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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

Coupling between optical Tamm states and fluorescent nanocrystals ; determination of the dipole nature of single colloidal nanoplatelets / Propriétés optiques du couplage entre les nanocrystaux et optique mode Tamm et détermination la nature et l'orientation du dipôle associé à un nanoplaquette

Feng, Fu 19 September 2016 (has links)
Ce travail de thèse porte sur le couplage d’émetteurs fluorescents (en l’occurrence des nanostructures semi-conductrices colloïdales) à leur environnement optique. Il se décompose en deux parties : dans la première, des structures photoniques (modes de Tamm optiques) sont caractérisées par le biais de la fluorescence de nanocristaux insérés dans ces structures. Dans la seconde, des nanoplaquettes individuelles de CdSe/CdS sont caractérisées par des études de microphotoluminescence sur différents types de substrats. Dans ces deux études, la mesure du diagramme de rayonnement par imagerie dans le plan de Fourier joue un rôle important, et son principe sera présenté en détail. Le mode optique de Tamm est un mode électromagnétique confiné entre un miroir de Bragg et une couche métallique. Nous avons couplé une couche de nanocristaux de CdSe/CdS avec des modes de Tamm optiques 2D et 0D. Le confinement latéral dans le cas du mode 0D est mis en évidence. Nous avons étudié la relation de dispersion de l’émission issue de différentes portions du disque et comparé ces résultats avec les simulations numériques. Enfin, en excitant différentes position sur le disque, nous avons montré que la direction d’émission dépend fortement de la position de la source au sein de la structure. D’autre part, nous avons mis en place une méthode fine pour déterminer la nature dipolaire (dipôle 1D ou 2D) et l’orientation d’un nano-émetteur individuel. L’idée principale est de mesurer à la fois, pour un seul émetteur, le diagramme de rayonnement et la polarisation d’émission. En choisissant un substrat adapté (de l’or ou du verre), ces mesures donnent des résultats théoriques très différents selon la nature et l’orientation du dipôle. Nous avons ensuite appliqué cette méthode sur les émetteurs nanoplaquettes de CdSe/CdS (dimensions 20x20x2 nm). Un accord parfait entre les mesures et les calculs analytiques nous confirme que l’émission d’une plaquette carrée peut être décrite par un dipôle 2D orienté dans le plan de la plaquette. Nous avons ensuite étudié l’émission d’une plaquette rectangulaire et montré une asymétrie dans le dipôle émetteur. Cette étude montre le rôle de la forme de la plaquette sur son dipôle d’émission, qui pourrait être expliqué par un effet d’antenne diélectrique. / Technological progress in the recent 30 years for reducing the size of semi-conductor materials offers the possibility to fabricate devices in which the electrons and holes are confined in a very small volume in three dimensions. When the dimension of the material is small (a few nanometers), the charges experience quantum confinement effects. This kind of nanomaterial is called nanocrystal or quantum dot [1]. These structures have the remarkable property that the energy levels are discretized, in a sense making them artificial atoms. At the beginning of 1980s, Efros, Ekimov et al. started the growth of II/VI semi-conductor nanocrystals in a vitreous matrix [2]. A few years later, colloidal synthesis methods were developed and nanocrystals with increasingly good optical properties were obtained [3-5]. These emitters have drawn intense attention because of their versatile manipulation in solution and biochemical functionalization, high quantum effciency, and photostability, tunable emission wavelength and broad absorption spectrum. By fluorescence microscopy, it is possible to study the optical properties of individual nanocrystals ; non classical effects such as single photon emission (even for nanocrystals at room temperature) are evidenced. Studying individual nano-emitters offers new ways to test the concepts of electromagnetics in the visible domain. Other manipulations are possible by nano structuring the environment around an emitter ; for instance, the use of antennas, which is ubiquitous in the radio and microwave domains, can be extended to nano-photonics, provided that sufficiently precise nano-fabrication techniques are available. The group "Nanophotonics and quantum optics" at the Institut de NanoSciences de Paris (INSP) studies how to manipulate light by coupling fluorescent emitters (individually or collectively) with their optical environment. The emission properties of nanoemitters depend strongly on their optical environment. This is expressed, as for the decay time of a radiating dipole, by Fermi's golden rule: where the initial and final state of the nanoemitter transition are taken into consideration; the polarization of these states can infuence highly the emission properties (determined by the symmetries of the transition and its associated orientation). The local state density which is mainly determined by the optical environment around the emitter and depends on the emission angular frequency. The electric field at the emitter position is included in the Hamiltonian (for a dipolar electric transition). Previously, our team has studied the coupling between the nanocrystal and different nanophotonic structures such as photonic crystals, plasmonic structures, plasmonic patch antennas etc...
2

Russian influences on Estonian literature a study of Jacob Tamm and Anton H. Tammsaare,

Judas, Elizabeth, January 1941 (has links)
Thesis (Ph. D.)--Columbia University. / Vita. "Russian literature in Estonian translation": p. 145-154. Bibliography: p. 155-159.
3

Neutrophil Diversity in the Pathogenesis of Ischemic Acute Kidney Injury

Winfree, Seth 09 1900 (has links)
Indiana University-Purdue University Indianapolis (IUPUI) / Acute kidney injury (AKI) affects millions of patients worldwide yet has few treatment options. There is a critical need to identify novel interventions for AKI, especially approaches targeting cell types that are central to the disease, such as neutrophils. Neutrophils are professional phagocytic cells that respond early to tissue injury. In rodent models of severe ischemic-reperfusion-injury AKI, neutrophils transiently infiltrate the injured kidney, appearing within 6 hours, and are gone by 72 hours. These infiltrating neutrophils are considered proinflammatory and harmful to tissue repair and recovery of kidney function. However, neutrophils can exhibit atypical activity such as antigen presentation and have a central role in recovery from myocardial ischemic injury. Furthermore, little is known of neutrophil polarization, atypical activity, or neutrophil diversity in AKI. Lastly, the kidney generated and renal-protective immunomodulatory protein uromodulin (Tamm-Horsfall Protein, THP) regulates granulopoiesis. In the absence of uromodulin, there is a systemic increase in neutrophils and mouse kidneys are sensitive to injury in AKI. To elucidate neutrophil diversity in AKI and their sensitivity to uromodulin, I performed a series of single-cell sequencing experiments to generate transcriptional profiles of neutrophils from the blood and kidneys of wild-type and THPknockout mice after renal ischemic-reperfusion-injury (IRI). Neutrophil diversity was detected following IRI of the mouse kidney in the blood and kidney. The distribution of subpopulations was sensitive to the kidney milieu. Within the kidney, this diversity and the transcriptional programs of neutrophil subpopulations was sensitive to the severity of ischemic injury. Lastly, Cxcl3 was uniquely upregulated in specific neutrophils after severe ischemic injury. Using single-cell sequencing of uromodulin knock-out mice, I detected the upregulation of toll-like receptor pathways and complement cascades across neutrophil subpopulations in a THP sensitive manner. Furthermore, CXCR2 ligand expression was a combination of moderate and severe injury in wild-type mice. This confirmed previously reported cytokine dysregulation in the uromodulin knock-out mouse after IRI and uncovers a novel role for Cxcl3. Thus, upon revisiting the well-studied neutrophil, I have uncovered novel neutrophil diversity that correlates with recovery of kidney function in AKI and suggests new roles for an old player.
4

Efeitos de tamanho finito e de interfaces em super-redes InP/In IND. 0.53 Ga IND. 0.47As. / Effects of finite size and super-network interfaces in InP / \'In IND. 0:53 \'\' Ga IND. 12:47 \'Overpriced

Hanamoto, Luciana Kazumi 14 December 2001 (has links)
Neste trabalho, estudamos as propriedades eletrônicas e estruturais de super-redes InP/In IND. 0.53 Ga IND. 0.47As dopadas fortemente com Si (densidade equivalente no bulk superior a 4.4 x 10 POT. 18cm POT. -3). O espectro de Fourier das oscilações de Shubnikov-de Haas apresenta um dubleto característico de elétrons que populam uma minibanda de energia, assim como uma freqüência de oscilação associada a elétrons confinados em uma camada superficial bidimensional (elétrons de Tamm). Verificamos que, para descrever o espectro de energia dos elétrons da minibanda, o modelo de Kronig-Penney é em geral suficiente porém, para descrever adequadamente os estados de Tamm é necessário recorrer a um cálculo auto-consistente completo. A boa resolução do dubleto associado aos elétrons que populam a minibanda de energia permitiu extrair as mobilidades quânticas dos elétrons associados aos hodógrafos extremais (\"cintura\" e \"pescoço\") da mini-superfície de Fermi. O tratamento de dados foi efetuado com a utilização de procedimentos especialmente desenvolvidos, que apresentam a vantagem de não necessitar da utilização de filtros de Fourier sofisticados. A detecção do estado de Tamm nas oscilações de Shubnikov-de Haas é inétida por se tratar de estados de Tamm degenerados. Por ser a mobilidade quântica dos elétrons de Tamm quase duas vezes maior do que a mesma mobilidade para os elétrons da minibanda, em campos magnéticos fracos as oscilações de Shubnikov-de Haas são dominadas pelos elétrons de Tamm, apesar da quantidade de elétrons de Tamm corresponder a apenas em torno de 10% do total de portadores livres em nossas amostras. As super-redes InP/In IND. 0.53 Ga IND. 0.47As:Si apresentam, também, grande redução de portadores livres com a diminuição do período das super-redes. A perda de portadores livres é de 60% quando o período é diminuído em 20%. Esta redução está correlacionada com a quantidade de átomos de ) dopantes que recai na camada interfacial de InAs IND. X P IND. 1-X que se forma quando InP é depositado sobre In IND. 0.53 Ga IND. 0.47As. Um estudo de um conjunto de 8 amostras nos permitiu estimar que a espessura da camada interfacial é de aproximadamente 20 ANGSTRONS. Os dados experimentais indicam que os átomos de Si que recaem nas camadas interfaciais, ao invés de formarem doadores rasos, formam centros profundos com energia de ativação superior a 50 meV. / In this work the electronic and structural properties of InP/In IND. 0.53 Ga IND. 0.47As superlattices heavily doped with Si (bulk equivalent density greater than 4.4 x 10 POT. 18cm POT. -3) were studied. The Fourier spectrum of the Shubnikov-de Haas oscillations presents a double peak characteristic of electrons which populate the first miniband of the energy spectrum, and an additional peak associated to electrons confined in a two-dimensional surface layer (Tamm electrons). We verified that the Kronig-Penney model is, in general, a good approximation to describe the energy spectrum of electrons in the miniband. However, to describe adequately the Tamm states, it is necessary to resort to a full self-consistent calculation of the energy levels in the effective mass approximation. The well-resolved doublet associated to the electrons in the miniband allowed us to extract the quantum mobilities associated to both extremal orbits of the Fermi mini-surface (belly and neck). The data analysis was done by using specially developed procedures, which have the advantage of not requiring the use of sophisticated Fourier filters. The detection of Tamm states throught Shubnikov-de Haas oscillations was done for the first time in superlattices in which the Tammm states are degenerate. On account of the fact that the quantum mobility of the Tamm electrons is about a factor of two greater than the quantum mobility of the miniband electrons, the Shubnikov-de Haas oscillations are dominated by electrons from the Tamm states, especially at weak magnetic fields, despite of the fact that the amount of Tamm electrons is only about 10% of the total amount of free carriers in our sample. The InP/In IND. 0.53 Ga IND. 0.47As:Si superlattices also display a strong reduction in the amount of free carriers when the period of the superlattice decreases. This reduction reaches 60% when the superlatticess period is decreased by only 20%. This reduction correlates with the amount of doping atoms that fall into the interfacial layer InAs IND. X P IND. 1-X which is formed when InP is grown on In IND. 0.53 Ga IND. 0.47As. A study of a set of 8 samples allowed us to estimate that the interfacial layer is approximately 20 ANGSTRONS thick. The experimental data indicate that the Si atoms which fall into the interfacial form deep levels with an activation energy larger than 50 meV.
5

Coherence and Coupling of Cavity Photons and Tamm Plasmons in Metal-Organic Microcavities / Kohärenz und Kopplung von Resonatorphotonen und Tamm Plasmonen in Metall-Organik Mikroresonatoren

Brückner, Robert 04 July 2013 (has links) (PDF)
The subject of this thesis is the investigation of organic microcavities with implemented unstructured and laterally structured metal layers. The optical properties are studied by means of various spectroscopic techniques and are compared to conventional metal-free devices. It is shown that the large expected absorption caused by the embedded metal is reduced compared to the case of a free-standing metal layer of the same thickness. As a consequence of the interaction of the photonic cavity mode with the metallic structures, two new coupled modes emerge which are called Tamm plasmons. The strength of this coupling and the resulting spectral difference of these modes are defined by the thickness of both the metal layer and the adjacent dielectric layers. These control parameters enable the optimization of the structural design. Accordingly, coherent emission from Tamm plasmons is realized at room temperature. An analytical approach is developed accounting for the experimentally observed polarization splitting of detuned resonances. Next, laterally structured metal layers embedded into organic microcavities are considered. The structuring leads to a confinement of the photonic density of states evident from a clear discretization in energy of the corresponding modes. Applying a photolithographic technique to structure the metal layer into a pattern of regularly placed stripes leads to additional effects due to the resulting periodicity. By exciting this hybrid structure above a certain threshold, periodic arrays of localized cavity modes and metal-based Tamm plasmons are generated. These Bloch-like excited states are capable of phase coupling across the grating. Additionally, surface plasmon polaritons (SPPs) are excited propagating at the interface of the silver and the adjacent dielectric layers. Thanks to the periodicity of the metallic stripes, SPPs are subject to efficient Bragg scattering into the light cone in air. Modes up to order number 30 are detectable as quasi-linear periodic lines in the dispersion pattern. A Fourier analysis reveals an in- or out-of-phase coupling of the modes and a spread of the coherence over macroscopic distances of more than 40 µm. This strategy of embedding metal patterns into an organic microcavity yields a viable route towards electrically contacted organic solid-state lasers. / In dieser Arbeit werden erstmals dünne, unstrukturierte sowie lateral strukturierte metallische Schichten in organische Mikroresonatoren eingebettet und anschließend die optischen Eigenschaften mittels spektroskopischer Verfahren untersucht. Es zeigt sich, dass die erwarteten hohen optischen Verluste durch die Absorption des elektrischen Feldes im Metall deutlich reduziert sind, verglichen mit dem Fall einer freistehenden, nicht eingebetteten Metallschicht gleicher Dicke. Als Folge der Wechselwirkung der photonischen Kavitätsmode mit dem Metall spaltet diese in zwei miteinander gekoppelte Moden auf. Diese neuartigen Moden werden als Tamm-Plasmonen bezeichnet. Die Kopplung sowie die spektrale Differenz beider Moden ist zum einen durch die optischen Eigenschaften und die Dicke der eingebetteten Metallschicht definiert, zum anderen durch die optische Dicke der angrenzenden dielektrischen Schichten. Dadurch ist eine Optimierung des Systems im Hinblick auf Absorption und Emissionswellenlänge der Bauteile möglich, so dass selbst bei Raumtemperatur kohärente Emission eines Tamm-Zustands erzielt werden kann. Eine erarbeitete analytische Rechnung bestätigt und erklärt die experimentell gemessene, polarisationsabhängige Aufspaltung der auftretenden resonanten Moden. Im zweiten Teil der Arbeit sind organische Mikroresonatoren, deren eingebettete Metallschicht in lateraler Richtung auf verschiedene Weisen strukturiert sind, Gegenstand der Untersuchungen. Als Folge dieser Strukturierung kommt es zur lateralen Beschränkung der photonischen Zustandsdichte, was durch eine Diskretisierung der Energiespektren der resultierenden optischen Moden experimentell nachweisbar ist. Werden periodische Metallstreifen mittels Photolithographie erzeugt, so kommt es neben einer weiteren Beeinflussung der Zustandsdichte auch zu Effekten, die durch diese Periodizität bedingt sind. Entsprechend reproduziert sich die Kavitätsmode mehrfach im Impulsraum. Oberflächenplasmonen, die auf der Grenzfläche zwischen dem Metall und den dielektrischen Schichten propagieren, werden auf Grund der Periodizität bis in den experimentell zugänglichen Lichtkegel gestreut. Dabei werden Plasmonenresonanzen bis hin zur 30. Ordnung gemessen. Im letzten Experiment werden derart periodisch strukturierte Metall-Organik-Mikroresonatoren auf ihre Lasertätigkeit hin untersucht. Eine lokal begrenzte optische Anregung mittels eines gepulsten Lasers führt zur Ausbildung verschiedener Bloch-ähnlicher Moden, deren Kohärenz sich lateral bis zu 40 µm ausbreitet. Eine Fourieranalyse zeigt eindeutige und feste Phasenbeziehungen zwischen angrenzenden Maxima der Moden. Zusammenfassend ergeben sich interessante metall-organische Systeme, die minimale Absorption und niedrige Laserschwellen aufweisen und die prinzipielle Eignung zur elektrischen Kontaktierung besitzen.
6

Det kvinnliga medborgarskapet och jordfrågans lösning : En undersökning av Elisabeth Tamms artiklar utifrån ett ekofeministiskt perspektiv / The female citizenship and the solution of the agricultural question. : A survey of Elisabet Tamm's ecofeminist ideas the years 1923-1936

Lindgren, Martina January 2014 (has links)
This master thesis is about one of the first female in the Swedish Parliament, Elisabeth Tamm (1880–1958), and her political articles in the magazine Tidevarvet. The aim of this study is to find similarities with Tamm’s political thoughts with the Ecofeministic theory. Due to women’s right to vote 1919 women citizenship was in a political debate. Tamm was one of many speakers and she combine the question with the Swedish agriculture and farming. Ecofeminism generally believe that women and nature are subordinate by the capitalist, patriarchal and Western society. This master thesis examine the degree to which Tamm’s political view coincides with the Ecofeministic perspective. The results which have been obtained through this study are that Tamm share a lot of the Ecofeministic view points and was before her time with these ideas. She also has the same belief concerning women and nature subjugation. The main difference between Ecofeminism and Tamm is the view of nature; Ecofeminism perceive nature as its own subject and not for human to control while Tamm view nature as something which human shall cultivate and cherish for future generations.   This study gives contribution to new knowledge for different interested parties. Ecofeminism is relatively new in science and I hope this conducted thesis has usability and will open up for future research and learn people of today more about our idea of nature and gender.
7

Efeitos de tamanho finito e de interfaces em super-redes InP/In IND. 0.53 Ga IND. 0.47As. / Effects of finite size and super-network interfaces in InP / \'In IND. 0:53 \'\' Ga IND. 12:47 \'Overpriced

Luciana Kazumi Hanamoto 14 December 2001 (has links)
Neste trabalho, estudamos as propriedades eletrônicas e estruturais de super-redes InP/In IND. 0.53 Ga IND. 0.47As dopadas fortemente com Si (densidade equivalente no bulk superior a 4.4 x 10 POT. 18cm POT. -3). O espectro de Fourier das oscilações de Shubnikov-de Haas apresenta um dubleto característico de elétrons que populam uma minibanda de energia, assim como uma freqüência de oscilação associada a elétrons confinados em uma camada superficial bidimensional (elétrons de Tamm). Verificamos que, para descrever o espectro de energia dos elétrons da minibanda, o modelo de Kronig-Penney é em geral suficiente porém, para descrever adequadamente os estados de Tamm é necessário recorrer a um cálculo auto-consistente completo. A boa resolução do dubleto associado aos elétrons que populam a minibanda de energia permitiu extrair as mobilidades quânticas dos elétrons associados aos hodógrafos extremais (\"cintura\" e \"pescoço\") da mini-superfície de Fermi. O tratamento de dados foi efetuado com a utilização de procedimentos especialmente desenvolvidos, que apresentam a vantagem de não necessitar da utilização de filtros de Fourier sofisticados. A detecção do estado de Tamm nas oscilações de Shubnikov-de Haas é inétida por se tratar de estados de Tamm degenerados. Por ser a mobilidade quântica dos elétrons de Tamm quase duas vezes maior do que a mesma mobilidade para os elétrons da minibanda, em campos magnéticos fracos as oscilações de Shubnikov-de Haas são dominadas pelos elétrons de Tamm, apesar da quantidade de elétrons de Tamm corresponder a apenas em torno de 10% do total de portadores livres em nossas amostras. As super-redes InP/In IND. 0.53 Ga IND. 0.47As:Si apresentam, também, grande redução de portadores livres com a diminuição do período das super-redes. A perda de portadores livres é de 60% quando o período é diminuído em 20%. Esta redução está correlacionada com a quantidade de átomos de ) dopantes que recai na camada interfacial de InAs IND. X P IND. 1-X que se forma quando InP é depositado sobre In IND. 0.53 Ga IND. 0.47As. Um estudo de um conjunto de 8 amostras nos permitiu estimar que a espessura da camada interfacial é de aproximadamente 20 ANGSTRONS. Os dados experimentais indicam que os átomos de Si que recaem nas camadas interfaciais, ao invés de formarem doadores rasos, formam centros profundos com energia de ativação superior a 50 meV. / In this work the electronic and structural properties of InP/In IND. 0.53 Ga IND. 0.47As superlattices heavily doped with Si (bulk equivalent density greater than 4.4 x 10 POT. 18cm POT. -3) were studied. The Fourier spectrum of the Shubnikov-de Haas oscillations presents a double peak characteristic of electrons which populate the first miniband of the energy spectrum, and an additional peak associated to electrons confined in a two-dimensional surface layer (Tamm electrons). We verified that the Kronig-Penney model is, in general, a good approximation to describe the energy spectrum of electrons in the miniband. However, to describe adequately the Tamm states, it is necessary to resort to a full self-consistent calculation of the energy levels in the effective mass approximation. The well-resolved doublet associated to the electrons in the miniband allowed us to extract the quantum mobilities associated to both extremal orbits of the Fermi mini-surface (belly and neck). The data analysis was done by using specially developed procedures, which have the advantage of not requiring the use of sophisticated Fourier filters. The detection of Tamm states throught Shubnikov-de Haas oscillations was done for the first time in superlattices in which the Tammm states are degenerate. On account of the fact that the quantum mobility of the Tamm electrons is about a factor of two greater than the quantum mobility of the miniband electrons, the Shubnikov-de Haas oscillations are dominated by electrons from the Tamm states, especially at weak magnetic fields, despite of the fact that the amount of Tamm electrons is only about 10% of the total amount of free carriers in our sample. The InP/In IND. 0.53 Ga IND. 0.47As:Si superlattices also display a strong reduction in the amount of free carriers when the period of the superlattice decreases. This reduction reaches 60% when the superlatticess period is decreased by only 20%. This reduction correlates with the amount of doping atoms that fall into the interfacial layer InAs IND. X P IND. 1-X which is formed when InP is grown on In IND. 0.53 Ga IND. 0.47As. A study of a set of 8 samples allowed us to estimate that the interfacial layer is approximately 20 ANGSTRONS thick. The experimental data indicate that the Si atoms which fall into the interfacial form deep levels with an activation energy larger than 50 meV.
8

Mikroskopické jaderné modely pro jádra s nezaplněnými slupkami / Microscopic nuclear models for open-shell nuclei

Herko, Jakub January 2017 (has links)
Title: Microscopic nuclear models for open-shell nuclei Author: Jakub Herko Institute: Institute of Particle and Nuclear Physics Supervisor: Mgr. František Knapp, Ph.D., Institute of Particle and Nuclear Physics Abstract: Since the nucleus is a quantum many-body system consisting of con- stituents whose mutual interaction is not satisfactorily known, it is necessary to use approximate methods when describing the nucleus. Basic approximate approaches in the microscopic theory of the nucleus are the Hartree-Fock the- ory, Tamm-Dancoff approximation and random phase approximation. They are described in the first chapter of this thesis. The main aim was to develop mi- croscopic models for open-shell nuclei with two valence particles or holes. They are described in the second chapter, which contains detailed derivations of the relevant formulae. These methods have been numerically implemented. The re- sults of the calculations of the nuclear spectra and the electromagnetic transition probabilities are presented in the third chapter. Keywords: Tamm-Dancoff approximation, random phase approximation, open- shell nuclei, nuclear spectra, electromagnetic transition probabilities ii
9

Coherence and Coupling of Cavity Photons and Tamm Plasmons in Metal-Organic Microcavities

Brückner, Robert 31 May 2013 (has links)
The subject of this thesis is the investigation of organic microcavities with implemented unstructured and laterally structured metal layers. The optical properties are studied by means of various spectroscopic techniques and are compared to conventional metal-free devices. It is shown that the large expected absorption caused by the embedded metal is reduced compared to the case of a free-standing metal layer of the same thickness. As a consequence of the interaction of the photonic cavity mode with the metallic structures, two new coupled modes emerge which are called Tamm plasmons. The strength of this coupling and the resulting spectral difference of these modes are defined by the thickness of both the metal layer and the adjacent dielectric layers. These control parameters enable the optimization of the structural design. Accordingly, coherent emission from Tamm plasmons is realized at room temperature. An analytical approach is developed accounting for the experimentally observed polarization splitting of detuned resonances. Next, laterally structured metal layers embedded into organic microcavities are considered. The structuring leads to a confinement of the photonic density of states evident from a clear discretization in energy of the corresponding modes. Applying a photolithographic technique to structure the metal layer into a pattern of regularly placed stripes leads to additional effects due to the resulting periodicity. By exciting this hybrid structure above a certain threshold, periodic arrays of localized cavity modes and metal-based Tamm plasmons are generated. These Bloch-like excited states are capable of phase coupling across the grating. Additionally, surface plasmon polaritons (SPPs) are excited propagating at the interface of the silver and the adjacent dielectric layers. Thanks to the periodicity of the metallic stripes, SPPs are subject to efficient Bragg scattering into the light cone in air. Modes up to order number 30 are detectable as quasi-linear periodic lines in the dispersion pattern. A Fourier analysis reveals an in- or out-of-phase coupling of the modes and a spread of the coherence over macroscopic distances of more than 40 µm. This strategy of embedding metal patterns into an organic microcavity yields a viable route towards electrically contacted organic solid-state lasers. / In dieser Arbeit werden erstmals dünne, unstrukturierte sowie lateral strukturierte metallische Schichten in organische Mikroresonatoren eingebettet und anschließend die optischen Eigenschaften mittels spektroskopischer Verfahren untersucht. Es zeigt sich, dass die erwarteten hohen optischen Verluste durch die Absorption des elektrischen Feldes im Metall deutlich reduziert sind, verglichen mit dem Fall einer freistehenden, nicht eingebetteten Metallschicht gleicher Dicke. Als Folge der Wechselwirkung der photonischen Kavitätsmode mit dem Metall spaltet diese in zwei miteinander gekoppelte Moden auf. Diese neuartigen Moden werden als Tamm-Plasmonen bezeichnet. Die Kopplung sowie die spektrale Differenz beider Moden ist zum einen durch die optischen Eigenschaften und die Dicke der eingebetteten Metallschicht definiert, zum anderen durch die optische Dicke der angrenzenden dielektrischen Schichten. Dadurch ist eine Optimierung des Systems im Hinblick auf Absorption und Emissionswellenlänge der Bauteile möglich, so dass selbst bei Raumtemperatur kohärente Emission eines Tamm-Zustands erzielt werden kann. Eine erarbeitete analytische Rechnung bestätigt und erklärt die experimentell gemessene, polarisationsabhängige Aufspaltung der auftretenden resonanten Moden. Im zweiten Teil der Arbeit sind organische Mikroresonatoren, deren eingebettete Metallschicht in lateraler Richtung auf verschiedene Weisen strukturiert sind, Gegenstand der Untersuchungen. Als Folge dieser Strukturierung kommt es zur lateralen Beschränkung der photonischen Zustandsdichte, was durch eine Diskretisierung der Energiespektren der resultierenden optischen Moden experimentell nachweisbar ist. Werden periodische Metallstreifen mittels Photolithographie erzeugt, so kommt es neben einer weiteren Beeinflussung der Zustandsdichte auch zu Effekten, die durch diese Periodizität bedingt sind. Entsprechend reproduziert sich die Kavitätsmode mehrfach im Impulsraum. Oberflächenplasmonen, die auf der Grenzfläche zwischen dem Metall und den dielektrischen Schichten propagieren, werden auf Grund der Periodizität bis in den experimentell zugänglichen Lichtkegel gestreut. Dabei werden Plasmonenresonanzen bis hin zur 30. Ordnung gemessen. Im letzten Experiment werden derart periodisch strukturierte Metall-Organik-Mikroresonatoren auf ihre Lasertätigkeit hin untersucht. Eine lokal begrenzte optische Anregung mittels eines gepulsten Lasers führt zur Ausbildung verschiedener Bloch-ähnlicher Moden, deren Kohärenz sich lateral bis zu 40 µm ausbreitet. Eine Fourieranalyse zeigt eindeutige und feste Phasenbeziehungen zwischen angrenzenden Maxima der Moden. Zusammenfassend ergeben sich interessante metall-organische Systeme, die minimale Absorption und niedrige Laserschwellen aufweisen und die prinzipielle Eignung zur elektrischen Kontaktierung besitzen.
10

Generalizations of the Mandelstam-Tamm Quantum Speed Limit

Hörnedal, Niklas January 2021 (has links)
Quantum speed limits are lower bounds on the evolution time for quantum systems. In this thesis, we consider closed quantum systems. We investigate how different principal bundles offers a geometrical method for obtaining generalizations of the Mandelstam-Tamm quantum speed limit for mixed states. We look at three different principal bundles from which we derive two already known quantum speed limits, the Uhlmann and Andersson QSLs, and one which is new, the Grassmann QSL. We also investigate the tightness of these quantum speed limits and how they compare with each other.

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