• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 41
  • 8
  • 5
  • 4
  • 3
  • 2
  • 1
  • 1
  • 1
  • Tagged with
  • 79
  • 79
  • 52
  • 30
  • 30
  • 21
  • 16
  • 14
  • 12
  • 11
  • 11
  • 10
  • 9
  • 9
  • 9
  • 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.
21

Holographie adaptative pour la réalisation de capteurs à fibres optiques de très grande sensibilité : application à la détection d’ondes acoustiques sous-marines / Adaptive holographic interferometry for high sensitivity fiber optic sensors : study of underwater acoustic waves detection

Peigné, Arnaud 25 February 2016 (has links)
Ces dernières années, des avancées considérables ont été obtenues dans le domaine des capteurs à fibres optiques, principalement grâce à l’élan des applications industrielles, de plus en plus diverses et nombreuses (monitoring de structures, surveillance, environnement, applications médicales, ….). Cette thèse concerne le domaine des antennes acoustiques SONAR en technologie « tout-optique » Dans ce travail, nous nous sommes intéressés à l’étude d’un capteur de contrainte longitudinale à fibre optique. La modulation de phase optique induite par la contrainte est démodulée par un interféromètre adaptatif basé sur le principe de l’holographie dynamique. Cet interféromètre permet, par essence, (i) le filtrage des perturbations basse fréquence de l’environnement, (ii) un fonctionnement en régime linéaire (iii) la démodulation d’un front d’onde complexe, type speckle issu d’une fibre optique multimode. L’holographie dynamique repose sur l’interaction entre deux ondes optiques dans un milieu non-linéaire. Pour notre application, le milieu non-linéaire retenu est un modulateur spatial de lumière adressé optiquement (OASLM) à 1,55 μm. Nous présentons tout d’abord nos travaux de conception, réalisation et caractérisation de l’interféromètre adaptatif. Nous démontrons ensuite un capteur de contrainte à fibre optique basé sur cet interféromètre. Nous étudions également l’augmentation de sensibilité du capteur par l’utilisation d’une fibre optique multimode. Nous discutons finalement nos résultats et le potentiel de la technologie étudiée au regard de l’application visée. / Fiber optic sensors are a key technology for future developments with a large field of applications ranging from structure health monitoring to medical applications. Due to its high compactness, its electromagnetic immunity and the low transmission losses in the telecom window, optical fibers are very promising for underwater acoustic waves detection. We present a method relying on adaptive holographic interferometry based on two beam coupling in an optically addressed spatial light modulator (OASLM). This method allows filtering the slow phase perturbations coming from the environment directly on the sensing optical fiber. In this work, we will first introduce the OASLM operating at 1,55 μm that we have manufactured and the realization of an adaptive holographic interferometer based on this component. Moreover, we will show that it is possible to associate this demodulation method with a multimode optical fiber to reach a better sensitivity. Finally, we will focus on sensors architectures to evaluate the benefit of this technology compared to conventional techniques.
22

Eigenmode multiplexing with SLM for volume holographic data storage

Takashima, Yuzuru, Chen, Guanghao, Miller, Bo E. 23 August 2017 (has links)
The cavity supports the orthogonal reference beam families as its eigenmodes while enhancing the reference beam power. Such orthogonal eigenmodes are used as additional degree of freedom to multiplex data pages, consequently increase storage densities for volume Holographic Data Storage Systems (HDSS) when the maximum number of multiplexed data page is limited by geometrical factor. Image bearing holograms are multiplexed by orthogonal phase code multiplexing via Hermite- Gaussian eigenmodes in a Fe: LiNbO3 medium with a 532 nm laser at multiple Bragg angles by using Liquid Crystal on Silicon (LCOS) spatial light modulators (SLMs) in reference arms. Total of nine holograms are recorded with three angular and three eigenmode.
23

Studies in Applied and Fundamental Quantum Mechanics: Duality, Tomography, Cryptography and Holography

Bolduc, Eliot January 2013 (has links)
This thesis encompasses a collection of four pieces of work on wave-particle duality, weak-value-assisted tomography, high-dimensional quantum key distribution, and phase-only holograms. In the work on duality, we derive a novel duality relation, and we sketch a thought experiment that leads to an apparent violation of the duality principle. In the project on tomography, we perform a state determination procedure with weak values, and we study the accuracy of the method. In the quantum cryptography project, we optimize an experimental implementation of a quantum cryptography system where two parties share information with the orbital angular momentum degree of freedom of entangled photon pairs. Finally, in the work on holography, we establish the exact solution to the encryption of a phase-only hologram, and experimentally demonstrate its application to spatial light modulators. The four projects provide improvements on measurement procedures in applied and fundamental quantum mechanics.
24

Fabrication and Study of the Optical Properties of 3D Photonic Crystals and 2D Graded Photonic Super-Crystals

Lowell, David 12 1900 (has links)
In this dissertation, I am presenting my research on the fabrication and simulation of the optical properties of 3D photonic crystals and 2D graded photonic super-crystals. The 3D photonic crystals were fabricated using holographic lithography with a single, custom-built reflective optical element (ROE) and single exposure from a visible light laser. Fully 3D photonic crystals with 4-fold, 5- fold, and 6-fold symmetries were fabricated using the flexible, 3D printed ROE. In addition, novel 2D graded photonic super-crystals were fabricated using a spatial light modulator (SLM) in a 4f setup for pixel-by-pixel phase engineering. The SLM was used to control the phase and intensity of sets of beams to fabricate the 2D photonic crystals in a single exposure. The 2D photonic crystals integrate super-cell periodicities with 4-fold, 5-fold, and 6-fold symmetries and a graded fill fraction. The simulations of the 2D graded photonic super-crystals show extraordinary properties such as full photonic band gaps and cavity modes with Q-factors of ~106. This research could help in the development of organic light emitting diodes, high-efficiency solar cells, and other devices.
25

Phase Change Materials for Optoelectronic Devices and Memories: Characterization and Implementation

Sevison, Gary A. 06 January 2022 (has links)
No description available.
26

High-speed Imaging with Less Data

Baldwin, Raymond Wesley 09 August 2021 (has links)
No description available.
27

Analysis And Design Of Wide-angle Foveated Optical Systems

Curatu, George 01 January 2009 (has links)
The development of compact imaging systems capable of transmitting high-resolution images in real-time while covering a wide field-of-view (FOV) is critical in a variety of military and civilian applications: surveillance, threat detection, target acquisition, tracking, remote operation of unmanned vehicles, etc. Recently, optical foveated imaging using liquid crystal (LC) spatial light modulators (SLM) has received considerable attention as a potential approach to reducing size and complexity in fast wide-angle lenses. The fundamental concept behind optical foveated imaging is reducing the number of elements in a fast wide-angle lens by placing a phase SLM at the pupil stop to dynamically compensate aberrations left uncorrected by the optical design. In the recent years, considerable research and development has been conducted in the field of optical foveated imaging based on the LC SLM technology, and several foveated optical systems (FOS) prototypes have been built. However, most research has been focused so far on the experimental demonstration of the basic concept using off the shelf components, without much concern for the practicality or the optical performance of the systems. Published results quantify only the aberration correction capabilities of the FOS, often claiming diffraction limited performance at the region of interest (ROI). However, these results have continually overlooked diffraction effects on the zero-order efficiency and the image quality. The research work presented in this dissertation covers the methods and results of a detailed theoretical research study on the diffraction analysis, image quality, design, and optimization of fast wide-angle FOSs based on the current transmissive LC SLM technology. The amplitude and phase diffraction effects caused by the pixelated aperture of the SLM are explained and quantified, revealing fundamental limitations imposed by the current transmissive LC SLM technology. As a part of this study, five different fast wide-angle lens designs that can be used to build practical FOSs were developed, revealing additional challenges specific to the optical design of fast wide-angle systems, such as controlling the relative illumination, distortion, and distribution of aberrations across a wide FOV. One of the lens design examples was chosen as a study case to demonstrate the design, analysis, and optimization of a practical wide-angle FOS based on the current state-of-the-art transmissive LC SLM technology. The effects of fabrication and assembly tolerances on the image quality of fast wide-angle FOSs were also investigated, revealing the sensitivity of these fast well-corrected optical systems to manufacturing errors. The theoretical study presented in this dissertation sets fundamental analysis, design, and optimization guidelines for future developments in fast wide-angle FOSs based on transmissive SLM devices.
28

Investigation of Liquid Crystal Spatial Light Modulators to Simulate Speckle Fields

Cordray, Jared M. 05 May 2010 (has links)
No description available.
29

Complex Optical Fields Generation Using a Vectorial Optical Field Generator

Zhou, Sichao 18 May 2016 (has links)
No description available.
30

Optical sorting and manipulation of microscopic particles

Milne, Graham January 2007 (has links)
Over the last few decades, the use of light to control and manipulate microscopic particles has become widespread. These methods are enabling new areas of research to flourish across the physical and biological sciences. This thesis describes investigations into both optical trapping and the closely related field of optical sorting. It documents the development of a variety of new techniques. The thesis begins with a short review of optical trapping and existing methods for sorting mixtures of microscopic particles. The first half of this chapter highlights some of the reasons behind optical trapping's rapid growth in popularity. By reviewing an array of methods for sorting particles and discussing the relative merits of each, the case for optical sorting is established. The second chapter describes research into using a spatial light modulator to create three-dimensional optically trapped colloidal structures using the time-sharing technique. Limiting factors inherent in the technology are discussed in detail. The third chapter reviews a sophisticated particle-tracking software package that has proved to be a considerable success. It was developed explicitly with colloidal microscopy in mind and experimental plots produced by the software are used throughout the thesis. Experimental studies have been performed into the behaviour of microscopic particles moving under the influence of two classes of propagation-invariant beams: Mathieu beams and Bessel beams. The Bessel beam studies have been complimented by a theoretical model and have led ultimately to a new method for the static optical sorting of both solid particles and biological cells, with particular emphasis on human blood. The fifth and final chapter describes how re-configurable optical devices can be implemented to spatially separate different colloidal species. A new method for creating arbitrary optical landscapes using an acousto-optic modulator is reported. This new technique is then used to optically sort four particle species simultaneously - the first experimental demonstration of polydisperse optical fractionation. Additionally, experiments are reported that demonstrate controlled, static optical sorting using a spatial light modulator.

Page generated in 0.0632 seconds