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Rabb, David J. "The spherical fourier cell and application for true-time delay." The Ohio State University, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=osu1197045216.
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Smartt, Christopher James. "Fourier methods for the analysis of integrated optics devices." Thesis, University of Nottingham, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.294708.
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Chew, Theam Yong. "Wavefront sensors in Adaptive Optics." Thesis, University of Canterbury. Electrical and Computer Engineering, 2008. http://hdl.handle.net/10092/1645.
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Atmospheric turbulence limits the resolving power of astronomical telescopes by distorting
the paths of light between distant objects of interest and the imaging camera at the telescope.
After many light-years of travel, passing through the turbulence in that last 100km of a
photon’s journey results in a blurred image in the telescope, no less than 1” (arc-second)
in width. To achieve higher resolutions, corresponding to smaller image widths, various
methods have been proposed with varying degrees of effectiveness and practicality.
Space telescopes avoid atmospheric turbulence completely and are limited in resolution
solely by the size of their mirror apertures. However, the design and maintenance cost of
space telescopes, which increases prohibitively with size, has limited the number of space
telescopes deployed for astronomical imaging purposes. Ground based telescopes can be
built larger and more cheaply, so atmospheric compensation schemes using adaptive optical
cancellation mirrors can be a cheaper substitute for space telescopes.
Adaptive optics is referred to here as the use of electronic control of optical component to
modify the phase of an incident ray within an optical system like an imaging telescope. Fast
adaptive optics systems operating in real-time can be used to correct the optical aberrations
introduced by atmospheric turbulence. To compensate those aberrations, they must first
be measured using a wavefront sensor. The wavefront estimate from the wavefront sensor
can then be applied, in a closed-loop system, to a deformable mirror to compensate the
incoming wavefront.
Many wavefront sensors have been proposed and are in used today in adaptive optics and
atmospheric turbulence measurement systems. Experimental results comparing the performance
of wavefront sensors have also been published. However, little detailed analyses
of the fundamental similarities and differences between the wavefront sensors have been
performed.
This study concentrates on fourmain types of wavefront sensors, namely the Shack-Hartmann,
pyramid, geometric, and the curvature wavefront sensors, and attempts to unify their description
within a common framework. The quad-cell is a wavefront slope detector and is
first examined as it lays the groundwork for analysing the Shack-Hartmann and pyramid
wavefront sensors.
The quad-cell slope detector is examined, and a new measure of performance based on the
Strehl ratio of the focal plane image is adopted. The quad-cell performance based on the
Strehl ratio is compared using simulations against the Cramer-Rao bound, an information
theoretic or statistical limit, and a polynomial approximation. The effects of quad-cell
modulation, its relationship to extended objects, and the effect on performance are also
examined briefly.
In the Shack-Hartmann and pyramid wavefront sensor, a strong duality in the imaging and
aperture planes exists, allowing for comparison of the performance of the two wavefront
sensors. Both sensors subdivide the input wavefront into smaller regions, and measure the
local slope. They are equivalent in every way except for the order in which the subdivision
and slope measurements were carried out. We show that this crucial difference leads to a
theoretically higher performance from the pyramid wavefront sensor. We also presented
simulations showing the trade-off between sensor precision and resolution.
The geometric wavefront sensor can be considered to be an improved curvature wavefront
sensor as it uses a more accurate algorithm based on geometric optics to estimate the wavefront.
The algorithm is relatively new and has not found application in operating adaptive
optics systems. Further analysis of the noise propagation in the algorithm, sensor resolution,
and precision is presented. We also made some observations on the implementation
of the geometric wavefront sensor based on image recovery through projections.
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Sitter, David Norbert. "Space invariant modeling in three-dimensional optical image formation." Diss., Georgia Institute of Technology, 1991. http://hdl.handle.net/1853/13450.
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Blanchard, Romain. "Fourier optics for wavefront engineering and wavelength control of lasers." Thesis, Harvard University, 2013. http://dissertations.umi.com/gsas.harvard:11216.
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Since their initial demonstration in 1994, quantum cascade lasers (QCLs) have become prominent sources of mid-infrared radiation. Over the years, a large scientific and engineering effort has led to a dramatic improvement in their efficiency and power output, with continuous wave operation at room temperature and Watt-level output power now standard. However, beyond this progress, new functionalities and capabilities need to be added to this compact source to enable its integration into consumer-ready systems. Two main areas of development are particularly relevant from an application standpoint and were pursued during the course of this thesis: wavelength control and wavefront engineering of QCLs. The first research direction, wavelength control, is mainly driven by spectroscopic applications of QCLs, such as trace gas sensing, process monitoring or explosive detection. We demonstrated three different capabilities, corresponding to different potential spectroscopic measurement techniques: widely tunable single longitudinal mode lasing, simultaneous lasing on multiple well-defined longitudinal modes, and simultaneous lasing over a broad and continuous range of the spectrum. The second research direction, wavefront engineering of QCLs, i.e. the improvement of their beam quality, is relevant for applications necessitating transmission of the QCL output over a large distance, for example for remote sensing or military countermeasures. To address this issue, we developed plasmonic lenses directly integrated on the facets of QCLs. The plasmonic structures designed are analogous to antenna arrays imparting directionality to the QCLs, as well as providing means for polarization control. Finally, a research interest in plasmonics led us to design passive flat optical elements using plasmonic antennas. All these projects are tied together by the involvement of Fourier analysis as an essential design tool to predict the interaction of light with various gratings and periodic arrays of grooves and scatterers.Engineering and Applied Sciences
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Zhou, Zhiping James. "Diffractive optical elements for interconnections." Diss., Georgia Institute of Technology, 1993. http://hdl.handle.net/1853/13033.
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Khodabakhsh, Amir. "Fourier transform and Vernier spectroscopy using optical frequency combs." Doctoral thesis, Umeå universitet, Institutionen för fysik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-134439.
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Optical frequency comb spectroscopy (OFCS) combines two previously exclusive features, i.e., wide optical bandwidth and high spectral resolution, enabling precise measurements of entire molecular bands and simultaneous monitoring of multiple gas species in a short measurement time. Moreover, the equidistant mode structure of frequency combs enables efficient coupling of the comb power to enhancement resonant cavities, yielding high detection sensitivities. Different broadband detection methods have been developed to exploit the full potential of frequency combs in spectroscopy, based either on Fourier transform spectroscopy or on dispersive elements.There have been two main aims of the research presented in this thesis. The first has been to improve the performance of mechanical Fourier transform spectrometers (FTS) based on frequency combs in terms of sensitivity, resolution and spectral coverage. In pursuit of this aim, we have developed a new spectroscopic technique, so-called noise-immune cavity-enhanced optical frequency comb spectroscopy (NICE-OFCS), and achieved a shot-noise-limited sensitivity and low ppb (parts-per-billion, 10−9) CO2 concentration detection limit in the near-infrared range using commercially available components. We have also realized a novel method for acquisition and analysis of comb-based FTS spectra, a so-called sub-nominal resolution method, which provides ultra-high spectral resolution and frequency accuracy (both in kHz range, limited only by the stability of the comb) over the broadband spectral range of the frequency comb. Finally, we have developed an optical parametric oscillator generating a frequency comb in the mid-infrared range, where the strongest ro-vibrational molecular absorption lines reside. Using this mid-infrared comb and an FTS, we have demonstrated, for the first time, comb spectroscopy above 5 μm, measured broadband spectra of several species and reached low ppb detection limits for CH4, NO and CO in 1 s.The second aim has been more application-oriented, focused on frequency comb spectroscopy in combustion environments and under atmospheric conditions for fast and sensitive multispecies detection. We have demonstrated, for the first time, cavity-enhanced optical frequency comb spectroscopy in a flame, detected broadband high temperature H2O and OH spectra using the FTS in the near-infrared range and showed the potential of the technique for flame thermometry. For applications demanding a short measurement time and high sensitivity under atmospheric pressure conditions, we have implemented continuous-filtering Vernier spectroscopy, a dispersion-based spectroscopic technique, for the first time in the mid-infrared range. The spectrometer was sensitive, fast, robust, and capable of multispecies detection with 2 ppb detection limit for CH4 in 25 ms.Optisk frekvenskamspektroskopi (OFCS) kombinerar två tidigare icke förenliga egenskaper, dvs. ett brett optiskt frekvensområde med en hög spektral upplösning, vilket möjliggör noggranna mätningar av hela molekylära absorptionsband och detektion av flera gaser samtidigt med en kort mättid. Eftersom frekvenskammar har en regelbunden struktur med jämnt separerade laser moder kan man effektivt koppla kammen till en optisk kavitet och därmed möjliggöra frekvenskamsdetektion med hög känslighet. Olika metoder har utvecklats för att utnyttja frekvenskammarnas fulla potential för spektroskopi, baserad på antingen Fouriertransform-spektroskopi eller dispersiva element.Forskningen som presenteras i denna avhandling har haft två huvudmål. Det första har varit att förbättra prestandan hos mekaniska Fourier-transformspektrometrar (FTS) baserat på frekvenskammar med avseende på känslighet, upplösning och spektral täckning. I strävan efter detta har vi utvecklat en ny spektroskopisk teknik, benämnd brusimmun kavitetsförstärkt optisk frekvenskamspektroskopi (NICE-OFCS), och uppnått en hagelbrusbegränsad känslighet och detektionsgränser ner till låga ppb koncentrationer (miljarddelar, 10−9) för CO2 i det när-infraröda frekvensområdet enbart med användning av kommersiellt tillgängliga komponenter. Vi har också utvecklat en ny metod för insamling och analys av kambaserade FTS-spektra, som betecknas ha sub-nominell upplösning. Metoden gör det möjligt att uppnå ultrahög spektral upplösning och hög frekvensnoggrannhet (båda i kHz-området, endast begränsad av kammens stabilitet) över kammens hela frekvensområde. Slutligen har vi utvecklat en optisk parametrisk oscillator som genererar en frekvenskam i det mid-infraröda frekvensområdet, där de starkaste rotations-vibrationsmolekylära absorptionslinjerna finns. Med hjälp av denna kam och en FTS har vi för första gången demonstrerat frekvenskamspektroskopi över 5 μm. Vi har detekterat bredbandsspektra av flera molekylära gaser och har, för mättider på 1 s, uppnått detektionsgränser ner till låga ppb halter för CH4, NO och CO.Det andra syftet har varit mer applikationsorienterat: att använda frekvenskamspektroskopi i förbränningsmiljö och under atmosfäriska förhållanden för snabb och känslig multiämnesdetektion. Vi har för första gången demonstrerat kavitetsförstärkt optisk frekvenskamspektroskopi i en flamma, där vi har detekterat högtemperaturspektra av H2O och OH i det när-infraröda området med användning av FTS och visat teknikens potential för termometrisk karakterisering av flammor. För applikationer som kräver en kort mättid och hög känslighet under atmosfäriska förhållanden har vi utvecklat ett detektionssystem baserat på Vernier-spektroskopi med kontinuerlig filtrering, vilket är en dispersionsbaserad teknik, för första gången i det mid-infraröda frekvensområdet. Det befanns att spektrometern var känslig, snabb, robust och kapabel till multiämnesdetektion med en detektionsgräns på 2 ppb för CH4 för korta mättider (25 ms).
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Noorizadeh, Sahand. "SLM-based Fourier Differential Interference Contrast Microscopy." PDXScholar, 2014. https://pdxscholar.library.pdx.edu/open_access_etds/2011.
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Optical phase microscopy provides a view of objects that have minimal to no effect on the detected intensity of light that are unobservable by standard microscopy techniques. Since its inception just over 60 years ago that gave us a vision to an unseen world and earned Frits Zernike the Nobel prize in physics in 1953, phase microscopy has evolved to find various applications in biological cell imaging, crystallography, semiconductor failure analysis, and more. Two common and commercially available techniques are phase contrast and differential interference contrast (DIC). In phase contrast method, a large portion of the unscattered light that accounts for the majority of the light passing unaffected through a transparent medium is blocked to allow the scattered light due to the object to be observed with higher contrast. DIC is a self-referenced interferometer that transduces phase variation to intensity variation. While being established as fundamental tools in many scientific and engineering disciplines, the traditional implementation of these techniques lacks the ability to provide the means for quantitative and repeatable measurement without an extensive and cumbersome calibration. The rapidly growing fields in modern biology meteorology and nano-technology have emphasized the demand for a more robust and convenient quantitative phase microscopy. The recent emergence of modern optical devices such as high resolution programmable spatial light modulators (SLM) has enabled a multitude of research activities over the past decade to reinvent phase microscopy in unconventional ways. This work is concerned with an implementation of a DIC microscope containing a 4-f system at its core with a programmable SLM placed at the frequency plane of the imaging system that allows for employing Fourier pair transforms for wavefront manipulation. This configuration of microscope provides a convenient way to perform both wavefront shearing with quantifiable arbitrary shear amount and direction as well as phase stepping interferometry by programming the SLM with a series of numerically generated patterns and digitally capturing interferograms for each step which are then used to calculate the objects phase gradient map. Wavefront shearing is performed by generating a pattern for the SLM where two phase ramp patterns with opposite slopes are interleaved through a random selection process with uniform distribution in order to mimic the simultaneous presence of the ramps on the same plane. The theoretical treatment accompanied by simulations and experimental results and discussion are presented in this work.
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Noureddine, Mohamed. "Fourier variational methods for the analysis of optical waveguides and lasers." Thesis, University of Nottingham, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.263466.
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Hjältén, Adrian. "Modeling the cavity dispersion in cavity-enhanced optical frequency comb Fourier transform spectroscopy." Thesis, Umeå universitet, Institutionen för fysik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-157146.
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Cavity enhanced optical frequency comb spectroscopy is a technique that allows for quick and sensitive measurements of molecular absorption spectra. Locking the comb lines of an optical frequency comb to the cavity modes of an enhancement cavity and then extracting the spectral information with a Fourier transform spectrometer grants easy access to wide segments of absorption spectra. One of the main obstacles complicating the analysis of the measurements is the inevitable dispersion occurring inside the cavity. In this project, absorption measurements of CO2 were performed using an existing and well established setup consisting of a near-infrared optical frequency comb locked to a Fabry- Pérot enhancement cavity using the Pound-Drever-Hall technique, and a Fourier transform spectrometer. The purpose was to improve theoretical models of the measured absorption spectra by creating and verifying a model for the cavity dispersion, stemming mostly from the cavity mirrors but also from the normal dispersion of the intracavity medium. Until now, the cavity dispersion has been treated as an unknown and was included as a fitting parameter together with the CO2 concentration when applying fits to the absorption measurements. The dispersion model was based on previously performed precise measurements of the positions of the cavity modes. The model was found to agree well with measurements. In addition, pre-calculating the dispersion drastically reduced computation time and seemed to improve the overall robustness of the fitting routine. A complicating factor was found to be small discrepancies between the locking frequencies as determined prior to the measurements and the values yielding optimum agreement with the model. These apparent shifts of the locking points were found to have a systematic dependence on the distance between the locking points. The exact cause of this was not determined but the results indicate that with the locking points separated by more than about 10nm the shifts are negligible.
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Parks, Daniel. "X-ray Scattering Techniques for Coherent Imaging in Reflection Geometry, Measurement of Mutual Intensity, and Symmetry Determination in Disordered Materials." Thesis, University of Oregon, 2013. http://hdl.handle.net/1794/13221.
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The advent of highly-coherent x-ray light sources, such as those now available world-wide in modern third-generation synchrotrons and increasingly available in free-electron lasers, is driving the need for improved analytical and experimental techniques which exploit the coherency of the generated light. As the light illuminating a sample approaches full coherence, a simple Fourier transform describes the diffraction pattern generated by the scattered light in the far field; because the Fourier transform of an object is unique, coherent scattering can directly probe local structure in the scattering object instead of bulk properties.
In this dissertation, we exploit the coherence of Advanced Light Source beamline 12.0.2 to build three types of novel coherent scattering microscopes. First, we extend the techniques of coherent diffractive imaging and Fourier transform holography, which uses iterative computational methods to invert oversampled coherent speckle patterns, into reflection geometry. This proof-of-principle experiment demonstrates a method by which reflection Bragg peaks, such as those from the orbitally-ordered phase of complex metal oxides, might eventually be imaged. Second, we apply a similar imaging method to the x-ray beam itself to directly image the mutual coherence function with only a single diffraction pattern.
This technique supersedes the double-slit experiments commonly seen in the scattering literature to measure the mutual intensity function by using a set of apertures which effectively contains all possible double slit geometries. Third, we show how to evaluate the speckle patterns taken from a labyrinthine domain pattern for "hidden" rotational symmetries. For this measurement, we modify the iterative algorithms used to invert speckle patterns to generate a large number of domain configurations with the same incoherent scattering profile as the candidate pattern and then use these simulations as the basis for a statistical inference of the degree of ordering in the domain configuration. We propose extending this measurement to position-resolved speckle patterns, creating a symmetry-sensitive microscope. The three new techniques described herein may be employed at current and future light sources.
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Matalgah, Mustafa M. "Geometric theory for designing optical binary amplitude and binary phase-only filters /." free to MU campus, to others for purchase, 1996. http://wwwlib.umi.com/cr/mo/fullcit?p9717158.
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Fauvarque, Olivier. "Optimisation des analyseurs de front d'onde à filtrage optique de Fourier." Thesis, Aix-Marseille, 2017. http://www.theses.fr/2017AIXM0257/document.
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L'Europe prépare actuellement le plus grand télescope du monde : l'European Extremely Large Telescope (E-ELT). Prévu vers 2026, ce télescope géant permettra de répondre à des questions fondamentales de l'astrophysique contemporaine. L'imagerie d'objets astrophysiques depuis des télescopes au sol est cependant perturbée par l'atmosphère qui réduit la capacité des instruments au sol à distinguer les objets proches. L'Optique Adaptative (OA) permet de restaurer cette résolution angulaire en corrigeant en temps réel (via un miroir déformable) le front d'onde perturbé par l'atmosphère (mesuré par l'Analyseur de Surface d'Onde (ASO)). Jusqu'à récemment, la majorité des systèmes d'OA utilisaient des ASO Shack-Hartmann (SH). Des concepts concurrents basés sur le filtrage optique de Fourier (le senseur Pyramide ou l'analyseur Zernike) viennent cependant d'être mis en fonctionnement et leurs résultats semblent surpasser les performances du SH. En vue de leur potentielle utilisation sur les ELTs, cette thèse vise à consolider leur compréhension théorique ainsi qu'à optimiser ces ASO basés sur le filtrage de Fourier. Cette thèse développe un cadre mathématique qui décrit sous un unique formalisme ces ASO. Il permet de généraliser les designs préexistants -passant ainsi d'ASO uniques à des "classes d'ASO"- en transformant leurs grandeurs caractéristiques à l'origine fixées en degrés de liberté. Les classes Pyramide et Zernike sont donc explorées dans le but d'optimiser ces ASO au regard des attentes expérimentales. Des configurations inédites de la classe Pyramide -ASO que l'on appelle Pyramides aplaties- s'avèrent notamment prometteuses et font l'objet d'une étude plus pousséeEurope is currently preparing the largest telescope of the world: the European Extremely Large Telescope (E-ELT). Planned by 2026, this huge telescope will allow to answer fundamental questions of contemporary astrophysics. However, images of astrophysical objects done by ground based telescopes suffer from the atmospheric turbulence which reduces the capacity of instruments to distinguish objects too close to each other. The Adaptive Optics (AO) allows to restore this loss of angular resolution by correcting (thanks to a deformable mirror) in real time the perturbed wave front (measured by the WaveFront Sensor (WFS)).Until very recently, the majority of AO systems had used the Shack-Hartmann (SH) WFS. New concepts based on Fourier filtering (the Pyramid or the Zernike WFSs) have however just been put in operation in several professional observatories and their results seem to outperform the SH. Since they would potentially be chosen for the AO systems of the future ELTs, this thesis aims to consolidate their theoretical understanding and to optimize these Fourier based WFSs.We firstly develop a mathematical framework which describes all these WFSs under an unique formalism. It allows to generalize the pre-existent designs -a WFS thus becomes a "WFS class"- by considering their optical parameters as flexible quantities. We then explored the two Pyramid and Zernike classes to identify the influence of class' parameters on performance criteria in order to optimize optical designs with regard to the instrumental requirements. New configurations of the Pyramid class -that we called Flattened pyramids- show promising behaviors and are studied in details
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Lucotte, Bertrand M. "Fourier optics approaches to enhanced depth-of-field applications in millimetre-wave imaging and microscopy." Thesis, Heriot-Watt University, 2010. http://hdl.handle.net/10399/2323.
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In the first part of this thesis millimetre-wave interferometric imagers are considered for short-range applications such as concealed weapons detection. Compared to real aperture systems, synthetic aperture imagers at these wavelengths can provide improvements in terms of size, cost, depth-of-field (DoF) and imaging flexibility via digitalrefocusing. Mechanical scanning between the scene and the array is investigated to reduce the number of antennas and correlators which drive the cost of such imagers. The tradeoffs associated with this hardware reduction are assessed before to jointly optimise the array configuration and scanning motion. To that end, a novel metric is proposed to quantify the uniformity of the Fourier domain coverage of the array and is maximised with a genetic algorithm. The resulting array demonstrates clear improvements in imaging performances compared to a conventional power-law Y-shaped array. The DoF of antenna arrays, analysed via the Strehl ratio, is shown to be limited even for infinitely small antennas, with the exception of circular arrays. In the second part of this thesis increased DoF in optical systems with Wavefront Coding (WC) is studied. Images obtained with WC are shown to exhibit artifacts that limit the benefits of this technique. An image restoration procedure employing a metric of defocus is proposed to remove these artifacts and therefore extend the DoF beyond the limit of conventional WC systems. A transmission optical microscope was designed and implemented to operate with WC. After suppression of partial coherence effects, the proposed image restoration method was successfully applied and extended DoF images are presented.
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Martinache, Frantz, Nemanja Jovanovic, and Olivier Guyon. "Subaru Coronagraphic eXtreme Adaptive Optics: on-sky performance of the asymmetric pupil Fourier wavefront sensor." SPIE-INT SOC OPTICAL ENGINEERING, 2016. http://hdl.handle.net/10150/622025.
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The Subaru Coronagraphic Extreme Adaptive Optics (SCExAO) instrument relies on a technique known as the asymmetric pupil Fourier wavefront sensor (APF-WFS) to compensate for the non-common path error that affects the performance of high contrast imaging instruments. The APF-WFS is a powerful tool that senses the wavefront at the level of the science detector, and leads to unbiased wavefront estimates. This paper presents the latest status, linearity properties and reports on the on-sky performance of this sensor, as it is implemented on SCExAO, used to control low-order Zernike modes in a close-loop system.
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Hansson, Peter. "Surface Characterization using Radiometric and Fourier Optical Methods." Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis : Univ.-bibl. [distributör], 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-3569.
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Huff, Kevin G. "Comparison of the mid-frequency line edge noise algorithms of Jim Hamerly and Yigal Gur for best correlation to the psychophysical defect known as raggedness /." Online version of thesis, 1987. http://hdl.handle.net/1850/10135.
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Burki, Jehanzeb. "Fast circular aperture synthesis in sar all-aspect target imaging." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/26514.
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Thesis (Ph.D)--Electrical and Computer Engineering, Georgia Institute of Technology, 2009.Committee Chair: Christopher F. Barnes; Committee Member: Andrew F. Peterson; Committee Member: Douglas B. Williams; Committee Member: Haomin Zhou; Committee Member: Justin K. Romberg. Part of the SMARTech Electronic Thesis and Dissertation Collection.
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Weiss, Thomas. "Advanced numerical and semi-analytical scattering matrix calculations for modern nano-optics." Thesis, Clermont-Ferrand 2, 2011. http://www.theses.fr/2011CLF22150.
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Les propriétés optiques des nanomatériaux, tels que les cristaux photoniques ou les métamatériaux, ont reçu beaucoup d’attention dans les dernières années [1–9]. La dérivation numérique de ces propriétés se révèle pourtant très compliquée, en particulier dans le cas des structures métallo-diélectriques, qui comportent des résonances plasmoniques. C’est pourquoi des méthodes numériques avancées et des modèles semi-analytiques sont nécessaires. Dans cette thèse, nous montrerons que le formalisme de la matrice de diffraction peut satisfaire ces deux aspects. La méthode de la matrice de diffraction est un concept très général en physique. Dans le cas des structures périodiques, on peut dériver la matrice de diffraction à l’aide de la méthode modale de Fourier [10]. Pour la description exacte des géométries planes, nous avons développé la méthode des coordonnées adaptées [11], qui nous donne un nouveau système de coordonnées, dans lequel les interfaces des matériaux sont des surfaces de coordonnées constantes. En combinaison avec la méthode de la résolution spatiale adaptative, la méthode des coordonnées adaptées permet d’améliorer considérablement la convergence de la méthode modale de Fourier, de telle sorte qu’on peut calculer des structures métalliques compliquées très efficacement. Si on utilise la matrice de diffraction, il est non seulement possible de dériver les propriétés optiques en illumination de champ lointain, comme la transmission, la réflexion, l’absorption, et le champ proche, mais aussi de décrire l’émission d’un objet à l’intérieur d’une structure et d’obtenir les résonances optiques d’un sytème. Dans cette thèse, nous présenterons une méthode efficace pour la dérivation des résonances optiques tridimensionnelles, utilisant directement la matrice de diffraction [14]. Si on connaît les résonances d’un système isolé, il est aussi possible d’obtenir une approximation des résonances dans le cas d’un système combiné à l’aide de notre méthode du couplage des résonances [15, 16]. Cette méthode permet de décrire le régime de couplage des champs lointain et proche, y compris le couplage fort avec les résonances Fabry-Perot, pour des systèmes qui se composent d’un empilement de deux structures planes et périodiques. Pour cette raison, on peut étudier efficacement le couplage de ces systèmes. Cette thèse est écrite de manière à donner une idée d’ensemble du formalisme de la matrice de diffraction et de la méthode modale de Fourier. En outre, nous décrivons notre généralisation de ces méthodes et nous montrons la validité de nos approches pour différents exemplesThe optical properties of nanostructures such as photonic crystals and metamaterials have drawn a lot of attention in recent years [1–9]. The numerical derivation of these properties, however, turned out to be quite complicated, especially in the case of metallo-dielectric structures with plasmonic resonances. Hence, advanced numerical methods as well as semi-analytical models are required. In this work, we will show that the scattering matrix formalism can provide both. The scattering matrix approach is a very general concept in physics. In the case of periodic grating structures, the scattering matrix can be derived by the Fourier modal method [10]. For an accurate description of non-trivial planar geometries, we have extended the Fourier modal method by the concept of matched coordinates [11], in which we introduce a new coordinate system that contains the material interfaces as surfaces of constant coordinates. In combination with adaptive spatial resolution [12,13], we can achieve a tremendously improved convergence behavior which allows us to calculate complex metallic shapes efficiently. Using the scattering matrix, it is not only possible to obtain the optical properties for far field incidence, such as transmission, reflection, absorption, and near field distributions, but also to solve the emission from objects inside a structure and to calculate the optical resonances of a system. In this work, we provide an efficient method for the ab initio derivation of three-dimensional optical resonances from the scattering matrix [14]. Knowing the resonances in a single system, it is in addition possible to obtain approximated resonance positions for stacked systems using our method of the resonant mode coupling [15, 16]. The method allows describing both near field and far field regime for stacked two-layer systems, including the strong coupling to Fabry-Perot resonances. Thus, we can study the mutual coupling in such systems efficiently. The work will provide the reader with a basic understanding of the scattering matrix formalism and the Fourier modal method. Furthermore, we will describe in detail our extensions to these methods and show their validity for several examples
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North, Jan Arthur. "Fourier image synthesis and slope spectrum analysis of deepwater, wind-wave scenes viewed at Brewster's angle /." Online version of thesis, 1989. http://hdl.handle.net/1850/11520.
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Perreault, John D. "Using Atom Optics to Measure van der Waals Atom-Surface Interactions." Diss., Tucson, Arizona : University of Arizona, 2005. http://etd.library.arizona.edu/etd/GetFileServlet?file=file:///data1/pdf/etd/azu%5Fetd%5F1317%5F1%5Fm.pdf&type=application/pdf.
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Brenan, Colin John Herbert. "Design, operation and applications of a visible-light confocal scanning Fourier transform Raman microscope for volumetric Raman spectrochemical imaging." Thesis, McGill University, 1996. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=41989.
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A new type of confocal Raman microscope called a Fourier transform confocal Raman microscope (FT-CRM) was designed, built and characterized with respect to its spatio-spectral imaging properties. Several different applications of the FT-CRM are presented that take advantage of its unique spectral and spatial imaging characteristics. The instrument combines focused illumination with spatially-filtered detection in a confocal optical configuration to collect photons scattered from a diffraction-limited volume in the sample (typically ${<}5 times10 sp{-18} m sp3)$ and reject photons from outside that region. The molecular vibrational information encoded in the inelastic, or Raman, spectral component of light scattered from the confocal volume is measured with a visible light Fourier transform Raman spectrometer. By scanning the sample relative to the confocal volume, a volumetric Raman spectrochemical image of the sample can be constructed.Raman scattering is an inherently inefficient process; hence an optimal radius pinhole must be found that balances the FT-CRM optical throughput against the microscope spatial resolution and image contrast. Detailed experimental measurements mapped out the FT-CRM spatial response (axial and lateral), optical throughput and image signal-to-background and signal-to-noise ratios as a function of pinhole radius. Excellent agreement was found between these measurements and the predictions of a theoretical microscope model also developed as part of this thesis. Several applications of the FT-CRM included volumetric compositional imaging of three-dimensional chemically inhomogeneous materials such as cellulose and polyester fibers in water or two immiscible optically-similar liquids, water and trichloroehthylene, in a porous quartz sandstone matrix. The potential of the FT-CRM for non-invasive spectrochemical detection and imaging through a turbid tissue-like medium was demonstrated and a new spectral estimator, Fast Orthogonal Search, was evaluated to replace the discrete Fourier transform to improve the microscope performance.
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Dilhan, Lucie. "Programming and Optimisation of a Digital Holographic Microscope for the Study of Eye Tissue." Thesis, KTH, Tillämpad fysik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-292357.
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The objectives of the present project were to set up, optimise and characterise a digitalholographic microscopy (DHM) laboratory set-up designed for the study of eyetissue and to implement and optimise digital data processing and noise reductionroutines. This work is part of a collaborative project aiming to provide quantitativemethods for the in vitro and in vivo characterisation of human corneal transparency.The laboratory set-up is based on a commercial laboratory microscope with zoomfunction (a “macroscope”). In continuation of previous work, we completed and optimised,and extended a software for holographic signal processing and numericalpropagation of the wavefront.To characterise the set-up and quantify its performances for standard operationand in its DHM configuration, we compare the magnification and resolution to theoreticalvalues for a given set of parameters. We determined the magnification factorand the rotation angle between the object and camera planes. With a laser wavelengthof 532 nm, a x1 objective and a zoom setting of x2.9 (which corresponds to aplane sample wavefront), we measured a magnification of 1.68. With the same parameters,we measure a holographic resolution of about 11 m. The wavefront phasecould be determined with a precision of a fraction of the wavelength.We subsequently performed analysis of the relative contribution of coherent noiseand implemented and evaluated several noise reduction routines. While the impactof coherent noise remained visible in the amplitude image, interferometric precisionwas obtained for the phase of the wavefront and the set-up was considered qualifiedfor its intended use for corneal characterisation.A first test measurement was performed on primate cornea.Subsequent work will address the further quantitative characterisation of the setupfor the full set of parameters (objectives, zoom positions, wavelengths), test measurementson samples with known transmission and light scattering properties (e.g.solutions of PMMA beads) and the comparison of the results with the predictions ofa theoretical model, and measurements on animal and human tissue.
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Hutchinson, William Edward. "Molecular sensing using immobilized IR-active carbonylmetal probe groups." Thesis, Nottingham Trent University, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.369254.
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Rowe, John M. "Quantitative acoustic microscopy of surfaces." Thesis, University of Oxford, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.670362.
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Tenefrancia, Sandra L. "Optical pattern comparison by interferometry." Thesis, Virginia Polytechnic Institute and State University, 1988. http://hdl.handle.net/10919/53191.
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By placing two similar input transparencies adjacent to each other in the same plane, and illuminating them with coherent light, it is possible to create parallel fringes that will modulate the composite Fraunhofer diffraction pattern of the two input objects. The power spectrum of the combined inputs, i.e. test and reference signal Fourier transform, is analyzed for regularity of the fringe pattern. The method of interference used on input with small rotational errors and on relatively large displacements of the input does not affect the recognition capabilities of the system. This optical method is useful for making rapid pattern comparisons, where the signal to noise ratio is large.Master of Science
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Garcia, Mina Diego Felipe. "Bi-tapered Fiber Sensor Using a Supercontinuum Light Source for a Broad Spectral Range." University of Dayton / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1492001857501804.
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Wang, Zongzhao [Verfasser], Frank [Gutachter] Wyrowski, Jürgen [Gutachter] Jahns, and Jari [Gutachter] Turunen. "Fourier transform techniques for fast physical optics modeling / Zongzhao Wang ; Gutachter: Frank Wyrowski, Jürgen Jahns, Jari Turunen." Jena : Friedrich-Schiller-Universität Jena, 2021. http://d-nb.info/1228432244/34.
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Liu, Yifan. "The True-Time-Delay (TTD) Laser Beam Steering System Design Based on Fourier Cell." The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1237915468.
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Yildirim, Murat. "Design And Construction Of An Experimental Apparatus For The Interferometric Measurement Of Micrometer Level Clearances." Master's thesis, METU, 2009. http://etd.lib.metu.edu.tr/upload/12610704/index.pdf.
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In this study a fiber optic interferometer (FOI) was designed and constructed to measure micron level clearances occurring in piston cylinder arrangements. A Cartesian model of the piston cylinder assembly is manufactured and lateral motion and vertical displacement are generated via a step motor, and micrometers, respectively. Clearance measurements are conducted in air and also in a lubricant. The range of vertical displacements is kept between 0-50 μ
m, and the lateral motion is 13.5 mm. The effect of the step motor and lateral motion carriage on distance measurement is determined and this is used to correct displacement measurements.
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Lee, Kwan-Seop. "Studies on the decay and recovery of higher-order solitons, initiated by localized channel perturbations." Diss., Available online, Georgia Institute of Technology, 2004:, 2004. http://etd.gatech.edu/theses/available/etd-04122004-143924/unrestricted/Lee%5FKwanseop%5F200405%5FPhD.pdf.
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Thesis (Ph. D.)--Electrical and Computer Engineering, Georgia Institute of Technology, 2004.John A. Buck, Committee Chair ; Stephen E. Ralph, Committee Member ; Gee-Kung Chang, Committee Member ; Rick Trebino, Committee Member ; Glenn S. Smith, Committee Member. Includes bibliographical references (leaves 102-104).
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Peloux, Marius. "Nouveaux composants optiques pixellisés pour la correction visuelle : modélisation, optimisation et évaluation." Thesis, Paris 11, 2011. http://www.theses.fr/2011PA112202/document.
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Ce manuscrit de thèse traite de l’étude de verres ophtalmiques microstructurés et plus particulièrement pixellisés, ces derniers pouvant présenter un intérêt particulier en optique active pour la correction de la presbytie. Une étude théorique est proposée, permettant d’analyser les performances optiques d’une lentille pixellisée en termes de transport d’image et d’identifier les paramètres qui ont un impact direct sur ces performances. Après validation expérimentale des résultats obtenus, nous constatons puis expliquons l’effet sur l’observation d’une scène de l’excentrement de l’œil par rapport à la fonction de phase du verre. Nous étudions l’effet du repliement de phase inhérent aux limites des technologies de fabrication, qui vient ajouter un chromatisme axial aux défauts visuels engendrés par la pixellisation. Nous nous intéressons ensuite aux applications possibles de la pixellisation en optique passive. Nous prouvons que pour une application visée, des lentilles binaires non pixellisées, dont nous optimisons la qualité optique, conduisent à de meilleurs résultats que les lentilles pixellisées. L’impact sur l’acuité visuelle des phénomènes diffractifs parasites induits par la pixellisation est évalué au moyen d’un banc de mesure utilisant la simulation de certaines images telles qu’elles seraient vues au travers de verres ophtalmiques pixellisés. Enfin, nous menons une étude de l’aspect esthétique d’un verre pixellisé vu par un observateur externe, à partir de modèles de calcul hybrides mêlant optique géométrique et optique de FourierThis thesis investigates microstructured and more particularly pixelated ophthalmic glasses, the latter raising some hope for the active correction of presbyopia. A theoretical study is developed for the analysis of the optical performances of a pixelated lens in terms of image transport and leads to the identification of the parameters which have an impact on these performances. After experimental validation of the results obtained, we note and then explain the effect on the observation of a scene of eye displacement with respect to the optical function of the eyeglass. We study the effect of phase wrapping, which is inherent in the limits of the technologies implied in the manufacturing process and adds an axial chromatism effect to the visual defects generated by pixelation. We are also interested in the potential applications of pixelation in the field of passive optics. We prove that for a given application, non pixelated binary lenses, the optical quality of which we optimize, lead to better results than pixelated lenses. The impact on visual acuity of the parasitic diffractive phenomena induced by pixelation is evaluated with an optical bench using the simulation of test images seen through pixelated lenses. Finally, we study the aesthetic aspect of a pixelated component as seen by an external observer, using hybrid calculation models based on both geometrical and Fourier optics
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Garay, Avendaño Roger Leonardo 1984. "Formulação analítica exata de feixes eletromagnéticos não paraxiais." [s.n.], 2013. http://repositorio.unicamp.br/jspui/handle/REPOSIP/259682.
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Orientador: Michel Zamboni RachedDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação
Made available in DSpace on 2018-08-22T19:43:51Z (GMT). No. of bitstreams: 1 GarayAvendano_RogerLeonardo_M.pdf: 3532246 bytes, checksum: c57f4a9f337b3e0e75f701a896e690a0 (MD5) Previous issue date: 2013
Resumo: Embora a propagação de feixes ópticos seja um tema muito investigado, existe ainda uma grande variedade de estudos a se efetuar, principalmente no desenvolvimento de métodos que permitam, de forma analítica, a descrição exata da enorme diversidade de feixes com propriedades distintas. A principal contribuição desta dissertação é a proposta de uma metodologia matemática para a obtenção de feixes escalares e eletromagnéticos não paraxiais puramente propagantes como soluções analíticas exatas da equação de onda e das equações de Maxwell. Tal método baseia-se em uma solução analítica para as integrais que descrevem superposições de feixes de Bessel de ordem zero (não evanescentes) com qualquer tipo de função espectral. Exemplos de feixes não paraxiais são apresentados para a validação do método proposto neste trabalho, os quais provam a grande eficiência em termos do pouco esforço computacional quando são comparados com os métodos de outros autores
Abstract: Although the propagation of optical beams has been vastly studied, there is still a huge amount of research topics to be exploited, mainly regarding the developing of exact analytic methods. The main contribution of this work is the development of a mathematical methodology to obtain nonparaxial propagating scalar and electromagnetic beams as exact analytic solutions of the wave equation and Maxwell's equations, respectively. This method is based on a very general solution to the continuous superposition of zero order Bessel beams (non-evanescent) with any kind of spectral function. Examples of non paraxial beams are shown to validate the method proposed in this work, which proves to be very efficient, based on low computational effort when compared to other author's methods
Mestrado
Telecomunicações e Telemática
Mestre em Engenharia Elétrica
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Moncada, Javier Augusto Jurado. "Aplicação da técnica de contraste de fase da ordem zero na geração de pinças ópticas multi-feixe." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/18/18155/tde-22122017-080731/.
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Um sistema multi-feixe de pinças ópticas baseado na técnica de contraste de fase da ordem zero pode apresentar vantagens significativas sobre sistemas mecanicamente complexos e sensíveis ao alinhamento, e sobre tecnologias que, apesar de serem similares, requerem a customização de componentes ópticos. Porém, ao nosso conhecimento, este sistema até agora não tem sido implementado experimentalmente. Neste trabalho tem-se desenvolvido, como prova de princípio, o primeiro sistema baseado na técnica de contraste de fase da ordem zero gerador de múltiplas pinças ópticas. Esta técnica da óptica de Fourier utiliza conceitos do contraste de fase de Zernike e técnicas de codificação de dois pixels para gerar padrões de intensidade no plano da imagem que são diretamente relacionados a distribuições de fase no plano de entrada do sistema, o qual é formado por um modulador espacial de luz (SLM). Esta dissertação de mestrado descreve detalhadamente os passos tomados com o propósito de utilizar os campos estruturados de luz gerados pelo sistema de contraste de fase da ordem zero para aprisionar esferas de 2 µm de diâmetro de sílica fundida. Neste trabalho apresentamos os fundamentos teóricos do aprisionamento óptico e da técnica de contraste de fase da ordem zero, seguidos pela implementação de experimentos independentes em cada modalidade, e finalmente apresentamos a integração de ambos os sistemas dentro um sistema único de pinças ópticas multi-feixe. Apesar da baixa eficiência óptica do sistema, foi possível implementar um sistema de pinças ópticas duplas. Finalizamos o nosso trabalho na discussão detalhada das limitações do nosso arranjo óptico e comentamos sobre potenciais melhorias para aumentar a rigidez das pinças ópticas e a qualidade geral do sistema.A multi-beam optical trapping system based on the zero order phase contrast technique may offer significant advantages over mechanically-complex, alignment-sensitive optical trapping systems, and over technologies that, though similar, require the customization of optics components. However, to our knowledge, such a system has not been yet implemented experimentally. We have developed, as a proof of principle, what we think is the first system based on the zero order phase contrast technique to successfully generate multiple optical traps. This Fourier optics technique makes use of existing concepts of Zernike phase contrast and two-pixel encoding techniques to generate intensity patterns in the image plane that are directly related to phase distributions in the input plane, which is comprised by a spatial light modulator (SLM). This master\'s dissertation describes in detail the steps taken towards using the structured light fields generated by a zero order phase contrast system to trap 2 µm diameter fused silica beads. We present the theoretical foundations of optical trapping and the zero order phase contrast technique, followed by the implementation of independent laboratory experiments in each modality, and finally integrate both systems into a single optical setup for multi-beam trapping. In spite of the low optical efficiency of the system, we were able to implement dual optical traps. We finalize by discussing in detail the limitations of our experimental setup in and comment on potential improvements to increase the stiffness of the optical traps and the overall quality of the system.
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Kang, Hoyoung. "New approaches in optical lithography technology for subwavelength resolution /." Link to online version, 2005. https://ritdml.rit.edu/dspace/handle/1850/1119.
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Roth, Matthias, Jörg Heber, and Klaus Janschek. "System design of programmable 4f phase modulation techniques for rapid intensity shaping: A conceptual comparison." SPIE, 2016. https://tud.qucosa.de/id/qucosa%3A35096.
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The present study analyses three beam shaping approaches with respect to a light-efficient generation of i) patterns and ii) multiple spots by means of a generic optical 4f-setup. 4f approaches share the property that due to the one-to-one relationship between output intensity and input phase, the need for time-consuming, iterative calculation can be avoided. The resulting low computational complexity offers a particular advantage compared to the widely used holographic principles and makes them potential candidates for real-time applications. The increasing availability of high-speed phase modulators, e.g. on the basis of MEMS, calls for an evaluation of the performances of these concepts.
Our second interest is the applicability of 4f methods to high-power applications. We discuss the variants of 4f intensity shaping by phase modulation from a system-level point of view which requires the consideration of application relevant boundary conditions. The discussion includes i) the micro mirror based phase manipulation combined with amplitude masking in the Fourier plane, ii) the Generalized Phase Contrast, and iii) matched phase-only correlation filtering combined with GPC. The conceptual comparison relies on comparative figures of merit for energy efficiency, pattern homogeneity, pattern image quality, maximum output intensity and flexibility with respect to the displayable pattern. Numerical simulations illustrate our findings.
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Paul, Jagannath. "Coherent Response of Two Dimensional Electron Gas probed by Two Dimensional Fourier Transform Spectroscopy." Scholar Commons, 2017. http://scholarcommons.usf.edu/etd/6738.
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Advent of ultrashort lasers made it possible to probe various scattering phenomena in materials that occur in a time scale on the order of few femtoseconds to several tens of picoseconds. Nonlinear optical spectroscopy techniques, such as pump-probe, transient four wave mixing (TFWM), etc., are very common to study the carrier dynamics in various material systems. In time domain, the transient FWM uses several ultrashort pulses separated by time delays to obtain the information of dephasing and population relaxation times, which are very important parameters that govern the carrier dynamics of materials. A recently developed multidimensional nonlinear optical spectroscopy is an enhanced version of TFWM which keeps track of two time delays simultaneously and correlate them in the frequency domain with the aid of Fourier transform in a two dimensional map. Using this technique, the nonlinear complex signal field is characterized both in amplitude and phase. Furthermore, this technique allows us to identify the coupling between resonances which are rather difficult to interpret from time domain measurements. This work focuses on the study of the coherent response of a two dimensional electron gas formed in a modulation doped GaAs/AlGaAs quantum well both at zero and at high magnetic fields.
In modulation doped quantum wells, the excitons are formed as a result of the inter- actions of the charged holes with the electrons at the Fermi edge in the conduction band, leading to the formation of Mahan excitons, which is also referred to as Fermi edge singularity (FES). Polarization and temperature dependent rephasing 2DFT spectra in combination with TI-FWM measurements, provides insight into the dephasing mechanism of the heavy hole (HH) Mahan exciton. In addition to that strong quantum coherence between the HH and LH Mahan excitons is observed, which is rather surprising at this high doping concentration. The binding energy of Mahan excitons is expected to be greatly reduced and any quantum coherence be destroyed as a result of the screening and electron-electron interactions. Such correlations are revealed by the dominating cross-diagonal peaks in both one-quantum and two-quantum 2DFT spectra. Theoretical simulations based on the optical Bloch Equations (OBE) where many-body effects are included phenomenologically, corroborate the experimental results. Time-dependent density functional theory (TD-DFT) calculations provide insight into the underlying physics and attribute the observed strong quantum coherence to a significantly reduced screening length and collective excitations of the many-electron system. Furthermore, in semiconductors under the application of magnetic field, the energy states in conduction and valence bands become quantized and Landau levels are formed. We observe optical excitation originating from different Landau levels in the absorption spectra in an undoped and a modulation doped quantum wells. 2DFT measurements in magnetic field up to 25 Tesla have been performed and the spectra reveal distinct difference in the line shapes in the two samples. In addition, strong coherent coupling between landau levels is observed in the undoped sample. In order to gain deeper understanding of the observations, the experimental results are further supported with TD-DFT calculation.
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Mengin, Fondragon Mikhael de. "Etude d'un spéctromètre intégré SWIFTS pour réaliser des capteurs optiques fibrés pour les sciences de l'observation." Thesis, Grenoble, 2014. http://www.theses.fr/2014GRENT085/document.
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SWIFTS (pour Stationary-Wave Integrated Fourier-Transform Spectrometer) est un concept de spectromètre s'appuyant sur l'optique intégrée pour proposer un système de mesure compact et de très haute résolution. Il combine une technique d'interférométrie développée par Gabriel Lippmann avec des technologies de microélectroniques actuelles. La technologie SWIFTS sera ici utilisée en tant qu'interrogateur de fibre de Bragg. En effet, combiner ce spectromètre avec des fibres de Bragg très sensibles, telle qu'une cavité Fabry-Perot à réseaux de Bragg (GFPC) d'une longueur de 20 mm, permettra de mesurer des variations de température et de déformation très précises. Les applications des fibres de Bragg sont nombreuses, particulièrement dans la surveillance de structure de génie civil ou dans la sureté nucléaire avec des précisions de l'ordre du microstrain. Cependant, les capteurs par fibres de Bragg n'ont jamais atteint la sensibilité nécessaire aux observations en science de la terre. Une précision de quelques dizaines de nanostrain serait pourtant d'un intérêt majeur dans l'étude des processus volcaniques et sismologiques. Je présente dans cette thèse la première utilisation d'un tel spectromètre de Fourier associé à des capteurs de Bragg pour mesurer des déformations dans différentes gammes allant du millistrain au nanostrain. Dans un premier temps, des déformations sur une petite structure en béton armé amenée jusqu'à l'état limite de fissuration permettront de qualifier différents capteurs à fibres de Bragg dans leur milieu d'usage. Dans un deuxième temps, des mesures de déformations liées au phénomène de la marrée terrestre sont proposées. Ces mesures, effectuées au Laboratoire Souterrain à Bas Bruit (LSBB) de Rustrel, donnent des précisions de l'ordre de 30 nanostrains sur une courte base et ouvrent la voie à d'autres mesures de phénomènes géophysiques pour cet instrumentSWIFTS, or Stationary-Wave Integrated Fourier-Transform Spectrometer, is an extremely integrated very high resolution spectrometer. This spectroscopy technology represents a major advance in the field and will be used here as a Fiber Bragg Gratings interrogator. Combining such a spectrometer with very sensitive Bragg sensors, like grating Fabry-Perot cavity (GFPC) as long as 20 mm, will allow to measure high precision temperature or strain variation. Applications of Bragg sensors are numerous, especially in structure monitoring and nuclear power plants safety. Despite promising capabilities, Bragg sensors never reached the desired sensibility for earth-science observation purposes. Present applications are restricted to civil-engineering strain-gauge sensors with microstrain sensitivity. However, the ability to detect and record signals of the order of a few tens of nanostrain is of great interest to monitor and model the volcanic and seismological processes. I demonstrate in this thesis the first use of a Fourier-Transform spectrometer combined with Fiber Bragg Sensors in a field configuration to achieve extremely high precision measurement on earth's crustal deformation. Precisions of thirty nanostrains on a very short base were achieved in the Low-Noise Underground Laboratory (LSBB) at Rustrel. Crustal monitoring opens the way for numerous applications especially in geophysics. A second study presented in this thesis aims at benchmarking several strain sensors based on optical fiber Bragg grating. For this purpose, two reinforced concrete beams have been tested in three points bending up to ultimate limit state
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Ford, William Paul. "Development of a Fourier Transform Far Infrared (FTFIR) Spectrometer to Characterize Broadband Transmission Properties of Common Materials in the Terahertz Region." Wright State University / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=wright1158508606.
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Treptow, Dorian. "Holographic light shaping through acousto-optic deflectors." Doctoral thesis, Universitat de Barcelona, 2021. http://hdl.handle.net/10803/671825.
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The invention of the laser in the 1960s triggered a new era of optical technologies which revolutionized many fields of industry and research. At the same time, a new demand for technologies emerged that allow to dynamically control the optical properties of a laser beam and to shape laser light into arbitrary patterns.
This need led to the development of spatial light modulators, which are programmable diffractive elements that shape laser light into well-defined intensity distributions through optical phase or amplitude modulation. Their capability to display computer generated holograms made them an indispensable tool in a broad range of optics and photonics applications, because it allows to reconstruct optical wavefronts from digital models without the need of physical counterparts. This most versatile control over an optical wavefront enables complex functionalities such as holographic beam shaping, aberration correction, adaptive optics applications and optical micro-manipulation, to name only a few.
Various spatial light modulator technologies exist with inherent capabilities that define their possible applications. The high light efficiency and outstanding modulation capabilities of spatial light modulators based on liquid crystals (LC-SLMs) found a myriad of applications and represent the current standard for dynamic light modulation based on digital holograms. There are, however, several applications that require other capabilities than those offered by LC-SLMs. Ultra-fast light modulation, high laser power applications and high-quality pattern formation are difficult to achieve with liquid crystal devices, so that alternatives to this prevailing technology are needed.
An interesting candidate for high performance spatial light modulation are acousto-optic deflectors (AODs). These devices are commonly used for high-speed beam deflection, but it has also been demonstrated in few scattered precedents that they are capable of holographic light modulation. Acousto-optic deflectors are based on a considerably different technology than LC-SLMs, which complicates their use as full-fledged spatial light modulators. But at the same time, they provide promising light modulation capabilities, such as very high optical power thresholds, modulation rates of several kilohertz and a continuous (non-pixelated) wavefront modulation, which potentially make them a complement or even competitor to existing spatial light modulator technologies.
The scope of this thesis is the investigation and application of the holographic modulation capabilities of a spatial light modulator system based on acousto-optic deflectors. Such a system is realized in the frame of this work as a common optical Fourier transform setup with off the shelf hardware. The principal effort in the implementation is the development of calculation methods for acousto-optic holograms and the corresponding electronic driving signals, which on the one hand need to consider the specific capabilities and constraints of AODs, and on the other hand have to provide high light efficiencies of the displayed holograms and a high reconstruction quality of the formed patterns. Thus, the one-dimensionality of the acousto-optic modulation and the resulting separability restrictions for two-dimensional AOD modulation are discussed, and different reconstruction strategies for arbitrary two-dimensional patterns are investigated. Furthermore, various image degrading effects are analyzed, and corresponding correction methods are proposed. Especially the inherent reduction of coherent artifacts through the motion of acousto-optic holograms is analyzed in detail.
The capabilities of such implemented acousto-optic SLM are demonstrated by reconstructing arbitrary laser patterns with very high perceived image fidelity. Through the combination of different correction methods, also high-speed reconstructions of separable patterns at rates of several kilohertz are achieved, which eventually come into play in a structured illumination microscope.Los moduladores espaciales de luz (SLM) son herramientas optoelectrónicas versátiles que dan forma holográfica a la luz láser en patrones de intensidad complejos para su uso en una amplia gama de aplicaciones ópticas y fotónicas. Existe una variedad de tecnologías SLM, pero los moduladores espaciales de luz basados en cristales líquidos han prevalecido debido a su alta eficiencia lumínica y a sus excepcionales capacidades de modulación. Sin embargo, a esta tecnología le cuesta cumplir con los requisitos de las aplicaciones que necesitan velocidades de modulación en el régimen de los kilohercios, altas potencias de láser o proyección de patrones de alta fidelidad. Un enfoque alternativo es la modulación espacial de la luz basada en deflectores acusto-ópticos. Estos dispositivos se utilizan comúnmente para la deflexión de un haz de luz a alta velocidad y son bien conocidos por sus excelentes tasas de modulación y su resistencia a altas potencias ópticas. Los deflectores acusto-ópticos también pueden modular espacialmente la amplitud y fase de un haz de láser, pero la volatilidad y unidimensionalidad de su modulación dificulta su uso en pie de igualdad con otros SLM. En este trabajo, se investiga la modulación holográfica de la luz a través de deflectores acusto-ópticos y se desarrolla un marco metodológico que hace accesibles sus intrigantes capacidades de modulación espacial. El sistema experimental consiste en dos AOD alineados perpendicularmente en una configuración de transformada óptica de Fourier, que es capaz de reconstruir patrones separables unidimensionales y bidimensionales. Se discute la restricción de separabilidad y se proponen estrategias para la generación de patrones bidimensionales arbitrarios. Los hologramas de Fourier se muestran en los AOD inyectando señales de direccionamiento moduladas complejas, que se adaptan a las propiedades particulares de la modulación de luz acusto-óptica. Demostramos, tanto teórica como experimentalmente, que el movimiento de los hologramas acusto-ópticos reduce de forma inherente los artefactos coherentes que son omnipresentes en la holografía digital. Este fenómeno permite reconstruir holográficamente patrones de intensidad de muy alta calidad, indicados por valores de contraste de "speckle" medidos experimentalmente de tan solo 0.02. También se muestra que este efecto permite proyecciones a alta velocidad de patrones separables hasta 21 kHz mientras se mantiene una buena fidelidad en dichos patrones. Además, se presenta la aplicación del proyector de patrones universal implementado como fuente de iluminación estructurada para un microscopio confocal.
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Vievard, Sébastien. "Développement et validation d'un analyseur de surface d'onde en plan focal pour un instrument multi-pupilles." Thesis, Paris 6, 2017. http://www.theses.fr/2017PA066327/document.
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L’instrumentation multi-pupille permet de repousser les limitations actuelles des diamètres des télescopes monolithiques. L’alignement des sous-pupilles est donc une problématique incontournable pour les futurs projets de télescopes au sol comme dans l’espace. Un Analyseur de Surface d’Onde (ASO) est alors nécessaire pour mesurer les aberrations spécifiques au cas multi-pupille que sont le piston différentiel (différence de marche entre les sous-pupilles), le tip et le tilt (basculements différentiels entre les sous-pupilles). Nous nous attachons à réaliser des ASOs non supervisés et simples d’implantation, permettant l’alignement total d’un instrument multi-pupille. L’algorithme ELASTIC repose sur l’analyse de la corrélation entre deux images focales prises successivement, différant par une perturbation maîtrisée et appliquée directement sur les sous-pupilles. ELASTIC permet d’une part d’estimer les grandes erreurs de tip/tilt, pour effectuer un alignement géométrique et d’autre part de stabiliser le tip/tilt pendant la minimisation des grandes erreurs de piston, pour l’alignement interférométrique. Enfin, un second algorithme appelé LAPD permet, au moyen de deux images prises simultanément dans un plan focal et dans un plan légèrement défocalisé, d’estimer les petites erreurs de piston/tip/tilt pour le cophasage fin. Ces différents algorithmes sont caractérisés au moyen de simulations numériques, pour différents types de télescopes multi-pupilles. Nous démontrons expérimentalement les briques de la chaîne d’alignement sur un instrument à 6 sous-pupilles. Ces ASOs permettent de simplifier le dimensionnement des futurs télescopesThe resolution of a telescope is ultimately limited by its aperture diameter, but the size of mirrors is bounded by current technology to about 10m on the ground and to a few meters in space. To overcome this limitation, interferometry consists in making an array of sub-apertures interfere; the resulting instrument is called an interferometer or a multi-aperture telescope. To reach the diffraction limit of such instruments, all sub-apertures must be phased to within a small fraction of wavelength. A critical sub-system of interferometers is the Cophasing Sensor (CS), whose goal is to measure the relative positioning errors between the sub-apertures (differential piston, tip and tilt), which are the specific low-order aberration of an interferometer and the main source of wave-front degradation. We aim to develop unsupervised and easy-to-implement CSs for the global multi-aperture telescope alignment. ELASTIC algorithm provides a solution for large amplitude tip/tilt error measurement from a modified cross-spectrum of two diversity images, allowing the geometrical alignment. ELASTIC also provides tip/tilt stability for the large amplitude piston error minimization, called the interferometric alignment. Finally a second algorithm called LAPD uses focal and slightly defocused images for the small amplitude piston/tip/tilt error measurement, allowing the fine phasing. Numerical simulations of several types of multi-aperture telescopes are performed in order to test our algorithms. We experimentally demonstrate the efficiency of the different algorithms on a 6-sub-aperture instrument. These algorithms should simplify the design of the future telescopes
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Thompson, Bruce Thomas. "Fourier transform infrared spectroscopic measurement of carbon monoxide and nitric oxide in sidestream cigarette smoke in real time using a hollow waveguide gas cell and nonimaging optics." Diss., Available online, Georgia Institute of Technology, 2004:, 2004. http://etd.gatech.edu/theses/available/etd-06232004-172923/unrestricted/thompson%5Fbruce%5Ft%5F200407%5Fphd.pdf.
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Thesis (Ph. D.)--Chemistry and Biochemistry, Georgia Institute of Technology, 2005. Directed by Boris Mizaikoff.Hunt, William, Committee Member ; Weck, Marcus, Committee Member ; Mizaikoff, Boris, Committee Chair ; Janata, Jiri, Committee Member ; Orlando, Thomas, Committee Member. Includes bibliographical references.
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Brown, Janis Michelle. "Production of controlled networks and morphologies in toughened thermosetting resins using real-time, in-situ cure monitoring." Diss., Virginia Tech, 1994. http://hdl.handle.net/10919/40306.
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Chemical and physical changes occur during the processing of toughened thermosetting resins. A number of properties are related to the type and sequence of these changes. There is a need for the development of in-situ real-time sensors to follow these changes.
Once these sensors are developed, they can be used to preferentially select networks and/or morphologies by feedback-controlled "intelligent" processing.
A practical, durable, inexpensive Fourier Transform NearInfrared (FTNIR) fiber optic sensor was developed and the cure of a model toughened cyanate as well as a commercial paste adhesive was followed with this sensor In the near-infrared. The design was suitable for many applications. A mold was designed to incorporate the fiber sensor for composite applications.
The growth of the normalized triazine (crosslink) peak appeared to follow second order kinetics. The normalized peak reflected chemical as well as physical changes. Analysis of the individual peaks showed significant physical effects. Conversion based on triazine concentration did not follow second order kinetics.Ph. D.
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Nattinger, Kevin T. "Experimental Validation of the Generalized Harvey-Shack Surface Scatter Theory." Wright State University / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=wright1536246922074747.
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Arnison, Matthew Raphael. "Phase control and measurement in digital microscopy." Thesis, The University of Sydney, 2003. http://hdl.handle.net/2123/569.
Full textAbstract:
The ongoing merger of the digital and optical components of the modern microscope is creating opportunities for new measurement techniques, along with new challenges for optical modelling. This thesis investigates several such opportunities and challenges which are particularly relevant to biomedical imaging. Fourier optics is used throughout the thesis as the underlying conceptual model, with a particular emphasis on three--dimensional Fourier optics. A new challenge for optical modelling provided by digital microscopy is the relaxation of traditional symmetry constraints on optical design. An extension of optical transfer function theory to deal with arbitrary lens pupil functions is presented in this thesis. This is used to chart the 3D vectorial structure of the spatial frequency spectrum of the intensity in the focal region of a high aperture lens when illuminated by linearly polarised beam. Wavefront coding has been used successfully in paraxial imaging systems to extend the depth of field. This is achieved by controlling the pupil phase with a cubic phase mask, and thereby balancing optical behaviour with digital processing. In this thesis I present a high aperture vectorial model for focusing with a cubic phase mask, and compare it with results calculated using the paraxial approximation. The effect of a refractive index change is also explored. High aperture measurements of the point spread function are reported, along with experimental confirmation of high aperture extended depth of field imaging of a biological specimen. Differential interference contrast is a popular method for imaging phase changes in otherwise transparent biological specimens. In this thesis I report on a new isotropic algorithm for retrieving the phase from differential interference contrast images of the phase gradient, using phase shifting, two directions of shear, and non--iterative Fourier phase integration incorporating a modified spiral phase transform. This method does not assume that the specimen has a constant amplitude. A simulation is presented which demonstrates good agreement between the retrieved phase and the phase of the simulated object, with excellent immunity to imaging noise.
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Briard, Paul. "Caractérisation 3D d’un nuage de particules par imagerie interférométrique de Fourier : positions relatives 3D, tailles et indices de réfraction." Thesis, Rouen, INSA, 2012. http://www.theses.fr/2012ISAM0023/document.
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Dans ce mémoire, je propose une nouvelle technique optique de mesure de positions relatives 3D, tailles et indices de réfraction d’un ensemble de particules, éclairées par un faisceau laser plan pulsé : l’imagerie interférométrique de Fourier (FII). Dans le cadre de ce travail, les particules sont sphériques, homogènes transparentes et isotropes. Lorsque ces particules sont éclairées, elles se comportent comme des sources d’ondes lumineuses sphériques qui interférent entre elles. L’enregistrement des franges d’interférences et leur analyse par transformation de Fourier peut permettre d’accéder aux caractéristiques des particules. Dans ce mémoire, je décris l’influence des caractéristiques de particules sur les représentations spectrales des franges d’interférences crées par les couples de particules éclairées dans l’espace de Fourier 2D. Les franges d’interférences sont simulées numériquement en utilisant la théorie de Lorenz-Mie. Puis j’aborde le problème inverse en montrant comment il est possible de retrouver les caractéristiques des particules, en me servant de l’optique géométrique et du filtrage spatial par transformation de FourierIn this thesis, I propose a new optical technique for measuring 3D relative positions, sizes and refractive indices of a set of particles, which are illuminated by a plane and pulsed laser beam. In this work, the particles are spherical, transparent, homogeneous and isotropic. When these particles are illuminated, they have the behavior of sources of spherical light waves which interfere. The recording of interference fringes and analysisby Fourier transform can measure the characteristics of the particles. I describe the influence of particle characteristics on spectral representations of the interference fringes created by the pairs of particles illuminated in 2D Fourier space. The interference fringes are simulated numerically using the Lorenz-Mietheory. The inverse problem is approached by showing how it is possible to measure the characteristics of particles with geometrical optics and spatial filtering by Fourier transformation
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Qvarngård, Daniel. "Modeling Optical Parametric Generation in Inhomogeneous Media." Thesis, Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-74256.
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Arnison, Matthew Raphael. "Phase control and measurement in digital microscopy." University of Sydney. Physics, 2003. http://hdl.handle.net/2123/569.
Full textAbstract:
The ongoing merger of the digital and optical components of the modern microscope is creating opportunities for new measurement techniques, along with new challenges for optical modelling. This thesis investigates several such opportunities and challenges which are particularly relevant to biomedical imaging. Fourier optics is used throughout the thesis as the underlying conceptual model, with a particular emphasis on three--dimensional Fourier optics. A new challenge for optical modelling provided by digital microscopy is the relaxation of traditional symmetry constraints on optical design. An extension of optical transfer function theory to deal with arbitrary lens pupil functions is presented in this thesis. This is used to chart the 3D vectorial structure of the spatial frequency spectrum of the intensity in the focal region of a high aperture lens when illuminated by linearly polarised beam. Wavefront coding has been used successfully in paraxial imaging systems to extend the depth of field. This is achieved by controlling the pupil phase with a cubic phase mask, and thereby balancing optical behaviour with digital processing. In this thesis I present a high aperture vectorial model for focusing with a cubic phase mask, and compare it with results calculated using the paraxial approximation. The effect of a refractive index change is also explored. High aperture measurements of the point spread function are reported, along with experimental confirmation of high aperture extended depth of field imaging of a biological specimen. Differential interference contrast is a popular method for imaging phase changes in otherwise transparent biological specimens. In this thesis I report on a new isotropic algorithm for retrieving the phase from differential interference contrast images of the phase gradient, using phase shifting, two directions of shear, and non--iterative Fourier phase integration incorporating a modified spiral phase transform. This method does not assume that the specimen has a constant amplitude. A simulation is presented which demonstrates good agreement between the retrieved phase and the phase of the simulated object, with excellent immunity to imaging noise.
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Mohamad, Habib. "Développement de la méthode différentielle associée à la Fast Fourier Factorization pour la photonique : étude de réseaux diffractifs complexes et modélisation de structures en optique intégrée." Thesis, Université Grenoble Alpes, 2020. http://www.theses.fr/2020GRALT032.
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Pour concevoir au mieux des dispositifs photoniques, il est important d’avoir des outils de modélisation fiables et efficaces. En effet si le quadrillage de paramètres technologiques est envisageable pour des dispositifs simples, son coût en nombre de tests devient rapidement un frein à l’optimisation de structures. Il devient donc indispensable de disposer de simulations totalement vectorielles, avec des matériaux à indices de réfraction complexes, de garantir la prise en compte de l’ensemble des modes de propagation (modes guidés, rayonnés et évanescents), bidirectionnelles … La simulation de structures à fort contraste d’indice de réfraction (photonique sur silicium) ou les structures utilisant des motifs métalliques générant des modes plasmoniques ou des motifs sub-longueur d’onde comme les métamatériaux … est un ensemble d’exemples qui nécessite l’utilisation de ces outils. Ces derniers se différencient par leur méthode de calcul utilisée : calcul dans le domaine fréquentiel par différences finies ou éléments finis, méthode temporelle par la méthode des différences finies … Par exemple, la FDTD est devenue ces dernières années un outil de référence dans le milieu de la photonique sur silicium. Cependant, ces méthodes ne sont pas forcément optimales. Elles diffèrent par les ressources numériques nécessaires notamment sur la mémoire utilisée, le temps de calcul, la prise en comptes des conditions de continuité, la discrétisation de la structure ainsi que leur domaine d’application (spectral ou spatial) … Ces quinze dernières années au sein du laboratoire (IMEP-Lahc), des outils basés sur la RCWA ont été développés dans ce sens pour simuler des structures très différentes allant de l’optique diffractive à l’optique guidée. Néanmoins, cette méthode comme la FDTD peut générer des approximations induisant des imprécisions ou une augmentation des ressources numériques utilisées dans certaines configurations. L’objectif de cette thèse est de développer un outil plus général dans le but de réduire ces imperfections tout en gardant la possibilité de l’utiliser sur une multitude d’applications de la photonique (optique diffractive, optique guidée …). Mon choix s’est porté sur la méthode différentielle largement utilisée pour l’étude des réseaux de diffraction. Cette méthode peut être plus efficace que la RCWA mais peut avoir aussi des limites pour la simulation de structures à profil complexe notamment en polarisation TM. Depuis les années 2000, l’ajout d’un nouveau module dénommé FFF (Fast Fourier Factorisation), permet de résoudre cette problématique et ouvrir de nouvelles potentialités à cette méthode. Après une introduction générale, la méthode différentielle associée à la FFF est présentée en détails. Ensuite, une solution simple et rapide qui permet de résoudre le problème des divergences numériques dans le cas des métaux ayant une permittivité purement réelle et négative est proposée. Puis, l’étude complète d’une structure diffractive diélectrique utilisée pour des applications de sécurité visuelle est proposée. La simulation de la structure diffractive est associée à un module utilisant un réseau de neurones pour le design et la modélisation optimale de ces structures. Finalement, pour adapter la méthode aux structures photoniques guidées, une transformée de coordonnées inspirée par la FMM apériodique a été implémentée dans l’algorithme de la MD-FFF transformant cette dernière en une méthode apériodique pour la simulation 2D de structures optiques intégrées utilisant des matériaux à indice de réfraction complexe, non-isotropes et non-magnétiques. La décomposition de la propagation sur une base de modes propres peut permettre d’accéder à des informations non directement accessibles avec la FDTD par exemple. Des résultats plus précis, plus rapides et plus rigoureux ont été obtenues par rapport à laFMM notamment en polarisation TM avec des profils curvilignes comme dans le cas des structures cylindriquesNowadays to design photonic devices, it is important to have reliable and efficient simulation tools. In fact, if exploiting the technological grids of the design parameters is considered possible for the simple devices, its cost in terms of number of tests becomes an obstacle to the optimization of the structures. Therefore, it is essential to develop fully vectorial simulations, with complex or/and real refractive indices materials, to guarantee that all the propagation modes (guided, radiated and evanescent modes) are taken into account. The simulations of the structures with high contrast refractive index (Silicon photonics for example) or structures using metallic layer and generating plasmonic modes or sub-wavelength structures like metamaterials are a set of examples that requires the use of these tools. These methods can be differentiated by their used calculation algorithm: calculation in the frequency domain by finite differences or finite elements, Fourier based methods, or calculation in the temporal domain with the finite difference method... For example, the FDTD has become in the recent years a reference tool in the domain of silicon photonics. However, almost all these methods are not necessarily optimal. They can be distinguishable by the required numerical resources, particularly in terms of the used memory, the execution time, the take into account of the boundary conditions, the discretization of the structure, or their workspace domain (spectral or spatial) ... Over the last fifteen years, the group involved with the development of electromagnetic tools in the laboratory (IMEP-Lahc), headed towards the development of RCWA based numerical tools to simulate and design the optical response of diffractive and guided optic structures. However, this last method as the FDTD can generate approximations inducing inaccuracies or an increase in the numerical resources used for certain configurations (memory, execution time...). The objective of this thesis is to develop a more general tool aiming to reduce these imperfections while retaining the possibility of using it on a multitude of photonics applications (diffractive optics, guided optics, etc.). My choice fell on the differential method which is widely used for the study of diffraction gratings. This method can be more efficient than the RCWA but it also has limitations especially for the simulation of periodic structures with complex profile in TM polarization. Since the 2000s, the association of a new module called FFF (Fast Fourier Factorization) has solved this problem and opened up new possibilities for this method. After a general introduction, the differential method associated with the FFF is presented in detail. Then, a simple and fast solution which makes the use of this method with metals having a purely real and negative permittivity is proposed and solve the problem of divergence faced before. Consequently, a complete study of a dielectric diffractive structure visual security applications is subsequently detailed. Moreover, the developed code of the DM-FFF is integrated in neural networks algorithm for optimal modeling and design of visual security structures. Finally, to meet the condition of generalizing the method for the different photonic structures (guided and diffractive), a coordinate transform inspired from the aperiodic FMM was implemented in the algorithm of the DM-FFF transforming the last one into an aperiodic method for the simulation of 2D integrated optical structures for complex, non-isotropic and non-magnetic materials. The decomposition of the propagation of eigenmode basis can provide access to information which are not directly provided by the FDTD for example (guided modes, radiated modes …). More precise, faster and more rigorous results were obtained compared to a-FMM especially in TM polarization with curvilinear profiles such as the case of cylindrical structures
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Roberto, Luciana Brassolatti. "Aplicação da holografia computacional para o cálculo de elementos ópticos difrativos." Universidade de São Paulo, 2000. http://www.teses.usp.br/teses/disponiveis/18/18133/tde-14112017-103154/.
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A Holografia Computacional é uma técnica bem conhecida que permite a realização de uma grande variedade de Elementos Ópticos Difrativos. Elementos Ópticos Difrativos são dispositivos ópticos \"moldadores\" de onda projetados com base nas propriedades de difração de suas interfaces micro-estruturadas (ou de seus variáveis índices de refração). Considerando-se sua vasta escala de tecnologias de integração e repetição, usadas na fabricação de circuitos micro-eletrônicos, eles possuem um baixo custo de fabricação. Neste trabalho, o Algoritmo Iterativo da Transformada de Fourier foi aplicado para o cálculo de hologramas de Fourier binários destinados à modelagem da luz laser. A finalidade foi simular as propriedades dos elementos, considerando algumas distribuições luminosas desejadas, e gerar o \"layout\" das máscaras de fabricação destes hologramas. Urna das implementações realizadas, para que os resultados fossem melhorados durante as iterações, foi o cálculo de uma correção na janela de reconstrução que considera o erro de amplitude da reconstrução anterior. A possibilidade de visualizar as reconstruções binárias também é demonstrada, onde o olho humano é tratado como uma lente de Fourier. Um dispositivo óptico difrativo híbrido com perfil binário e contínuo, capaz de dividir um feixe de laser monocromático em um número arbitrário de linhas com um alto ângulo também é apresentado. Hologramas de Fourier de fase contínua e com 4 níveis de fase são implementados utilizando-se o Algoritmo Iterativo da Transformada de Fourier. Cálculos para a geração de hologramas de fase de Fresnel são realizados, combinando o Algoritmo Iterativo da Transformada de Fourier com a propagação da luz no espaço livre.The Computer Holography is a well known technique that enables one to realize a wide range of Diffractive Optical Elements. Diffractive Optical Elements are optical waveshaping devices designed with base on the diffraction properties of their microstructured interfaces (or refractive-index gradients). They have potential low fabrication cost, considering their very large scale integration and replication technologies used in the fabrication of microelectronics circuits. In this work, the Iterative Fourier Transform Algorithm was applied for the calculation of binary computer generated Fourier holograrns for laser beam shaping. The purpose was to simulate the elements proprieties considering some desired light distributions and to generate the fabrication masks Iayout of these holograms. One of the implementations, performed to improve the results during the iterations, was the calculation of a amplitude correction in the reconstruction window that considers the amplitude error from the previous reconstruction. The possibility to visualize the binary holograms reconstructions is also demonstred, where the human eye is treated as a Fourier lens. A hybrid binary and continuous profile diffractive optical device capable of splitting a monochromatic laser beam into an arbitrary number of tines over wide angle is also presented. Continuous phase and four phase levels Fourier holograms are implemented using the lterative Fourier Transform Algorithm. Fresnel phase holograms calculations are performed by combining the Iterative Fourier Transform Algorithm with the free space light propagation.