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Tesi sul tema "Beam optics"
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1
McLaughlin, Lisa. "Optical beam control using adaptive optics." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2005. http://library.nps.navy.mil/uhtbin/hyperion/05Dec%5FMcLaughlin.pdf.
Testo completoAbstract (sommario):
Thesis (M.S. in Astronautical Engineering)--Naval Postgraduate School, December 2005.<br>Thesis Advisor(s): Brij Agrawal, Ty Martinez. Includes bibliographical references (p. 75-76). Also available online.
2
Corley, Melissa S. "Maritime adaptive optics beam control." Monterey, California. Naval Postgraduate School, 2010. http://hdl.handle.net/10945/10559.
Testo completoAbstract (sommario):
The Navy is interested in developing systems for horizontal, near ocean surface, high-energy laser propagation through the atmosphere. Laser propagation in the maritime environment requires adaptive optics control of aberrations caused by atmospheric distortion. In this research, a multichannel transverse adaptive filter is formulated in Matlab's Simulink environment and compared to a complex lattice filter that has previously been implemented in large system simulations. The adaptive filters are used to augment a classical adaptive optics controller and are also compared to a Kalman filter augmenting a classical controller. Additionally, the Naval Postgraduate School's first laboratory testbed to use adaptive optics for the compensation of atmospheric turbulence is designed and built. The control algorithms are evaluated both in simulation and in the presence of a laboratory-generated disturbance. Finally, effects of horizontal propagation through deep turbulence are created in the lab. Beam control algorithms are tested in this environment to draw initial conclusions about performance in deep turbulence. For the system implemented in this research, the simple transverse filter in combination with a classical proportional-integral controller performs comparably to the complex lattice filter and the Kalman filter in a standard turbulence scenario and demonstrates more robust performance in the deep turbulence scenario. The adaptive optics testbed itself can be transitioned easily between traditional and deep turbulence scenarios and can support a wide range of atmospheric realizations for further beam control research.
3
Münnich, Matthias. "Beam Deflection." Master's thesis, University of Central Florida, 2013. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/5823.
Testo completoAbstract (sommario):
In order to fully understand the third order nonlinear optical response of materials under high irradiance excitation it is necessary to study the temporal and polarization dependence of nonlinear refraction and absorption. There are several existing approaches such as Z-scan and pump-probe techniques to determine those responses. As part of this work, these approaches will be briefly outlined before presenting beam deflection, applied from photothermal beam deflection, as an alternative experimental technique to determine the nonlinear refraction with its temporal and polarization dynamics. This technique measures the angle of the probe beam deflected via the index gradient of the material induced by strong excitation beam, to determine both the sign and magnitude of the nonlinear refraction. The temporal and tensor properties of the nonlinear refractive index can be determined by introducing a delay line, and by varying the polarization of the excitation and probe beam, respectively. To demonstrate the practicality of the beam deflection technique, we performed measurements on Fused Silica, Carbon Disulfide and Zinc Oxide. Each of these samples shows quite different nonlinear responses. Amorphous fused silica exhibits nonlinear refraction purely from instantaneous electronic contribution; while Carbon Disulfide shows a much slower response, originating not only from the electronic contribution but also from non-instantaneous nuclear movements (e.g. molecular orientation). These two contributions can be separated by varying the polarization direction of the excitation and probe beam. By introducing lock-in detection technique, a sensitivity of /5500 can be achieved. In Zinc Oxide, a wide-bandgap semiconductor, we measure both nonlinear refraction and two-photon absorption simultaneously. Therefore the beam deflection is a sensitive technique, which can be used to measure the time and polarization dynamics of the nonlinear response of the material.<br>M.S.<br>Masters<br>Optics and Photonics<br>Optics and Photonics<br>Optics; International
4
Evans, Jonathan W. "Beam Switching of an Nd:YAG Laser Using Domain Engineered Prisms in Magnesium Oxide Doped Congruent Lithium Niobate." University of Dayton / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1281366442.
Testo completo
5
Eckhardt, Stephen Karl. "Beam propagation and shift-variant optics." Diss., The University of Arizona, 1990. http://hdl.handle.net/10150/185110.
Testo completoAbstract (sommario):
The goal of the research described in this dissertation is to be able to model propagation of light through shift-variant optics. Shift-variant optical elements have a point spread function which is a function of the transverse coordinates. This shift-variance can be caused by aberration or by the first order properties of the optical system. In this work the latter is emphasized. Specifically, this dissertation discusses propagation through lenses and prisms and between tilted planes or a plane and a spherical surface. Extension to other types of shift-variant optical elements is possible. Two methods for performing the propagation are described. One, the beam division model, divides the beam into isoplanatic patches, separately propagates the patches and recombines them on the observation surface. The second method, the mapping model, maps the beam into a space in which the propagation is shift-invariant, propagates and then maps back into real space. Experimental verification of these methods is demonstrated by means of the Talbot effect. The setup consists of a collimated laser beam passing through a Ronchi ruling of about ten cycles per millimeter. With no intervening optics, Talbot images of the ruling are formed which are parallel to the wavefronts. When a prism at minimum deviation is placed in the outgoing beam, it causes the Talbot images to be tilted with respect to the wavefronts. If a stigmatic unit magnification telescope replaces the prism, the Talbot images are formed on surfaces congruent to the Petzval surface.
6
李銘 and Ming Li. "Optical studies of a slow-position beam." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1995. http://hub.hku.hk/bib/B31213364.
Testo completo
7
Li, Ming. "Optical studies of a slow-position beam /." Hong Kong : University of Hong Kong, 1995. http://sunzi.lib.hku.hk/hkuto/record.jsp?B17310970.
Testo completo
8
Penner, Robert Scott. "Focusing, wavelength tuning, beam steering and beam shaping of circular grating surface emitting distributed Bragg reflector lasers." Diss., The University of Arizona, 1999. http://hdl.handle.net/10150/284042.
Testo completoAbstract (sommario):
Over the past decade, circular grating surface emitting DBR lasers (CGSELs) have progressed from theory to reality. These devices possess several properties that make them attractive options for such applications as optical interconnects and laser arrays. These advantages include low divergence angles, circular beam profiles, and high power output. In this dissertation, the addition of new functionality to these lasers including wavelength tunability, focusing, beam steering and beam shaping is investigated. The theory governing device operation is presented. Pertinent discussions include the coupled mode equations, grating coupling, focusing and changes to the effective index of refraction resulting from current injection through a transparent electrode on the grating. The development and refinement of the device fabrication process is detailed. Key milestones in the grating writing process included achieving first order gratings (Λ = 0.15 μm), creating chirped period gratings for focusing and optimizing the linewidth and uniformity of the grating for high power devices. Of equal importance in obtaining high efficiency devices was the reactive ion etch process. Two different etch recipes were developed: one for mesa-definition and a shallower grating-defining etch. Significant evaluation of the electrical and optical properties of the transparent electrode, Indium Tin Oxide, was performed. Incorporating ITO into the fabrication process required optimization of deposition, patterning, etching and annealing. Device performance, efficiency and functionality improved with each generation. Consequentially, over 225 mW of output power for a injection current of 600 mA, or a slope efficiency of 0.43 mW/mA, was produced by the final generation of high power CGSELs. Focusing was demonstrated by the creation of individual devices with different focal lengths. Coarse mode selection was obtained by removing radial segments of the circular grating thereby eliminating both feedback coupling and surface outcoupling. Dynamic functionality such as beam steering and wavelength tuning was also realized for devices with ITO. Over 1° of beam steering was achieved for an ITO injection current of 35 mA. Similarly, over 1 nm of tuning, or 0.5 nm of continuous tuning, was accomplished. In conclusion, possibilities for improvements in device performance and future work are suggested.
9
Porembski, Joseph Paul. "Optical Beam Steering using a MEMS-driven White Cell." The Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1267553518.
Testo completo
10
Mourka, Areti. "Probing the modal characteristics of novel beam shapes." Thesis, University of St Andrews, 2014. http://hdl.handle.net/10023/4287.
Testo completoAbstract (sommario):
In this thesis, an investigation into the modal characteristics of novel beam shapes is presented. Sculpting the phase profile of a Gaussian beam can result in the generation of a beam with unique properties. Described in this thesis are Laguerre-Gaussian (LG), Hermite-Gaussian (HG) and Bessel beams (BBs). The diffraction of LG beam modes from a triangular aperture is explored and this effect can be used for the efficient measurement of the azimuthal mode index l that indicates the number of multiples of 2π of phase changes that the field displays around one circumference of the optical axis. In this study, only LG beams with zero radial mode index p, with p + 1 denoting the number of bright high intensity concentric rings around the optical axis, were considered. Then, a powerful approach to simultaneously determine both mode indices of a pure LG beam using the principal component analysis (PCA) algorithm on the observed far-field diffraction patterns was demonstrated. Owing to PCA algorithm, the shape of the diffracting element used to measure the mode indices is in fact of little importance and the crucial step is ‘training' any diffracting optical system and transforming the observed far-field diffraction patterns into the uncorrelated variables (principal components). Our PCA method is generic and it was extended to other families of light fields such as HG, Bessel and superposed beams. This reinforces the widespread applicability of this method for various applications. Finally, both theoretically and experimentally investigations using interferometry show the definitive linkage between both the radial and azimuthal mode indices of a partially coherent LG beam and the dislocation rings in the far-field cross-correlation function (CCF).
11
Mokhov, Sergiy V. "Theoretical study of beam transformations by volume diffraction." Doctoral diss., University of Central Florida, 2011. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/4986.
Testo completoAbstract (sommario):
Laser beams can be manipulated by volume diffractive elements in addition to conventional optical elements like mirrors, lenses, and beam splitters. Conventional optical elements can be described by applying the basic laws of reflection and refraction at the surfaces of the elements. Even diffraction by surface gratings utilizes relatively simple mathematics. This is to be contrasted with the volume diffraction, which requires coupled wave theory in the slowly varying envelope approximation (SVEA) to obtain accurate results. Efficient spatially distributed diffraction of laser beams is possible due to the high coherence of laser light, and it occurs at specific resonant Bragg conditions. This research work is inspired and driven by the successful development of recording technology for robust, high-efficiency volume Bragg gratings (VBGs) in photo-thermo-refractive (PTR) glass. Mostly VBGs of the reflective type are discussed in this dissertation. Starting with an analysis of electro-magnetic wave propagation in layered media, we have reformulated Fresnel and volume reflection phenomena in terms of a convenient parameter--strength of reflection. The influence that the different non-uniformities inside a VBG have on its spectral properties has been examined. One important result of this work is the proposal of moire VBG and the derivation of an analytical expression for its bandwidth. A multiplexed VBG used as a coherent combiner is discussed as well. Beam distortion via transmission through and/or reflection by a heated VBG due to residual absorption is analyzed.<br>ID: 030423243; System requirements: World Wide Web browser and PDF reader.; Mode of access: World Wide Web.; Thesis (Ph.D.)--University of Central Florida, 2011.; Includes bibliographical references (p. 114-127).<br>Ph.D.<br>Doctorate<br>Optics and Photonics
12
Zhang, Shuyan. "Spatial beam shaping of high-power ultrashort laser pulses." W&M ScholarWorks, 2007. https://scholarworks.wm.edu/etd/1539623522.
Testo completoAbstract (sommario):
This thesis presents both theoretical and experimental studies of a diffractive beam shaping system for ultrashort high-power laser pulses.;A theoretical model is developed to simulate the reshaped intensity profiles for a 100-fs pulse with various energy levels. Both temporal evolution and spatial intensity distribution of the pulse at the target plane of the beam shaping system are calculated. Numerical simulation shows that after passing through the beam shaping system, the pulse front is significantly curved due to the propagation time delay, and the pulse duration time through the target plane is broadened because of the group velocity dispersion. However, for relatively low energy pulses (on the order of millijoules), although the intensity distribution is changed considerably, the fluence top-hat profile is well maintained. This feature extends the application of this beam shaping system into the regime of ultrashort laser pulses. Theoretical calculation also shows the limit when the top-hat profile starts to degrade. For very high-energy laser pulses (>20 mJ per pulse), the homogeneous fluence profile, as well as the intensity distribution, is destroyed due to the non-linear self phase modulation.;This thesis also presents an experimental study of the beam shaping system for ultrashort high-power laser pulses. A terawatt CPA laser amplification system was built in order to verify the theoretical simulation in experiment. The laser amplification system adopts a multi-pass configuration. The output of this CPA amplifier is operating at 30 Hz repetition rate with a pulse energy of 20 mJ/pulse. The compressed pulse duration is 70 fs, resulting in a pulse peak power of 0.3 TW. Experimental results of the beam shaping system with ultrashort laser pulse input agree with the numerical simulation of the reshaped fluence profiles at various energy levels from 6nJ to 20 mJ. The experimental results confirm the validity of this diffractive beam shaping system for ultrashort pulses with a pulse energy on the order of millijoulses. While millijoule pulses are commonly used in the micromachining technology, the adaptability of this diffractive beam shaping system is greatly improved.
13
Tovar, Anthony A. "Beam Modes of Lasers with Misaligned Complex Optical Elements." PDXScholar, 1995. https://pdxscholar.library.pdx.edu/open_access_etds/1363.
Testo completoAbstract (sommario):
A recurring theme in my research is that mathematical matrix methods may be used in a wide variety of physics and engineering applications. Transfer matrix techniques are conceptually and mathematically simple, and they encourage a systems approach. Once one is familiar with one transfer matrix method, it is straightforward to learn another, even if it is from a completely different branch of science. Thus it is useful to overview these methods, and this has been done here. Of special interest are the applications of these methods to laser optics, and matrix theorems concerning multipass optical systems and periodic optical systems have been generalized here to include, for example, the effect of misalignment on the performance of an optical system. In addition, a transfer matrix technique known as generalized beam method has been derived to treat misalignment effects in complex optical systems. Previous theories used numerical or ad hoc analytical solutions to a complicated diffraction integral. The generalized beam matrix formalism was also extended to higher-order beam modes of lasers and used to study mode discrimination in lasers with misaligned complex optical elements.
14
Chen, Hongwei. "Optical Beam Scanning Using Potassium Tantalate Niobate." University of Dayton / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1444868170.
Testo completo
15
Blanco, Sonia GarciÌa. "Electron-beam modification of silica for integrated optics." Thesis, University of Glasgow, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.272890.
Testo completo
16
Rafayelyan, Mushegh. "Singular beam shaping from spin-orbit flat optics." Thesis, Bordeaux, 2017. http://www.theses.fr/2017BORD0583/document.
Testo completoAbstract (sommario):
Dans ce travail nous avons résolu deux problèmes principaux de la mise en forme topologique de faisceau paraxial pour les composants plans : la modalité et le polychromatisme.Nous les résolvons en introduisant de nouveaux concepts d’éléments optiques à interaction spin orbite,à savoir la “q-plate modale” et la “q-plate Bragg-Berry”. D’un côté, la q-plate modale convertit un faisceau gaussien incident en un faisceau de Laguerre-Gauss pour un indice radial et un indice d’azimut donnés, ce qui par conséquent dépasse les capacités des q-plates conventionnelles qui ne modifient que le degré de liberté azimutal, c.à.d. le moment orbital angulaire de la lumière. À des fins expérimentales, deux approches ont été développées : une basée sur des lames de verres nanostructurées artificiellement, l’autre sur des défauts topologiques de cristaux liquides auto-organisés naturellement. D’un autre côté, la q-plate Bragg-Berry consiste en une fine couche inhomogène de cristaux liquides chiraux (cholestériques) devant un miroir, ce qui fournit une mise en forme de faisceau spin-orbite pleinement efficace sur une large bande spectrale du faisceau incident, contrairement au q-plates conventionnelles qui ne sont fabriqués que pour une longueur d’onde donnée. Par ailleurs, nous obtenons une mise en forme de faisceau spin-orbite ultra-large bande en induisant une modulation de la structure supramoléculaire torsadée des cristaux liquides cholestériques selon la direction de propagation de la lumière. Nous montrons également que la présence du miroir derrière permet un puissant contrôle spatio-temporel des propriétés vectorielles de la polarisation du champ lumineux générées par la q-plate Bragg-Berry<br>It is well-known that paraxial coherent electromagnetic fields can be completelycharacterized in terms of their radial and azimuthal spatial degrees of freedom in the transverse planethat add to the polarization degree of freedom and wavelength. In this work we address two mainissues of paraxial beam shaping that are the modality and the polychromaticity in the context of flatopticsthat we address by introducing novel concepts of spin-orbit optical elements. Namely, the‘modal q-plate’ and the ‘Bragg-Berry q-plate’. On the one hand, modal q-plate converts an incidentfundamental Gaussian beam into a Laguerre-Gaussian beam of given radial and azimuthal indices,hence going beyond the capabilities of conventional q-plates that only control the azimuthal degreeof freedom, i.e. the orbital angular momentum content of light. Towards experimental realization ofmodal q-plates, two approaches are developed: one based on artificially nanostructured glasses andanother based on naturally self-organized liquid crystal topological defects. On the other hand,Bragg-Berry q-plate consist of mirror-backed inhomogeneous thin film of chiral liquid crystal(cholesteric) that provides fully efficient spin-orbit beam shaping over broad spectral range of theincident beam, in contrast to the conventional q-plates that are designed for single wavelength.Furthermore, ultra-broadband spin-orbit beam shaping is achieved by inducing an extra modulationof the supramolecular twisted structure of the cholesteric liquid crystal along the propagationdirection. We also show that the presence of a back-mirror allows a powerful spatio-temporal controlof the polarization vectorial properties of the light fields generated by Bragg-Berry q-plate
17
Morris, Jill E. "Studies of novel beam shapes and applications to optical manipulation." Thesis, University of St Andrews, 2010. http://hdl.handle.net/10023/1699.
Testo completoAbstract (sommario):
In this thesis an investigation into novel beams and optical manipulation is presented. Sculpting the phase profile of a Gaussian beam can result in the generation of a beam with unusual properties. Described in this thesis are optical vortices, Bessel beams and Airy beams. Additionally, optical manipulation was investigated using both novel beams and Gaussian beams with an emphasis on the use of a broad bandwidth laser source. The generation of multiple broadband optical trap sites was explored, and the transfer of orbital angular momentum from a broadband optical vortex to trapped microspheres was demonstrated. An introduction to the thesis and an overview of laser sources used for optical manipulation is presented in Chapters 1 and 2. Chapters 3 and 4 detail the background of optical manipulation and novel beam shaping. In Chapter 5, an investigation into the generation of multiple broadband optical trap sites is presented. Chapter 6 details the use of a ‘white light’ optical vortex to transfer orbital angular momentum to trapped microspheres. Chapter 7 presents the results of an investigation carried out using a supercontinuum source to characterise the wavelength and spatial coherence dependence of the properties of an optical Airy beam. The use of a monochromatic laser to generate Bessel beams that propagate along curved trajectories is detailed in Chapter 8. Chapter 9 summarises the thesis and suggests future work.
18
Sudradjat, Faisal. "50%-50% Beam Splitters Using Transparent Substrates Coated by Single- or Double-Layer Quarter-Wave Thin Films." ScholarWorks@UNO, 2006. http://scholarworks.uno.edu/td/376.
Testo completoAbstract (sommario):
A pair of light beams that have orthogonal polarizations and equal intensity can be generated through reflection and refraction of a monochromatic light at a dielectric surface. Sytematic procedures to design beam splitters which can produce such output light beams are described in this thesis. Two designs that are of particular interest are prismatic substrates coated by a single layer and a double layer of thin films. Specific examples of each beam splitter in the visible and infrared are included. The performance of each beam splitter as a function of incidence angle, film thickness, and wavelength is also discussed.
19
Barcík, Peter. "Rozložení relativní variance optické intenzity ve svazcích." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2012. http://www.nusl.cz/ntk/nusl-219880.
Testo completoAbstract (sommario):
This master´s thesis provides basic properties and measurement of optical beams. In the first chapter is shown division of light on ray, wave and beam optics. Atmospheric optics and properties associated with propagation of light through the earth's atmosphere is presented in the second chapter. In the third part are shown basic techniques for Gaussian beam shaping. The last chapter deals with measurement of optical beam after propagating through a turbulent medium. In this section is shown distribution of relative variance of optical intensity in Gaussian and Top-Hat beam. There is also measured spatial coherence of laser beam in the turbulent atmospheric transmission media. Finally effect of the beam wander is investigated.
20
Mart, Cody W. "Characterization and Power Scaling of Beam-Combinable Ytterbium-Doped Microstructured Fiber Amplifier." Thesis, The University of Arizona, 2017. http://pqdtopen.proquest.com/#viewpdf?dispub=10621184.
Testo completoAbstract (sommario):
<p> In this dissertation, high-power ytterbium-doped fiber amplifiers designed with advanced waveguide concepts are characterized and power scaled. Fiber waveguides utilizing cladding microstructures to achieve wave guidance via the photonic bandgap (PBG) effect and a combination of PBG and modified total internal reflection (MTIR) have been proposed as viable single-mode waveguides. Such novel structures allow larger core diameters (>35 ?m diameters) than conventional step-index fibers while still maintaining near-diffraction limited beam quality. These microstructured fibers are demonstrated as robust single-mode waveguides at low powers and are power scaled to realize the thermal power limits of the structure. Here above a certain power threshold, these coiled few-mode fibers have been shown to be limited by modal instability (MI); where energy is dynamically transferred between the fundamental mode and higher-order modes. Nonlinear effects such as stimulated Brillouin scattering (SBS) are also studied in these fiber waveguides as part of this dissertation. Suppressing SBS is critical towards achieving narrow optical bandwidths (linewidths) necessary for efficient fiber amplifier beam combining. Towards that end, new effects that favorably reduce acoustic wave dispersion to increase the SBS threshold are discovered and reported. </p><p> The first advanced waveguide examined is a Yb-doped 50/400 μm diameter core/clad PBGF. The PBGF is power scaled with a single-frequency 1064 nm seed to an MI-limited 410 W with 79% optical-to-optical efficiency and near-diffraction limited beam quality (M-Squared < 1.25) before MI onset. To this author’s knowledge, this represents 2.4x improvement in power output from a PBGF amplifier without consideration for linewidth and a 16x improvement in single-frequency power output from a PBGF amplifier.</p><p> During power scaling of the PBGF, a remarkably low Brillouin response was elicited from the fiber even when the ultra large diameter 50 μm core is accounted for in the SBS threshold equation. Subsequent interrogation of the Brillouin response in a pump probe Brillouin gain spectrum diagnostic estimated a Brillouin gain coefficient, gB, of 0.62E<sup>-11 </sup> m/W; which is 4x reduced from standard silica-based fiber. A finite element numerical model that solves the inhomogenous Helmholtz equation that governs the acoustic and optical coupling in SBS is utilized to verify experimental results with an estimated gB = 0.68E<sup>-11</sup> m/W. Consequently, a novel SBS-suppression mechanism based on inclusion of sub-optical wavelength acoustic features in the core is proposed.</p><p> The second advanced waveguide analyzed is a 35/350 μm diameter core/clad fiber that achieved wave guidance via both PBG and MTIR, and is referred to as a hybrid fiber. The waveguide benefits mutually from the amenable properties of PBG and MTIR wave guidance because robust single-mode propagation with minimal confinement loss is assured due to MTIR effects, and the waveguide spectrally filters unwanted wavelengths via the PBG effect. The waveguide employs annular Yb-doped gain tailoring to reduce thermal effects and mitigate MI. Moreover, it is designed to suppress Raman processes for a 1064 nm signal by attenuating wavelengths > 1110 nm via the PBG effect. When seeded with a 1064 nm signal deterministically broadened to ∼1 GHz, the hybrid fiber was power scaled to a MI-limited 820 W with 78% optical-to-optical efficiency and near diffraction limited beam quality of M_Squared ∼1.2 before MI onset. This represents a 14x improvement in power output from a hybrid fiber, and demonstrates that this type of fiber amplifier is a quality candidate for further power scaling for beam combining.</p><p>
21
Rosenbusch, Peter. "Atom optics with an adaptable magnetic reflector." Thesis, University of Sussex, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.341516.
Testo completo
22
Watkins, R. Joseph. "The adaptive control of optical beam jitter." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2004. http://library.nps.navy.mil/uhtbin/hyperion/04Dec%5FWatkins%5FPhD.pdf.
Testo completoAbstract (sommario):
Thesis (Ph. D. in Mechanical Engineering)--Naval Postgraduate School, December 2004.<br>Thesis advisor(s): Brij N. Agrawal, Young S. Shin. Includes bibliographical references (p. 163-165). Also available online.
23
RIOS, PAULO B. "Linha de transporte de feixe do acelerador microtron do IFUSP." reponame:Repositório Institucional do IPEN, 2002. http://repositorio.ipen.br:8080/xmlui/handle/123456789/11064.
Testo completoAbstract (sommario):
Made available in DSpace on 2014-10-09T12:47:43Z (GMT). No. of bitstreams: 0<br>Made available in DSpace on 2014-10-09T14:10:27Z (GMT). No. of bitstreams: 1
08347.pdf: 3195632 bytes, checksum: 315dd33e8ef379364634f9993e972f7d (MD5)<br>Dissertacao (Mestrado)<br>IPEN/D<br>Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
24
Tsampoula, Xanthi. "Femtosecond cellular transfection using novel laser beam geometries." Thesis, St Andrews, 2009. http://hdl.handle.net/10023/909.
Testo completo
25
Shaklan, Stuart Bruce. "Multiple beam correlation using single-mode fiber optics with application to interferometric imaging." Diss., The University of Arizona, 1989. http://hdl.handle.net/10150/184827.
Testo completoAbstract (sommario):
A study of the application of single-mode fiber optics to the multiple-beam interferometric recombination problem is presented. In the laboratory, the fibers have been used in wide bandwidth, two-arm, Mach-Zehnder test interferometers as well as a 5-telescope imaging interferometer connected to an all-fiber beam combiner. Based upon these experiments and some theoretical studies it is shown that fiber optics and fiber optic components such as directional couplers provide an excellent alternative to conventional optics such as mirrors, beamsplitters, and relay lenses. The equations describing the measurement of the complex degree of coherence in an interferometer with a single-mode fiber in each arm are derived. The equations reveal an important feature of the fibers: they filter phase fluctuations due to aberrations and turbulence at the input and convert them to intensity fluctuations at the output. This leads to a simplification of the calibration of measured visibilities. The coupling efficiency of light which has passed through a turbulent atmosphere is also studied as a function of fiber parameters and turbulence conditions for both image motion stabilized and non-stabilized cases. For the former case, coupling efficiency remains greater than 50% as long as telescope diameter is no larger than the turbulence coherence length. Beam combination architectures using arrays of directional couplers are fully discussed. Arrays accommodating up to 20 input beams are presented. The arrays require only N detector pixels for N input beams. A scheme of temporal multiplexing of the phase of each beam is used to identify individual fringe pairs. One possible scheme allows wide bandwidths even for large numbers of beams. A 5-telescope interferometer has been constructed and connected to an all-fiber beam combiner. Two extended objects were observed and reconstructed using standard radio astronomy VLBI software. The interferometer and beam combiner had good thermal and polarization stability and high throughput. Reconstructed images had dynamic ranges of about 50.
26
Horger, John. "Multiple plane wave analysis of acousto-optic diffraction of Gaussian shaped light beams." Thesis, Virginia Tech, 1987. http://hdl.handle.net/10919/44053.
Testo completoAbstract (sommario):
A short history of acousto-optics research is presented
along with a general description of how light and sound
interact.
<p>The Multiple Scattering model is derived and used with
a Gaussian light beam to observe the distortion in light
beam profile within the sound field. Numerical results are
presented for comparison to previous studies using thick
holograms and two orders of light. The results from using
two light orders are compared to four light order results.
<p>A Hamming sound amplitude distribution is introduced as
a possible way to reduce the amount of light beam profile
distortion.<br>Master of Science
27
Sparkes, Martin. "Automatic COâ†2 laser beam alignment systems." Thesis, University of Liverpool, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.263766.
Testo completo
28
Rivera, Michael 1968. "Bent waveguide analysis with a modified version of the beam propagation method." Diss., The University of Arizona, 1996. http://hdl.handle.net/10150/282158.
Testo completoAbstract (sommario):
To study propagation in bent waveguides numerically the most common technique used is the Beam Propagation Method (BPM), with either the split-step procedure and Fast Fourier Transform algorithm, or a finite difference approach. Most versions are based on a first order modification of the permittivity profile for scalar or full vector wave equations. Others are based on a longitudinally variant index profile and wide angle beam propagation techniques. New device applications are well beyond the limitations of the present numerical approaches. An example of these applications are polymer and semiconductor ring lasers, (de)multiplexing systems, and polarization converters based on bent waveguides. They will require more accurate and novel numerical approaches to solve more complex problems at smaller radii. Important issues are characteristics such as: the modal spectra, total loss and loss rates, and modal field distributions.
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Victor, Brian M. "Custom Beam Shaping for High-Power Fiber Laser Welding." The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1238014676.
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Zhao, Hongyan. "A theoretical and experimental study of the optical forces from a laser beam /." Thesis, McGill University, 1991. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=61216.
Testo completoAbstract (sommario):
A practical geometric optics method for derivation of the optical forces from light rays was described. By this method, the forces from a G.P.W. (Gaussian Plane Wave) and a general TEM$ sb infty$ laser beam were calculated and studied. For a G.P.W. beam, there were two forces which acted on small particles located inside the electromagnetic field; one, called the scattering force, directed in the beam propagation direction, pushed particles axially. The other, called the gradient force, due to the non-uniformity of the electromagnetic field, acted like an optical well and confined the particles of the beam axis. The forces from a general TEM$ sb infty$ beam behaved differently due to the profile of the beam. It was shown that axial confinement was also possible for a highly focused TEM$ sb infty$ beam, therefore providing the possibility of single beam trapping. The relationship between the forces and the profile of a TEM$ sb infty$ laser beam was investigated comprehensively.<br>Three experimental stations were designed and built. Both upward and downward accelerating experiments were constructed to confirm the existences of the scattering force and the gradient force in a G.P.W. beam. Furthermore, the scattering force was studied quantitatively. A single beam trapping experiment was designed to verify the possibility of axial constraint of small particles by a higher focused TEM$ sb infty$ laser beam. The single beam trapping conditions found in the experiment were in agreement with the results of the theoretical analysis.
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Hastings, Jeffrey Todd 1975. "Nanometer-precision electron-beam lithography with applications in integrated optics." Thesis, Massachusetts Institute of Technology, 2003. http://hdl.handle.net/1721.1/29949.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2003.<br>Includes bibliographical references (p. 179-185).<br>Scanning electron-beam lithography (SEBL) provides sub-10-nm resolution and arbitrary-pattern generation; however, SEBL's pattern-placement accuracy remains inadequate for future integrated-circuits and integrated-optical devices. Environmental disturbances, system imperfections, charging, and a variety of other factors contribute to pattern-placement inaccuracy. To overcome these limitations, spatial-phase locked electron-beam lithography (SPLEBL) monitors the beam location with respect to a reference grid on the substrate. Phase detection of the periodic grid signal provides feedback control of the beam position to within a fraction of the period. Using this technique we exposed patterns globally locked to a fiducial grid and reduced local field-stitching errors to a < 1.3 nm. Spatial-phase locking is particularly important for integrated-optical devices that require pattern-placement accuracy within a fraction of the wavelength of light. As an example, Bragg-grating based optical filters were fabricated in silicon-on-insulator waveguides using SPLEBL. The filters were designed to reflect a narrow-range of wavelengths within the communications band near 1550-nm. We patterned the devices in a single lithography step by placing the gratings in the waveguide sidewalls. This design allows apodization of the filter response by lithographically varying the grating depth. Measured transmission spectra show greatly reduced sidelobe levels for apodized devices compared to devices with uniform gratings.<br>by Jeffrey Todd Hastings.<br>Ph.D.
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Cheng, Wen. "Optical Vortex Beams: Generation, Propagation and Applications." University of Dayton / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1375370902.
Testo completo
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LaPean, James William. "Beam scanning offset Casegrain reflector antennas by subreflector movement." Thesis, This resource online, 1993. http://scholar.lib.vt.edu/theses/available/etd-06302009-040304/.
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Dicaire, Marie-Claude. "Generation of Vortex Beam Superpositions Using Angular Gratings." Thesis, Université d'Ottawa / University of Ottawa, 2017. http://hdl.handle.net/10393/35999.
Testo completoAbstract (sommario):
Beams of light carrying orbital angular momentum, such as vortex beams, have many applications in imaging and micromanipulation. We focus on applications in communication, in particular for quantum key distribution, where the security of communication channels is enhanced with the laws of quantum mechanics. However, this procedure requires superpositions of vortex beams. We want to generate such beams using integrated optics components due to their small size and their advantages in scalability and stability.
Angular gratings, which are ring resonators with an embedded Bragg grating, are integrated structures known to generate vortex beams. We propose that a ring resonator with two embedded Bragg gratings, each on the inner and outer sidewalls, would generate a superposition of vortex beams. We verify this claim through analytical models, simulations and experiments.
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胡一帆 and Yifan Hu. "Improvement in positron beam optics and some positron beam studies of GaN and Amorphous-si:H thin films." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2000. http://hub.hku.hk/bib/B4257559X.
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Hu, Yifan. "Improvement in positron beam optics and some positron beam studies of GaN and Amorphous-si:H thin films." Click to view the E-thesis via HKUTO, 2000. http://sunzi.lib.hku.hk/hkuto/record/B4257559X.
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Petersson, L. E. Rickard. "Analysis of two problems related to a focused beam measurement system." Diss., Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/13545.
Testo completo
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Fisher, Shari Powell. "Fabrication of advanced optical devices by molecular beam deposition." Thesis, Heriot-Watt University, 1992. http://hdl.handle.net/10399/808.
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McClelland, Toby Edward. "Beam coupling and space-charge waves in photorefractive materials." Thesis, University of Kent, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.309780.
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Said, Ali A. (Ali Ahmad). "Development and Application of a Nonlinear Optical Characterization Technique." Thesis, University of North Texas, 1991. https://digital.library.unt.edu/ark:/67531/metadc332709/.
Testo completoAbstract (sommario):
This dissertation reports a sensitive single beam experimental technique for measuring nonlinear refraction and nonlinear absorption in a wide variety of materials. The experimental setup is described and a comprehensive theoretical analysis including cases where nonlinear refraction and nonlinear absorption are also presented.
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Han, Wei. "Transmissive beam steering through Electrowetting Microprism arrays." University of Dayton / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1262130475.
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Ament, Craig A. "High numerical aperture axial and transverse beam shaping using diffractive optics." Honors in the Major Thesis, University of Central Florida, 2010. http://digital.library.ucf.edu/cdm/ref/collection/ETH/id/1348.
Testo completoAbstract (sommario):
This item is only available in print in the UCF Libraries. If this is your Honors Thesis, you can help us make it available online for use by researchers around the world by following the instructions on the distribution consent form at http://library.ucf.edu/Systems/DigitalInitiatives/DigitalCollections/InternetDistributionConsentAgreementForm.pdf You may also contact the project coordinator, Kerri Bottorff, at kerri.bottorff@ucf.edu for more information.<br>Bachelors<br>Sciences<br>Physics
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Taylor, Laurence Charles. "A beam tracing model for electromagnetic scattering by atmospheric ice crystals." Thesis, University of Hertfordshire, 2016. http://hdl.handle.net/2299/17645.
Testo completoAbstract (sommario):
While exact methods, such as DDA or T-matrix, can be applied to particles withsizes comparable to the wavelength, computational demands mean that they are size limited. For particles much larger than the wavelength, the Geometric Optics approximation can be employed, but in doing so wave effects, such as interference and diffraction, are ignored. In between these two size extremes there exists a need for computational techniques which are capable of handling the wide array of ice crystal shapes and sizes that are observed in cirrus clouds. The Beam Tracing model developed within this project meets these criteria. It combines aspects of geometric optics and physical optics. Beam propagation is handled by Snell's law and the law of reflection. A beam is divided into reflected and transmitted components each time a crystal facet is illuminated. If the incident beam illuminates multiple facets it is split, with a new beam being formed for each illuminated facet. The phase-dependent electric field amplitude of the beams is known from their ampli- tude (Jones) matrices. These are modified by transmission and reflection matrices, whose elements are Fresnel amplitude coefficients, each time a beam intersects a crystal facet. Phase tracing is carried out for each beam by considering the path that its 'centre ray' would have taken. The local near-field is then mapped, via a surface integral formulation of a vector Kirchhoff diffraction approximation, to the far-field. Once in the far-field the four elements of the amplitude matrix are trans- formed into the sixteen elements of the scattering matrix via known relations. The model is discussed in depth, with details given on its implementation. The physical basis of the model is given through a discussion of Ray Tracing and how this leads to the notion of Beam Tracing. The beam splitting algorithm is described for convex particles followed by the necessary adaptations for concave and/or ab- sorbing particles. Once geometric aspects have been established details are given as to how physical properties of beams are traced including: amplitude, phase and power. How diffraction is implemented in the model is given along with a review of existing diffraction implementations. Comparisons are given, first against a modified Ray Tracing code to validate the geometric optics aspects of the model. Then, specific examples are given for the cases of transparent, pristine, smooth hexagonal columns of four different sizes and orientations; a highly absorbing, pristine, smooth hexagonal column and a highly absorbing, indented, smooth hexagonal column. Analysis of two-dimensional and one-dimensional intensity distributions and degree of linear polarisation results are given for each case and compared with results acquired through use of the Amster- dam Discrete-Dipole Approximation (ADDA) code; with good agreement observed. To the author's best knowledge, the Beam Tracer developed here is unique in its ability to handle concave particles; particles with complex structures and the man- ner in which beams are divided into sub-beams of quasi-constant intensity when propagating in an absorbing medium. One of the model's potential applications is to create a database of known particle scattering patterns, for use in aiding particle classification from images taken by the Small Ice Detector (SID) in-situ probe. An example of creating such a database for hexagonal columns is given.
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Morgan, Rhonda Michelle. "Achromatic nulling beam combiner for the detection of extrasolar planets." Diss., The University of Arizona, 2001. http://hdl.handle.net/10150/279844.
Testo completoAbstract (sommario):
Nulling stellar interferometry may enable the discovery of earth-like planets around other stars. In nulling mode, the zero order fringe is destructive and on axis, thus canceling light from a bright source and detecting dimer off-axis features. To create deep on-axis nulls, the phase must be shifted half a wave achromatically over a broad band. The phase shift is created by adding optical path thickness with dielectric plates. Plates of different materials can balance dispersion. The nulling solutions found for TPF (infrared) and for SIM (visible) are promising. This dissertation describes the implementation of a nulling beam combiner test bed and presents data characterizing its performance. Although the implementation was limited so that a broad band null of 10E-4 was not attained, the test bed revealed the extreme challenges of this technique and provided very valuable lessons that will enable future implementations to be successful and more precise. The nulling beam combiner testbed was implemented in the laboratory as a Michelson interferometer with the goal of achieving a stabilized, l0E-4 null over a spectral region from 600 nm to 800 nm. The beam combiner system has three tiers of control. Tier 1 controls phase achromaticity by tilting optical plates and is a static control loop. Tier 2 sweeps through the white light fringe and then searches for the null as the air path drifts over minutes. Tier 3 stabilizes the null with a 300 hertz servo loop. A scheme for active control of the optical thicknesses was developed. The phase as a function of wavelength was measured by performing PSI on a spectrally dispersed fringe. The phase was fit to a model to solve for the optical thicknesses. The optical thicknesses were then adjusted to match the ideal thicknesses of an optimized solution. This process of measuring and adjusting the optical thicknesses is performed iteratively to achromatize the phase. The stabilizing servo loop sensed on a grey fringe at a short wavelength. At the shorter wavelength, the fringe was 90 degrees out of phase with the main pass band resulting in a grey fringe. The grey fringe intensity is more sensitive to OPD changes.
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Werntz, Paul C. "A high gain tri-reflector antenna configuration for beam scanning." Diss., This resource online, 1993. http://scholar.lib.vt.edu/theses/available/etd-07112007-092852/.
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Jiang, Miao. "DESIGNS AND APPLICATIONS OF PLASMONIC METAMASKS FOR TOPOLOGICAL DEFECT ENGINEERING AND MANUFACTURING OF PANCHARATNAM FLAT OPTICAL ELEMENTS." Kent State University / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=kent1533742796947775.
Testo completo
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Kudjoe, John. "Design and development of field emission electron columns with variable beam energy." Thesis, University of York, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.259834.
Testo completo
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Furness, Charles Zachary. "Parameter identification of a flexible beam using a modal domain optical fiber sensor." Thesis, Virginia Tech, 1990. http://hdl.handle.net/10919/42058.
Testo completoAbstract (sommario):
<p>An optical fiber sensor is used for identification of a cantilevered beam
under conditions of various concentrated mass loadings. A model of the sensor as
well as the dynamic system is developed and used to test the reliability of the
identification. Input/output data from an experiment is gathered and used in the
identification. A survey of the existing areas of damage detection and parameter
identification is included, along with suggestions for incorporating fiber optic
sensors into existing techniques. The goal of this research was to show that the
fiber sensor can be used for identification purposes, and that it is sensitive to
parameter changes within the system (in this case concentrated mass changes).</p><br>Master of Science
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Rubenstein, Richard Alan 1971. "Longitudinal atom optics : measuring the density matrix of a matter wave beam." Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/85255.
Testo completo
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Manfrinato, Vitor Riseti. "Electron-beam lithography towards the atomic scale and applications to nano-optics." Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/101466.
Testo completoAbstract (sommario):
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2015.<br>This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.<br>Cataloged from student-submitted PDF version of thesis.<br>Includes bibliographical references (pages 146-163).<br>Electron-beam lithography (EBL) is a high-resolution pattern generation technique widely used in research and development. However, EBL resolution has been limited to 4 nm isolated features and 16 nm periodic structures. Furthermore, the physical mechanisms that limit EBL resolution are not quantitatively clear. The fundamental understanding of the resolution limits of EBL is critically important to push nanotechnology toward the atomic scale. In this thesis we show a comprehensive study of the resolution limiting factors of EBL. We demonstrated that low-energy (sub-5 keV) EBL is able to achieve sub-10 nm half-pitch structures. We investigated the resolution of EBL using an aberration-corrected scanning transmission electron microscope as the exposure tool at 200 keV. We achieved isolated features with critical dimensions of 2 nm and 5 nm half-pitch in hydrogen silsesquioxane resist. We analyzed the resolution limits of this technique by measuring the lithographic point-spread function (PSF). In addition, we measured the delocalized energy transfer in EBL exposure by using chromatic aberration-corrected energy-filtered transmission electron microscopy (EFTEM) at the sub-10 nm scale. We have defined the role of spot-size, electron scattering, secondary electrons, and volume plasmons in the lithographic PSF by performing EFTEM, momentum-resolved electron energy loss spectroscopy (EELS), sub-10 nm EBL, and Monte Carlo simulations. Finally, we show two applications in nano-optics that demand sub-10 nm EBL. First, we performed lithographic placement of nanometer-sized photon sources, i.e., 5-nm-diameter colloidal quantum dots. Second, we fabricated sub-20 nm plasmonic antennas designed to engineer surface and volume plasmons in the ultraviolet region of the electromagnetic spectrum (3 to 30 eV).<br>by Vitor Riseti Manfrinato.<br>Ph. D.