In this thesis, the characteristics and the applications of Kerr-like nonlinear optical waveguide structures have been studied. The nonlinear optical waveguide is a medium whose refractive index changes with the electric field intensity. In the characteristics of Kerr-like nonlinear optical waveguide structures, we propose a general method for analyzing the three-layer optical waveguide structure with all nonlinear layers by using modal theory. Based on this method, the analysis of transforming arbitrary nonlinear layer into linear layer can be achieved easily by modifying nonlinear coefficient. All kinds of the transverse electric field distributions and the dispersion relation in the three-layer Kerr-like nonlinear optical waveguide structure have been obtained. In the application of Kerr-like nonlinear optical waveguide structures, the Mach-Zehnder waveguide interferometer structure will be discussed. Based on the asymmetric medium and asymmetric construction, the new all-optical router switching device and dense wavelength division multiplexing device have been proposed. The numerical results show that the proposed structures could function as all-optical switch devices and all-optical dense wavelength division multiplexing device.

No description available.

Articial spin ice structures are two-dimensional systems of lithographically fabricated lattices ofelongated ferromagnetic islands, which interact via dipolar interaction. These systems have beenshown to be a suitable playground to study the magnetic, monopole-like, excitations, similar tothose in three-dimensional rare-earth pyrochlores. Therefore, such articial structures can be potentialmaterials for investigations of magnetricity [1]. The investigations of these articial spin icestructures stretches from the direct imaging of the magnetic congurations among the islands to indirectinvestigation methods allowing to determine the phase transitions occurring in such systems. Inthis project, square articial spin ice arrays were investigated employing magneto-optical Kerr eectfor the measurement of the magnetic susceptibility. The susceptibility dependence on temperaturewas measured at dierent frequencies of the applied AC magnetic eld for arrays of the dierentisland spacing and at two dierent incident light directions with the respect to the direction of theislands. A peak shift of the real part of susceptibility, χ', with increasing frequency towards thehigher temperatures was observed. Furthermore, a rough estimation of the relaxation times of themagnetic moments in the islands is given by the analysis of the susceptibility data.

Canadian remembrance of the Great War (1914-1918) in the early twenty-first century is often associated with grand gestures at national monuments like the opening of the new Canadian War Museum in 2005 and the restoration of the Vimy Ridge Memorial in 2007. However, these sites of memory, what Pierre Nora terms lieux de mémoire, are not part of the everyday environments of memory, the milieux de mémoire, of most Canadians. In my investigation of three contemporary works of Canadian literature: The Danger Tree by David Macfarlane, Broken Ground by Jack Hodgins, and Unity (1918) by Kevin Kerr, locally-based storytellers describe the continued influence of the Great War on their individual Canadian communities. The fictionalized narrating personas in these three works create what I refer to as bio-geographies: first-person accounts of the narrator’s particular social and memory environments. While the bio-geographers in these three texts lack first-hand experience of the Great War, their writing reflects the continued repercussions of the conflict in the weeks, years, and decades after the 1918 armistice. The Great War differentially affected thousands of communities in Canada and Newfoundland. Constructing a coherent national narrative that accounts for the multiple lived experiences of individuals in communities across North America is virtually impossible. Turning to local representations of the Great War (in the case of the three bio-geographic texts: depictions of communities in Newfoundland, British Columbia, and Saskatchewan) provides a sense of the nation as a diverse landscape of memory with multiple vantage points. Negotiating the complex terrain of self, place, and memory, the bio-geographers in the three works I examine create representations of the past that reveal how sites of memory, lieux de mémoire, come to be firmly embedded in the ongoing lived experiences of comunity members, the milieux de mémoire.

The design procedure for ultrafast silicon electro-optic switches using photonic crystals in order optimize the operation of the electro-optic switch is presented. The material medium selected for propagation of the optical signal through the switch is silicon nanocrystals in silica. A patterned slot waveguide with one-dimensional photonic crystals is proposed as the preferred slow light waveguide to be used in the design of the electro-optic switch. The ultrafast quadratic electro-optic Kerr effect is the physical effect utilized, and its analysis for slot waveguides is discussed. The optical structure analysis of the electro-optic switch using a ring resonator is presented and it is shown that the use of a slow light waveguide in the ring resonator can reduce the required externally applied electric field and the radius of the ring resonator.

Optical regeneration has the potential to significantly increase the reach of long-haul transmission systems. In this thesis, wavelength-preserving polarization-insensitive all-optical 3R regeneration is investigated and demonstrated for 10 and 40 Gb/s signals. The all-optical regenerator utilizes a self-pulsating laser for clock recovery, cross-phase modulation (XPM) based spectral broadening in a highly nonlinear fiber (HNLF) and offset filtering for retiming, and self-phase modulation based spectral broadening in a HNLF and offset filtering for reshaping. Raman amplification is used to increase the XPM-based spectral broadening and thus allow a design that meets the tradeoffs involved in simultaneously achieving good retiming and reshaping performance. The regenerator is shown to reduce amplitude noise and timing jitter while not causing a BER penalty. To fully validate the regeneration scheme, the cascadability is demonstrated using a recirculating loop. For a 10 Gb/s signal, with a regenerator spacing of 240 km, a return-to-zero, on-off-keyed (RZ-OOK) signal was transmitted over 18,000 km (75 loops) with a power penalty of 1.6 dB at a BER of 1E-9 compared to the back-to-back case. For a 40 Gb/s signal, with a regenerator spacing of 80 km, a RZ-OOK signal was transmitted over 8,000 km (100 loops) with a power penalty of 1.2 dB. In addition, all-optical 3R regeneration is demonstrated using a multimode quantum-dot Fabry Petot laser with ultra-low timing jitter. / Thesis (Ph.D, Electrical & Computer Engineering) -- Queen's University, 2009-10-19 14:11:53.826

Cette thèse concerne l'étude et la visualisation par imagerie magnéto-optique Kerr à la température ambiante du mode de retournement de l'aimantation au sein de couches minces ferromagnétiques de manganites de composition La0,7Sr0,3MnO3 (LSMO). Au cours du travail de thèse, un banc d'imagerie a été réalisé et une méthode d'imagerie vectorielle de l'aimantation a été proposée. Ce système d'imagerie a été utilisé pour étudier d'une part l'influence du substrat et des contraintes qu'il induit dans la couche mince et d'autre part l'influence de la forme des échantillons, sur le piégeage et le mode de retournement des domaines magnétiques présents dans la couche mince. Dans le cas du substrat LSAT ((LaAlO3)0.3(Sr2AlTaO6)0.7), la compression induite dans la couche mince fait apparaître une composante d'aimantation hors du plan et un plan de facile aimantation sans direction privilégiée dans ce plan. Le retournement des domaines planaires est alors de type cohérent. Dans le cas du substrat STO (SrTiO3), d'orientation (001), l'anisotropie magnétique est biaxiale et le retournement d'aimantation s'opère par nucléation puis propagation de domaines. Dans le cas de substrats vicinaux de STO, l'anisotropie magnétique devient uniaxiale et l'axe de facile aimantation est parallèle aux marches en surface de la couche. Le retournement de domaines se produit par nucléation et propagation dans le cas où le champ magnétique est appliqué parallèlement aux marches du substrat vicinal. Quand le champ magnétique est appliqué perpendiculairement aux marches du substrat vicinal, on assiste à un retournement cohérent des domaines magnétiques. Ces travaux constituent une première étape dans la compréhension et la maîtrise du comportement magnétique de dispositifs spintroniques.

Zugl.: Berlin, Freie Univ., Diss., 2006

Thesis (Ph.D.)--University of Pennsylvania, 2002. / Includes bibliographical references (p. 339-357).

Thesis--University of Chicago. / Bibliography: p. 147-153.