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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
41

Liquid Crystal on Silicon Displays Characterization for Diffractive Applications and for Holographic Data Storage in Photopolymers / Caracterización de pantallas LCoS para aplicaciones en óptica difractiva y almacenamiento holográfico de información en fotopolímeros

Martínez Guardiola, Francisco Javier 23 July 2015 (has links)
In this PhD Thesis I present some methods for characterizing PA-LCoS microdisplays. It is useful to fully characterize this type of devices for evaluating its performance required in different applications. We have tested its validity in different applications such as diffractive optics elements (DOEs). Finally we apply these microdisplays in a full holographic data storage scheme using a photopolymer as holographic recording medium. We evaluate the capability of PVA/AA photopolymer for this holographic data storage system that incorporates as a novelty a convergent correlator geometry.
42

Characterisation of Group III nitrides using hard X-ray synchrotron radiation

Mudie, Stephen January 2004 (has links)
Abstract not available
43

Optical measuring system using a camera and laser fan-out for narrow mounting on a miniaturized submarine

Berglund, Martin January 2009 (has links)
<p>The aim was to develop, manufacture and evaluate diffractive lenses, or diffractive optical elements (DOE), for use in correlation with a camera to add perspective in pictures. The application is a miniaturized submarine developed in order to perform distant exploration and analysis in harsh and narrow environments. The idea is to project a laser pattern upon the observed structure and thereby add geometrical information to pictures acquired with an onboard CMOS camera. The design of the DOE-structures was simulated using the optimal rotational angle method (ORA). A set of prototype DOEs were realized using a series of microelectromechanical system (MEMS) processes, including photolithography, deposition and deep reactive-ion etching (DRIE). The projected patterns produced by the manufactured DOEs were found to agree with the simulated patterns except for the case where the DOE feature size was too small for the available process technology to handle. A post-processing software solution was developed to extract information from the pictures, called Laser Camera Measurement (LCM). The software returns the x, y and z coordinate of each laser spot in a picture and provides the ability to measure a live video stream from the camera. The accuracy of the measurement is dependent of the distance to the object. Some of the patterns showed very promising results, giving a 3-D resolution of ~0.6 cm, in each dot, at a distance of 1 m from the camera. Lengths can be resolved up til 3 m distance from the submarine.</p> / <p>Tillämpningen finns i en miniatyriserad ubåt framtagen för utforskning och analys av svåråtkomliga och trånga håligheter. Målet var att designa, tillverka och utvärdera en diffraktiv lins (DOE) för användning tillsammans med en kamera för att skapa perspektiv i bilder. Idén var att projicera ett lasermönster på objektet och därmed lägga till geometrisk information till bilderna tagna med CMOS kameran. Utformningen av DOE-strukturerna simulerades med the optimal rotational angle method (ORA). En uppsättning av prototyp DOE-linser tillverkades med hjälp av en serie mikrostrukturteknikprocesser, bland annat fotolitografi, deponering och plasmaetsning. Mönster projicerade med de tillverkade DOE-linserna stämde väl överens med önskade mönster, med undantag för de DOEs där strukturstorleken underskred processens begränsningar. En programvara, kallad Laser Camera Measurement (LCM), utvecklades för att extrahera information från bilderna. Programvaran returnerar x, y, och z koordinaterna för varje laserpunkt i en bild och ger möjlighet att mäta i en kontinuerlig videoström från kameran.  Mätosäkerheten är beroende av avståndet till objektet. Vissa mönster gav mycket lovande resultat, med en 3-D upplösning på ~0.6 cm, i varje punkt, på ett avstånd av 1 m från kameran. Längder kan upplösas upp till 3 m från kameran där ett så kallat far-field uppstår.</p> / DADU
44

Studies of Diffractive Scattering of Photons at Large Momentum Transfer And of the VFPS Detector at HERA

Hreus, Tomas 26 September 2008 (has links)
In this thesis, two studies of the diffractive phenomena in the electron proton collisions with the H1 detector at HERA are presented. The first is the study of the inclusive elastic diffractive events $ep o eXp$ in the regime of high photon virtuality ($Q^2 >$ few GeV$^2$), with the scattered proton detected by the Very Forward Proton Spectrometer (VFPS). The VFPS detector, designed to measure diffractive scattered protons with high acceptance, has been installed in 2004 to benefit from the HERA II luminosity increase. The selected event sample of an integrated luminosity of 130.2 pb$^{-1}$ was collected in years 2006-2007. Data sample distributions are compared to the prediction based on the diffractive parton distribution functions, as extracted from the H1 measurement of the diffractive structure function $F_2^{D(3)}$ at HERA I. After the study of the VFPS efficiency, the VFPS acceptance as a function of $xpom$ is estimated and studied in relation to the forward proton beam optics. The second study leads to the cross section measurement of the diffractive scattering of quasi-real photons off protons, $gamma p o gamma Y$, with the large momentum transfer, $|t|$. The final state photon is separated from the proton dissociation system, $Y$, by a large rapidity gap and has a large transverse momentum, $p_T > 2$ GeV. Large $p_T$ imply the presence of the hard scale $t$ ($|t| simeq p_T^2$) and allows predictions of the perturbative QCD to be applied. The measurement is based on an integrated luminosity 46.2 pb$^{-1}$ of data collected in the 1999-2000 running period. Cross sections $sigma(W)$ as a function of the incident photon-proton centre of mass energy, $W$, and $ud sigma/ud |t|$ are measured in the range $Q^2 < 0.01$ GeV$^2$, $175 < W < 247$ GeV, $4 < |t| < 36$ GeV$^2$ and $ypom < 0.05$. The cross section measurements have been compared to predictions of LLA BFKL calculations.
45

Axicon imaging by scalar diffraction theory

Burvall, Anna January 2004 (has links)
Axicons are optical elements that produce Bessel beams,i.e., long and narrow focal lines along the optical axis. Thenarrow focus makes them useful ine.g. alignment, harmonicgeneration, and atom trapping, and they are also used toincrease the longitudinal range of applications such astriangulation, light sectioning, and optical coherencetomography. In this thesis, axicons are designed andcharacterized for different kinds of illumination, using thestationary-phase and the communication-modes methods. The inverse problem of axicon design for partially coherentlight is addressed. A design relation, applicable toSchell-model sources, is derived from the Fresnel diffractionintegral, simplified by the method of stationary phase. Thisapproach both clarifies the old design method for coherentlight, which was derived using energy conservation in raybundles, and extends it to the domain of partial coherence. Thedesign rule applies to light from such multimode emitters aslight-emitting diodes, excimer lasers and some laser diodes,which can be represented as Gaussian Schell-model sources. Characterization of axicons in coherent, obliqueillumination is performed using the method of stationary phase.It is shown that in inclined illumination the focal shapechanges from the narrow Bessel distribution to a broadasteroid-shaped focus. It is proven that an axicon ofelliptical shape will compensate for this deformation. Theseresults, which are all confirmed both numerically andexperimentally, open possibilities for using axicons inscanning optical systems to increase resolution and depthrange. Axicons are normally manufactured as refractive cones or ascircular diffractive gratings. They can also be constructedfrom ordinary spherical surfaces, using the sphericalaberration to create the long focal line. In this dissertation,a simple lens axicon consisting of a cemented doublet isdesigned, manufactured, and tested. The advantage of the lensaxicon is that it is easily manufactured. The longitudinal resolution of the axicon varies. The methodof communication modes, earlier used for analysis ofinformation content for e.g. line or square apertures, isapplied to the axicon geometry and yields an expression for thelongitudinal resolution. The method, which is based on abi-orthogonal expansion of the Green function in the Fresneldiffraction integral, also gives the number of degrees offreedom, or the number of information channels available, forthe axicon geometry. Keywords:axicons, diffractive optics, coherence,asymptotic methods, communication modes, information content,inverse problems
46

Ultrafast Coherent X-ray Diffractive Nanoimaging

R. N. C. Maia, Filipe January 2010 (has links)
X-ray lasers are creating unprecedented research opportunities in physics,chemistry and biology. The peak brightness of these lasers exceeds presentsynchrotrons by 1010, the coherence degeneracy parameters exceedsynchrotrons by 109, and the time resolution is 105 times better. In theduration of a single flash, the beam focused to a micron-sized spot has the samepower density as all the sunlight hitting the Earth, focused to a millimetresquare. Ultrafast coherent X-ray diffractive imaging (CXDI) with X-ray lasers exploitsthese unique properties of X-ray lasers to obtain high-resolution structures fornon-crystalline biological (and other) objects. In such an experiment, thesample is quickly vaporised, but not before sufficient scattered light can berecorded. The continuous diffraction pattern can then be phased and thestructure of a more or less undamaged sample recovered% (speed of light vs. speed of a shock wave).This thesis presents results from the first ultrafast X-ray diffractive imagingexperiments with linear accelerator-driven free-electron lasers and fromoptically-driven table-top X-ray lasers. It also explores the possibility ofinvestigating phase transitions in crystals by X-ray lasers. An important problem with ultrafast CXDI of small samples such as single proteinmolecules is that the signal from a single measurement will be small, requiringsignal enhancement by averaging over multiple equivalent samples. We present anumerical investigation of the problems, including the case where samplemolecules are not exactly identical, and propose tentative solutions. A new software package (Hawk) has been developed for data processing and imagereconstruction. Hawk is the first publicly available software package in thisarea, and it is released as an open source software with the aspiration offostering the development of this field.
47

Optical measuring system using a camera and laser fan-out for narrow mounting on a miniaturized submarine

Berglund, Martin January 2009 (has links)
The aim was to develop, manufacture and evaluate diffractive lenses, or diffractive optical elements (DOE), for use in correlation with a camera to add perspective in pictures. The application is a miniaturized submarine developed in order to perform distant exploration and analysis in harsh and narrow environments. The idea is to project a laser pattern upon the observed structure and thereby add geometrical information to pictures acquired with an onboard CMOS camera. The design of the DOE-structures was simulated using the optimal rotational angle method (ORA). A set of prototype DOEs were realized using a series of microelectromechanical system (MEMS) processes, including photolithography, deposition and deep reactive-ion etching (DRIE). The projected patterns produced by the manufactured DOEs were found to agree with the simulated patterns except for the case where the DOE feature size was too small for the available process technology to handle. A post-processing software solution was developed to extract information from the pictures, called Laser Camera Measurement (LCM). The software returns the x, y and z coordinate of each laser spot in a picture and provides the ability to measure a live video stream from the camera. The accuracy of the measurement is dependent of the distance to the object. Some of the patterns showed very promising results, giving a 3-D resolution of ~0.6 cm, in each dot, at a distance of 1 m from the camera. Lengths can be resolved up til 3 m distance from the submarine. / Tillämpningen finns i en miniatyriserad ubåt framtagen för utforskning och analys av svåråtkomliga och trånga håligheter. Målet var att designa, tillverka och utvärdera en diffraktiv lins (DOE) för användning tillsammans med en kamera för att skapa perspektiv i bilder. Idén var att projicera ett lasermönster på objektet och därmed lägga till geometrisk information till bilderna tagna med CMOS kameran. Utformningen av DOE-strukturerna simulerades med the optimal rotational angle method (ORA). En uppsättning av prototyp DOE-linser tillverkades med hjälp av en serie mikrostrukturteknikprocesser, bland annat fotolitografi, deponering och plasmaetsning. Mönster projicerade med de tillverkade DOE-linserna stämde väl överens med önskade mönster, med undantag för de DOEs där strukturstorleken underskred processens begränsningar. En programvara, kallad Laser Camera Measurement (LCM), utvecklades för att extrahera information från bilderna. Programvaran returnerar x, y, och z koordinaterna för varje laserpunkt i en bild och ger möjlighet att mäta i en kontinuerlig videoström från kameran.  Mätosäkerheten är beroende av avståndet till objektet. Vissa mönster gav mycket lovande resultat, med en 3-D upplösning på ~0.6 cm, i varje punkt, på ett avstånd av 1 m från kameran. Längder kan upplösas upp till 3 m från kameran där ett så kallat far-field uppstår. / DADU
48

Volume Grating Couplers for Optical Interconnects: Analysis, Design, Fabrication, and Testing

Villalaz, Ricardo A. 12 July 2004 (has links)
Optical interconnects are important to the future development of microelectronics. Volume grating couplers (VGCs) provide a compact, efficient coupling mechanism that is compatible with microelectronics fabrication processes. In this dissertation, some of the performance characteristics of VGCs are investigated. Also, integration of VGCs with Sea of Polymer Pillars (SoPP), an emerging high-density input/output interconnect technology, is demonstrated and its performance quantitatively investigated. First, the polarization-dependent performance of VGCs is analyzed, and the design constraints for achieving high-efficiency polarization-dependent and polarization-independent VGCs are examined. The effects of loss on VGC performance are also presented. Then, the wavelength response of VGCs and its dependence on grating parameters is quantitatively examined. Experimental demonstrations of polarization-dependent and polarization-independent VGCs are then presented. Finally, a VGC integrated with a SoPP is demonstrated and its performance characterized.
49

Optical Properties of Plasmonic Zone Plate Lens, SERS-active Substrate and Infrared Dipole Antenna

Kim, Hyun Chul 2009 August 1900 (has links)
Nowadays plasmonics is rapidly developing areas from fundamental studies to more application driven research. This dissertation contains three different research topics on plasmonics. In the first research topic, by modulating the zone width of a plasmonic zone plate, we demonstrate that a beam focused by a proposed plasmonic zone plate lens can be achieved with higher intensity and smaller spot size than the diffraction-limited conventional zone plate lens. This sub-diffraction focusing capability is attributed to extraordinary optical transmission, which is explained by the complex propagation constant in the zone regions afforded by higher refractive index dielectric layer and surface plasmons. On the other hand, the resulted diffraction efficiency of this device is relatively low. By introducing a metal/dielectric multilayered zone plate, we present higher field enhancement at the focal point. This higher field enhancement originates not only from surface plasmon polaritons-assisted diffraction process along the propagation direction of the incident light (longitude mode), but also from multiple scattering and coupling of surface plasmons along the metal/dielectric interface (transverse mode). In the second research topic, we suggest a novel concept of SERS-active substrate applications. The surface-enhanced Raman scattering enhancement factor supported by gap surface plasmon polaritons is introduced. Due to higher effective refractive index induced by gap surface plasmon polaritons in the spacer region between two metal plates, incident light tends to localize itself mostly in the medium with higher refractive index than its adjacent ones and thereby the lights can confine with larger field enhancement. In the last research topic, we offer a simple structure in which a gold dipole antenna is formed on the SiC substrate. Surface phonon polaritons, counterparts of surface plasmon polaritons in the mid-infrared frequencies, are developed. Due to the synergistic action between the conventional dipole antenna coupling and the resonant excitation of surface phonon polaritons, strong field enhancement in the gap region of dipole antenna is attained. Most of research topics above are expected to find promising applications such as maskless nanolithography, high resolution scanning optical microscopy, optical data storage, optical antenna, SERS-active substrate, bio-molecular sensing and highly sensitive photo-detectors.
50

Axicon imaging by scalar diffraction theory

Burvall, Anna January 2004 (has links)
<p>Axicons are optical elements that produce Bessel beams,i.e., long and narrow focal lines along the optical axis. Thenarrow focus makes them useful ine.g. alignment, harmonicgeneration, and atom trapping, and they are also used toincrease the longitudinal range of applications such astriangulation, light sectioning, and optical coherencetomography. In this thesis, axicons are designed andcharacterized for different kinds of illumination, using thestationary-phase and the communication-modes methods.</p><p>The inverse problem of axicon design for partially coherentlight is addressed. A design relation, applicable toSchell-model sources, is derived from the Fresnel diffractionintegral, simplified by the method of stationary phase. Thisapproach both clarifies the old design method for coherentlight, which was derived using energy conservation in raybundles, and extends it to the domain of partial coherence. Thedesign rule applies to light from such multimode emitters aslight-emitting diodes, excimer lasers and some laser diodes,which can be represented as Gaussian Schell-model sources.</p><p>Characterization of axicons in coherent, obliqueillumination is performed using the method of stationary phase.It is shown that in inclined illumination the focal shapechanges from the narrow Bessel distribution to a broadasteroid-shaped focus. It is proven that an axicon ofelliptical shape will compensate for this deformation. Theseresults, which are all confirmed both numerically andexperimentally, open possibilities for using axicons inscanning optical systems to increase resolution and depthrange.</p><p>Axicons are normally manufactured as refractive cones or ascircular diffractive gratings. They can also be constructedfrom ordinary spherical surfaces, using the sphericalaberration to create the long focal line. In this dissertation,a simple lens axicon consisting of a cemented doublet isdesigned, manufactured, and tested. The advantage of the lensaxicon is that it is easily manufactured.</p><p>The longitudinal resolution of the axicon varies. The methodof communication modes, earlier used for analysis ofinformation content for e.g. line or square apertures, isapplied to the axicon geometry and yields an expression for thelongitudinal resolution. The method, which is based on abi-orthogonal expansion of the Green function in the Fresneldiffraction integral, also gives the number of degrees offreedom, or the number of information channels available, forthe axicon geometry.</p><p><b>Keywords:</b>axicons, diffractive optics, coherence,asymptotic methods, communication modes, information content,inverse problems</p>

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