Microring resonators are a fundamental building block for integrated optical filters, and have both modulation and waveform generation applications. A hybrid chalcogenide (As2S3) on titanium diffused (Ti:LiNbO3) waveguide platform has been developed to realize tunable microring resonators on a lithium niobate (LiNbO3) substrate. The use of a LiNbO3 substrate allows for electro-optic tuning, which is demonstrated for the first time on an As2S3 guided optical mode. While optical modes confined in diffused waveguides are commonly electro-optically tuned, the use of a rib waveguide external to the substrate poses new design challenges. Simulation work to determine the optimum electrode design was carried out, while also taking into account the limitations of working with a low melting temperature chalcogenide material. The tuning of this hybrid As2S3 on Ti:LiNbO3 device structure is demonstrated with fabricated Mach-Zehnder interferometers and ring resonators. Electro-optic tuning of the TM polarization utilizing the r13 LiNbO3 tuning coefficient is shown, yielding results that show an improvement over previous tunable LiNbO3 microring resonators. Simulations are also carried out to show the waveform generating capabilities of this hybrid device platform.

Thin film technology is of great significance for a variety of products, such as electronics, anti-reflective or hard coatings, sensors, solar cells, etc. This thesis concerns the synthesis of thin functional films, reactive magnetron sputter deposition process as such and the physical and functional characterization of the thin films synthesized. Characteristic for reactive sputtering processes is the hysteresis due to the target poisoning. One particular finding in this work is the elimination of the hysteresis by means of a mixed nitrogen/oxygen processing environment for dual sputtering of Alumina-Zirconia thin films. For a constant moderate flow of nitrogen, the hysteresis could be eliminated without significant incorporation of nitrogen in the films. It is concluded that optimum processing conditions for films of a desired composition can readily be estimated by modeling. The work on reactively sputtered SiO2–TiO2 thin films provides guidelines as to the choice of process parameters in view of the application in mind, by demonstrating that it is possible to tune the refractive index by using single composite Six/TiO2 targets with the right composition and operating in a suitable oxygen flow range. The influence of the target composition on the sputter yield is studied for reactively sputtered titanium oxide films. It is shown that by using sub-stoichiometric targets with the right composition and operating in the proper oxygen flow range, it is possible to increase the sputter rate and still obtain stoichiometric coatings. Wurtzite aluminum nitride (w-AlN) thin films are of great interest for electro-acoustic applications and their properties have in recent years been extensively studied. One way to tailor material properties is to vary the composition by adding other elements. Within this thesis (Al,B)N films of the wurtzite structure and a strong c-axis texture have been grown by reactive sputter deposition. Nanoindentation experiments show that the films have nanoindentation hardness in excess of 30 GPa, which is as hard as commercially available hard coatings such as TiN. Electrical properties of w-(Al,B)N thin films were investigated. W-(Al,B)N thin films are found to have a dielectric strength of ~3×106 V/cm, a relatively high k-value around 12 and conduction mechanisms similar to those of AlN. These results serve as basis for further research and applications of w-(Al,B)N thin films. An AlN thin film bulk acoustic resonator (FBAR) and a solidly mounted resonator (SMR) together with a microfluidic transport system have been fabricated. The fabrication process is IC compatible and uses reactive sputtering to deposit piezoelectric AlN thin films with a non-zero mean inclination of the c-axis, which allows in-liquid operation through the excitation of the shear mode. The results on IC-compatibility, Q-values, operation frequency and resolution illustrate the potential of this technology for highly sensitive low-cost micro-biosensor systems for applications in, e.g. point-of-care testing.

Zugl.: Kassel, Univ., Diss., 2005

University, Diss., 2005--Kassel.

University, Diss., 2005--Kassel.

Zugl.: Kassel, Univ., Diss., 2005 / Download lizenzpflichtig

Universiẗat, Diss., 2005--Kassel. / Download lizenzpflichtig.

Techn. Universiẗat, Diss., 2005--Chemnitz.

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.

abstract: Micro-electro-mechanical systems (MEMS) film bulk acoustic resonator (FBAR) demonstrates label-free biosensing capabilities and is considered to be a promising alternative of quartz crystal microbalance (QCM). FBARs achieve great success in vacuum, or in the air, but find limited applications in liquid media because squeeze damping significantly degrades quality factor (Q) and results in poor frequency resolution. A transmission-line model shows that by confining the liquid in a thickness comparable to the acoustic wavelength of the resonator, Q can be considerably improved. The devices exhibit damped oscillatory patterns of Q as the liquid thickness varies. Q assumes its maxima and minima when the channel thickness is an odd and even multiple of the quarter-wavelength of the resonance, respectively. Microfluidic channels are integrated with longitudinal-mode FBARs (L-FBARs) to realize this design; a tenfold improvement of Q over fully-immersed devices is experimentally verified. Microfluidic integrated FBAR sensors have been demonstrated for detecting protein binding in liquid and monitoring the Vroman effect (the competitive protein adsorption behavior), showing their potential as a promising bio-analytical tool. A contour-mode FBAR (C-FBAR) is developed to further improve Q and to alleviate the need for complex integration of microfluidic channels. The C-FBAR consists of a suspended piezoelectric ring made of aluminum nitride and is excited in the fundamental radial-extensional mode. By replacing the squeeze damping with shear damping, high Qs (189 in water and 77 in human whole blood) are obtained in semi-infinite depth liquids. The C-FBAR sensors are characterized by aptamer - thrombin binding pairs and aqueous glycerine solutions for mass and viscosity sensing schemes, respectively. The C-FBAR sensor demonstrates accurate viscosity measurement from 1 to 10 centipoise, and can be deployed to monitor in-vitro blood coagulation processes in real time. Results show that its resonant frequency decreases as the viscosity of the blood increases during the fibrin generation process after the coagulation cascade. The coagulation time and the start/end of the fibrin generation are quantitatively determined, showing the C-FBAR can be a low-cost, portable yet reliable tool for hemostasis diagnostics. / Dissertation/Thesis / Ph.D. Electrical Engineering 2011