The diploma thesis deals with the experimental study of surface plasmon polaritons (SPPs) on nano-structures with the Au/Co/Au multilayer. Plasmonic structures were prepared by the electron beam lithography and by the focused ion beam. A Scanning optical near-field microscope was used for detection of surface plasmon polaritons. SPPs were confirmed by the experiment with different polarizations of the illuminating light. Furthermore, differences in plasmon interference wavelengths was measured for different surface dielectric functions. Finally, the decantation of the SPPs interference image was measured in dependence on the external magnetic field.

Das Laserstrahlhartlöten ermöglicht die Herstellung von Fügeverbindungen mit exzellenten Nahtqualitäten. Daher hat es sich bei anspruchsvollen Anwendungen, wie zweiteiligen Heckklappen und der Verbindung von Dach und Seitenwandrahmen (Dachnullfuge) etabliert. Um die hohen Qualitätsanforderungen durch das Laserstrahlhartlöten realisieren zu können, sind allerdings anspruchsvolle konstruktive Randbedingungen zu erfüllen, die über die Fertigungskette nicht immer vollständig sicherzustellen sind. Das Ergebnis solcher Fertigungs- und Materialschwankungen äußert sich dann oft als Nahtimperfektionen, die während des Laserlötprozesses entstehen. Diese verursachen vor allem mit steigenden Prozessgeschwindigkeiten einen erhöhten und kostenintensiven Nacharbeitsaufwand und sollten daher vermindert bzw. gänzlich vermieden werden. Das Ziel ist somit den Laserlötprozess so robust wie möglich auszulegen, um auf diese Fertigungsschwankungen ohne Einschränkungen in der Nahtqualität reagieren zu können. Im ersten Teil dieser Arbeit werden wesentliche Einflussfaktoren auf die Ausbildung der Nahtqualität am schrägen Bördelstoß untersucht und die systemtechnischen Grenzen mit einem statischen und runden Laserspot aufgezeigt. Weiterhin werden die resultierenden Nahtqualitäten durch das Laserstrahllöten mit gescanntem Laserstrahl in Vorschubrichtung untersucht. Die Ergebnisse zeigen, dass sich die Nahtqualität mit diesem innovativen Ansatz bezüglich des Anbindungsquerschnittes und der Oberflächenqualität weiter steigern lassen. Dies lässt sich ebenfalls für höhere Prozessgeschwindigkeiten realisieren. Abschließend werden neuartige Möglichkeiten der Prozessüberwachung, sowie erste Ansätze zur Prozessregelung des Laserstrahlhartlötens am schrägen Bördelstoß vorgestellt. Die erzielten Resultate zeigen, dass sich der Laserstrahlhartlötprozess durch die Regelung der Laserleistung in Verbindung mit evaluierten Temperaturfeldern im Bereich der Prozesszone online kontrollieren und sich dadurch die Prozessstabilität merklich steigern lässt.

Modern communication systems face new technological challenges, such as the narrowness and overload of the conventional frequency bands employed for these applications. Nowadays, communication systems are expected to operate at higher frequencies, such as the mm-wave band. In particular, for space applications, specific environmental conditions make it necessary to design low-profile, lightweight and high gain systems with wide-angle scanning capabilities. Traditional solutions are reflectors antennas or planar arrays. Reflectors often end up being bulky, whereas array antennas are lossy and costly. Lens antennas, unpopular at low frequencies due to their large size, offer a better solution in this context, due to their focusing properties, wide-scanning capability, and broadband behaviour. Among lens antennas, geodesic lens antennas have recently increased interest since they are fullymetallic and easy to manufacture. Previous research aiming at reducing the profile of geodesic lens antennas, while preserving high performances, allowed a total height reduction by a factor 4. In this work, I investigate the possibility of reducing the profile even further by following a different approach. Instead of folding by mirroring the curved profile, the lens antenna is built with circular ridge structures, in an attempt to discretize the original profile. Different approaches have been proposed. First, designs with different numbers of squared ridges were proposed. The reflections are reduced by chamfering the corners of the ridges. Moreover, triangle ridges and alternating the ridges orientation have also been investigated. The final design has four squared ridges with the same orientation. This design was chosen due to its radiation performance. This approach reduces the profile by a factor 18. A prototype has been manufactured working on the frequency band [24,34] GHz. The scanning range is ±62◦ , reflections levels are below -15 dB and at 29 GHz the maximum realized gain is equal to 15.75 dBi. This solution offers attractive properties, mainly due to its compactness. The height of the lens antenna is restricted by the flare, which was set at λ/2. This means that this lens antenna can be stacked in a linear array with grating-lobe-free performance in the elevation plane. / Moderna kommunikationssystem står inför nya tekniska utmaningar, såsom smalheten samt överbelastning inom de konventionella frekvensband som avsatts för tillhörande applikationer. Nutida kommunikationssystem förväntas operera på högre frekvenser, vilket implicerar våglängder på millimeternivå. Särskilt inom rymdapplikationer så finns förutbestämda miljömässiga förhållanden som nödvändiggör användning av lågprofilerade och lättviktiga system med hög antennförstärkning samt möjlighet för vidvinkelskanning. Traditionella lösningar omfattar både reflektorantenner och plana gruppantenner, vilket antingen är otympligt respektive kostsamt. Linsantenner, otympliga och därav opopulära val inom lägre frekvenser, visar sig vara bra lösningar i given kontext. Detta följer av linsernas fokuseringsegenskaper, breda skanningsförmåga samt naturligt stora frekvensband. Inom guppen av linsantenner så har geodetiska linsantenner fått ökat intresse till följd av dess simpla tillverkningsprocess samt fullt metalliska struktur. Tidigare forskning som syftat åt att minska profilen tillsammande med bibehållen prestanda, har lyckats minska höjden men en faktor av fyra. I detta arbete så undersöks möjligheten att krympa profilen ytterligare via användning av ett nytt angreppssätt. I stället för att vika linsen överstämmande med en kurvig profil, så formas linsantennerna med cirkulära ås-strukturer (små böjningar) i strävan efter att diskretisera den ursprunglig profilen. Olika tillvägagångssätt visas i detta arbete. Först visas profiler med ett varierande antal kvadratiska åsar. Reflektioner längs profilen reduceras vid introduktion av fasningar av kvadratens tillhörande hörn. Ytterligare så har triangulära åsar samt riktningen (ås med riktning upp eller riktning ned längs den horisontella profilen) av samtliga typer utvärderats. Den slutliga designen har fyra kvadratiska åsar i samma riktning, ett designval baserat på strålningsprestanda. Arbetet visar att det sistnämnde tillvägagångssättet minskar profilen med en faktor av 18. En fungerande prototyp inom frekvensbandet [24,34] GHz har tillverkats baserat på sistnämnd design, som uppnår ett skanningsområde upp till 62◦ , en reflektionsnivå under -15 dB samt en maximal antennförstärkning på 15.75 dBi vid 29 GHz. Den föreslagna lösningen erhåller attraktiva egenskaper, främst med avseende på dess kompakthet. Höjden på linsantennen begränsas av en matchande flank med en halv våglängd stor öppning, så att flertalet linsantenner kan staplas och forma en linjär gruppantenn vars prestanda utesluter större sidolober längs höjdplanet.

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No description available.

Transmission Electron Microscopy (TEM) on light element materials and soft matters is problematic due to electron irradiation damage and low contrast. In this doctoral thesis techniques were developed to address some of those issues and successfully characterize these materials at high resolution. These techniques were demonstrated on graphene flakes, DNA/magnetic beads and a number of water containing biomaterials. The details of these studies are given below. A TEM based method was presented for thickness characterization of graphene flakes. For the thickness characterization, the dynamical theory of electron diffraction is used to obtain an analytical expression for the intensity of the transmitted electron beam as a function of thickness. From JEMS simulations (experiments) the absorption constant λ in a low symmetry orientation was found to be ~ 208 nm (225 ± 9 nm). When compared to standard techniques for thickness determination of graphene/graphite, the method has the advantage of being relatively simple, fast and requiring only the acquisition of bright-field (BF) images. Using the proposed method, it is possible to measure the thickness change due to one monolayer of graphene if the flake has uniform thickness over a larger area. A real-space TEM study on magnetic bead-DNA coil interaction was conducted and a statistical analysis of the number of beads attached to the DNA-coils was performed. The average number of beads per DNA coil was calculated around 6 and slightly above 2 for samples with 40 nm and 130 nm beads, respectively. These results are in good agreement with magnetic measurements. In addition, the TEM analysis supported an earlier hypothesis that 40 nm beads are preferably attached interior of the DNA-coils while 130 nm beads closer to the exterior of the coils. A focused ion-beam in-situ lift-out technique for hydrated biological specimens was developed for cryo-TEM. The technique was demonstrated on frozen Aspergillus niger spores which were frozen with liquid nitrogen to preserve their cellular structures. A thin lamella was prepared, lifted out and welded to a TEM grid. Once the lamella was thinned to electron transparency, the grid was cryogenically transferred to the TEM using a cryo-transfer bath. The structure of the cells was revealed by BF imaging. Also, a series of energy filtered images was acquired and C, N and Mn elemental maps were produced. Furthermore, 3 Å lattice fringes of the underlying Al support were successfully resolved by high resolution imaging, confirming that the technique has the potential to extract structural information down to the atomic scale. The experimental protocol is ready now to be employed on a large variety of samples e.g. soft/hard matter interfaces.

The clinical introduction of proton therapy requires an extensive analysis of its benefits compared to conventional radiotherapy and a detailed analysis of possible uncertainties which might have serious consequences for patient treatment. In the first part of the presented thesis, the expected toxicities were evaluated for a treatment of head and neck cancer patients using a biologically adapted dose escalation schedule with photon and proton therapy. The feasibility of the dose escalation schedule could be demonstrated for both photon and proton therapy, since only a small increase in toxicity risk occurred for most toxicities. However, the expected toxicity risks were in most cases smaller with proton therapy. Furthermore, a higher benefit was found for patients with primary tumour locations in the upper head and neck area, who thus might be preferably referred to proton therapy. In the second part of this thesis, an extensive analysis of the impact of tumour motion in lung cancer treatment with active-scanning proton therapy was conducted. It could be shown, that dose degradations were small for tumour motion amplitudes below 5 mm. Parameters like the target volume concept, the optimisation approach, changes in the motion pattern and application sequence times had additional impact on the dose degradation. However, their magnitude was patient specific. Since not all parameters can be assessed before treatment, e.g. the motion pattern during treatment, prospective estimations should be supplemented by retrospective analyses. / Die Einführung der Protonentherapie in die klinische Praxis erfordert umfassende Analysen ihrer Vor- und Nachteile im Vergleich zur konventionellen Photonentherapie sowie detaillierte Untersuchungen der Auswirkungen von Unsicherheiten in der Therapieapplikation. Im ersten Teil der vorliegenden Arbeit wurden die zu erwartenden Nebenwirkungen bei der Behandlung von Patienten mit Kopf-Hals-Tumoren mit einem biologisch-adaptierten Fraktionierungsschema inklusive Dosiseskalation mit Photonen- und Protonentherapie evaluiert. Dabei konnte gezeigt werden, dass die Dosiseskalation sowohl mit Photonen- als auch Protonentherapie angewandt werden kann, da die Wahrscheinlichkeit für das Auftreten von Nebenwirkungen in den meisten Fällen kaum erhöht wurde. Weiterhin wurden die Nebenwirkungswahrscheinlichkeiten mit der Protonentherapie im Vergleich zur Photonentherapie reduziert. Dies war vor allem für Patienten mit Tumoren im oberen Kopf-Hals-Bereich der Fall. Diese könnten daher bevorzugt zur Protonentherapie überwiesen werden. Darüber hinaus wurde im zweiten Teil der Arbeit eine umfassende Analyse des Einflusses der Tumorbewegung auf die Dosisverteilung bei Behandlung von Lungentumoren mit aktiver Protonenstrahlformierung durchgeführt. Dabei zeigte sich, dass Dosisdegradierungen bei Bewegungsamplituden unter 5mm gering sind. Parameter wie das Zielvolumenkonzept, Veränderungen des Bewegungsmusters oder der Applikationszeiten nehmen zusätzlich Einfluss auf die Dosisdegradierung, allerdings in unterschiedlichem Maß für individuelle Patienten. Da nicht alle Parameter vor Behandlung bekannt sein können, sollten prospektive Dosisabschätzungen durch retrospektive Analysen ergänzt werden.

The clinical introduction of proton therapy requires an extensive analysis of its benefits compared to conventional radiotherapy and a detailed analysis of possible uncertainties which might have serious consequences for patient treatment. In the first part of the presented thesis, the expected toxicities were evaluated for a treatment of head and neck cancer patients using a biologically adapted dose escalation schedule with photon and proton therapy. The feasibility of the dose escalation schedule could be demonstrated for both photon and proton therapy, since only a small increase in toxicity risk occurred for most toxicities. However, the expected toxicity risks were in most cases smaller with proton therapy. Furthermore, a higher benefit was found for patients with primary tumour locations in the upper head and neck area, who thus might be preferably referred to proton therapy. In the second part of this thesis, an extensive analysis of the impact of tumour motion in lung cancer treatment with active-scanning proton therapy was conducted. It could be shown, that dose degradations were small for tumour motion amplitudes below 5 mm. Parameters like the target volume concept, the optimisation approach, changes in the motion pattern and application sequence times had additional impact on the dose degradation. However, their magnitude was patient specific. Since not all parameters can be assessed before treatment, e.g. the motion pattern during treatment, prospective estimations should be supplemented by retrospective analyses. / Die Einführung der Protonentherapie in die klinische Praxis erfordert umfassende Analysen ihrer Vor- und Nachteile im Vergleich zur konventionellen Photonentherapie sowie detaillierte Untersuchungen der Auswirkungen von Unsicherheiten in der Therapieapplikation. Im ersten Teil der vorliegenden Arbeit wurden die zu erwartenden Nebenwirkungen bei der Behandlung von Patienten mit Kopf-Hals-Tumoren mit einem biologisch-adaptierten Fraktionierungsschema inklusive Dosiseskalation mit Photonen- und Protonentherapie evaluiert. Dabei konnte gezeigt werden, dass die Dosiseskalation sowohl mit Photonen- als auch Protonentherapie angewandt werden kann, da die Wahrscheinlichkeit für das Auftreten von Nebenwirkungen in den meisten Fällen kaum erhöht wurde. Weiterhin wurden die Nebenwirkungswahrscheinlichkeiten mit der Protonentherapie im Vergleich zur Photonentherapie reduziert. Dies war vor allem für Patienten mit Tumoren im oberen Kopf-Hals-Bereich der Fall. Diese könnten daher bevorzugt zur Protonentherapie überwiesen werden. Darüber hinaus wurde im zweiten Teil der Arbeit eine umfassende Analyse des Einflusses der Tumorbewegung auf die Dosisverteilung bei Behandlung von Lungentumoren mit aktiver Protonenstrahlformierung durchgeführt. Dabei zeigte sich, dass Dosisdegradierungen bei Bewegungsamplituden unter 5mm gering sind. Parameter wie das Zielvolumenkonzept, Veränderungen des Bewegungsmusters oder der Applikationszeiten nehmen zusätzlich Einfluss auf die Dosisdegradierung, allerdings in unterschiedlichem Maß für individuelle Patienten. Da nicht alle Parameter vor Behandlung bekannt sein können, sollten prospektive Dosisabschätzungen durch retrospektive Analysen ergänzt werden.

In the sub-THz frequency range, the geodesic lens can realize low losses and beam scanning capability with high gain and high aperture efficiency due to its fully metallic property and rotational symmetry. Therefore, in high-frequency applications, a geodesic lens is considered a more promising solution in comparison to phased arrays or other beamforming techniques. To realize dual polarization for geodesic lenses, a polarization rotator using fully metallic screens can be placed at the lens aperture to increase the channel capacity. In this thesis, we propose a dual-polarized fully metallic geodesic lens antenna with the operation frequency centered at 120 GHz. The proposed design contains two layers of geodesic lenses and two polarization rotators placed in their respective apertures with ±45° polarization. By using a twist waveguide for the feeding, we eliminate the leakage caused by the air gap between the metal plates. The simulation results show that the dual-polarized lens can achieve an angular scanning range of ±60° and its scanning loss is 0.6 dB, with an aperture efficiency of 90%. Finally, we propose a prototype design with mechanical considerations to ensure robustness in future manufacturing, assembly, and testing. / Geodetiska linser kan tillämpas åt frekvenser under THz för att realisera låga förluster och strålscanningskapacitet med både hög förstärkning och apertureffektivitet, detta på grund av dess fullt metalliska egenskaper samt rotationssymmetri. I högfrekventa tillämpningar anses därför en geodetisk lins vara lovande i jämförelse med en fasstyrda gruppantenn eller andra strålformningstekniker. Ytterligare så kan polarisationsrotatorer med helt metalliska skärmar kan placeras vid linsöppningen för att realisera korspolariserade fält samt öka kanalkapaciteten hos geodetiska linser. I denna avhandling föreslårs en justerbar korspolariserad samt fullt metallisk geodetisk linsantenn centrerad runt 120 GHz. Den föreslagna designen innehåller två lager geodetiska linser och två polarisationsrotatorer placerade i sina respektive utgångar med respektive polarisatonsförskjutning på ±45°. Genom att använda en vriden vågledare för matningen så eliminerars läckaget som normalt följer av luftgapet mellan metallplattorna. Simuleringsresultaten visar att den korspolariserade linsen kan uppnå ett avsökningsområde inom vinklar ±60° men en skanningsförlust på 0,6 dB, detta med en apertureffektivitet på 90%. Slutligen föreslår vi en prototyp med hänsyn till mekaniska aspekter för att säkerställa robusthet i framtida tillverkning, montering och testning.

[pt] Este trabalho tem como objetivo apresentar o desenvolvimento de uma antena HAIA (Holographic Artificial Impedance Antenna) para potenciais aplicações em sistemas de satélites nas bandas X (8 - 12 GHz) e Ku (12 - 18 GHz), bem como na frequência de terahertz. Como prova de conceito, o protótipo é criado para operar na banda K (18 - 27 GHz), especificamente na frequência de 18,4 GHz. O HAIA é um tipo de antena com ondas vazadas, com um princípio operacional único para radiação de feixe controlado. Devido às suas amplas propriedades de radiação, o grau de liberdade do projeto nos permite explorar o comportamento de resposta da antena e diferentes parâmetros para sua modelagem são estudados. O projeto da antena obedece à teoria estabelecida para a radiação de ondas vazadas na conversão de uma onda de superfície para uma onda com vazamento, onde uma AIS (Artificial Impedance Surface) é caracterizada e distribuída em um substrato dielétrico usando o princípio holográfico desenvolvido no sistema óptico. A fim de minimizar as dimensões da antena, uma fonte planar é estudada para gerar uma onda de superfície e comparada com o desempenho da alimentação de onda de superfície convencional neste tipo de estrutura. Os diferentes projetos são avaliados para a conclusão do melhor resultado e comparados com outros trabalhos. O protótipo final é fabricado para testes experimentais, onde os resultados provam que a antena projetada responde às características modeladas, com uma boa concordância entre os resultados simulados e medidos. / [en] This work aims to present the development of a holographic artificial impedance antenna (HAIA) for potential applications in satellite systems in the X (8 - 12 GHz) and Ku (12 - 18 GHz) bands, as well as in the frequency of terahertz. As a proof of concept, the prototype is created to operate in the K (18 - 27 GHz) band, specifically at the design frequency of 18.4 GHz. HAIA is a kind of leaky-wave antenna (LWA) with a unique operating principle for controlled beam radiation. Due to their radiation characteristics are broad, and the degree of design freedom allows us to explore the antenna performance, different parameters are studied for modeling. The antenna design obeys the established theory for the leaky-wave radiation in the conversion of a surface wave into a leaky-wave, where an artificial impedance surface (AIS) is characterized and distributed on a dielectric substrate using the holographic principle developed in the optical system. In order to minimize the dimensions of the HAIA, a planar surface wave launcher is studied and compared with the performance of conventional surface wave feeding used in this type of structure. A series of designs are evaluated for the conclusion of the best result and compared with other works. The final prototype is manufactured for experimental tests, where the results show that the designed antenna responds to the modeled characteristics with a good agreement between the simulated and measured results.