<p>Optical waveguide is a very important component in numerous optical structures, devices and photonic circuits. With the rapid development of fabrication technologies, increasing integrated complexity and different materials characteristics, there is higher demand on high-index contrast waveguide with arbitrary cross section and anisotropic material, which indicates the need to develop an efficient, high-performance mode solver to analyze optical waveguides to reduce the fabrication cycle and total cost. Modeling and simulation methods, including Finite Difference Time-Domain (FDTD) method, Finite Element Method (FEM), Beam Propagating Method (BPM), Mode Matching Method (MMM) and Couple Mode Theory (CMT), etc, have been popular for years. Among those methods, FEM is a good and efficient method, especially for its superiority on arbitrary meshes.</p> <p>In this thesis, both scalar and vectorial FEM mode solvers are implemented with an emphasis on dealing with the radiation and evanescent modes by enclosing the whole region with the Perfect Matched Layer (PML) and Perfect Reflecting Boundary (PRB). Thus, the unbounded and continuous radiation modes together with evanescent modes are replaced by what we called "complex modes", but still keeping the completeness and orthogonality properties.</p> / Master of Applied Science (MASc)

<p> The purpose of this study is to design, fabricate and test a CMOS compatible 3-axis Hall effect sensor capable of detecting the earth&rsquo;s magnetic field, with strength&rsquo;s of &sim;50 &mu;T. Preliminary testing of N-well Van Der Pauw structures using strong neodymium magnets showed proof of concept for hall voltage sensing, however, poor geometry of the structures led to a high offset voltage. A 1-axis Hall effect sensor was designed, fabricated and tested with a sensitivity of 1.12x10^-3 mV/Gauss using the RIT metal gate PMOS process. Poor geometry and insufficient design produced an offset voltage of 0.1238 volts in the 1-axis design; prevented sensing of the earth&rsquo;s magnetic field. The new design features improved geometry for sensing application, improved sensitivity and use the RIT sub-CMOS process. The completed 2-axis device showed an average sensitivity to large magnetic fields of 0.0258 &mu;V/Gauss at 10 mA supply current.</p>

No description available.

<p>A new external microprobe beamline for irradiation experiments has been commissioned and constructed at the Louisiana Accelerator Center. This microprobe was designed to use the Oxford Triplet lens con?guration with no scanning system. The beamline was designed to allow for the post focus expansion of the ion beam to create an even ?led of current distribution at a sample. The samples are irradiated in air in a glove box so that a Biosaftey-Level 2 (BSL-2) environment is created, reducing risk of contamination for biological sample irradiation. The nature of a microprobe allows the ?ux, and therefore the dose, to be su?ciently low for space radiation studies. The beamline was designed using WinTRAX [18] and constriction has been completed. This thesis is an overview of what a microprobe is, how the new microprobe was designed, and how the beamline was constricted.

Photoelasticity is an optical technique that measures the difference of the principal stresses plus the principal stress direction. A complementary technique is thermoelasticity which measures the sum of the principal stresses. Combining these two full-field, non-contact nondestructive evaluation techniques allows the individual stress components to be measured. One of the main difficulties in merging these two measurement systems is in identifying an appropriate surface coating. Thermoelasticity demands a highly emissive surface, while photoelasticity requires a thick, stress-birefringent, transparent coating with a retro-reflective backing. Two coatings have been identified that can be used for combined thermoelastic and photoelastic stress measurements: PMMA and polycarbonate.;An anisotropic electromagnetic boundary value model was developed to understand more fully the mechanisms through which photoelastic stress patterns are produced. This model produced intensity contour maps which matched the fringe patterns observed in the laboratory, and allowed the effect of measurement errors on the calculated stress tensor to be quantified. One significant source of error was the retro-reflective backing, which depolarized the light and degraded the resulting photoelastic fringes. A quantitative analysis of the degraded fringes, to be used as a rating scheme for reflective backing materials, showed that the isoclinic lines shift position as a result of the backing roughness and oblique incidence. This is a concern when calculating the stress components through the combination of photoelasticity and thermoelasticity because the data maps are integrated at the pixel level. Small shifts in the photoelastic fringes result in incorrect information being assigned to some pixels and hence lead to uncertainties in the stress tensor components. Progress in the understanding of the depolarization at the reflective backing allows the specification of new materials that will minimize this effect, as well as the development of robust computer algorithms to correct for any remaining depolarization.

Over the last several decades, two methods have emerged as the standard tools for the calculation of electronic band structures. These methods, the Car-Parinello plane wave method and the linear augmented plane wave method (LAPW), each have strengths and weaknesses in different regimes of physical problems. The Car-Parinello algorithm is ideal for calculations with soft pseudopotentials and large numbers of atoms. The LAPW method, on the other hand, easily handles all-electron and hard-core pseudopotential calculations with a small number of atoms. The projector basis method, presented here, is a hybrid mixed basis method which allows the calculation of moderately large ({dollar}\sim{dollar}200) numbers of atoms represented by hard pseudopotentials. This method will then be used to calculate two members of a relatively new mass of materials, called electrides, in which the anion has been replaced with a localized electron.

The conversion from low speed to high speed and vice versa in various forms, including rotary and linear motion, is a requirement for a wide range of applications. For example, wind power generation requires a conversion of low speed rotation of turbine blades to high speed generator rotation, and ocean wave power generation is achievable by conversion of low speed linear motion to either high speed rotation or high speed linear motion. Mechanical gearboxes, hydraulic and pneumatic actuators are commonly used to achieve these conversions. However, these systems suffer from reliability issues, high maintenance requirements, noise, and lack of overload protection. As an alternative, electromagnetic actuators overcome most of the issues related to the mechanical, hydraulic and pneumatic mechanisms. However, magnetic shear stress is constraint by current density and magnetic saturation. Recently, magnetic gearboxes have been proposed, which rely only on magnetic loading. They provide speed and force conversion like their mechanical counterparts, but without thermal constraints (current density limits). Unlike mechanical gears, magnetic gear contact-less operation enables it to operate without lubrication and with low noise, and higher efficiency. Its reliance on magnetic loading also provides overload protection. This dissertation focuses on investigating two new types of magnetic gears; first a magnetically-geared lead screw is proposed, which converts a low speed linear motion to a high speed rotary motion. The proposed actuator is a combination of two previously proposed actuators, the linear magnetic gear and the magnetic lead screw. Unlike these two topologies, the translator part of the proposed magnetically geared lead screw is made entirely of low-cost ferromagnetic steel. Therefore, the translator stroke length can be long without requiring more magnet material. In the second part of this dissertation, an axial flux magnetic gear is proposed that has an integrated outer stator. This axial flux magnetically-geared motor is unique in that the stator shares the high-speed rotor with the magnetic gear, so there is no need for a separate rotor. The high speed and low speed rotors use a flux-focusing typology. The stator is mounted outside the axial flux magnetic gear. This makes the design mechanically less complex. It also enables the stator to be cooled more easily. In the last part of this dissertation, analytical-based models are proposed for a linear permanent magnet coupling and magnetic lead screw. These models help to find the upper bound of the similar devices, which require a scaling analysis. Numerical methods like finite element analysis are accurate and effective enough for modeling various electromechanical and electromagnetic devices. However, these simulations are usually computationally expensive; they require a considerable amount of memory and time, especially when considering 3D finite element simulation. The proposed analytical models offer exact field solution while significantly reducing the computational time. Detailed analysis of two magnetic gears is given under their corresponding chapters. Preliminary experimental results are also provided. The analytical-based model is presented and verified by FEA results. A summary of research contributions and future works is outlined.

No description available.

In this work we investigated a new class of subwavelength focusing device, termed the holographic metallic screen. We first proposed a generalized procedure which takes a holographic record of a subwavelength electromagnetic field distribution. Subsequently we synthesized this record using two types of holographic metallic screen – the slot antenna hologram (SAH) and the resonant slot antenna hologram (RSAH). We designed both holograms and evaluated their performances through full-wave simulations, and experimentally demonstrated subwavelength focusing for the RSAH. Simulations and experiments illustrated various attractive properties of the subwavelength focusing RSAH, which included (a) a tighter focal width than a single subwavelength aperture; (b) a focal field amplitude surpassing the incident field amplitude; and (c) a simple design scalable to a wide range of frequencies from microwave to optical. These properties should serve to motivate further development on the holographic metallic screen towards potential applications such as sensing, imaging and lithography.

In this work we investigated a new class of subwavelength focusing device, termed the holographic metallic screen. We first proposed a generalized procedure which takes a holographic record of a subwavelength electromagnetic field distribution. Subsequently we synthesized this record using two types of holographic metallic screen – the slot antenna hologram (SAH) and the resonant slot antenna hologram (RSAH). We designed both holograms and evaluated their performances through full-wave simulations, and experimentally demonstrated subwavelength focusing for the RSAH. Simulations and experiments illustrated various attractive properties of the subwavelength focusing RSAH, which included (a) a tighter focal width than a single subwavelength aperture; (b) a focal field amplitude surpassing the incident field amplitude; and (c) a simple design scalable to a wide range of frequencies from microwave to optical. These properties should serve to motivate further development on the holographic metallic screen towards potential applications such as sensing, imaging and lithography.