suitable dielectric constant, good temperature stability, and low dielectric loss. In this study, the crystalline phase and the microwave dielectric properties of the (1-x)Al2O3 - xTiO2 (x=0.08, 0.12, 0.16) compositions with 2wt%, 4wt%, 6wt%, and 8wt% MgO-CaO-Al2O3-SiO2 (MCAS) glass addition have been investigated. By combining the material Al2O3 with negative temperature coefficient of the resonant frequency (£nf = -55 ppm/¢J) and the material TiO2 with positive £nf value (£nf = +450 ppm/¢J), it is desired to produce the ceramics with £nf ~0 ppm/¢J. The MCAS is used as liquid-phase sintering aid to lower down the sintering temperature. In the MCAS-doped (1-x)Al2O3 - xTiO2 system, the Al2TiO5 phase starts to appear at about 1250¢J, and then the crystalline intensity of Al2TiO5 phase increases with the increase of sintering temperatures and MCAS glass content, until the temperatures that TiO2 is consumed. As the sintering temperature increases, the maximum dielectric constants and Q¡Ñf values can be obtained at 1250¢J, and the £nf values shift from positive to negative. The optimum £nf value of ¡V0.6 ppm/¢J exists in the 88mol%Al2O3 - 12mol%TiO2 composition with 2wt% MCAS addition and sintering temperature of 1300¢J. The MCAS content, TiO2 content, and sintering temperature will result in the variation of microwave dielectric properties. In this study, MCAS-doped (1-x)Al2O3 - xTiO2 system exhibits the microwave dielectric properties of¡G £`r=7~9.5, Q¡Ñf=6500~11000, and £nf = -60 to +40ppm/¢J. By adjusting the MCAS content, TiO2 content, and sintering temperatures, ceramics with good microwave properties can be obtained in the MCAS-doped (1-x)Al2O3 - xTiO2 system.

In this thesis two different research topics are undertaken, both in the area of compact RF/microwave circuits design. The first topic involves the design of a compact circularly polarized (CP) slot-ring antenna. A study of several compact CP microstrip and slotline antennas reported in the past has been carried out. In this research, a method of reducing the size of a printed slot-ring antenna is proposed. The reduction in size is achieved by introducing meandered-slot sections in the ring. Circular polarization is achieved by introducing an asymmetry, also a meandered-slot section, and feeding the antenna at an angle of 45o from the asymmetry using a microstrip feed line. The minimum axial ratio of 0.4 dB is obtained at 2.46 GHz, which is the operating frequency of the antenna. The size of the proposed antenna is reduced by about 50% compared to a conventional CP slot-ring antenna and it displays a CP bandwidth of about 2.5%. The simulated and measured results are presented, and they are in good agreement. The small size of the antenna makes it very suitable for use in modern RF/microwave wireless systems which require compact, low cost, and high performance circuits. Moreover, its CP behavior makes it more attractive for applications such as satellite communications. The second topic in the thesis involves the design of a compact microstrip bandpass filter using triangular open-loop resonators. A new compact three-pole microstrip bandpass filter using four triangular open-loop resonators is presented. A fourth resonator is placed to provide cross-coupling in the structure which gives a better skirt rejection. The measured pass-band center frequency is 2.85 GHz. The filter demonstrates about 7% bandwidth with insertion loss of less than 1 dB in the passband, a return loss of greater than 15 dB and out-of-band rejection of greater than 30 dB. The simulated and measured results are in good agreement. The proposed filter is very attractive for use in modern wireless systems which require bandpass filters having compact size, low insertion loss, high selectivity, and good out-of-band rejection.

With the rapidly progress in the microwave communication systems, miniaturization and performance enhancement have become two main requirements of the microwave devices. Microwave dielectric substrates would be the best choice for these requirements, because high dielectric constant of the substrates would reduce the size of the devices, high quality factor of the substrates would improve the microwave characteristics of the devices, and low temperature coefficient of resonant frequency would reduce the shift of the operating frequencies due to the variation of temperature. As mentioned above, the main research of this dissertation is divided into two parts: microwave dielectric materials and microwave filters. 1. Microwave dielectric materials AB2O6 (A=Mg, Zn; B=Ta, Nb) microwave dielectric ceramics have been developed as the microwave dielectric resonators (DRs) in the past, because the dielectric resonators fabricated by AB2O6 ceramics reveal the good microwave dielectric characteristics. However, the temperature coefficients of resonant frequency of MgTa2O6, MgNb2O6, ZnTa2O6, and ZnNb2O6 ceramics are still not good enough for the applications at the microwave frequency. In addition, MgTa2O6 and ZnTa2O6 ceramics reveal positive temperature coefficients of resonant frequency but the MgNb2O6 and ZnNb2O6 ceramics reveal negative temperature coefficients of resonant frequency. In this study, combining of MgNb2O6 ceramics (with negative temperature coefficients of resonant frequency) and MgTa2O6 ceramics (with positive temperature coefficients of resonant frequency) to form Mg(Ta1-xNbx)2O6 ceramics and combining of ZnNb2O6 ceramics (with negative temperature coefficients of resonant frequency) and ZnTa2O6 ceramics (with positive temperature coefficients of resonant frequency) to form Zn(Ta1-xNbx)2O6 ceramics, which all reveal near-zero temperature coefficients of resonant frequencyand are suitable for the applications of microwave communication devices. The sintering and microwave dielectric characteristics of the Mg(Ta1-xNbx)2O6 and Zn(Ta1-xNbx)2O6 dielectric ceramics are also investigated. 2. Wide-band, dual-band, tri-band, and tetra-band bandpass filters Microwave filters have been widely used in the communication systems. The optimal microwave dielectric characteristics of AB2O6 ceramics developed in this thesis were adopted as the substrates of the filters. The performance of the filters was improved obviously due to the high dielectric constant and high quality factor of the microwave dielectric ceramic substrates. At first, a wide-band and a dual-band (2.45/5.2 GHz) bandpass filters are developed by the combination technique of modified end-coupled microstrip lines and half-wavelength ombination technique will generate three transmission zeros easily in the stop-band to improve the characteristics of the filters. And the next, the tri-band (1.57/2.45/5.2 GHz) bandpass filters are developed by the combination of modified end-coupled microstrip lines, outer-frame structures and half-wavelength U-shaped hairpin resonators. The Defected Grounded Structures (DGS) are add into the ground planes of the tri-band bandpass filters to generate the fourth frequency (3.5 GHz), hence, the tetra-band (1.57/2.45/3.5/5.2 GHz) bandpass filters are accomplished. In addition, due to the uses of the high dielectric constant ceramic substrates and the combination techniques, the size of this tetra-band bandpass filter is only 26.3 mm*9.9 mm. Besides, six deeply transmission zeros are generated in the stop-band to improve the characteristics of the filters (1~7 GHz), all the characteristics of this tetra-band filters (frequency, bandwidth, insertion loss, and stop-band rejection) are suitable for the applications of modern communication systems.

The solidly mounted resonator (SMR) is constructed of a Bragg reflector and a piezoelectric layer AlN. In order to obtain an appropriate SMR for the high frequency communication applications and high sensitivity bio-sensor applications, the Bragg reflector, the AlN, and the loading effect have been investigated thoroughly. The thesis presents the influences of surface roughness of the Bragg reflector and materials¡¦ selection on the resonance characteristics of an SMR. Three combinations of thin films, AlN/Al, Mo/Ti, and Mo/SiO2, are adopted. Originally, an AlN/Al multi-layer is used as the Bragg reflector. The poor surface roughness of this Bragg reflector results in a poor SMR frequency response. To improve the surface roughness of Bragg reflectors, a Mo/Ti multi-layer with a similar coefficient of thermal expansion is adopted. By controlling deposition parameters, the surface roughness of the Bragg reflector is improved. Finally, a material combination of Mo/SiO2 with high acoustic impedance ratio of 4.7 is adopted. Better resonance characteristics of SMR are obtained. The experimental results show a distinct resonance phenomenon around 2.5 GHz and excellent noise restraint. Afterwards, a ¼£f mode SMR is experimentally realized. The selection of high and low acoustic impedance for the first layer beneath piezoelectric layer results in the ¼£f mode and ½ £f mode resonance configurations, respectively. The coupling coefficient Keff2 of 6.9% is obtained, which is in agreement with the theoretical analysis. Following, the theoretical analysis upon the dual mode frequency-shift was characterized, and a modified formula was carried out. The c-axis tilted angle of AlN was altered as well as the various mass loading on the SMR. Based on the experimental results, the dual resonance frequencies showed a nonlinear decreasing trend with a linear increase of the mass loading. Furthermore, the ratio of the longitudinal resonant frequency to the shear resonant frequency remained at a range around 1.76 despite the various c-axis tilted angles of AlN and gradual mass loading on the SMR. The electromechanical coupling coefficient, keff2, of the shear resonance rose with the increase of the c-axis tilted angle of AlN. However, the longitudinal resonance fades away with the AlN c-axis tilted angle, and the quality factor of the longitudinal resonance decreases. Finally, the dual mode resonances are improved by tilting the off-center substrates toward the sputtering source and successfully enhance the longitudinal resonance while preserve the shear resonance at the same time. Not only the shear resonance for the liquid-based sensing application, but also an outstanding longitudinal resonance could be obtained. The practicability of the dual-mode resonator is extended for the applications of high frequency wireless communication and high sensitivity bio-chemical sensors.

Microresonators are devices that confine light in small volumes through total internal reflection. Introducing an emissive species into a microresonator allows for resonance enhanced emission at frequencies where the spectrum of the emissive species overlaps with the resonant frequencies of the microresonator. Previous research has led to a good understanding of these phenomena in 1D and 2D microresonators, but many 3D microresonator geometries have not yet been investigated. This work details the successful creation and demonstration of a cubic polymeric optical microresonator.

Our burgeoning appetite for data relentlessly demands exponential scaling of computing and communications resources leading to an overbearing and ever-present drive to improve efficiency while reducing on-chip area even as photonic components expand to fill application spaces no longer satisfied by their electronic counterparts. With a high index contrast, low optical loss, and compatibility with the CMOS fabrication infrastructure, silicon-on-insulator technology delivers a mechanism by which efficient, sub-micron waveguides can be fabricated while enabling monolithic integration of photonic components and their associated electronic infrastructure. The result is a solution leveraging the superior bandwidth of optical signaling on a platform capable of delivering the optical analogue to Moore's Law scaling of transistor density. Device size is expected to end Moore's Law scaling in photonics as Maxwell's equations limit the extent to which this parameter may be reduced. The focus of the work presented here surrounds photonic device miniaturization and the development of 3D optical interconnects as approaches to optimize performance in densely integrated optical interconnects. In this dissertation, several technological barriers inhibiting widespread adoption of photonics in data communications and telecommunications are explored. First, examination of loss and crosstalk performance in silicon nitride over SOI waveguide crossings yields insight into the feasibility of 3D optical interconnects with the first experimental analysis of such a structure presented herein. A novel measurement platform utilizing a modified racetrack resonator is then presented enabling extraction of insertion loss data for highly efficient structures while requiring minimal on-chip area. Finally, pioneering work in understanding the statistical nature of doublet formation in microphotonic resonators is delivered with the resulting impact on resonant device design detailed.

Several free-free beam micro-resonators are designed and fabricated using two commercially available surface micromachining processes, the UW-MEMS process and PolyMUMPs. Theoretical derivations of the design parameters are presented and an electrical lumped behavior model is developed for a single resonator with direct mechanic-to-electric analogy. A finite-element analysis (FEA) tool, the COMSOL Multiphysics 4.2a, is utilized to simulate the effects of the critical structural dimensions and electromechanical coupling. A variety of analyses, such as modal, static and dynamic responses are performed in FEA and the results are compared with the analytical solutions. The static and dynamic performances of the fabricated UW-MEMS resonators are tested using the Vecco NT-9100 In-Motion System. The electrical testing is carried out to obtain the frequency characteristics in electrical domain of the device. Measured data are compared with the analytical and simulation results. Discrepancies are discussed and analyzed.

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