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Dissertations / Theses on the topic 'Optical waves'
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1
Rostad, Torbjørn. "Optical Detection of Surface Acoustic Waves." Thesis, Norwegian University of Science and Technology, Department of Electronics and Telecommunications, 2006. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-9487.
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This project was worked on during the autumn 2005 at the Norwegian University of Science and Technology, Department of Electronics and Telecommunications. The assignment was to write a new LabVIEW programme that is to run the measurement procedure of a laser probe setup. The setup is used in characterization of surface acoustic waves(SAW). A programme was written that contained the necessary functionality and proved to operate satisfactorily. Several measurements were made on a SAW transducer, accurately picturing the wave. Fourier analysis were performed on the collected data in order to separate the propagation directions. An absolute amplitude measurement was made on a heterodyne interferometer, and the result was compared to a similar scan made using the laser probe. The work shows that the setup is ready for calibration against the heterodyne interferometer, in order to enable the laser probe to measure absolute amplitude by itself.
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Mak, William Chi Keung Electrical Engineering & Telecommunications Faculty of Engineering UNSW. "Coupled Solitary Waves in Optical Waveguides." Awarded by:University of New South Wales. Electrical Engineering and Telecommunications, 1998. http://handle.unsw.edu.au/1959.4/17494.
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Soliton states in three coupled optical waveguide systems were studied: two linearly coupled waveguides with quadratic nonlinearity, two linearly coupled waveguides with cubic nonlinearity and Bragg gratings, and a quadratic nonlinear waveguide with resonant gratings, which enable three-wave interaction. The methods adopted to tackle the problems were both analytical and numerical. The analytical method mainly made use of the variational approximation. Since no exact analytical method is available to find solutions for the waveguide systems under study, the variational approach was proved to be very useful to find accurate approximations. Numerically, the shooting method and the relaxation method were used. The numerical results verified the results obtained analytically. New asymmetric soliton states were discovered for the coupled quadratically nonlinear waveguides, and for the coupled waveguides with both cubic nonlinearity and Bragg gratings. Stability of the soliton states was studied numerically, using the Beam Propagation Method. Asymmetric couplers with quadratic nonlinearity were also studied. The bifurcation diagrams for the asymmetric couplers were those unfolded from the corresponding diagrams of the symmetric couplers. Novel stable two-soliton bound states due to three-wave interaction were discovered for a quadratically nonlinear waveguide equipped with resonant gratings. Since the coupled optical waveguide systems are controlled by a larger number of parameters than in the corresponding single waveguide, the coupled systems can find a much broader field of applications. This study provides useful background information to support these applications.
3
Skryabin, Dmitry Vladimirovich. "Modulational instability of optical solitary waves." Thesis, University of Strathclyde, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.366995.
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Pack, Jeong-Ki. "A wave-kinetic numerical method for the propagation of optical waves." Thesis, Virginia Polytechnic Institute and State University, 1985. http://hdl.handle.net/10919/104527.
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Zandi, Bahram. "Propagation of optical waves in tapered fibers and metallic wave guides." PDXScholar, 1986. https://pdxscholar.library.pdx.edu/open_access_etds/2693.
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The equations tor the propagation of Electromagnetic and Optical waves in tapered fibers and metallic waveguides are derived. Solutions are derived for the displacement of the beam from the waveguide axis as a function of distance along the axis, and also tor the beam width as a function of distance. These equations are solved numerically for a variety of tapered guides. Experiments are conducted which verify the theoretical results.
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MacNeil, John Michael Larratt. "Solitary waves in focussing and defocussing nonlinear, nonlocal optical media." Thesis, University of Edinburgh, 2016. http://hdl.handle.net/1842/20951.
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Nonlinear, nonlocal optical media has emerged as an ideal setting for experimentally observing and studying spatial optical solitary waves which otherwise cannot occur in Kerr media. Of particular interest is the eventual application to all-optical circuits. However, there is considerable work left to do on the theoretical end before this is a possibility. In this thesis we consider three problems. The first is how to solve the governing equations for optical beam propagation in the particular medium of the nematic liquid crystal (NLC), which is used as a prototypical example, exactly and approximately. In this respect we provide the first known, explicit solutions to the model as well as a comprehensive assessment on how to use variational, or modulation theory, in this context. This leads to the discovery of a novel form of bistability in the system, which shows there are two stable solitary wave solutions for a fixed power or L2 norm. We then consider how to approximate solutions for optical solitary waves propagating in a more general class of nonlocal nonlinear media using asymptotic methods. This is a long open problem and is resolved in the form of a simple to implement method with excellent accuracy and general applicability to previously intractable models. We conclude with the discovery and characterization of an instability mechanism in a coupled, defocussing nonlinear Schrodinger system. We show there is no stable, coupled, localized solution. This result is compared with the more well-studied bright solitary wave system and physical and mathematical explanations are offered.
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Lloyd-Hart, Michael. "Novel techniques of wavefront sensing for adaptive optics with array telescopes using an artificial neural network." Diss., The University of Arizona, 1992. http://hdl.handle.net/10150/185749.
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Atmospheric turbulence causes severe degradation of the resolving and signal-to-noise properties of present optical telescopes. Diffraction-limited resolution can be recovered through the use of a deformable ('adaptive') optical element to correct the atmospheric wavefront error. An adaptive optics system operating in the near infrared (1.7 - 3.5 μm) has been developed for use at the Multiple Mirror Telescope (MMT), an array of six co-mounted 1.8 m telescopes, in which six flat mirrors are used to correct the wavefront tilt across each aperture, and the phase differences between apertures. This can reduce the error sufficiently to achieve a diffraction-limited image with a central peak of 0.06 arcseconds full width at half maximum at 2.2 μm wavelength. A number of algorithms are used to drive the adaptive mirror in a closed servo loop, including a trained artificial neural network which deduces the wavefront aberration from a pair of simultaneous in- and out-of-focus images of a star, taken at the combined focal plane of the telescope. Computer simulations have shown that the net is capable of deriving the wavefront for the full six-mirror aperture, and in practice, the net has been demonstrated in the lab to maintain two- and three-aperture diffraction-limited beam profiles in the presence of distorting effects. On the sky, with a real star, the net has successfully restored the diffraction limit for two adjacent MMT segments. High resolution images have been obtained of various objects with a wide-field camera looking in the field around the wavefront reference star. Work has also been carried out to characterise the wavefront aberration at the MMT, which confirms the Kolmogorov model of turbulence. Finally, a new algorithm is discussed which shows great promise for correction of phase errors in array telescopes.
8
Maldonado, Theresa A. "Analysis of electro-optic/gyrotropic biaxial crystals for bulk and waveguide applications." Diss., Georgia Institute of Technology, 1990. http://hdl.handle.net/1853/15851.
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Woithe, Jonathan Mark. "Optical studies of the mesospheric region." Title page, contents and abstract only, 2000. http://web4.library.adelaide.edu.au/theses/09PH/09phw847.pdf.
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Includes copies of articles co-authored by the author during the preparation of this thesis. Includes bibliographical references (leaves 233-245). A three-field photometer was employed at the University of Adelaide's Buckland Park field site to collect optical observations of the 557.7nm OI and 730nm OH airglow emissions on an almost continuous basis since May 1995 to May 2000, with observations made whenever the moon was not up.
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De, Deuge Maria. "Optical observations of gravity waves in the high-latitude thermosphere /." Title page, abstract and contents only, 1990. http://web4.library.adelaide.edu.au/theses/09SM/09smd485.pdf.
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Schuetz, Christopher Arnim. "Optical techniques for millimeter-wave detection and imaging." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 179 p, 2007. http://proquest.umi.com/pqdweb?did=1397913011&sid=3&Fmt=2&clientId=8331&RQT=309&VName=PQD.
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Rainisch, Uri. "Detection of Ultrasonic Lamb Waves in Paper Using an Optical MEMS Microphone." Thesis, Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/4779.
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Laser ultrasonics has been used to measure the bending stiffness of paper products by measuring the dispersion of ultrasonic plate waves. In laser ultrasonics, ultrasound can be generated by absorption of pulsed laser spot while detection can be carried out by Laser Doppler Interferometry. The research presented in this paper describes a new method to detect ultrasonic plate waves using a recently developed acoustic transducer, more specifically an optical Micro ElectroMechanical System (MEMS) microphone with broadband capability. The MEMS device operates as a non-contact proximity probe placed less than ¼ a millimeter away from the plate. The signals are detected with a capacitive micromachined ultrasonic transducer (cMUT) in which the back electrode of the capacitive transducer on a transparent substrate is shaped as an optical diffraction grating. The displacement of the transducer membrane is determined using an optical interferometer. By applying voltage to deflect the membrane electrostatically, the detection sensitivity is kept at an optimum level.
The main purpose of the research presented herein was to test this MEMSs ability to detect ultrasonic waves propagating through paper, to increase the signal-to-noise ratio (SNR), and to calibrate the device in order to quantify the limitations on sensitivity in the context of the detection of ultrasound in paper. Similar tests were conducted for comparison with a modified Mach-Zehnder Interferometer, a more traditional method used for laser ultrasonic detection, and its results are presented in this paper.
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Toenger, Shanti. "Linear and Nonlinear Rogue Waves in Optical Systems." Thesis, Besançon, 2016. http://www.theses.fr/2016BESA2029/document.
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Ces travaux de thèse présentent l’étude des différentes classes d’effets linéaires et non-linéaires en optiquequi génèrent des événements extrêmes dont les propriétés sont analogues à celles des « vagues scélérates » destructrices qui apparaissent à la surface des océans. La thèse commence avec un bref aperçu de l’analogie physique entre la localisation d’onde dans les systèmes hydrodynamique et les systèmes optique, pour lesquels nous décrivons les mécanismes de génération de vagues scélérates linéaire et non-linéaire. Nous présentons ensuite quelques résultats numérique et expérimentaux de la génération de vagues scélérates dans un système optique linéaire dans le cas d’une propagation spatiale d’un champ optique qui présenteune phase aléatoire, où nous interprétons les résultats obtenus en terme de caustiques optiques localisées.Nous considérons ensuite les vagues scélérates obtenues dans des systèmes non-linéaires qui présentent une instabilité de modulation décrite par l’équation de Schrödinger non-linéaire (ESNL). Nous présentons une étude numérique détaillée comparant les caractéristiques spatio-temporelles des structures localisées obtenues dans les simulation numérique avec les différentes solutions analytiques obtenues à partir de l’ESNL.Deux études expérimentales d’instabilités de modulation sont ensuite effectuées. Dans la première, nous présentons des résultats expérimentaux qui étudient les propriétés d’instabilité de modulation en utilisant un système d’agrandissement temporel par lentille temporelle; dans la deuxième, nous rapportons des résultats expérimentaux sur les propriétés des instabilités de modulation dans le domaine fréquentiel en utilisant une technique de mesure spectrale en temps-réel. Cette dernière étude examine l’effet sur la bande spectrale et surla stabilité d’un faible champ perturbateur. Tous les résultats expérimentaux sont comparés avec la simulation d’ESNL et abordés en termes des propriétés qualitatives d’instabilité de modulation. Dans toutes ces études,différentes propriétés statistiques sont analysées en rapport avec l’apparition des vagues scélératesThis thesis describes the study of several different classes of linear and nonlinear effects in optics that generatelarge amplitude extreme events with properties analogous to the destructive “rogue waves” on the surface of theocean. The thesis begins with a brief overview of the analogous physics of wave localisation in hydrodynamicand optical systems, where we describe linear and nonlinear rogue wave generating mechanisms in bothcases. We then present numerical and experimental results for rogue wave generation in a linear opticalsystem consisting of free space propagation of a spatial optical field with random phase. Computed statisticsbetween experiment and modelling are in good agreement, and we interpret the results obtained in termsof the properties of localised optical caustics. We then consider rogue waves in the nonlinear system ofmodulation instability described by the Nonlinear Schrodinger Equation (NLSE), and a detailed numericalstudy is presented comparing the spatio-temporal characteristics of localised structures seen from numericalsimulations with different known analytic solutions to the NLSE. Two experimental studies of modulationinstability are then reported. In the first, we present experimental results studying the properties of modulationinstability using a time-lens magnifier system; in the second, we report experimental results studying thefrequency-domain properties of modulation instability using real-time spectral measurements. The latter studyexamines the effect of a weak seed field on spectral bandwidth and stability. All experimental results arecompared with the NLSE simulations and discussed in terms of the qualitative properties of modulationinstability, in order to gain new insights into the complex dynamics associated with nonlinear pulse propagation.In all of these studies, different statistical properties are analised in relation to the emergence of rogue waves
14
Zhou, Chuang. "Multimode wavelength division multiplexing and demultiplexing using substrate-guided waves and volume holographic gratings /." Digital version accessible at:, 1998. http://wwwlib.umi.com/cr/utexas/main.
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Fragos, Anastasios. "Lagrangian modelling of nonlinear waves in optical fibres." Thesis, University of Glasgow, 1997. http://theses.gla.ac.uk/1215/.
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The Lagrangian perturbation method for the NLS is revisited in the form of an equivalent direct problem. The analogy can be extended to arbitrarily perturbed systems. It is then possible to provide first order perturbation expansions for the fundamental soliton. The case of the damped NLS is considered and shown to fully comply with IST predictions. Subsequently the problem of NLS initial condition not corresponding to an exact soliton is examined. There are two issues that need to be considered: the location of the soliton solution and the modelling of the continuum. The location of the soliton solution is handled by considering the integrals of motion of the NLS. The improvement arises by the inclusion of the contributions due to the continuum. The results are compared with numerical calculations and are proved to be satisfactory provided that the initial pulse shape does not depart greatly from the Asech(z) functional form. The propagation problem is handled by considering the evolution of the soliton and the continuum separately and recombining them at the required time. Two cases are considered: the far field pattern and the position where the peak of the soliton lies. For the former the recombination of continuum with the soliton is achieved with the help of the inverse part of the IST. For the peak position a Bäcklund transform is considered. Results from both regimes are compared with numerical results and shown to agree satisfactorily.
16
Newboult, Gail. "Some mathematical problems of nonlinear guided optical waves." Thesis, University of Nottingham, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.328409.
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Chiao, Jung-Chih Rutledge David B. Rutledge David B. "Quasi-optical components for millimeter and submillimeter waves /." Diss., Pasadena, Calif. : California Institute of Technology, 1996. http://resolver.caltech.edu/CaltechETD:etd-12182007-105428.
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Sriratanavaree, Suchara. "The characterisation of acoustic waves in optical waveguides." Thesis, City University London, 2014. http://openaccess.city.ac.uk/11795/.
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Photonic active devices exploit the interaction of light with other physical effects such as carrier, fields, power density, stress, temperature, or sound. The Stimulated Brillouin scattering (SBS) in optical waveguide is an important nonlinear effect results from the coherent interactions between optical and acoustic modes. The SBS can be considered as a primary obstacle effect in limiting the power scaling in many high power photonic devices because it normally has a lower threshold than other nonlinear effects. However, it is also well known that the interaction of light and sound can be exploited in several key applications. The guiding of acoustic wave in of optical waveguides allow interactions of light wave with the related phenomena of Brillouin Scattering (BS), Stimulated Brillouin Scattering (SBS) and Guided Acoustic Wave Brillouin Scattering (GAWBS). This thesis describes and studies the characteristics of different acoustic modes in optical waveguides by using the finite element method (FEM). A numerical approach based on the versatile FEM has been developed and employed for the analysis of acoustic modes in optical waveguides and also their interactions with optical modes. The high and low index contrast waveguides which can be designed, fabricated and optimized for different applications. The detailed spatial variations of the transverse and longitudinal displacement vectors are shown for longitudinal, bending, torsional, radial and torsional-radial modes in these waveguides. The vectorial acoustic modes in optical waveguides are shown for both the high and mlow index contrast silica waveguide along with their dispersion curves, the displacement vectors for transverse and longitudinal movements and the modal hybridness have been mdetermined and shown. Stimulated Brillouin Scattering (SBS) frequencies are also reported here for subwavelength size silica, Ge-doped rectangular and silicon slot optical waveguides. Variation of the displacement vectors, modal hybridness, and modal dispersion are also shown. A finite element based computer code is developed using a full vectorial acoustic model and combining this with another full vectorial optical model, the interaction between acoustic and optical modes are presented here and their overlap integrals have also been calculated.
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STEIJN, KIRK WILLIAM. "COUPLING AND PROPAGATION OF SURFACE PLASMONS IN THE FAR-INFRARED (NEAR-MILLIMETER WAVES, SUB-MILLIMETER WAVES)." Diss., The University of Arizona, 1986. http://hdl.handle.net/10150/183973.
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This work describes a study of the propagation properties of a modified surface plasmon mode, and of the coupling properties of that mode using a grating coupler. The surface plasmon, a polariton involving coupling of electromagnetic waves to the plasma oscillations of a metal, is modified by the application of a dielectric overlayer to the interface between the metal and air. In the far infrared region of the electromagnetic spectrum, the overlayer causes dramatic changes in several properties of the mode, which can be verified by measuring the propagation length of the mode. Measurements at a wavelength of 118.8 μm of the propagation length as a function of the thickness of a polycrystalline silicon overlayer on silver showed that the mode has the expected properties. They also indicated that the Drude model of the dielectric function of the silver is valid at 118.8 μm, even when using established Drude parameters, which are based on measurements in the visible and near infrared region of the electromagnetic spectrum. The coupling study measured the fundamental coupling parameters, also at a wavelength of 118.8 μm, for coupling via a grating between free-space waves and the surface plasmon, and measured the effect of the overlayer on these parameters. Efficient coupling was achieved, but a theoretical treatment of the coupling system proved to be beyond the scope of first-order grating-coupler theory. This was true despite the fact that the grating amplitude was a small fraction of the wavelength, a common criterion for the application of such a theory. Several possible reasons for the breakdown of the theory were considered, but definite answers require additional experiments. The most prominent possibilities are the shape factor, and the depth of the grating compared to the penetration depth of the fields into the metal. Though not all the data is completely explained, the studies herein demonstrate that the overlayer eliminates many of the deficiencies which limit the generation and control of far-infrared surface plasmons.
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Kuhn, Robert. "Coherent transport of matter waves in disordered optical potentials." [S.l.] : [s.n.], 2007. http://opus.ub.uni-bayreuth.de/volltexte/2007/287.
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Aközbek, Neset. "Optical solitary waves in a photonic band gap material." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape15/PQDD_0007/NQ35096.pdf.
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Khalaf, Reem. "Image reconstruction for optical tomography using photon density waves." Thesis, University of Hertfordshire, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.302304.
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Kbashi, Hani. "Vector optical rogue waves in mode-locked fibre lasers." Thesis, Aston University, 2018. http://publications.aston.ac.uk/37771/.
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The project consists of an experimental characterisation of optical vector rogue wave (RW) events by using three different testbed fibre laser setups. The first testbed is a long cavity fibre laser (615 m). Here, we have demonstrated for the first time, a new type of vector resonance multimode instability that inherits some features of modulation and multimode instability. This instability leads to emerging different pulse laser regimes from longitudinal modes synchronization to different types of optical RW events. Using the same testbed fibre laser, we have also shown experimentally for the first time fibre twist-based chiral symmetry breaking. This leads to versatile laser dynamics tuneable from a periodic pulse similar mode-locked regime to chaotic oscillations which are revealed as a mechanism for the emergence of RW events. The observed optical RW events have been classified as fast optical RWs or slow optical RWs depending on the autocorrelation function of the experimental data. The classified optical RWs have been studied by collecting experimental data of a 19x19 grid of polarization positions through tuning both intra-cavity and pump polarization controllers. The second testbed is a passively mode-locked fibre laser. Using this system, the control, appearance and disappearance of the soliton rain flow were demonstrated for the first time using a low range of pump power. Harmonics soliton rain, soliton fission and soliton-soliton interactions leading to the emergence of optical RWs have also been demonstrated in this experiment at a different pump power and intra-cavity birefringence. High harmonic (902 MHz) mode-locked fibre laser based on acoustic-optic effect has been realized in the same laser experiment. In the third laser testbed experiment with, a stretched mode-locked fibre laser, vector bright-dark optical RWs were observed experimentally for the first time. These bright-dark RWs have formed in the laser cavity due to modulation instability at close pump power threshold or due to the polarization instability (incoherent coupling) at higher pump power.
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Tarlis, Aggelos. "Study of surface plasmon optical waves for sensing applications." Thesis, University of Bath, 2007. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.438617.
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Hole, Erik Lillebø. "Optical Fiber sensing of acoustic waves using overlapping FBGs." Thesis, Mittuniversitetet, Institutionen för elektronikkonstruktion, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:miun:diva-37779.
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The objective of this thesis was to investigate if an optical fiber sensing method with the use of two overlapping fiber Bragg gratings to measure Lamb wave $S_0$ modes in a steel plate, and how it would compare to traditional PZT transducers. A solution was proposed where the use of an optical fiber sensing system was built and took advantage of the strain dependence of a fiber Bragg grating mounted to a steel plate. Together with an overlapping reference fiber Bragg grating, the system can translate strain to light intensity. A method of controlling the Bragg wavelength of the reference fiber Bragg grating to optimize the overlap between the two fiber Bragg gratings, enabling the system to compensate for drift in the sensing fiber Bragg grating. Testing of the system was performed and yielded promising results, being able to measure the Lamb wave signal from the steel plate. The system showed some sensitivity limitations and signal to noise ratio, as well as the software created to compensate for the drift. With the improvement proposed for further work with the system in terms of improving the system's sensitivity, signal to noise ratio and drift control should make the system able to perform at levels as traditional PZT transducers.
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Lowney, Joseph Daniel. "Manipulating and Probing Angular Momentum and Quantized Circulation in Optical Fields and Matter Waves." Diss., The University of Arizona, 2016. http://hdl.handle.net/10150/612898.
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Methods to generate, manipulate, and measure optical and atomic fields with global or local angular momentum have a wide range of applications in both fundamental physics research and technology development. In optics, the engineering of angular momentum states of light can aid studies of orbital angular momentum (OAM) exchange between light and matter. The engineering of optical angular momentum states can also be used to increase the bandwidth of optical communications or serve as a means to distribute quantum keys, for example. Similar capabilities in Bose-Einstein condensates are being investigated to improve our understanding of superfluid dynamics, superconductivity, and turbulence, the last of which is widely considered to be one of most ubiquitous yet poorly understood subjects in physics. The first part of this two-part dissertation presents an analysis of techniques for measuring and manipulating quantized vortices in BECs. The second part of this dissertation presents theoretical and numerical analyses of new methods to engineer the OAM spectra of optical beams. The superfluid dynamics of a BEC are often well described by a nonlinear Schrodinger equation. The nonlinearity arises from interatomic scattering and enables BECs to support quantized vortices, which have quantized circulation and are fundamental structural elements of quantum turbulence. With the experimental tools to dynamically manipulate and measure quantized vortices, BECs are proving to be a useful medium for testing the theoretical predictions of quantum turbulence. In this dissertation we analyze a method for making minimally destructive in situ observations of quantized vortices in a BEC. Secondly, we numerically study a mechanism to imprint vortex dipoles in a BEC. With these advancements, more robust experiments of vortex dynamics and quantum turbulence will be within reach. A more complete understanding of quantum turbulence will enable principles of microscopic fluid flow to be related to the statistical properties of turbulence in a superfluid. In the second part of this dissertation we explore frequency mixing, a subset of nonlinear optical processes in which one or more input optical beam(s) are converted into one or more output beams with different optical frequencies. The ability of parametric nonlinear processes such as second harmonic generation or parametric amplification to manipulate the OAM spectra of optical beams is an active area of research. In a theoretical and numerical investigation, two complimentary methods for sculpting the OAM spectra are developed. The first method employs second harmonic generation with two non-collinear input beams to develop a broad spectrum of OAM states in an optical field. The second method utilizes parametric amplification with collinear input beams to develop an OAM-dependent gain or attenuation, termed dichroism for OAM, to effectively narrow the OAM spectrum of an optical beam. The theoretical principles developed in this dissertation enhance our understanding of how nonlinear processes can be used to engineer the OAM spectra of optical beams and could serve as methods to increase the bandwidth of an optical signal by multiplexing over a range of OAM states.
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Jia, Zhensheng. "Optical millimeter-wave signal generation, transmission and processing for symmetric super-broadband optical-wireless access networks." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/24640.
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Thesis (Ph.D.)--Electrical and Computer Engineering, Georgia Institute of Technology, 2009.Committee Chair: Gee-Kung Chang; Committee Co-Chair: Jianjun Yu; Committee Member: John A. Buck; Committee Member: Joy Laskar; Committee Member: Umakishore Ramachandran; Committee Member: Ye Li
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Reich, Oliver, Hans-Gerd Löhmannsröben, and Frank Schael. "Optical sensing with photon density waves: investigation of model media." Universität Potsdam, 2003. http://opus.kobv.de/ubp/volltexte/2007/1314/.
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Investigations with frequency domain photon density waves allow elucidation of absorption and scattering properties of turbid media. The temporal and spatial propagation of intensity modulated light with frequencies up to more than 1 GHz can be described by the P1 approximation to the Boltzmann transport equation. In this study, we establish requirements for the appropriate choice of turbid model media and characterize mixtures of isosulfan blue as absorber and polystyrene beads as scatterer. For these model media, the independent determination of absorption and reduced scattering coefficients over large absorber and scatterer concentration ranges is demonstrated with a frequency domain photon density wave spectrometer employing intensity and phase measurements at various modulation frequencies.
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Farnum, Edward D. "Stability and dynamics of solitary waves in nonlinear optical materials /." Thesis, Connect to this title online; UW restricted, 2005. http://hdl.handle.net/1773/6766.
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Wong, Luen Yan. "Optical trapping and binding of colloidal microparticles in evanescent waves." Thesis, Durham University, 2012. http://etheses.dur.ac.uk/3391/.
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Optical trapping of colloidal microparticle arrays in evanescent fields is a relatively new area of study. Optically driven array formation is a complex and fascinating area of study, since light mediated interactions have been shown to cause significantly different behaviour for multiple particles when compared with the behaviour of a single particle in an optical field. Array formation was studied with interference fringes in the counterpropagating evanescent fields so as to investigate the effect of a periodic trapping potential. A subtle balance between optical trapping and optical binding forces is shown to produce modulated lines and arrays. Optically trapped colloidal arrays were also studied in the absence of interference fringes, by using either orthogonally polarised laser beams or a beam delay line. When interference fringes were absent, the formation of arrays was mainly due to gradient forces and optical binding. The experimental studies presented here include the optical trapping of dielectric soft and hard spheres, Au colloids, and Janus particles.
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Kim, Arnold D. "Optical pulse propagation, diffusion and depolarization in discrete random media /." Thesis, Connect to this title online; UW restricted, 2000. http://hdl.handle.net/1773/6770.
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Sun, Xuan. "A study of ion acceleration, asymmetric optical pumping and low frequency waves in two expanding helicon plasmas." Morgantown, W. Va. : [West Virginia University Libraries], 2005. https://eidr.wvu.edu/etd/documentdata.eTD?documentid=4319.
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Thesis (Ph. D.)--West Virginia University, 2005.Title from document title page. Document formatted into pages; contains v, 152 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references.
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Swacek, Christian Bernhard. "Optical generation of tone-burst Rayleigh surface waves for nonlinear ultrasonic measurements." Thesis, Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/45812.
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Conventional contact ultrasonic methods suffer from large variability, which
is known to originate from a number of sources such as coupling variability, and the
surface roughness at the transducer/specimen interface. The inherently small higherharmonic
signals can be significantly influenced by the changes in contact conditions,
especially in nonlinear ultrasonic measurements. For this reason, the noncontact
generation and detection techniques are very attractive. This research first focuses
on the optical generation of tone-burst surface acoustic waves in a metallic specimen.
Two methods that use laser light as an optical source are compared for generating
surface acoustics waves in the 5 MHz range. Both the shadow mask and diffraction
grating are used to convert a laser pulse to a tone-burst signal pattern on the specimen.
The generated signals are detected by a wedge transducer at a fixed location and then
the harmonic contents in the generated signals and the repeatability of the methods
are evaluated. Finally, the developed method is used to characterize the material
nonlinearity of aluminum (Al 6061) and steel (A36). The results showed repeatable
measurements for ablative signal excitation on aluminum.
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Schiffers, Werner Paul. "Optical and acoustic investigation of laser-generated cavitation." Thesis, Loughborough University, 1997. https://dspace.lboro.ac.uk/2134/26862.
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Cavitation is the formation of vapour filled bubbles in a liquid. They can be generated either by the reduction of the ambient water pressure at constant temperature or by a temperature increase at constant pressure. In the results of the experiments presented in this work a range of different diameter cavitation bubbles were generated by focusing pulses of near IR radiation (le = 1064 nm) from a Q-switched Nd:YAG laser of varying energy in a small water tank. Single exposure high speed shadow photography and Schlieren techniques are used to visualise the oscillating motion of the cavitation bubbles with high temporal and spatial resolution. The optical analysis of the cavitation bubble in free water shows a smooth symmetrical oscillating motion during the first cycle. When the bubble is collapsing near a solid boundary the motion becomes asymmetrical. The Schlieren images in combination with matching plots of a thin film polyvinylidene fluoride (PVDF) pressure transducer confirm the formation of a liquid jet as well as different shock wave emissions for certain bubble to boundary parameters. They also indicate the importance of the resulting fluid flow to stresses induced in the solid boundary. In an attempt to visualise the fluid flow field around an oscillating cavitation bubble the IR laser radiation is focused in a solution of copper sulphate (CUS04) for contrast enhancement. High speed photography in combination with an accurately positioned Schlieren knife edge displays the heated path of the laser beam and the different shapes of the cavitation bubble. For the case of a bubble in free space the marked laser path indicates radial fluid flow only. For a bubble in front of a solid boundary the marked laser path clearly shows the motion of the fluid into the toroidal shaped bubble during the collapse process. For this case the marked paths are similar to numerically calculated streamline plots. In contrast to the solid boundary a flexible boundary was also used. The interaction of the cavitation bubble with the flexible boundary visualises partially the movement of the water but is found to still destroy some of the symmetry of the bubble.
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Sarrafzadeh-Khoee, Adel. "Small displacement measurement in ultrasound: quantitative optical noncontacting detection methods." Diss., Virginia Polytechnic Institute and State University, 1986. http://hdl.handle.net/10919/76498.
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In this study the description and development of intensity-based laser interferometric techniques for the detection and measurement of ultrasonic stress waves and their small displacement amplitudes is presented. The dynamic displacement sensitive interferometers described in the following chapters allow the quantitative point-by-point measurement of both in-plane and out-of-plane components of surface displacement motion.
These uniquely developed interferometric sensors are:
1) an optical system design for the detection of the surface acoustic wave (Rayleigh wave). The technique is based on the Fourier analysis of coherent light and diffraction imaging properties of an illuminated grating;
2) the design and construction of a two-beam unequal-path laser interferometer for the measurement of out-of-plane surface displacement of ultrasonic waves;
3) extension of a flexible fiber optic probing device which is optically coupled to the test arm of the above two-beam interferometer. This permits scanning of the test surface which may be at some distance from the main optical system components;
4) the design and construction of a laser speckle interferometer for retro-reflective diffusing surfaces in which the in-plane displacements of the ultrasonic wave are interrogated.
The inherent advantages of these newly designed optical configurations in terms of their greater simplicity, feasibility, and sensitivity over the conventional counterparts (classical/speckle laser interferometers) are explained. The function-response limitations of these interferometric sensors on lateral displacement resolution, on upper and lower-bound displacement sensitivity (dynamic range), on high-frequency bandwidth probing capability, on low-frequency environmentally associated noise disturbance, and on specularly reflective or diffusively retro-reflective specimen surface preparation are also mentioned.
Finally, in a series of experimental observations, the application of a couple of these acoustic sensors in pulsed-excitation ultrasonic Specifically, the optically testing methods is cited. detected ultrasonic signals revealing the true nature of the various surface displacement modes of vibration are presented.Ph. D.
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El-Ganainy, Ramy. "Optical Nonlinear Interactions In Dielectric Nano-Suspensions." Doctoral diss., University of Central Florida, 2009. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/4122.
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This work is divided into two main parts. In the first part (chapters 2-7) we consider the nonlinear response of nano-particle colloidal systems. Starting from the Nernst-Planck and Smoluchowski equations, we demonstrate that in these arrangements the underlying nonlinearities as well as the nonlinear Rayleigh losses depend exponentially on optical intensity. Two different nonlinear regimes are identified depending on the refractive index contrast of the nanoparticles involved and the interesting prospect of self-induced transparency is demonstrated. Soliton stability is systematically analyzed for both 1D and 2D configurations and their propagation dynamics in the presence of Rayleigh losses is examined. We also investigate the modulation instability of plane waves and the transverse instabilities of soliton stripe beams propagating in nonlinear nano-suspensions. We show that in these systems, the process of modulational instability depends on the boundary conditions. On the other hand, the transverse instability of soliton stripes can exhibit new features as a result of 1D collapse caused by the exponential nonlinearity. Many-body effects on the systems' nonlinear response are also examined. Mayer cluster expansions are used in order to investigate particle-particle interactions. We show that the optical nonlinearity of these nano-suspensions can range anywhere from exponential to polynomial depending on the initial concentration and the chemistry of the electrolyte solution. The consequence of these inter-particle interactions on the soliton dynamics and their stability properties are also studied. The second part deals with linear and nonlinear properties of optical nano-wires and the coupled mode formalism of parity-time (PT) symmetric waveguides. Dispersion properties of AlGaAs nano-wires are studied and it is shown that the group velocity dispersion in such waveguides can be negative, thus enabling temporal solitons. We have also studied power flow in nano-waveguides and we have shown that under certain conditions, optical pulses propagating in such structures will exhibit power circulations. Finally PT symmetric waveguides were investigated and a suitable coupled mode theory to describe these systems was developed.Ph.D.
Optics and Photonics
Optics and Photonics
Optics PhD
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Cooper, G. S. "Pulsed and CW waves in nonlinear optical fibre and planar waveguides." Thesis, University of Salford, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.381647.
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Barnes, W. L. "Guided optical waves in Langmuir-Blodgett films of 22-tricosenoic acid." Thesis, University of Exeter, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.374945.
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Mahdieh, Mohammad Hossain. "Optical diagnosis of shock waves driven by high power laser pulses." Thesis, University of Essex, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.307858.
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Urgiles, Ortiz Patricio Fernando. "2D and 3D visualization of acoustic waves by optical feedback interferometry." Thesis, Toulouse, INPT, 2019. http://www.theses.fr/2019INPT0094.
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La visualisation des phénomènes physiques est l’un des défis que les chercheurs tentent de relever en concevant et en mettant en œuvre différents capteurs qui fournissent des informationsproches de la réalité grâce à la modifications d’un des paramètres qu’ils mesurent. Historiquement, la visualisation des variations des phénomènes physiques a permis une une meilleure compréhension du problème étudié et a changé notre perception du monde et de nousmêmes pour toujours. Au cours des 300 dernières années, en particulier, de très nombreuses méthodes ont été développées pour visualiser le son à travers une représentation visuelle. Dans le domaine de l’acoustique, les scientifiques ont tenté de développer une représentation visuelle des ondes sonores à l’aide de transducteurs détectant deux composantes fondamentales du son : la pression acoustique et la vitesse des particules. En d’autres termes, la mesure de l’énergie cinétique et du potentiel, dont les quantités fournissent des informations sur le phénomène physique de propagation acoustique. Dans ce résumé, nous présentons succinctement les travaux de la thèse intitulée "2D and 3D visualization of acoustic waves by Optical Feedback Interferometry" dans laquelle un nouvel outil de visualisation des phénomènes acoustique a été dévelopé. Ce système est basé sur un capteur optique dit à réinjection dans une diode laser et permet de reconstruire en 2D et en 3D l’image d’une onde acoustique se propageant. Le manuscrit est divisé en 3 chapitres : • un premier chapitre présente les méthodes connues pour la visualisation des phénomènes acoustiques et présente le contexte des recherches menées, • un second chapitre, permet de détailler le principe de mesure et son application à la réalisation d’une image en deux dimensions de l’onde acoustique, • enfin, dans le dernier chapitre, nous démontrons comment par une méthode tomographique, une image en trois dimensions peut être réaliséeThe visualization of physical phenomena is one of the challenges that researchers are trying to overcome by designing and implementing different sensors that provide information close to realitythrough changes in one of the parameters they measure. Historically, the visualization of variations in physical phenomena has allowed for a better understanding of the problem being studied and has changed our perception of the world and ourselves forever. Over the last 300 years, in particular, many methods have been developed to visualize sound through a visual representation. In the field of acoustics, scientists have attempted to develop a visual representation of sound waves using transducers detecting two fundamental components of sound: sound pressure and particle velocity. In other words, the measurement of kinetic energy and potential, whose quantities provide information on the physical phenomenon of acoustic propagation. In this summary, we briefly present the work of the thesis entitled "2D and 3D Visualizations of Acoustic Waves by Optical Feedback Interferometry" in which a new visualization tool for acoustic phenomena was developed. This system is based on an optical sensor said reinjection in a laser diode and allows to reconstruct in 2D and 3D the image of a propagating acoustic wave. The manuscript is divided into 3 chapters: • a first chapter presents the known methods for the visualization of the acoustic phenomena and presents the context of the research carried out, • a second chapter, allows to detail the principle of measurement and its application to the realization of a two-dimensional image of the acoustic wave • finally, in the last chapter, we demonstrate how a tomographic method can be used to create a three-dimensional image
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Wilkinson, Sonja Renae. "A study of the optical transmission properties of the polymer HPG /." Full-text version available from OU Domain via ProQuest Digital Dissertations, 2000.
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Alcock, Robin D. "Transducers for measuring acoustic transients." Thesis, Loughborough University, 1997. https://dspace.lboro.ac.uk/2134/32473.
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This thesis is concerned with the design and development of measuring devices for the characterisation of acoustic transients with high temporal and spatial resolution. Three new techniques are demonstrated characterising acoustic transients generated by Nd-YAG laser (1060nm, 30ns, 55mJ) assisted breakdown of water and air. The first technique demonstrates the use of a high power semiconductor laser in a high speed multiple exposure imaging system. This system developed is capable of illuminating an event with up to 10 pulses of light at a maximum repetition rate of 5MHz, with a timing accuracy of ≈5ns. Each semiconductor laser light pulse has a FWHM duration of 50ns, peak power of 30W, and a wavelength of 860nm. Images of individual acoustic transients are displayed on the same CCD camera frame, and it was found that this is best achieved using a dark field imaging technique such as Schlieren imaging.
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Twardowski, T. "Exact theory of surface-guided TM and coupled TE-TM nonlinear electromagnetic waves." Thesis, University of Salford, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.381757.
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Pack, Jeong-Ki. "Numerical simulation of optical wave propagation through random media." Diss., Virginia Polytechnic Institute and State University, 1988. http://hdl.handle.net/10919/82642.
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The propagation of optical plane waves through a one-dimensional Gaussian phase screen and a two-dimensional Gaussian extended medium are simulated numerically, and wave statistics are calculated from the data obtained by the numerical simulation. For instantaneous realization of a random medium, a simplified version of the random-motion model [77] is used, and for wave-propagation calculation the wave-kinetic numerical method and/or the angular-spectral representation of the Huygens-Fresnel diffraction formula are used. For the wave-kinetic numerical method, several different levels of approximations are introduced, and the region of validity of those approximations is studied by single-realization calculations. Simulation results from the wave-kinetic numerical method are compared, either with those from the existing analytical expressions for the phase-screen problem, or with those from the Huygens-Fresnel diffraction formula for the extended-medium problem. Excellent agreement has been observed. Extension to two-dimensional media with the power-law spectrum or three-dimensional problems is straight-forward. We may also deal with space-time correlations using, for example, Taylor's frozen-in hypothesis.Ph. D.
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Nau, Gregory Merrill. "Optical fiber detection of ultrasonic vibration and acoustic emission." Thesis, This resource online, 1992. http://scholar.lib.vt.edu/theses/available/etd-09292009-020053/.
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Wirsz, Douglas Franklin. "Factor analysis processing of inductively coupled plasma optical emission spectra recorded using a photodiode array spectrometer." Thesis, University of British Columbia, 1990. http://hdl.handle.net/2429/31418.
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Multivariate methods have been developed to assist in the interpretation of multiwavelength spectral data. When carrying out an elemental analysis by optical emission spectrometry, the analyst is faced with a choice of many spectral lines on which to base the analysis. The problem of choosing a suitable line depends upon other components in the sample, as some of these lines may suffer from spectral interferences, depending upon the nature of the sample matrix. The selection of the most suitable line for the determination of a desired component is conventionally accomplished by consulting tables of spectral emissions, and selecting a line on the basis of freedom from spectral overlap, taking into consideration the bandwidth of the spectrometer. Unfortunately, many weaker lines are not tabulated, although they may nevertheless interfere if the interfering element is at a high enough concentration. As well, emissions from sample-specific species, such as molecular species, will not be tabulated. As the possibility that a spectral line will cause a significant interference depends upon interferent concentration, the analyst has previously required detailed knowledge of the nature of other components in a sample.
The methods developed in this thesis facilitate the determination of a desired component in binary, ternary, or more complex mixtures without prior knowledge of the nature of any interfering components. This automatic line selection allows the matrix-dependent tailoring of the lines chosen to the element or elements of interest. Factor analysis determines those wavelengths where an unidentified interferent contributes to the measured intensity. A multivariate analysis based on selected wavelengths gives the concentrations of all desired components while avoiding error in these concentrations due to interferents.
Using a related method, the best analytical line for the determination of a specified analyte is selected from a set of lines on the basis of the least interference in a particular sample matrix, by several cycles of mathematical analysis. Unsuitable lines are rejected in the first few cycles, the best lines being retained until last. A multivariate analysis after each cycle provides an updated estimate of the analyte concentration. As with other methods in this thesis, this process is performed without reference to spectral tables.
Application of these methods to a recently developed high resolution photodiode array based polychromator system is also discussed. This has consequences for the design and selection of spectral masks to assist in multielement analysis on this spectrometer.
In the course of development of these multivariate methods, the need for improved dynamic range in the photodiode array was seen. An algorithm for the generation of dynamic range enhanced photodiode array spectra has been developed and implemented.Science, Faculty of
Chemistry, Department of
Graduate
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Schediwy, Sascha W. "Optical spring parametric interactions in a macroscopic opto-mechanical resonator." University of Western Australia. School of Physics, 2007. http://theses.library.uwa.edu.au/adt-WU2007.0161.
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[Truncated abstract] The research described in this thesis investigated optical spring interactions and instabilities in a macroscopic opto-mechanical resonator. The thesis describes an experiment designed to model an optical spring `tranquiliser’ cavity which has been proposed to suppress the predicted parametric instabilities in the next generation of interferometric gravitational wave detectors. In a series of experiments, the optical spring effect was observed in macroscopic optical cavities through measured changes in mechanical stiffness, and measured changes in mechanical loss. The optical spring effect was further characterised through investigation of its dependent parameters. Two pairs of identical, low optical loss mirrors were bonded to a mechanical structure using a novel low mechanical loss technique, forming an opto-mechanical composite resonator. The technique uses the naturally occurring resin Yacca gum as a bonding agent. This resulted in the formation of two optical cavities with a length of l = 0.100±0.001m, only one of which was used in experiments. Using finite element modelling, the resonator?s two lowest modes, with frequencies of fm1 = 722.8Hz and fm2 = 747.9Hz, and an effective mass 0.0323±0.0001kg, were found to be subject to the optical spring effect. ... The instabilities are expected to have a parametric gain factor of up to 100 in the frequency range of 15-120kHz. Therefore, if optical spring damping can be made large enough to reduce the Q-factor of the Advanced LIGO test-masses by a factor of 100, all parametric instabilities should be eliminated. For a simple servo loop and an optical cavity with the practically achievable finesse of F = 30,000, a tranquiliser cavity length of 1.3cm was found to produce optimum enhanced damping. This configuration only requires 1.47W of input power, resulting in an intra-cavity power of 5.72kW. The cavity mirrors were assumed to have optical coatings with a damage threshold of 1MW/cm2, which limited the spot size to a minimum area of 0.572mm2, or a radial beam waist of w = 0.427mm. This nearly flat-flat cavity has a stability g-factor of 0.9997. Even given these technical challenges, suppression of the parametric instabilities predicted to occur in the next generation of interferometric detectors is possible to achieve practically using enhanced optical spring damping. A possible design for such a tranquiliser cavity is also suggested.
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Lima, Francisco Tiago. "Numerical Study of Optical Bistabilidade in an Acousto Optical Tunable Filter Hybrid." Universidade Federal do CearÃ, 2010. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=10854.
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CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel SuperiorIn this work, we show the initial results of Acousto Optical Tunning Filter in hybrid configuration (HAOTF). This hibrid device have a feedback circuit that connect in SAW can be influence by output in only one mode polarization of the AOTF. Such the croostalk and transmission characteristic of AOTF dependent â output, result in behavior bistable. We analyze the input power by output power in device opering with continuos wave (CW), nonlinear (SPM) and without loss. Obtain the loop of bistability to display the relation between input power and output power considering parameters of AOTF, since: the product among coupling coefficient (κ ) and deviceâs length (ξL ), gain ( G ) and phase mismatching ( ∆β ).
Nesta dissertaÃÃo, apresentamos os resultados de um estudo sobre um AOTF numa configuraÃÃo hÃbrida, caracterizada pela presenÃa de um circuito de realimentaÃÃo. Este circuito de realimentaÃÃo permite que a tensÃo elÃtrica, aplicada ao transdutor (SAW), possa ser influenciada pela potencia de saÃda de uma das polarizaÃÃes do AOTF. Desta forma, a condiÃÃo de casamento de fase (freqÃÃncia de ressonÃncia) e as caracterÃsticas de transmissÃo do AOTF tornam-se dependentes da potencia de saÃda, resultando numa resposta biestÃvel. Inicialmente esta anÃlise consiste em observar a potÃncia do campo incidente pela potÃncia do campo emergente, com o dispositivo operando sob a aÃÃo de uma onda contÃnua no tempo (CW), em regime nÃo linear (SPM) e sem perdas. Neste sentido, obtemos as curvas de biestabilidade, mostrando a relaÃÃo entre as potÃncias de entrada e saÃda, em funÃÃo de diversos parÃmetros do AOTF, como: o produto entre a constante de acoplamento ( κ ) e o comprimento do dispositivo ( ξL ), alÃm do fator de conversÃo potencia - constante de propagaÃÃo de onda ( G ) e do descasamento de fase ( ∆β ).
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Iskandarani, Saad S. "Electromagnetic wave propagation in anisotropic uniaxial slab waveguide." Ohio : Ohio University, 1989. http://www.ohiolink.edu/etd/view.cgi?ohiou1182437230.
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Taouk, Habib B. "Optical wave propagation in active media." Ohio : Ohio University, 1991. http://www.ohiolink.edu/etd/view.cgi?ohiou1173729381.
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