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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

A Microwave study of the Goos-Hänchen Shift

Bezner, Hart C. 08 1900 (has links)
<p> When a beam of electromagnetic radiation, limited by an aperture, undergoes total internal reflection, a sideways displacement of the reflected beam results. This displacement is known as the Goos-Hänchen Shift. </p> <p> In this work the Goos-Hänchen Shift is studied with 3.2 cm microwaves. The observed shifts disagree with three existing theories. For this reason a modified theory is developed in this work. The throey regards the beam from a pyramidal horn antenna as a superposition of a large number of plane waves. The shift is calculated on this basis. Agreement between experiment and theory is good. </p> / Thesis / Doctor of Philosophy (PhD)
2

Threnos e goos: lamento e murmurio de andromaca / ThrÃnos and goos: lament and murmur of andromache

Luciano Heidrich Bisol 23 December 2016 (has links)
nÃo hà / O presente trabalho inclina-se sobre o mito grego de AndrÃmaca e tem por objetivo delimitar os caracteres de sua representaÃÃo. Consideraremos a evoluÃÃo das condiÃÃes de performance da autocaracterizaÃÃo da personagem, paralela à evoluÃÃo de dois gÃneros do discurso â os lamentos fÃnerarios thrÃnos (&#952;&#961;&#8134;&#957;&#959;&#962;) e goos (&#947;&#972;&#959;&#962;). Estas duas formas de lamento ritualÃstico manifestam-se sob forma de hexÃmetros em Homero e de versos elegÃacos em EurÃpides. Nesses lamentos, uma sÃrie de topoi â marido, cidade, viuvez, maternidade, alcova â sÃo utilizados pelos autores para delimitar os temas abrangidos pela personagem. Esta pesquisa investiga a autocaracterizaÃÃo feminina na Antiguidade. Buscamos reconhecer as relaÃÃes entre discurso e performance na Ãpica e na tragÃdia. Primeiramente, apresentamos um estudo em torno das origens do mito e sua circulaÃÃo, principalmente, entre autores da Antiguidade. Em seguida realizamos um estudo antropoliterÃrio em torno dos estatutos sociais femininos na Antiguidade, especialmente, na polis ateniense do sÃculo quinto. Sugerimos que esses estatutos dependem da relaÃÃo da mulher com sua alcova (&#952;&#940;&#955;&#945;&#956;&#959;&#962;). Esses estatutos serÃo discutidos atravÃs, sobretudo, do drama selecionado de EurÃpides. Por fim, verificamos a autocaracterizaÃÃo da personagem especificamente em uma sÃrie de trÃs lamentos encontrados na IlÃada de Homero (cantos VI, XXII e XXIV); e no lamento elegÃaco (v. 102 - 116) na tragÃdia AndrÃmaca (c. 425 a.C.) de EurÃpides (c. 480 - 406 a.C.).
3

An?lise do Efeito Goos-Hanchen e N?o-reciprocidade do fluxo de pot?ncia em antiferromagn?ticos

Lima, Francinete de 26 June 2009 (has links)
Made available in DSpace on 2015-03-03T15:16:23Z (GMT). No. of bitstreams: 1 FrancineteLpdf.pdf: 1184329 bytes, checksum: 1ecb5e42144a528c7629482882470ca0 (MD5) Previous issue date: 2009-06-26 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / Este estudo observa que, em certas situa??es, um raio de luz refletido pode ser deslocado lateralmente em rela??o ao raio incidente com incid?ncia normal (efeito Goos-H anchen). A n?o-reciprocidade da reflex?o e a propriedade fundamental para se conseguir este deslocamento lateral. Para isto, consideramos a reflex?o de um raio de luz em um antiferromagn?tico na presen?a de um campo magn?tico externo, nas frequ?ncias associadas com os polaritons de magnons. Este sistema, mesmo na aus?ncia de absor??o, mostra n?o-reciprocidade na fase da radia??o refletida, nas regi?es "reststrahl" (reflex?o total), no fluxo de pot?ncia dentro do antiferromagn?tico. Este fluxo se propaga paralelo a superf?cie mesmo em incid?ncia normal. Em um modelo simples, um raio finito pode ser considerado como uma soma Fourier de ondas planas. Na reflex?o em um antiferromagneto, devido a n?o-reciprocidade na fase, a interfer?ncia entre as ondas planas refletidas efetivamente gera um deslocamento lateral no raio refletido em rela??o ao raio incidente. Nas regi?es "reststrahl", o efeito tamb?m pode ser descrito em termos da propaga??o do fluxo de energia paralelo a superf?cie dentro do antiferromagneto. Para confirmar o efeito, e investig?-lo com mais profundeza, as seguintes simula??es foram feitas: Simula??o de reflex?o de um raio gaussiano incidente normalmente sobre o antiferromagneto MnF2. Um deslocamento do raio refletido e observado para frequ?ncias na regi?o de "reststrahl" e tamb?m na regi?o do volume. Os resultados est?o em acordo com o modelo cl?ssico do efeito Goos-Hanchen; Simula??o do perfil do campo no plano xy, onde y e perpendicular a superf?cie e z ? a dire??o do campo externo. A simula??o mostra n?o somente o deslocamento do raio refletido, mas tamb?m o perfil do campo dentro do antiferromagneto (representando essencialmente uma onda evanescente nas regi?es de "reststrahl") que tamb?m sofre um deslocamento lateral; Simula??o da transmiss?o atrav?s de um filme antiferromagneto. Os c?lculos mostram que o raio transmitido n?o sofre deslocamento. Este resultado est? associado com o fato que a fase transmitida e rec?proca; Simula??o do fluxo de pot?ncia nas regi?es "reststrahl" (reflex?o total) e regi?es de volume (transmiss?o dentro da amostra), com o objetivo de analisar o comportamento da energia nestas regi?es
4

O deslocamento de Goos-Hänchen e os fenômenos da quebra de simetria para feixes gaussianos / The Goos-Hänchen shift and the phenomena of symmetry breaking for gaussian beams

Araújo, Manoel Pedro de, 1980- 06 August 2015 (has links)
Orientadores: Stefano De Leo, Luis Eduardo Evangelista de Araújo / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin / Made available in DSpace on 2018-08-27T16:22:41Z (GMT). No. of bitstreams: 1 Araujo_ManoelPedrode_D.pdf: 1955745 bytes, checksum: d09312f15b1d058162aef061fcfc0682 (MD5) Previous issue date: 2015 / Resumo: Esta tese apresenta uma análise sobre o deslocamento de Goos-Hänchen, o desvio angular da lei de Snell e o efeito de interferência entre feixes ópticos gaussianos. Em nosso estudo o deslocamento de Goos-Hänchen foi obtido por meio do método da fase estacionária. No regime de incidência crítica, tal deslocamento apresenta uma forte dependência com a largura do feixe, em contraste com as expressões clássicas de Artmann, que predizem um deslocamento infinito. Também na incidência crítica, observamos que, dependendo da magnitude da largura da cintura do feixe, ocorre uma quebra de simetria na distribuição de momento. A maximização da quebra de simetria leva ao desvio angular da lei de Snell. Mostramos como reproduzir a máxima quebra de simetria por uma estrutura dielétrica. Como resultado, obtivemos uma nova fórmula analítica para o desvio angular. Ademais, foi possível estimar o deslocamento de Goos-Hänchen por meio do efeito de interferência entre feixes. Nesta análise, observamos que, na incidência crítica, a estimativa usada na literatura para o deslocamento de Goos-Hänchen não é válida. Portanto, uma nova fórmula foi introduzida para estimar tal deslocamento / Abstract: This thesis presents some of the main phenomena associated with Goos-Hanchen shift, the angular deviation of the Snell¿s law and the interference effect among Gaussian optical beams. In our study the Goos-Hänchen shift was obtained by using the stationary phase method. In the case of incidence at critical angle, such displacement shows a strong dependence on the beam width in contrast with the classical expressions of Artmann, which predict an infinite displacement. Also in the critical incidence we observed that, depending on the magnitude of the beam waist, there is a symmetry breaking in the momentum distribution. The maximization of symmetry breaking leads to the angular deviations of the Snell¿s law. In this analysis we showed how to maximize this breaking of the symmetry by a dielectric structure. As a result, we obtained an analytical formula to the Snell¿s law angular deviation. Furthermore, we could estimate the displacement of Goos- Hänchen through the interference effect among beams. The results of this analysis reveal that, for the critical incidence, the estimative used in the literature for the Goss-Hänchen shift is not valid. Therefore, a new formula was introduced to estimate such displacement. / Doutorado / Física / Doutor em Ciências
5

Medição fraca do deslocamento Goos-Hänchen próximo do ângulo crítico para reflexão interna total / Weak measurement of the Goos-Hänchen shift near the critical angle for total internal reflection

Santana, Octávio José Santos de, 1990- 08 July 2015 (has links)
Orientador: Luís Eduardo Evangelista de Araujo / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin / Made available in DSpace on 2018-08-28T09:20:19Z (GMT). No. of bitstreams: 1 Santana_OctavioJoseSantosde_M.pdf: 3448778 bytes, checksum: 7217b98747d619e694a9b6c7b21e9f36 (MD5) Previous issue date: 2015 / Resumo: Um feixe de luz, após sofrer uma reexão em uma interface plana, é deslocado do caminho previsto pela ótica geométrica. Este desvio do feixe é muito pequeno, tipicamente da ordem do comprimento de onda da luz, que é muito menor do que o tamanho do feixe. Portanto, é difícil de se medir. A técnica de medição fraca óptica tem sido utilizada com sucesso em investigações de deslocamentos de feixe, tal como o deslocamento Goos-Hänchen (GH) e o deslocamento Imbert-Fedorov (IF) (esses são deslocamentos longitudinal e perpendicular ao plano de incidência, respectivamente). Em uma medição fraca, o sistema de medida é projetado sobre um determinado estado nal (pós-seleção), quase ortogonal ao estado inicial (pré-seleção), dando origem a um valor fraco que pode assumir valores muito grandes (amplicados). Nesta dissertação estudamos experimentalmente o deslocamento Goos-Hänchen de um feixe gaussiano focalizado ao sofrer reexão interna total em um prisma via medida fraca. Investigamos este efeito em torno do ângulo crítico c para reflexão interna total. Nosso experimento demonstra pela primeira vez que há uma dependência axial do valor fraco que tem que ser levado em conta, além de um fator fenomenológico na equação de correção do valor fraco. Comparações entre os dados com e sem o fator fenomenológico foi feita, mostrando que ao utilizar esse fator, nossos resultados experimentais mostram um excelente acordo com a previsão teórica / Abstract: A beam of light, after reection from a planar interface, is shifted from the path predicted by ray optics. Such a beam shift is very small, typically of the order of the wavelength of light, which is much smaller than the physical size of the beam. Therefore, it is dicult to measure. The optical weak measurement technique has been successfully used in investigations of beam displacements such as the Goos-Hänchen (GH) and the Imbert-Fedorov (IF) shifts (these are longitudinal and perpendicular to the plane of incidence, respectively). In a weak measurement, the measured system is projected onto a certain nal state (postselected), nearly orthogonal to the inicial state (preselected), giving rise to a measured weak value that may take on very large (amplied). In this dissertation, we study experimentally the Goos-Hänchen shift of a focused Gaussian ligth beam undergoing total internal reection in a prism via weak measurement. We investigate this eect near the critical angle c for total internal reection. Our experiment demonstrates for the rst time that there is an axial dependence of the weak value that has to be taken into account, plus a phenomenological factor in the correction equation of the weak value. Comparisons between the data with and without the phenomenological factor was made, showing that by using this factor, our experimental results show an excellent agreement with the theoretical predication / Mestrado / Física / Mestre em Física / 1186838/2013 / CAPES
6

Divergence Model for Measurement of Goos-Hanchen Shift

Gray, Jeffrey Frank 08 August 2007 (has links)
In this effort a new measurement technique for the lateral Goos-Hanchen shift is developed, analyzed, and demonstrated. The new technique uses classical image formation methods fused with modern detection and analysis methods to achieve higher levels of sensitivity than obtained with prior practice. Central to the effort is a new mathematical model of the dispersion seen at a step shadow when the Goos-Hanchen effect occurs near critical angle for total internal reflection. Image processing techniques are applied to measure the intensity distribution transfer function of a new divergence model of the Goos-Hanchen phenomena providing verification of the model. This effort includes mathematical modeling techniques, analytical derivations of governing equations, numerical verification of models and sensitivities, optical design of apparatus, image processing
7

Strategic geographic positioning of sea level gauges to aid in early detection of tsunamis in the Intra-Americas sea

Henson, Joshua I 01 June 2006 (has links)
A tsunami is a series of large amplitude, shallow water waves generated by an event capable of displacing a massive volume of water. The displaced water propagates at speeds in excess of 800 kph until it dissipates or impacts a shoreline where it slows to 30 -- 50 kph [NOAA and USGS Fact Sheet, 2005]. Earthquakes are the predominant tsunamigenic event, however, landslides, avalanches, submarine slumps or slides, volcanic eruptions, volcano flank failure, and meteor impact into an ocean can also cause a tsunami [McCann, 2004; O'Loughlin and Lander, 2003; Pararas-Carayannis, 2004]. This study includes past Caribbean tsunamigenic events assumed to be regionally destructive and generated by earthquakes and/or massive submarine slides/slumps. The approximate study area is from 7°N, 59°W to 36°N, 98° W. Caribbean tsunami data suggests that a tsunami will occur in this region once every three years, and destructively once every 21 years [O'Loughlin and Lander, 2003]. Excluding the December 2004 Indian Ocean tsunami, approximately 13.8% of all tsunamis and 83% of all tsunami fatalities worldwide have occurred in the Caribbean [O'Loughlin and Lander, 2003]. In the past 150 years, 2,590 victims died from tsunamis in the Caribbean. As a result of these recorded fatalities and the rise of Caribbean population by almost 300% from 1950 to 2000 [CIAT et al., 2005], protection of human life is a primary reason for establishing a tsunami warning system in this region. The goal of this study is to identify the minimum number of sea level gauge locations to aid in tsunami detection in order to provide the most warning time to the largest number of people. This study defines which historical tsunamis were likely to have been regionally destructive, analyzes the tsunamigenic potential and population distribution of the Intra-Americas Sea (IAS), models 42 historical tsunamis with the United States Navy Coastal Ocean Model (NCOM), and recommends 12 prioritized locations for coastal sea level gauge installation. The results of this systematic approach to assess priority locations for coastal sea level gauges will assist in developing a tsunami warning system for the IAS and are currently being used by NOAA and IOCARIBE-GOOS.
8

Thrênos e goos: lamento e murmurio de andromaca / Thrênos and goos: lament and murmur of andromache

Bisol, Luciano Heidrich January 2016 (has links)
BISOL, Luciano Heidrich. Threnos e Goos: lamento e murmurio de Andromaca. 2016. 93f. Dissertação (Mestrado) – Universidade Federal do Ceará, Programa de Pós-Graduação em Letras, Fortaleza (CE), 2016. / Submitted by Gustavo Daher (gdaherufc@hotmail.com) on 2017-01-04T13:54:14Z No. of bitstreams: 1 Dissertacao de LUCIANO HEIDRICH BISOL.pdf: 1536518 bytes, checksum: 86bd5eba1391b5b760ea6ebfbd082d0d (MD5) / Rejected by Maria Josineide Góis (josineide@ufc.br), reason: on 2017-01-06T12:01:58Z (GMT) / Submitted by Gustavo Daher (gdaherufc@hotmail.com) on 2017-01-06T13:57:32Z No. of bitstreams: 1 2016_dis_lhbisol.pdf: 1536518 bytes, checksum: 86bd5eba1391b5b760ea6ebfbd082d0d (MD5) / Approved for entry into archive by Márcia Araújo (marcia_m_bezerra@yahoo.com.br) on 2017-01-25T10:48:13Z (GMT) No. of bitstreams: 1 2016_dis_lhbisol.pdf: 1536518 bytes, checksum: 86bd5eba1391b5b760ea6ebfbd082d0d (MD5) / Made available in DSpace on 2017-01-25T10:48:13Z (GMT). No. of bitstreams: 1 2016_dis_lhbisol.pdf: 1536518 bytes, checksum: 86bd5eba1391b5b760ea6ebfbd082d0d (MD5) Previous issue date: 2016 / O presente trabalho inclina-se sobre o mito grego de Andrômaca e tem por objetivo delimitar os caracteres de sua representação. Consideraremos a evolução das condições de performance da autocaracterização da personagem, paralela à evolução de dois gêneros do discurso – os lamentos fúnerarios thrênos (θρῆνος) e goos (γόος). Estas duas formas de lamento ritualístico manifestam-se sob forma de hexâmetros em Homero e de versos elegíacos em Eurípides. Nesses lamentos, uma série de topoi – marido, cidade, viuvez, maternidade, alcova – são utilizados pelos autores para delimitar os temas abrangidos pela personagem. Esta pesquisa investiga a autocaracterização feminina na Antiguidade. Buscamos reconhecer as relações entre discurso e performance na épica e na tragédia. Primeiramente, apresentamos um estudo em torno das origens do mito e sua circulação, principalmente, entre autores da Antiguidade. Em seguida realizamos um estudo antropoliterário em torno dos estatutos sociais femininos na Antiguidade, especialmente, na polis ateniense do século quinto. Sugerimos que esses estatutos dependem da relação da mulher com sua alcova (θάλαμος). Esses estatutos serão discutidos através, sobretudo, do drama selecionado de Eurípides. Por fim, verificamos a autocaracterização da personagem especificamente em uma série de três lamentos encontrados na Ilíada de Homero (cantos VI, XXII e XXIV); e no lamento elegíaco (v. 102 - 116) na tragédia Andrômaca (c. 425 a.C.) de Eurípides (c. 480 - 406 a.C.).
9

Mesoscopic wave phenomena in electronic and optical ring structures / Mesoskopische Wellenphänomene in elektronischen und optischen Ringstrukturen

Hentschel, Martina 14 November 2001 (has links) (PDF)
Gegenstand dieser Arbeit sind Wellenphänomene in mesoskopischen Ringstrukturen. In Teil I der Arbeit befassen wir uns mit spinabhängigem Transport von Elektronen in effektiv eindimensionalen Ringen in Gegenwart inhomogener Magnetfelder. Wir benutzen die exakten Lösungen der Schrödinger-Gleichung im allgemeinen nicht-adiabatischen Fall in einem Transfer-Matrix-Formalismus und untersuchen Auswirkungen von geometrischen Phasen auf den Magnetwiderstand. Für den Spezialfall eines Magnetfeldes in der Ringebene sagen wir einen interessanten Spin-Flip-Effekt vorher, der die Steuerung der Polarisationsrichtung von Elektronen über einen externen Aharonov-Bohm-Fluß erlaubt. Optische mesoskopische Systeme sind Thema von Teil II dieser Arbeit. Wir betrachten zweidimensionale annulare Strukturen, charakterisiert durch unterschiedliche Brechungsindizes, sowohl im klassischen Bild der geometrischen Optik als auch mit Wellenmethoden auf der Grundlage der Maxwellschen Gleichungen. Insbesondere diskutieren wir erstmals eine Streumatrixbeschreibung optischer Mikroresonatoren und wenden sie auf das dielektrische annulare Billard an. Ein Vergleich der Ergebnisse des Wellen- und Strahlenbildes liefert eine gute Übereinstimmung, jedoch sind im Grenzfall großer Wellenlängen von der Ordnung der Systemabmessungen Korrekturen zum Strahlenbild nötig. Wir zeigen am Beispiel von Fresnel-Gesetzen für gekrümmte Oberflächen erstmals, daß der Goos-Hänchen-Effekt diese Korrekturen quantitativ erfaßt. Ausgehend von der Wellenbeschreibung leiten wir neue analytische Formeln für verallgemeinerte Fresnel-Gesetze für beide möglichen Polarisationsrichtungen ab. Die Anwendung des Strahlenbildes erlaubt eine schlüssige Interpretation eines Experiments mit einer quadrupolaren Glasfaser, außerdem schlagen wir Strahlenkonzepte als Grundlage der Konstruktion von Mikrolasern mit maßgeschneiderten Charakteristika vor. / In this work we investigate wave phenomena in mesoscopic systems using different theoretical approaches. In Part I, we focus on effectively one-dimensional electronic ring structures and address the phenomenon of geometric phases in spin-dependent electronic transport in the presence of non-uniform magnetic fields. In the general non-adiabatic case, exact solutions of the Schrödinger equation are used in a transfer matrix formalism to compute the transmission probability through the ring. In the magneto-conductance we identify clear signatures of interference effects due to geometric phases, for example in rings where the non-uniform field is created by a central micromagnet. For the special case of an in-plane magnetic field we predict an interesting spin-flip effect that allows one to control the spin polarization of electrons by applying an external Aharonov-Bohm flux. Optical mesoscopic systems are the subject of Part II. We consider two-dimensional annular structures characterized by different refractive indices, and apply classical methods from geometric optics as well as wave concepts based on Maxwell's equations. For the first time, an S-matrix approach is successfully employed in the description of resonances in optical microresonators; in particular we propose the dielectric annular billiard as an attractive model system. Comparing ray and wave pictures, we find general agreement, except for large wavelengths of the order of the system size, where corrections to the ray model are necessary. The Goos-Hänchen effect as an extension of the ray picture is shown to quantitatively account for wave modifications of Fresnel's laws due to curved interfaces. We derive novel analytical expressions for the corrected Fresnel formulas for both polarizations of light. Motivated by the successful ray description, we give a conclusive interpretation of a recent filter experiment on a quadrupolar glass fibre, and suggest novel concepts for microresonator-based lasers.
10

Mesoscopic wave phenomena in electronic and optical ring structures

Hentschel, Martina 29 October 2001 (has links)
Gegenstand dieser Arbeit sind Wellenphänomene in mesoskopischen Ringstrukturen. In Teil I der Arbeit befassen wir uns mit spinabhängigem Transport von Elektronen in effektiv eindimensionalen Ringen in Gegenwart inhomogener Magnetfelder. Wir benutzen die exakten Lösungen der Schrödinger-Gleichung im allgemeinen nicht-adiabatischen Fall in einem Transfer-Matrix-Formalismus und untersuchen Auswirkungen von geometrischen Phasen auf den Magnetwiderstand. Für den Spezialfall eines Magnetfeldes in der Ringebene sagen wir einen interessanten Spin-Flip-Effekt vorher, der die Steuerung der Polarisationsrichtung von Elektronen über einen externen Aharonov-Bohm-Fluß erlaubt. Optische mesoskopische Systeme sind Thema von Teil II dieser Arbeit. Wir betrachten zweidimensionale annulare Strukturen, charakterisiert durch unterschiedliche Brechungsindizes, sowohl im klassischen Bild der geometrischen Optik als auch mit Wellenmethoden auf der Grundlage der Maxwellschen Gleichungen. Insbesondere diskutieren wir erstmals eine Streumatrixbeschreibung optischer Mikroresonatoren und wenden sie auf das dielektrische annulare Billard an. Ein Vergleich der Ergebnisse des Wellen- und Strahlenbildes liefert eine gute Übereinstimmung, jedoch sind im Grenzfall großer Wellenlängen von der Ordnung der Systemabmessungen Korrekturen zum Strahlenbild nötig. Wir zeigen am Beispiel von Fresnel-Gesetzen für gekrümmte Oberflächen erstmals, daß der Goos-Hänchen-Effekt diese Korrekturen quantitativ erfaßt. Ausgehend von der Wellenbeschreibung leiten wir neue analytische Formeln für verallgemeinerte Fresnel-Gesetze für beide möglichen Polarisationsrichtungen ab. Die Anwendung des Strahlenbildes erlaubt eine schlüssige Interpretation eines Experiments mit einer quadrupolaren Glasfaser, außerdem schlagen wir Strahlenkonzepte als Grundlage der Konstruktion von Mikrolasern mit maßgeschneiderten Charakteristika vor. / In this work we investigate wave phenomena in mesoscopic systems using different theoretical approaches. In Part I, we focus on effectively one-dimensional electronic ring structures and address the phenomenon of geometric phases in spin-dependent electronic transport in the presence of non-uniform magnetic fields. In the general non-adiabatic case, exact solutions of the Schrödinger equation are used in a transfer matrix formalism to compute the transmission probability through the ring. In the magneto-conductance we identify clear signatures of interference effects due to geometric phases, for example in rings where the non-uniform field is created by a central micromagnet. For the special case of an in-plane magnetic field we predict an interesting spin-flip effect that allows one to control the spin polarization of electrons by applying an external Aharonov-Bohm flux. Optical mesoscopic systems are the subject of Part II. We consider two-dimensional annular structures characterized by different refractive indices, and apply classical methods from geometric optics as well as wave concepts based on Maxwell's equations. For the first time, an S-matrix approach is successfully employed in the description of resonances in optical microresonators; in particular we propose the dielectric annular billiard as an attractive model system. Comparing ray and wave pictures, we find general agreement, except for large wavelengths of the order of the system size, where corrections to the ray model are necessary. The Goos-Hänchen effect as an extension of the ray picture is shown to quantitatively account for wave modifications of Fresnel's laws due to curved interfaces. We derive novel analytical expressions for the corrected Fresnel formulas for both polarizations of light. Motivated by the successful ray description, we give a conclusive interpretation of a recent filter experiment on a quadrupolar glass fibre, and suggest novel concepts for microresonator-based lasers.

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