Företaget Hajenterprise vill göra en forskning inom kommunikation för att hantera kontaktlösa betalningar för att kunna ta betalt kontaktlöst med hjälp av mobilen. Idag används bankkort för att betala för de flesta saker. Nya betalningssätt har rört sig mot kontaktlösa köp med hjälp av smarta telefoner och NFC-teknologier. Smarta telefoner har börjat användas mer och mer i kontaktlösa köp mot point of sale (POS) terminaler. Skulle det då gå att kunna ta bort POS-terminaler och använda smarta telefoner som POS-terminaler? För att besvara detta behövdes tester utföras för att se ifall en smart telefon skulle kunna läsa ett bankkort och behandla bankkortets information. Bankkort kunde läsas av de smarta telefonerna men informationen från bankkortet kunde inte användas av den smarta telefonen för att genomföra en betalning. Detta var eftersom beroende på telefon, öppnades Samsung, Google eller Apple pay. En smart telefon kunde alltså ta emot information från ett bankkort men telefonen kunde inte använda den information för att utföra en betalning på en terminal. Utöver forskningen av olika betalningssätt, skapades en applikation där betalning skulle kunna utföras från en mobil till en annan mobil. Detta skulle ske med hjälp av Near Field Communication (NFC) och blockchain, eftersom Hajenterprise vill ha en prototyp-applikation som skulle kunna betala och ta betalt över NFC mot deras blockchain. JavaScript användes för att skapa en react native applikation som kunde fungera på både Android och iOS. Detta lade grunden så att Hajenterprise kunde använda sitt blockchain-api för mobila betalningar. / The company Hajenterprise wanted to research the area of contactless payments to see if it’s possible to Pay contactless with a mobile phone. Today bank cards are used to pay for most things. New payment methods have moved toward contactless purchases using smart phones and NFC-technologies. Smart phones have begun to be used more and more in contactless purchases at point of sale (POS) terminals. The possibility to remove POS-terminals and use smartphones instead as POS-terminals could make it easier and faster to pay. To test this, several tests were needed to see if a smartphone could read a bank card and process the card's information. Bank cards could be read by the smartphone but the information from the bank card could not be used by the smartphone to make a payment. This was because depending on the phone, Samsung, Google or Apple Pay was opened. Thus, a smart phone could receive information from a card but the phone could not use that information to make a payment at a terminal. In addition, an application was created where one could make payments from one mobile to another mobile. This would be done using Near Field Communication (NFC) and blockchain, as Hajenterprise wanted a prototype-application that could pay and charge over NFC against their blockchain. JavaScript was used to create a react native application that could work on both Android and iOS. This laid the foundation for Hajenterprise to use its blockchain API for mobile payments.

The lack of medication adherence leads to an incremental risk of diseases which can be a major burden on the individual, healthcare system, and society. Hence, healthcare professionals have a central role and should manage, guide, educate, and make their patient more involved in their treatment and thereby promoting a better medication adherence. Medication adherence is a great challenge for many patients with chronic conditions, elderly patient, or patient prescribed to long-term medication. The rapid development and deployment of mobile phones in the healthcare industry has an important role to play in this area and has led to the development of new phone features and applications that can help both caregivers and patients with managing and monitoring medication intakes. This development and support of mobile phones and applications have created and improved doctor-patient interaction. Today, there is no easy way for healthcare professionals to monitor and help patients with their medication intakes. A solution to this problem is to develop a mobile application that communicates with a smart pillbox via near field communication (NFC) to monitor, manage, and improve patient’s medication intakes in an easy and accessible manner. Using NFC as a communication technology allows data to be wirelessly transferred from phone to pillbox and vice versa. This solution will help healthcare professionals to create better treatment conditions and fewer side effects for their patients. These patients will be more knowledgeable and motivated to take greater responsibility in following doctor’s instructions, thereby improving their treatment process. The application is tested and evaluated during every iteration phase of the development process. These tests have been conducted by allowing healthcare professionals to test the application and provide feedback on their experience when using the app. Conducting these tests have helped with generating new ideas, features, and functionalities, but also helped to improve the user interface to make the application as user-friendly as possible. / Bristen på medicinering följsamhet leder till en ökad risk för sjukdomar som kan vara en stor belastning för individen, vårdsystemet och samhället. Hälsooch sjukvårdspersonal har därför en central roll och bör hantera, vägleda, utbilda och göra patienten mer delaktig i behandlingen och därigenom främja en bättre medicinering följsamhet. Medicinering följsamhet är en stor utmaning för många patienter med kroniska tillstånd, äldre patient eller patient som är ordinerad för långvarig medicinering. Den snabba utvecklingen och användningen av mobiltelefoner inom vårdindustrin har en viktig roll att spela i detta område och har lett till utvecklingen av nya funktioner och applikationer som kan hjälpa både vårdgivare och patienter med att hantera och övervaka medicinsk intag. Denna utveckling och support av mobiltelefoner och applikationer har skapat och förbättrat interaktion mellan läkare och patient. Idag finns det inget enkelt sätt för sjukvårdspersonal att övervaka och hjälpa patienter med sina medicinintag. En lösning på detta problem är att utveckla en mobilapplikation som kommer att kommunicera med en smart pillbox via nära fältkommunikation (eng. Near Field Communication, NFC) för att övervaka, hantera och förbättra patientens medicinintag på ett enkelt och tillgängligt sätt. Med hjälp av NFC som kommunikationsteknik kommer data att överföras trådlöst från telefon till pillerdosa och vice versa. Denna lösning kommer att hjälpa vårdpersonal att skapa bättre behandlingsförhållanden och färre biverkningar för sina patienter. Dessa patienter kommer i sin tur att vara mer kunniga och motiverade att ta större ansvar i efterföljande läkares instruktioner och därigenom förbättra deras behandlingsprocess. Applikationen har testat och utvärderat under varje iteration av utvecklingsprocessen. Dessa tester har utförts genom att låta vårdpersonal testa applikationen och ge feedback på hur dem upplevar applikationen. Dessa tester hjälper till att skapa nya idéer, funktioner och funktioner som bör ingå i den slutliga applikationen, men också bidra till att förbättra användargränssnittet för att göra ansökan så användarvänlig som möjligt.

Att betala med kort är idag standardiserat, men något som också är väldigt vanligt är att betala kontaktlöst. Detta kan göras både med ett kontaktlöst kort eller med en smarttelefon. Teknologin som möjliggör detta är närfältskommunikation. Examensarbetet undersöker hur säkerheten i dessa betalningsmetoder är uppbyggd, vad det finns för säkerhetsproblem samt hur användningen kan se ut i framtiden. Den primära frågeställningen var att undersöka om det är lika säkert eller till och med säkrare att använda en smarttelefon för kontaktlösa betalningar jämfört med ett kontaktlöst kort. För att undersöka detta, gjordes en omfattande litteraturstudie och en enkätundersökning. Resultatet av examensarbetet visade på att det fanns olika typer av hot och sårbarheter som exempelvis avlyssning, modifikation och korruption av data, reläattacker, skadlig applikation och programvara, svag autentisering och manipulation av applikationer. Det fanns även flertalet aspekter som påverkade hur väl dessa hot kunde utföras, bland annat tokenisering, kryptering men även det korta avståndet som krävs och social ingenjörskonst. Det upptäcktes även att attackytan skiljde sig mellan metoderna. Smarttelefonen hade flertalet hot och sårbarheter som ofta baseras på att det finns ett användargränssnitt, att enheten har ett annat användningsområde, och exempelvis skadlig programvara och ”rootade” enheter. När en enhet är ”rootad” betyder det att användaren får en annan typ av åtkomstkontroll. Enkätundersökningen visade att ungefär hälften av deltagarna kan tänka sig använda smarttelefonen i framtiden för att utföra kontaktlösa betalningar. / To pay with a card is standardized today, but something that is also very common is to pay contactless. This is possible to do with a contactless card or with a smartphone. The technology that makes this possible is Near Field Communication. This thesis examines how the security in these payment methods is structured, which security issues exists but also how the use may look in the future. The thesis also includes to investigate if it is as safe or even safer to use a smartphone for contactless payments compared to a contactless card. To investigate this, an extensive literature study and a questionnaire survey was conducted. The results of the thesis showed that there were different types of threats and vulnerabilities such as eavesdropping, data modification, data corruption, relay-attacks but also malicious application and software, weak authentication, and manipulation of applications. However, there were also several aspects that affected how well these threats could be carried out, including tokenization, encryption but also the short distance required and social engineering. It was also discovered that the attack surface differed between the two methods. The smartphone had several threats and vulnerabilities many of them existed since there is a user interface, and that the device is used in other ways. For example, malware and “rooted” devices, when a device is “rooted” it means that the user gets another type of access control for the device. The survey showed that about half of the participants may be willing to use a smartphone in the future to make contactless payments.

Two classes of carbon nanomaterials—carbon nanotubes and graphene—have promoted the advancement of nanoelectronics, quantum computing, chemical sensing and storage, thermal management, and optoelectronic components. Studies of the thermal radiative properties of carbon nanotube thin film arrays and simple graphene hybrid structures reveal some of the most exciting characteristic electromagnetic interactions of an unusual sort of material, called hyperbolic metamaterials. The features and results on these materials in the context of both far-field and near-field radiation are presented in this dissertation. Due to the optically dark nature of pyrolytic carbon in the wavelength range from visible to infrared, it has been suggested vertically aligned carbon nanotube (VACNT) coatings may serve as effective radiative absorbers. The spectral optical constants of VACNT are modeled using the effective medium theory (EMT), which is based on the anisotropic permittivity components of graphite. The effects of other EMT parameters such as volume filling ratio and local filament alignment factor are explored. Low reflectance and high absorptance are observed up to the far-infrared and wide range of oblique incidence angles. The radiative properties of tilt-aligned carbon nanotube (TACNT) thin films are illustrated. Energy streamlines by tracing the Poynting vectors are used to show a self-collimation effect within the TACNT thin films, meaning infrared light can be transmitted along the axes of CNT filaments. Graphene, a single layer sheet of carbon atoms, produces variable conductance in the terahertz frequency regime by tailoring the applied voltage gating or doping. Periodically embedding between dielectric spacers, the substitution of graphene provides low radiative attenuation compared to traditional metal-dielectric multilayers. The hyperbolic nature, namely negative angle of refraction, is tested on the graphene-dielectric multilayers imposed with varying levels of doping. EMT should be valid for graphene-dielectric multilayers due to the nanometers-thick layers compared to the characteristic wavelength of infrared light. For metal- or semiconductor-dielectric multilayers with thicker or lossier layers, EMT may not hold. The validity of EMT for these multilayers is better understood by comparing against the radiative properties determined by layered medium optics. When bodies of different temperatures are separated by a nanometers-size vacuum gap, thermal radiation is enhanced several-fold over that of blackbodies. This phenomenon can be used to develop more efficient thermophotovoltaic devices. Due to their hyperbolic nature, VACNT and graphite are demonstrated to further increase evanescent wave tunneling. The heat flux between these materials separated by vacuum gaps smaller than a micron is vastly improved over traditional semiconductor materials. A hybrid structure composed of VACNT substrates covered by doped graphene is analyzed and is shown to further improve the heat flux, due to the surface plasmon polariton coupling between the graphene sheets.

This thesis focuses on the application of electromagnetic inverse source techniques to characterize antennas using phaseless (amplitude-only) near-field (NF) measurement data. Removing the need to measure phase reduces the overall cost of the measurement apparatus since simple power meters can be used instead of expensive vector network analyzers. It has also been shown in the literature that a phaseless approach can improve the accuracy of the calculated far-field (FF) pattern in the presence of probe positioning errors compared to the amplitude-and-phase approach. A brief discussion on the state-of-the-art methods for characterizing antennas using phaseless near-field measurement data is presented. Two general approaches used most often to perform near-field to far-field (NF-FF) transformations, namely modal expansion and source reconstruction, are explained in detail for scenarios with and without phase information. A phaseless source reconstruction method (SRM) is the primary focus of this work. The SRM is an application of an electromagnetic inverse source technique and therefore, the complexities of solving the associated ill-posed inverse source problem are discussed. The application of the SRM to spherical and planar measurement geometries are presented along with the concerns regarding regularization resulting from discretizing the ill-posed system. A multiplicative regularization (MR) scheme originally developed for inverse scattering is adapted to suit the nonlinear cost functional for the phaseless planar measurement case and the mathematical framework is derived in detail. The resulting MR-SRM is fully automated and incorporates adaptive regularization. The developed algorithms are evaluated using several examples with synthetic phaseless NF data demonstrating the benefits and limitations of the source reconstruction method and the multiplicative regularization scheme. The application of the SRM to antenna diagnostics using phaseless NF data is also shown. Finally, the developed planar algorithms are tested with experimentally collected phaseless measurement data to demonstrate their potential as suitable antenna characterization techniques that can be of interest to the antenna measurement community. / October 2016

L’objectif de cette thèse est le développement des détecteurs pour la microscopie champproche électromagnétique pour deux domaines fréquentiels. Pour le domaine des microondesnous présentons des micro-antennes non conventionnelles basées sur un guidagecoplanaire et l’effet de pointe. Nous pr´esentons les différentes étapes de la conceptionet de la réalisation avec les techniques de micro-fabrication. L’évaluation de leur performancea été obtenue avec une confrontation des résultats de mesure et de cartographie surdes éléments passifs et ceux d’une modélisation d’intégration finie. Pour le domaine desTérahertz, nous avons réalisé des micro-bolométres à température ambiante. Dans le butd’améliorer l’absorption de ces d´etecteurs, leur conception a été basée sur l’étude théoriquede l’absorption d’une onde électromagnétique en incidence normale sur un empilement descouches métalliques et diélectrique. Deux versions ont été réalisées et caractérisées é l’aidedes sources électroniques qui peuvent atteindre 1, 1 THz en continue. Les performancesde ces d´etecteurs en termes de bruit, de sensibilit´e et de temps de r´eponse sont mises enexergue. / The objective of this thesis is the development of detectors for near-field microscopy fortwo electromagnetic frequency domains. For microwave domain we present unconventionalmicro-antennas based on coplanar line and point effect. We present the different stages ofthe design and implementation with micro-fabrication technique. The evaluation of theirperformance was obtained with a comparison of measurement results and mapping ofpassive elements and those of a model of finite integration. For the THz domain, we performedroom temperature micro-bolometers. In order to improve the absorption of thesedetectors, their design was based on the theoretical study of the absorption of an electromagneticwave normally incident on a stack of metal and dielectric layers. Two versionswere prepared and characterized using electronic sources that can reach continuous 1,1THz. The performance of these detectors in terms of noise, sensitivity and time responseare highlighted.

Dans ce travail, nous exposons une méthode basée sur la détection localisée en couplage capacitif de la composante électrique du signal RMN via des micro/nano sondes spécifiquement développées. Dans la première étape de ce travail nous avons utilisé des NEMS à base de nanotube de carbone pour réaliser une détection du signal RMN à l'échelle nanométrique. En effet, grâce à un couplage électromécanique, nous avons caractérisé ces systèmes en émission de champ, déterminé expérimentalement leur fréquence de résonance et montré qu'ils sont capables de détecter un signal radiofréquence. Pour utiliser ces dispositifs en RMN, l'adaptation du champ statique B0 de l'aimant pour atteindre la valeur de la fréquence de Larmor d'un atome est nécessaire. L'excitation locale autour de ces systèmes permettra une caractérisation complète et fiable. Pour mettre en place cette excitation localisée, nous avons choisi, dans la deuxième étape de cette thèse, une sonde locale de champ électromagnétique à l'échelle micrométrique. D'abord, nous présentons des simulations autour de la microsonde, décrivant la propagation des champs électrique et magnétique injectée par la microsonde. Nous avons caractérisé la microsonde en mode collection. Nous montrons une décroissance de l'intensité du signal RMN, en fonction de la distance. Nous avons observé et modélisé démontrant ainsi que La microsonde est capable de détecter localement un signal RMN tandis que la bobine capte de façon globale. Nous présentons les premières expériences de l'utilisation de la microsonde en mode émission. Ces mesures nous fournissent un modèle qui décrit une excitation inhomogène, dûe à l'émission locale de la puissance (décroissance exponentielle de la puissance), proche de la microsonde. Une distribution des angles de basculement est répartie d'une façon inhomogène induisant une distribution des intensités du signal RMN autour de la microsonde. À la fin de cette thèse, nous avons réalisé deux expériences comme applications directes suite des études sur la caractérisation de la microsonde. La première consiste à imager un volume d'eau placé dans un bain d'huile de silicone. L'image est obtenue en déplaçant mécaniquement la microsonde et en réalisant pour chaque point une mesure de spectroscopie localisée. Dans la deuxième expérience, la microsonde est utilisée pour injecter dans ce volume d'eau des impulsions électromagnétiques et détecte à la suite le signal RMN. Notre étude sur la caractérisation de l'émission locale par une microsonde et la détection du signal radiofréquence par un NEMS à base de NTC, nous permet de proposer un nouveau type de dispositifs capable de détecter un signal RMN. / In this work, we explain our method based on the detection localized capacitive coupling of the electric component of the NMR signal via micro/nano probes specifically developeds. In the first stage of this work we use NEMS based on carbon nanotube to achieve a detection of the NMR signal at the nanoscale. Because of an electromechanical coupling, we characterize these systems in field emission, and we determine experimentally their resonance frequency and shown that they are able to detect a radio signal. To use these devices in NMR, it is necessary to adapt the value of the static field B0 of the magnet to reach the value of the Larmor frequency. We found that a local excitement around these systems gives them a reliable characterization, to avoid disrupting the parasite measurements. To implement this localized excitation, we choose a micro-probe (coaxial cable). First, we presente simulations, describing the propagation of electric and magnetic fields transmitted by the microprobe. After we characterize in collection mode the microprobe. This study shows us a decrease of the NMR signal as a function as distance. This proves that the microprobe is able to detect an NMR signal in near field, while the coil picks up globally. We characterize the microprobe in the transmit mode . These measurements provide us with a model that describes an inhomogeneous excitation of nuclei, due to the emission of power in vicinity of the microprobe. An inhomogeneous distribution of tilt angles induces an inhomogeneous distribution of the NMR signal around the microprobe. At the end of this thesis, we conducte two applications such as direct studies on the characterization of the microprobe. The first consist to image a small volume of water placed in silicone oil sample. The image obtained by mechanically moving of the microprobe and making a localized spectroscopy. In the second experiment, the microprobe injected into this volume and detects after the NMR signal. Finally, the characterization in transmit mode of the microprobe allows us to better understand the phenomenon of the trasmission of electromagnetic waves to excite the spins of the nuclei in vicinity of the NEMS based on CNT. The latter being used as NMR probe at the nanoscale, to detect a NMR signal.

A pattern-reconfigurable, low-profile, efficient, electrically small, near-field resonant parasitic (NFRP), Huygens source antenna is presented. The design incorporates both electric and magnetic NFRP elements. The electric ones are made reconfigurable by the inclusion of a set of p-i-n diodes. By arranging these electric and magnetic NFRP elements properly, a set of three Huygens sources are attained, each covering a 120 degrees sector. Pattern reconfigurability is obtained by switching the diodes on or off; it encompasses the entire 360 degrees azimuth range. A prototype was fabricated and tested. The numerical and experimental studies are in good agreement. The experimental results indicate that in each of its instantaneous states at f(0) = 1.564 GHz, the antenna provides uniform peak realized gains, front-toback ratios, and radiation efficiencies, respectively, as high as 3.55 dBi, 17.5 dB, and 84.9%, even though it is electrically small: ka = 0.92, and low profile: 0.05 lambda(0).

Diese Arbeit beschreibt eine ausfŸhrliche Untersuchung der physikalischen Eigenschaften von Mikrokugelresonatoren aus Quarzglas. Diese Resonatoren unterstŸtzen sogennante whispering-gallery Moden (WGM), die GŸten so hoch bis 109 bieten. Als experimentelle Hilfsmittel wurden ein Nahfeld- und ein Konfokalmikroskop benutzt, um die Struktur der Moden bezŸglich der Topographie des Resonators eindeutig zu identifizieren, oder um einzelne Quantenemitter zu detektieren und anzuregen. Die resonante †berhšhung des elektromagnetischen Feldes in den Moden des Resonators wurde ausgenutzt, um stimulierte Raman-Streuung mit extrem niedrigem Schwellenwert im Quarzglas zu beobachten. Ein Rekordschwellenwert von 4.5 Mikrowatts wurde gemessen. Mittels einer Nahfeldsonde wurde die Modenstruktur des Mikro-Ramanlasers gemessen. Mikroresonatoren stellen einen Grundbaustein der Resonator-Quantenelektrodynamik dar. In dieser Arbeit wurde die Kopplung von einem einzelnen strahlenden Dipol an die WGM sowohl theoretisch als auch experimentell untersucht. Die kontrollierte Kopplung von einem einzelnen Nanoteilchen an die WGM eines Mikrokugelresonators wurde nachgewiesen. Erste Ergebnisse in der Kopplung eines einzelnen Emitters an die Moden des Resonators wurden erzielt. Die resonante Wechselwirkung mit Resonatormoden wurde ausgenutzt, um den Photonentransfer zwischen zwei Nanoteilchen dramatisch zu verstŠrken. Schlie§lich wurde die bislang unbeachtete Analogie zwischen dem Quantensystem eines einzelnen Emitters in Wechselwirkung mit einer einzelnen Resonatormode und dem klassischen System zweier gekoppelten Moden experimentell untersucht. Es wurde bewiesen, wie die aus der Resonatorquantenelektrodynamik bekannten Kopplungsregime der starken und schwachen Kopplung in Analogie auch an einem klassischen System beobachtet werden kšnnen. Der †bergang von schwacher zu starker Kopplung wurde beobachtet, und bislang gemessene unerwartet hohe Kopplungsraten konnten einfach erklŠrt werden. / This work presents an extensive study of the physical properties of silica microsphere resonators, which support whispering-gallery modes (WGMs). These modes feature Q-factors as high as 109 corresponding to a finesse of 3 millions for spheres with a diameter of about 80 micrometers. These are to date among the highest available Q-factors, leading to cavity lifetimes of up to few microseconds. A near-field microscope and a confocal microscope are used as tools to unequivocally identify the mode structure related to the sphere topography, and for excitation and detection of single quantum emitters. The high field enhancement of the cavity modes is exploited to observe ultra-low threshold stimulated Raman scattering in silica glass. A record ultra-low threshold of 4.5 microwatts was recorded. The mode structure of the laser is investigated by means of a near-field probe, and the interaction of the probe itself with the lasing properties is investigated in a systematic way. Microcavities also one of the building blocks of Cavity QED. Here, the coupling of a radiative dipole to the whispering-gallery modes has been studied both theoretically and experimentally. The controlled coupling of a single nanoparticle to the WGMs is demonstrated, and first results in coupling a single quantum emitter to the modes of a microsphere are reported. The resonant interaction with these modes is exploited to enhance photon exchange between two nanoparticles. Finally a novel analogy between a system composed of a single atom interacting with one cavity mode on one side and intramodal coupling in microsphere resonators induced by a near-field probe on the other side is presented and experimentally explored. The induced coupling regimes reflect the different regimes of weak and strong coupling typical of Cavity QED. The transition between the two coupling regimes is observed, and a previously observed unexpectedly large coupling rate is explained.

Diese Arbeit leistet einen Beitrag zum Verständnis optischer Anregungen in metallischen Nanostrukturen. Am Beispiel ausgewählter Strukturen werden experimentell die Dynamik dieser Anregungen mit Femtosekunden-Zeitauflösung und ihre elektromagnetischen Moden auf der Nanometer-Längenskala untersucht. Anhand winkel- und zeitaufgelöster Transmissionsexperimente an metallischen Dünnfilmgittern wird gezeigt, dass resonante Oberflächenplasmon-Polaritonen (OPPen) wesentlich die optischen Eigenschaften dieser Strukturen beeinflussen. Die Lebensdauer solcher Anregungen wird ermittelt und damit nachgewiesen, dass Kopplungen zwischen OPP-Resonanzen drastische Lebensdauer-Modifikationen zur Folge haben. In einem eigens konstruierten, spektral auflösenden optischen Nahfeldmikroskop werden die elektromagnetischen Feldverteilungen der OPPen direkt abgebildet. Derartige Experimente erlauben erstmals eine Zuordnung der räumlichen Moden zur zeitlichen Dynamik verschiedener OPP-Resonanzen. Diese Erkenntnisse ermöglichen zudem eine Interpretation des nahfeldmikroskopischen Bildkontrasts bezüglich der Beiträge verschiedener vektorieller Komponenten des optischen Nahfeldes. Die selektive Abbildung unterschiedlicher elektrischer und magnetischer Feldkomponenten in Abhängigkeit vom Sondentyp wird demonstriert. Darüberhinaus wird die OPP-Erzeugung in einem Gitter auf dem Schaft einer Nahfeldspitze ausgenutzt, um propagierende OPPen im Apex zu konzentrieren. Ein weiterer Teil der Arbeit nutzt elektrische Feldüberhöhungen an scharfen Metallspitzen für die lokalisierte Erzeugung nichtlinearer optischer Signale. Die Beobachtung intensiver Multiphoton-Elektronenemission nach Femtosekundenanregung stellt ein zentrales Ergebnis dar. Dieser Prozess wird umfangreich charakterisiert und findet seine erste Anwendung in einer neuartigen Rastersondentechnik, in der die örtlich variierende Elektronenemission der Bildgebung dient. / This thesis contributes to the understanding of optical excitations in metallic nanostructures. In experiments on selected model structures, the dynamics of these excitations and their electromagnetic spatial modes are investigated with femtosecond temporal and nanometer spatial resolution, respectively. Angle- and time-resolved transmission experiments on metallic thin film gratings demonstrate the dominant role resonant surface plasmon polaritons (SPPs) play in the optical properties of such structures. The lifetimes of these excitations are determined, and it is shown that coherent couplings among SPP-resonances result in drastic lifetime modifications. The spatial SPP mode profiles are imaged using a custom-built near-field optical microscope. The experiments reveal a direct correlation between the spatial mode structure and the dynamics of different SPP resonances. These findings allow for an interpretation of the near-field optical image contrast in terms of the contributions of different vectorial components of the electromagnetic near-field. A selective imaging of different electric and magnetic field components is demonstrated for various types of near-field probes. Furthermore, the excitation of SPPs in periodic structures is employed in a novel type of near-field tip. The resonant excitation of SPPs in a nanofabricated grating on the shaft of a sharp metallic tip results in their concentration at the tip apex. The final part of the thesis highlights the importance of optical field enhancements for the local generation of nonlinear optical signals at the apex of sharp metallic tips. Specifically, the observation of intense multiphoton electron emission after femtosecond excitation is a major result. This process is thoroughly characterized, and a novel scanning microscopy application based on this effect is presented. In this technique, an image contrast with nanometer resolution arises from spatially varying electron emission rates.