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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

Development of Optoelectronic Devices and Computational Tools for the Production and Manipulation of Heavy Rydberg Systems

Philippson, Jeffrey 26 October 2007 (has links)
Experimental and theoretical progress has been made toward the production and manipulation of novel atomic and molecular states. The design, construction and characterization of a driver for an acousto-optic modulator is presented which achieves a maximum diffraction efficiency of 54 % at 200 MHz, using a commercial modulator. A novel design is presented for a highly sensitive optical spectrum analyzer for displaying laser mode structure in real time. Utilizing programmable microcontrollers to read data from a CMOS image sensor illuminated by the diffraction pattern from a Fabry-Perot interferometer, this device can operate with beam powers as low as 3.3 micro-watts, at a fraction of the cost of equivalent products. Computational results are presented analyzing the behaviour of a model quantum system in the vicinity of an avoided crossing. The results are compared with calculations based on the Landau-Zener formula, with discussion of its limitations. Further computational work is focused on simulating expected conditions in the implementation of the STIRAP technique for coherent control of atoms and molecules in the beam experiment. The work presented provides tools to further the aim of producing large, mono-energetic populations of heavy Rydberg systems. / Thesis (Master, Physics, Engineering Physics and Astronomy) -- Queen's University, 2007-10-03 17:17:56.841
2

Persistances, actualités et dynamiques du noir et blanc au cinéma dans les arts filmiques (1990-2010) / Permanence, topicality and dynamics of black and white in filmic arts (1990s-present)

Reiner, Gabrielle 07 May 2014 (has links)
Travailler le noir et blanc au cinéma sous-entend une alternative temporelle qui s’inscrit à l’image par une absence de couleur mimétique. C’est un cinéma qui a priori puise aux sources d'un passé revendiqué visuellement. Pourquoi et dans quelles intentions certains cinéastes persistent-ils à utiliser le noir et blanc alors que l’évolution historique du média invite à utiliser la couleur ? Comment ce choix à contre-courant permet-il de penser l'histoire du média ? Quels en sont les enjeux matériels, esthétiques et réflexifs ? Existe-t-il des styles du noir et blanc ancrés dans le présent, sans références techniques et plastiques à une histoire univoque des formes ? À une époque de domination économique de la couleur, réaliser des films en noir et blanc serait-il porteur d’une réflexion critique sur les procédés cinématographiques actuels et sur l’industrie qui les impose ? Bien loin d’une bichromie passéiste, en quoi, pourquoi et comment d’autres noir et blanc deviennent-ils des outils de prédilection pour établir l’état des lieux d’une plasticité critique de la représentation de l’industrie audiovisuelle ?Nous verrons qu’en optant pour le noir et blanc, la palette chromatique construit un espace propice à un cinéma différent en rupture avec les conventions du réalisme audiovisuel. Ce cinéma différent « réfléchit » le noir et blanc qui devient une source d’expériences holistiques à l’origine d’un redéploiement élargi du cinéma comme geste et art plastique fondateurs. Ce Doctorat en cartographie et en analyse la richesse et la diversité. / To work on cinematographic black and white is to enter an alternative temporality that incarnates itself on screen through an absence of mimetic colors. It is in theory a cinema rooted in the past and reclaiming it visually. Why do certain filmmakers persist in using black and white instead of following the course of evolution towards color ? Why do they reject the evolution of techniques ? How do they reflect on it, build new technical and esthetical frames ? Are there any styles of black and white which fully belong to the present and don't refer to past techniques and aesthetics ?In a time when color holds an economic supremacy on cinema, black and white films offer a form of technical criticism on the domination of an industry. Far from an bichromic old fashioned, why and how does others black and white become instruments of a new critical esthetics against industrial audiovisual representation ?Chosing black and white allows for a new, different cinema to break with the conventions of realism. This different cinema « reflects » on black and white, transcending it through holistic experiences, synesthetic and cognitive, redefining cinema as a broader act of creative art. This PhD attempts to map and analyse its richness and diversity.
3

Metoda pro zvýšení přesnosti měření optického frekvenčního spektra laditelnými optickými filtry / Design of the method to increasing of accuracy of the tunable optical filter optical spectra measurement

Jelínek, Michal January 2016 (has links)
The thesis deals with the method for the improvement of the measurement accuracy in the optical frequency spectra measurements based on tunable optical filters. The thesis starts with the selection of the proper optical filter that is suitable for accurate light spectrum measurement. The selected filter was then used for the design and realization of the measurement system for the inspection of the fibre Bragg gratings. The system incorporates a reference block for the compensation of environmental influences, an interferometric verification subsystem and a PC - based control software implemented in LabView. The preliminary experimental verification of the measurement principle and the measurement system functionality were carried out on a testing rig with a specially prepared concrete console in the UJV Řež. Advanced tests were conducted on nuclear power plant’s containment shape deformation measurement in Temelin.
4

DWDM v přístupových sítích / DWDM in access networks

Šifta, Radim January 2011 (has links)
The aim of this master´s thesis is an explanation of the problem of optical access networks with wavelength division multiplex, main purpose is to demonstrate the difference between simulation and real measurement. The thesis is divided into several basic thematic areas. At the beginning of thesis is outlined the basic division of multiplexing system, there are discussed the basic solutions of wavelength multiplexes and their possible combinations. The next chapter deals with the active elements, which are an essential part of xWDM systems such as optical lasers, detectors and amplifiers. The following chapter is focused on the passive elements, especially on the passive filters, which form a key part of the wavelength multiplex. Methods of measurement C/DWDM networks are discussed in the next part of thesis. The next chapter describes the topology used by active and passive optical networks. Penultimate part of this thesis consists of designs simulated models PON and WDM-PON networks and comparing their transmission parameters. The final part presents the results of practical measurements of experimental optical access network with wavelength division multiplex, the results are simultaneously compared with results of simulations.
5

Photonic Integrated Circuits Utilizing Nano-Electromechanical Systems on Silicon-on-Insulator Platform for Software Defined Networking in Elastic Optical Networks: New Insights Into Phased Array Systems, Tunable WDM, and Cascaded FIR and IIR Architectures

Hussein, Ali Abdulsattar 09 September 2019 (has links)
Optical communications systems operate at the limits of their margins to respond to increasing capacity demands. Some of the signal processing functions required must soon operate at speeds beyond electronic implementation. Optical signal processors are fundamentally analog which requires precise control of the operating state. Programmable optical components are consequently essential. The thesis explores and elucidates the properties of meshes of generalized Mach-Zehnder interferometers (GMZIs) amenable to silicon (Si) photonics integration that are based on multimode interference couplers with programmability achieved via voltage controlled phase-shift elements within the interferometer arms to perform a variety of finite impulse response (FIR) and infinite impulse response (IIR) signal processing functions. The thesis presents a novel class of integrated photonic phased array systems with a single-stage, multistage, and feedback architectures. The designed photonic integrated systems utilize nano-electromechanical-system (NEMS) operated phase shifters of cascaded free suspended slot waveguides that are compact and require a small amount of power to operate. The structure of the integrated photonic phased array switch (IPPAS) elements is organized such that it brings the NEMS-operated phase shifters to the exterior sides of the construction; facilitating electrical connection. The transition slot couplers used to interconnect the phase shifters to the rest of the silicon structure are designed to enable biasing one of the silicon beams of each phase shifter from an electrode located at the side of the phase shifter. The other silicon beam of each phase shifter is biased through the rest of the silicon structure of the fabric, which is taken as a ground. Phased array processors of 2×2 and 4×4 multiple-input-multiple-output (MIMO) ports are conveniently designed within reasonable footprints native to the current fabrication technologies. The response of the single-stage 4×4 broadband IPPAS element is determined, and its phase synthesis states required for single-throw, double-throw and broadcast routing operations are predicted. The transmission responses of the single-stage wavelength division multiplexing (WDM) processors of 2×2 and 4×4 MIMO ports are simulated. The wavelength steering capability of the transmission interferograms by applying progressive phase shifts through the array of NEMS-operated phase shift elements of the single-stage 4×4 WDM (de)multiplexer is demonstrated. The advantages of cascading broadband and WDM phased array sections are articulated through several study cases. Five different cascaded phased array architectures are trialed for the construction of non-blocking 4×4 IPPAS broadband switches that are essential elements in the construction of universal photonic processors. A cascaded 2×2 WDM (de)multiplexer that can set the bandwidth of the (de)multiplexed cyclic channels into a binary number of programmable values is demonstrated. The envelope and wavelength modulations of the transmission responses utilizing a cascaded forward structure of three 2×2 sections that can be utilized for the (de)multiplexing of different bandwidth channels are demonstrated providing individual wavelength steering capability of the narrowband and wideband channels and the individual wavelength steering capability of the slow envelope and wavelength modulating functions. Innovative universal 2×2 and 4×4 cascaded phased array processors of advanced high-order architectures that can function as both non-blocking broadband routers and tunable WDM (de)multiplexers with spectrum steering and bandwidth control of the (de)multiplexed demands are introduced. The multimode interference (MMI) coupler is utilized for the construction of several IIR feedback photonic processors. Tunable photonic feedback processors have the advantage of using less number of MMI couplers compared to their counterparts of FIR forward-path processors saving on the footprint and loss merits. A passive feedback 2×2 (de)multiplexer made of a 4×4 MMI coupler and two loopback paths is proposed. The inclusion of an imbalance in the lengths of the loopback paths of the same symmetrical feedback (de)multiplexer is demonstrated to achieve wavelength modulation of the (de)multiplexed transmission responses that are useful for the (de)multiplexing of different bandwidth channels. Several newly introduced IIR feedback architectures are demonstrated to function similarly as their counterparts of FIR forward-path processors as binary bandwidth variable (de)multiplexers, envelope and wavelength modulation (de)multiplexers, and universal feedback processors. The investigation provided in this thesis is also supported with dynamic zero-pole evolution analysis in the complex plane of analysis of the studied FIR and IIR photonic processors to enhance understanding the principle of operation. This research expands the prospective for constructing innovative silicon-on-insulator (SOI) based optical processors for applications in modern optical communication systems and programmable elastic optical networks (EONs).

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