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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
21

Application of laser tracker technology for measuring optical surfaces

Zobrist, Tom L. January 2009 (has links)
The pages of this dissertation detail the development of an advanced metrology instrument for measuring large optical surfaces. The system is designed to accurately guide the fabrication of the Giant Magellan Telescope and future telescopes through loose-abrasive grinding. The instrument couples a commercial laser tracker with an advanced calibration technique and a set of external references to mitigate a number of error sources. The system is also required to work as a verification test for the GMT principal optical interferometric test of the polished mirror segment to corroborate the measurements in several low-order aberrations. A set of system performance goals were developed to ensure that the system will achieve these purposes. The design, analysis, calibration results, and measurement performance of the Laser Tracker Plus system are presented in this dissertation.
22

Ultrafast nonlinear optics of wide-gap II-VI quantum wells and polymeric materials

Bakarezos, Efthimios January 2000 (has links)
No description available.
23

Development of electronic materials for infra-red detector systems

McChesney, John-James Stuart Duncan January 1999 (has links)
Indium antimonide (InSb) and gallium antimonide (GaSb) are technologically important III-V semiconductor materials used in infrared detector systems. Yet, the application of these materials is to a certain extent limited, in that the techniques currently used for their growth are both expensive and problematic. Semiconductor electrochemical deposition, which has been successfully applied to the generation of II-VI semiconductor materials, may offer the prospect of overcoming such limitations. This work presents results that represent a significant contribution to the development of electrochemical methods for both InSb and GaSb thin film growth. The direct electrochemical co-deposition of InSb was achieved via the potentiostatic electrolysis of aqueous halide/citric acid electrolyte solutions, and for the first time, non-aqueous (ethylene glycol) electrolyte solutions containing the halides and tetraethylammonium chloride. This choice of solvents allowed the compound's deposition to be studied over a wide range of temperatures (RT to 185 °C). A first report was also made of the direct potentiostatic co-deposition of GaSb from an aqueous solution containing Ga[2](SO[4])[3] and SbCl[3].An extensive study was carried out on the relationship between the technique's fundamental growth parameters (temperature, deposition potential, solution composition etc.) and the film's compositional, crystallographic and morphological properties. The material's characterisation showed that there was tendency for the films to be non-stoichiometric. X-Ray diffraction patterns obtained from InSb films deposited from aqueous electrolyte solutions showed them to generally consist of two phases, the compound and, depending mostly on deposition potential, one of the elements. Films containing three phases, the compound and both elements, were deposited on Ti substrates from aqueous solutions and on to ITO substrates from non-aqueous solutions. These results were interpreted from both thermodynamic and kinetic viewpoints. This led to the conclusion that kinetic barriers to the formation of InSb still existed, even at the highest temperature used (~185 °C). In respect of GaSb, the compound's formation was complicated by a side reaction involving the evolution of H[2].New studies involving Scanning Electron Microscopy of the electrodeposited materials showed that they exhibited a nodular morphology, which can be explained in terms of the film's limiting current growth conditions. Energy Dispersive X-Ray Analysis (EDX) and Glow Discharge Optical Emission Spectroscopy (GDOES) identified indium chloride as a major impurity in the InSb films, especially those deposited from non-aqueous solutions. A mechanism for the incorporation of indium chloride was proposed, based on the physical entrapment of a precipitate of the compound.
24

Caracterização de tecidos biológicos através de tomografia por coerência óptica

FREITAS, ANDERSON Z. de 09 October 2014 (has links)
Made available in DSpace on 2014-10-09T12:53:15Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:58:23Z (GMT). No. of bitstreams: 0 / Tese (Doutoramento) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
25

Caracterização de tecidos biológicos através de tomografia por coerência óptica

FREITAS, ANDERSON Z. de 09 October 2014 (has links)
Made available in DSpace on 2014-10-09T12:53:15Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:58:23Z (GMT). No. of bitstreams: 0 / Neste trabalho implementamos dois sistemas de OCT, um deles utilizando fibras ópticas e um estágio de translação linear como sistema de deslocamento e foi desenvolvido no departamento de Física da Universidade Federal de Pernambuco. O outro sistema de OCT foi baseado um interferômetro de Michelson convencional, foi implementado no Centro de Lasers e Aplicações no Ipen utilizando a técnica de introdução de atraso com grade de difração e galvanômetro (fast Fourier Scanning), como sistema de varredura longitudinal. Foi implementado e um programa computacional para aquisição de dados automática, com geração das imagens de OCT em \"tempo real\". Com os sistemas desenvolvidos, foi possível detectar objetos imersos em meios espalhadores, detectar lesões de cáries induzidas in vitro quimicamente ou microbiologicamente, sendo este último um resultado original, além de avaliar a qualidade de restaurações dentárias. É importante destacar ainda que as alterações nas propriedades ópticas dos tecidos cariados podem ser detectadas pelo método de OCT muito antes de se tornarem aparentes aos métodos convencionais de detecção. Ela pode extrair informações quantitativas sobre a birrefringência do tecido, quando a técnica for sensível à polarização. Demonstramos que a análise de Fourier aplicada ao sinal de OCT permite detectar deslocamentos em sistemas periódicos e quase periódicos, abaixo do limite de resolução espacial definido pelo comprimento de coerência da fonte óptica. Com o auxílio desta metodologia aqui desenvolvida, mostramos que nosso sistema, com resolução de 10 ?m, é capaz de detectar variações em redes periódicas de algumas centenas de nanômetros entre as estruturas espalhadoras. Este desenvolvimento é uma contribuição inédita às aplicações de OCT. / Tese (Doutoramento) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
26

Transient electric birefringence of macromolecular systems

Rudd, P. J. January 1974 (has links)
The transient electric birefringence method, i. e. the transient Kerr effect, has been employed to study the optical, electrical and geometrical properties of three macromolecular systems. An apparatus is described in which the birefringence could be measured when d. c. electric field pulses (of duration 1μs to 5s and strength up to 50 KV/cm) and a. c. electric field pulses (of duration greater than 5 ms, of frequency up to 20 kHz, and strength up to 3 KV/Cm) were applied to solutions of macromolecules. Both the linear and quadratic optical systems have been employed to measure the induced birefringence. A theoretical analysis and review of the errors implicit in such measurements is given, with suggested alignment and calibration procedures. For the first time in electro-optic work, a data-logging system and computer program have been developed and employed, and enabled the automatic recording of transient responses with subsequent high speed data analysis. Measurements have been made on a polypeptide poly – β – benzyl – 1 – aspartate in two solvents. These show how the method can be used to study a rigid macromolecule. A novel investigation was made on the interaction of an anionic surfactant, sodium dodecyl sulphate, with a flexible polymer, polyvinylpyrrolidone. The large variation of Kerr constant observed with addition of surfactant indicated a great potential use of this method for studying polymer surfactant interactions. An aqueous suspension of the bacteria E. coli was also studied, but changes in turbidity and not birefringence were the origin of the observed effects. Novel practical methods of investigation, and turbidity calculations carried out with the aid of a computer enabled size parameters and electrical properties to be determined for E. coli. For the first time such results were in agreement with electro-optic light scattering measurements.
27

ADDITIVE MANUFACTURING TECHNOLOGIES FOR FLEXIBLE OPTICAL AND BIOMEDICAL SYSTEMS

Bongjoong Kim (10716684) 28 April 2021 (has links)
<p>Advances in additive manufacturing technologies enable the rapid, high-throughput generation of mechanically soft microelectromechanical devices with tailored designs for many applications spanning from optical to biomedical applications. These devices can be softly interfaced with biological tissues and mechanically fragile systems, which enables to open up a whole new range of applications. However, the scalable production of these devices faces a significant challenge due to the complexity of the microfabrication process and the intolerable thermal, chemical, and mechanical conditions of their flexible polymeric substrates. To overcome these limitations, I have developed a set of advanced additive manufacturing technologies enabling (1) mechanics-driven manufacturing of quasi-three-dimensional (quasi-3D) nanoarchitectures with arbitrary substrate materials and structures; (2) repetitive replication of quasi-3D nanoarchitectures for infrared (IR) bandpass filtering; (3) electrochemical reaction-driven delamination of thin-film electronics over wafer-scale; (4) rapid custom printing of soft poroelastic materials for biomedical applications. </p> <p>First, I have developed a new mechanics-driven nanomanufacturing method enabling large-scale production of quasi-3D plasmonic nanoarchitectures that are capable of controlling light at nanoscale length. This method aims to eliminate the need for repetitive uses of conventional nanolithography techniques that are time- and cost-consuming. This approach is innovative and impactful because, unlike any of the conventional manufacturing methods, the entire process requires no chemical, thermal, and mechanical treatments, enabling a large extension of types of receiver substrate to nearly arbitrary materials and structures. Pilot deterministic assembly of quasi-3D plasmonic nanoarrays with imaging sensors yields the most important advances, leading to improvements in a broad range of imaging systems. Comprehensive experimental and computational studies were performed to understand the underlying mechanism of this new manufacturing technique and thereby provide a generalizable technical guideline to the manufacturing society. The constituent quasi-3D nanoarchitectures achieved by this manufacturing technology can broaden considerations further downscaled plasmonic metamaterials suggest directions for future research.</p> <p>Second, I have developed mechanics-driven nanomanufacturing that provides the capability to repetitively replicate quasi-3D plasmonic nanoarchitectures even with the presence of an extremely brittle infrared-transparent spacer, such as SU-8, thereby manipulating IR light (e.g., selectively transmitting a portion of the IR spectrum while rejecting all other wavelengths). Comprehensive experimental and computational studies were performed to understand the underlying nanomanufacturing mechanism of quasi-3D plasmonic nanoarchitectures. The spectral features such as the shape of the transmission spectrum, peak transmission and full width at half maximum (FWHM), etc. were studied to demonstrate the bandpass filtering effect of the assembled quasi-3D plasmonic nanoarchitecture.</p> <p>Third, I have developed an electrochemical reaction-driven transfer printing method enabling a one-step debonding of large-scale thin-film devices. Conventional transfer printing methods have critical limitations associated with an efficient and intact separation process for flexible 3D plasmonic nanoarchitectures or bio-integrated electronics at a large scale. The one-step electrochemical reaction-driven method provides rapid delamination of large-scale quasi-3D plasmonic nanoarchitectures or bio-integrated electronics within a few minutes without any physical contact, enabling transfer onto the target substrate without any defects and damages. This manufacturing technology enables the rapid construction of quasi-3D plasmonic nanoarchitectures and bio-integrated electronics at a large scale, providing a new generation of numerous state-of-art optical and electronic systems.</p> <p>Lastly, I have developed a new printing method enabling the direct ink writing (DIW) of multidimensional functional materials in an arbitrary shape and size to rapidly prototype stretchable biosensors with tailored designs to meet the requirement of adapting the geometric nonlinearity of a specific biological site in the human body. Herein, we report a new class of a poroelastic silicone composite that is exceptionally soft and insensitive to mechanical strain without generating significant hysteresis, which yields a robust integration with living tissues, thereby enabling both a high-fidelity recording of spatiotemporal electrophysiological activity and real-time ultrasound imaging for visual feedback. Comprehensive <i>in vitro</i>, <i>ex vivo</i>, and <i>in vivo</i> studies provide not only to understand the structure-property-performance relationships of the biosensor but also to evaluate infarct features in a murine acute myocardial infarction model. These features show a potential clinical utility in the simultaneous intraoperative recording and imaging on the epicardial surface, which may guide a definitive surgical treatment.</p>
28

Optical Orbital Angular Momentum from 3D-printed Microstructures for Biophotonics Applications

Reddy, Innem V.A.K. 11 1900 (has links)
This work aims to implement 3D microstructures that generate light with orbital angular momentum towards applications in Biophotonics. Over the past few decades, 3D printing has established itself as the most versatile technology with effortless adaptability. Parallel to this, the concept of miniaturiza tion has seen tremendous growth irrespective of the field and has become an estab lished trend motivated by the need for compact, portable and multi-function devices. Therefore, when these two concepts get together, i.e., 3D printing of miniaturized objects, it could lead to an exciting path with endless opportunities. When it comes to optics, miniaturized 3D printing offers the potential to create compact optical micro-systems and exhibits a way to manufacture freeform µ-optics. In particular, two-photon lithography (TPL) is a cutting edge 3D printing technology that has re cently demonstrated groundbreaking solutions for optics as it offers high resolution with a great degree of flexibility. With a TPL 3D printer, it is possible to fabricate complex µ-optical elements and employ them for compelling applications. In recent years, light with orbital angular momentum (OAM), or ”twisted” light, has captured the interests of several researchers due to its inspiring applications. Tra ditionally, to generate OAM beams, one would require bulk, table-top optics, restrict ing their applications to over-the-table setup. An alternative approach of OAM beam generation is through µ-structures over the fiber, as they can open up new opportu nities, especially in Bioscience, and facilitate in-vivo operations. In particular, this probe-like setup can be used for processes such as optical trapping, high-resolution microscopy, etc. Hence, I propose the development of a novel approach with un precedented capabilities for generating OAM beams right from single-mode optical fibers, by transforming its Gaussian-like output beam by using complex 3D printed microstructures. In this document, I will showcase designs and results on generating Bessel beams (both zeroth- and high-order) and high-NA converging beams (with and without OAM) for optical trapping from the fiber. Remarkably, I achieved the first-ever fiber-based high-order Bessel beam generation and the first-ever fiber optical tweezers with OAM.
29

Analysis and Comparison of System Performance Using Different Modulation Schemes for Long-Haul Optical Systems and Fiber-To-The-Home Passive Optical Networks

Zhu, Xianming 08 1900 (has links)
<p> Analytical expressions for the propagation impairments due to various noise sources in long-haul optical systems and fiber-to-the-home passive optical networks have been obtained. Extensive comparison has been made in this thesis for systems based on different modulation formats, and the advantage of one over the other is clearly stated.</p> <p> For long-haul fiber optical communication systems with inline amplifiers, we have studied the statistical properties of various noise sources in systems based on differential phase-shift keying (DPSK) such as the linear phase noise induced by the amplifier spontaneous emission (ASE) noise, the intra-channel four-wave mixing (IFWM) and the nonlinear phase noise induced by the interplay between ASE noise and fiber Kerr nonlinearity. The error probability of the system based on DPSK is evaluated semi-analytically. In addition, the error probability of the system based on on-off keying (OOK) is calculated taking into account the effects of ASE noise, and the intra-channel nonlinearities such as IFWM and intra-channel cross-phase modulation (IXPM). Comparison of the performance of systems based on DPSK and OOK is made thereafter.</p> <p> For fiber-to-the-home passive optical networks without inline active photonic devices, different modulation formats have been examined for the downstream and upstream data to enable full-duplex transmission. The statistical properties of Rayleigh backscattering in single-source bi-directional optical systems have been studied including the effects of the high speed external modulation signal and the laser phase noise for systems based on DPSK and OOK. The error probabilities for systems using OOK/OOK topology and DPSK/OOK topology for downstream/upstream transmission have been evaluated and compared.</p> <p> In addition, the interplay of the amplifier spontaneous emission noise, fiber nonlinearity and dispersion has been examined starting from the nonlinear Schrödinger equation on the receiver current fluctuation. The variance of the current noise has been evaluated analytically using the two dimensional perturbation theory.</p> / Thesis / Master of Applied Science (MASc)
30

Radiation-hard optoelectronic data transfer for the CMS tracker

Troska, Jan Kevin January 1999 (has links)
No description available.

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