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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.
1

Adaptive optics for microscopy and photonic engineering

Simmonds, Richard January 2012 (has links)
Aberrations affect the operation of optical systems, particularly those designed to work at the diffraction limit. These systems include high-resolution microscopes, widely used for imaging in biology and other areas. Similar problems are encountered in photonic engineering, specifically in laser fabrication systems used for the manufacture of fine structures. The work presented in this thesis covers various aspects of adaptive optics developed for applications in microscopes and laser fabrication. By mathematically modelling a range of idealised fluorescent structures, the effect of different aberrations on their intensity in various microscopes is presented. The effect of random aberrations on the contrast of these different structures is then calculated and the results displayed on idealised images. Images from a two-photon microscope demonstrate the predicted results. The contrast of two structures is compared when imaged first by a conventional microscope and then by the two-photon or confocal sectioning microscopes. The different specimen structures were seen to be affected to varying extents by each aberration mode. In order to correct for aberrations in microscopy and other photonic applications, adaptive elements such as deformable mirrors are incorporated into the optical setups. An important step is to train the deformable mirror so that it produces appropriate mode shapes to apply a phase to optical wavefronts. One such mirror is modelled using the membrane equation to predict the surface shape when an actuator is applied. Each of these influence functions is combined to produce a set of orthogonal mirror modes, which are used to experimentally produce a set of empirical modes in a two-photon microscope. An alternative method of training a deformable mirror from a spatial light modulator is employed. The focal spot of an optical system is imaged to provide a feedback metric for the mirror to replicate the phase pattern on the spatial light modulator. A two-photon microscope with adaptive optics is demonstrated by imaging the brains of Drosophila deep within the bulk, correcting for both system and specimen induced aberrations using the deformable mirror with empirical mirror modes applied. A harmonic generation microscope is also used to image both biological and non-biological specimens whilst performing aberration correction with a deformable mirror. Adaptive optical methods are also applied to a laser fabrication system, by constructing a dual adaptive optics setup to correct for aberrations induced when fabricating deep in the bulk of a substrate. The efficiency and fidelity of fabrication in diamond substrate is shown to be significantly increased as a result of the dual aberration correction. An outstanding problem in microscopy is the effect of spatially variant aberrations. Using measurements from the adaptive microscopes, the extent to which they are present in a range of specimens is quantified. One potential technique to be used to correct for these aberrations is multi-conjugate adaptive optics. Different configurations of a multi-conjugate adaptive optics system are modelled and the improvement on the Strehl ratio of aberrated images quantified for both simulated images and real data. The application of this technique in experimental microscopes is considered.
2

Optics optimization of longer L* Beam Delivery System designs for CLIC and tuning of the ATF2 final focus system at ultra-low β* using octupoles / Optimisation de la ligne de faisceau du système de focalisation finale à long L* du collisionneur linéaire CLIC et étude des optiques de focalisation de l'ATF2 à ultra-bas β* avec utilisation d'octupôles

Plassard, Fabien 06 July 2018 (has links)
Un défi important pour les futurs collisionneurs linéaires électron-positron est de pouvoir focaliser le faisceau à des tailles transverses de l’ordre du nanomètre au point d’interaction (IP), permettant d’atteindre la luminosité de conception. Le système délivrant les faisceaux d’e- et de e + de la sortie du Linac principal vers le point d’interaction, le Beam Delivery System (BDS), réalise les fonctions critiques requises pour atteindre l’objectif de luminosité, tel que la collimation et la focalisation du faisceau. Le faisceau est focalisé par le système de focalisation finale (FFS) tout en corrigeant les aberrations d’ordre supérieur propagées le long du système. Les effets chromatiques contribuant à l’élargissement de la taille du faisceau, sont amplifiés par la force de focalisation des deux derniers quadripôles QF1 et QD0, ou doublet final (FD), et par la longueur de la distance focale finale L* entre QD0 et l’IP. L’approche de correction de la chromaticité retenue pour les deux grands projets actuels de collisionneurs linéaires, CLIC et ILC, est fondée sur la correction locale de la chromaticité générée par le doublet final. Ce schéma est actuellement testé à l’ATF2 au KEK (Japon). Ce travail de thèse se concentre sur les problématiques liées au système de focalisation finale du projet CLIC re-optimisé avec un plus long L*, dans le cadre de la simplification de l’interface machine-détecteur (MDI), ainsi que sur le travail expérimental conduit à l’ATF2 pour l’optimisation et l’étude des optiques du système de focalisation finale à ultra-bas β* incluant les tout premiers est in situ des octupôles à l’ATF2. / The future machines considered to carry out high precision physics in the TeV energy regime are electron-positron (e+e−) linear colliders. Future linear colliders feature nanometer beam spot sizes at the Interaction Point. The Beam Delivery System (BDS) transports the e + and e− beams from the exit of the linacs to the IP by performing the critical functions required to meet the CLIC luminosity goal such as beam collimation and focusing. The beam is focused through the Final Focus System while correcting higher order transport aberrations in order to deliver the design IP beam sizes. The chromatic contributions are amplified by the focusing strength of the two last quadrupoles named QD0 and QF1, reffered to as the Final Doublet (FD), and by the length of the final focal distance L* between QD0 and the IP. The chromaticity correction approach chosen for the CLIC FFS is based on the Local chromaticity correction scheme which uses interleaved pairs of sextupole magnets in the FD region in order to locally and simultaneously correct horizontal and vertical chromaticity. The current linear collider projects, the Compact Linear Collider (CLIC) and the International Linear Collider (ILC) have FFS lattices based on the Local Chromaticity correction scheme. This scheme is being tested in the Accelerator Test Facility 2 (ATF2) at KEK (Japan). This thesis concentrates on problems related to the optimization of BDS lattices for the simplification of the CLIC Machine Detector Interface (MDI) and on the experimental work for the implementation and study of a CLIClike FFS optics for the ATF2, referred to as ultra-low β* optics.

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