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Thesis (M.S.)--Ohio University, June, 1986. / Title from PDF t.p.

The purpose of this thesis is to design and fabricate optical waveguide reflectors by the etched vertical mirror surfaces. In order to reflect the incident optical mode of multi-mode interference coupler, we fabricate the etched vertical reflective mirror surface with wet etch and dry etch processes. We used the design of etched vertical mirror surfaces to bend the incident optical mode, and changed the length of multi-mode interference coupler for the power splitting ratio and high power output. In order to reduce bending and transition losses and make the incident optical mode total internal reflection in the etched vertical mirror surfaces, we used ICP-RIE dry etch process to add the depth about 4 µm of the etched vertical mirror surfaces. A 1.52 µm symmetric multiple quantum well InGaAlAs/InGaAs epitaxial wafer is used to fabricate the devices. In the device design, we designed optical waveguide reflectors of one input and two inputs respectively, and utilized them to fabricate Fabry-Perot lasers. We also utilized a reflector of one input and two inputs directly to fabricate a Fabry-Perot laser. In addition, We fabricated a Fabry-Perot laser by two reflectors with 90¢X angle corner, a 1x2 3dB multi-mode interference coupler and a ring resonator. In fabrication process, firstly, we etched the epitaxial wafer the depth of about 1.79µm by multi-step wet etch to form waveguides. In order to reduce bending loss, we made deep etching for the outside of curve waveguides and optical waveguide reflectors. Then, we etched the reflective mirror to the depth of about 4µm by ICP-RIE dry etch process to have a greater variation of refractive index to reflect the optical mode of reflectors. Finally, we used polyimide to flatten the sides of the ridge waveguides and evaporated metal pad over the ridge waveguides to form the signal pad.

abstract: Demand for green energy alternatives to provide stable and reliable energy solutions has increased over the years which has led to the rapid expansion of global markets in renewable energy sources such as solar photovoltaic (PV) technology. Newest amongst these technologies is the Bifacial PV modules, which harvests incident radiation from both sides of the module. The overall power generation can be significantly increased by using these bifacial modules. The purpose of this research is to investigate and maximize the effect of back reflectors, designed to increase the efficiency of the module by utilizing the intercell light passing through the module to increase the incident irradiance, on the energy output using different profiles placed at varied distances from the plane of the array (POA). The optimum reflector profile and displacement of the reflector from the module are determined experimentally. Theoretically, a 60-cell bifacial module can produce 26% additional energy in comparison to a 48-cell bifacial module due to the 12 excess cells found in the 60-cell module. It was determined that bifacial modules have the capacity to produce additional energy when optimized back reflectors are utilized. The inverted U reflector produced higher energy gain when placed at farther distances from the module, indicating direct dependent proportionality between the placement distance of the reflector from the module and the output energy gain. It performed the best out of all current construction geometries with reflective coatings, generating more than half of the additional energy produced by a densely-spaced 60-cell benchmark module compared to a sparsely-spaced 48-cell reference module.ii A gain of 11 and 14% was recorded on cloudy and sunny days respectively for the inverted U reflector. This implies a reduction in the additional cells of the 60-cell module by 50% can produce the same amount of energy of the 60-cell module by a 48-cell module with an inverted U reflector. The use of the back reflectors does not only affect the additional energy gain but structural and land costs. Row to row spacing for bifacial systems(arrays) is reduced nearly by half as the ground height clearance is largely minimized, thus almost 50% of height constraints for mounting bifacial modules, using back reflectors resulting in reduced structural costs for mounting of bifacial modules / Dissertation/Thesis / Masters Thesis Mechanical Engineering 2019

Radar plays a major role in safety-critical applications mainly in the automotive industry due to its weather and lighting independence. The progress made in radar hardware technology has made it possible to detect objects more efficiently. Autonomous vehicles need to address a lot of problems encountered in their pathways which need proper detection and identification of obstacles for navigation purposes. Detection and identification of obstacles during navigation help in defining the trajectories for a vehicle so that collision can be avoided. A 77GHz radar system is used in many automotive industrial vehicles for automotive safety. At any given time, there is a possibility of multiple objects being in the vicinity of a vehicle that is not highly reflective which is based on its materialistic properties, such as prams or bicycles as compared to other road vehicles. In the work described in this thesis, we aim at designing, detecting, and identifying simple radar reflectors using copper sheets, which can be placed on such low reflective objects which helps in increasing pedestrian safety aspects. The software aspect of the radar module being used is achieved by using a demo application provided by the radar module manufacturer. This acts as the base structure for the python script which is used for detection and identification of the radar reflectors.

Made available in DSpace on 2014-10-09T12:28:30Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:56:15Z (GMT). No. of bitstreams: 0 / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

Made available in DSpace on 2014-10-09T12:28:30Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:56:15Z (GMT). No. of bitstreams: 0 / Na montagem de um farol automobilístico são utilizados diversos materiais, tais como insertos metálicos nas fixações, vidros nas lâmpadas, materiais poliméricos nas lentes, carcaças, molduras, vedações e refletores, além de vernizes, tintas, película de metal para reflexão do feixe luminoso. Há cerca de quatro décadas foi iniciada a confecção dos refletores utilizando o BMC (bulk moulding compound), sigla em inglês para composto para moldagem em forma de massa, que é um compósito polimérico termofixo. Este material apresenta inúmeras vantagens sobre o metal, tal como forma e geometria que podem se integrar facilmente ao desenho do carro, elevada produtividade, baixo custo e da elevada resistência térmica. Contudo, apresentam o inconveniente de não poderem ser reciclados. Uma opção ao BMC tem sido o PEI [poli (éter imida)], que é um material polimérico termoplástico de alto desempenho que apresenta propriedades atrativas para essa utilização. Oferece também elevada produtividade, porém com um custo elevado se comparado ao BMC. Tem a vantagem de pode ser reciclado. De modo a analisar o potencial dos dois materiais e extrair deles suas vantagens competitivas, bem como determinar suas possíveis limitações, o presente trabalho apresenta os resultados de caracterização mecânica, análise térmica, ensaios de impacto, ensaios de temperatura de deflexão térmica (HDT) e reaproveitamento de resíduos de BMC, incorporando-o ao PVC [poli (cloreto de vinila)], resultando uma nova blenda polimérica. O estudo conclui que ambos os materiais podem ser utilizados para fabricação de refletores automobilísticos. No entanto, o preço do PEI é maior que o do BMC, o que desestimula sua utilização em produtos de alta escala de produção, como, por exemplo, o produto do presente trabalho. O BMC por sua vez não pode ser reciclado, exigindo um custo adicional para seu reaproveitamento de maneira a evitar seu descarte em aterro sanitário. / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

Wurtzite III-nitride semiconductor materials have many technically important applications in optical and electronic devices. As GaN-based visible light-emitting diodes (LEDs) and lasers starts to mature, interest in developing UV devices starts to rise. The search for materials with larger bandgaps and high refractive index contrast in the UV range has inspired multiple studies of BN-based materials and their alloys with traditional III-nitrides. Additionally, alloying III-nitrides with boron can reduce their lattice parameters giving a new option for strain engineering and lattice matching. In this work I investigate the refractive indices of BAlN and BGaN over the entire compositional range using hybrid density functional theory (DFT). An interesting non-linear trend of the refractive index curves appears as boron content is increased in the BAlN and BGaN alloys. The results of this calculation were interpolated and plotted in three dimensions for better visualization. This interpolation gives a 3D dataset that can be used in designing a myriad of devices at all binary and ternary alloy compositions in the BAlGaN system. The interpolated surface was used to find an optimum design for a strain-free, high reflection coefficient and high bandwidth DBR. The performance of this DBR was quantitatively evaluated using finite element simulations. I found that the maximum DBR reflectivity with widest bandwidth for our materials occurs at a lattice parameter of 3.113 Å using the generated 3D dataset. I use the corresponding material pair to simulate a DBR at the wavelength 375 nm in the UVA range. A design with 25 pairs was found to have a peak reflectivity of 99.8%. This design has a predicted bandwidth of 26 nm measured at 90% peak performance. The high reflectivity and wide bandwidth of this lattice-matched design are optimal for UVA VCSEL applications. I have assisted in exploring different metalorganic chemical vapor deposition (MOCVD) techniques, continuous growth and pulsed-flow modulation, to grow and characterize BAlN alloys. Samples grown using continuous flow show better optical quality and are characterized using spectroscopic ellipsometry. The refractive index of samples obtained experimentally is significantly below the predicted value using DFT.

Reflectivity images of the lower crust and uppermost mantle beneath the Illinois basin have been derived from reprocessing of several hundred kilometers of industry seismic reflection data using extended vibroseis recorrelation. The recorrelation was based on extending an originally 4-s correlated record, acquired with a 16-s sweep from 14 to 126 Hz, to the absolute limit of the full 20 s (~70 km) listening travel time. The reconstructed bandwidth includes frequency components suitable for imaging structures from signals received from both sedimentary basin reflectors and those received from reflectors in the deep crust and upper mantle. Mantle and sub-Moho reflectors are imaged down to 18 s two-way travel time (~62 km) and are observed on intersecting profiles generally dipping to the southwest and striking northwest-southeast. Occasional Moho reflections are also observed across the profiles (~12 s or ~38 km) while reflectivity in the lower crust is generally marked by intermittent horizontal packages and short, gently dipping reflections and diffraction segments. The presence of newly observed mantle reflectivity beneath the Illinois basin indicates significant upper mantle heterogeneity, relative to other parts of the USA studied using reflection methods. The relatively isolated occurrence of mantle reflections beneath the basin makes it difficult to uniquely infer their origin. However, available geologic and geophysical constraints, especially from geochemical and geochronological studies of drilled basement rocks, effectively limit the possibilities to: (1) remnants or "scars" of sub-crustal processes associated with lithospheric extension or delamination related to the melting of the Proterozoic crust that led to the emplacement of the granite--rhyolite province that underlies much of USA Midcontinent; or (2) deformation caused by plate subduction associated with the hypothetical accretion of a juvenile arc to the pre-1.6 Ga southern margin of the Laurentian continent.

This project successfully designed, fabricated and characterized two highly reflective distributed Bragg reflectors for use with long wavelength vertical cavity surface emitting lasers. The first reflector consisted of 20 pairs of alternating lnP/Ino.64Gao.36Aso.777Po.223 layers grown on an InP substrate with a theoretically predicted normal incident reflectivity of 96.6% at a center wavelength of 1550nm. The second DBR had 20 pairs of alternating GaAs/Ino.484Gao.5i6P layers grown on a GaAs substrate with a theoretically predicted reflectivity of 94.9% at a center wavelength of 1550nm for normal incident light. Experimental results obtained using a specially designed reflectivity measurement setup confirmed reflectivity models and predictions at both normal and variable incident light angles. However, these measurements revealed a discrepancy between theoretical and experimental layer thickness values for both DBR structures. Applying perturbations to the theoretical models, the actual layer thicknesses ofthe DBRs were determined. X-ray analysis was employed to examine the periodicity of the super-lattices along with the accuracy of lattice matching to the substrate. Transmission electron microscopy revealed that no detectable drift in layer thickness was apparent during growth of the DBR structures. Photoluminescence was used to investigate any compositional variations ofthe quaternary layers in the first DBR stack. / Thesis / Master of Applied Science (MASc)