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Esta tesis trata sobre el fascinante fenómeno de la transmisión extraordinaria a través de láminas metálicas nonoestructuradas periódicamente con aperturas al corte. Un efecto relacionado con la excitación de un tipo de ondas superficiales como son los plasmones de superficie. Además, en aquellas estructuras formadas por el apilamiento de dos o más láminas metálicas se consiguen nuevas funcionalidades, como magnetismo artificial que da lugar a resonancias magnéticas y por tanto la posibilidad de obtener un índice de refracción negativo.Mediante un estudio teórico y numérico se ha comprobado que este tipo de respuesta magnética efectiva se debe a la excitación de resonancias plasmónicas internas en la estructura. Obteniéndose, bajo incidencia normal, un índice de refracción efectivo negativo en la dirección de propagación en el caso de que dichas resonancias se produzcan en zonas del espectro donde se obtenga la permitividad negativa, conectando el mundo de la plasmónica con el de los metamateriales. Uno de los principales objetivos en el diseño de metamateriales es obtener un índice de refracción negativo en un gran ancho de banda. Sin embargo, este objetivo suele ser complicado de conseguier al basar los diseños en fenómenos resonantes. Es por ello que en esta tesis se ha propuesto un diseño basado en el apilamiento de estructuras fishnet con diferentes grosores de dieléctrico para conseguir aumentar el ancho de banda en el cual se consigue un índice negativo. Básicamente, la obtención de tal efecto se basa en la excitación de resonancias plasmónicas a distintas frecuencias al estar formada la celda unidad por difentes grososres de dieléctrico. La hibridación que se produce entre dichas resonancias permite aumentar el ancho de banda con índice negativo. Aunque la transmisión extraordinaria esta principalmente relacionada con excitación de plasmones de superficie, los resultados mostrados en la tesis demuestran que para el caso de láminas metálicas rodeadas por dieléctricos también se consigue transmisión extraordinaria debido a la adaptación de la luz incidente a los modos soportados por los medios dieléctricos siempre y cuando el metal se encuentre estructurado periódicamente. / Ortuño Molinero, R. (2012). Extraordinary Transmission Filtering Structures based on Plasmonic Metamaterials [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/14639 / Palancia

Light interaction with matter has long been an area of interest throughout history, spanning many fields of study. In recent decades, the investigation of light-matter interactions with nanostructures has become an intense area of research in the field of photonics. Metallic nanostructures, in particular, are of interest due to the interesting properties that arise when interacting with light. The properties are a result of the excitation of surface plasmons which are the collective oscillation of the conduction electrons in the metal. Since the conduction electrons can be thought of as harmonic oscillators, they are quantized in a similar fashion. Just as a photon is a quantum of oscillations of an electromagnetic field, the plasmon is a quantum of electron oscillations of a metal. There are three types of plasmons: 1. Bulk plasmons, also called volume plasmons, are longitudinal density fluctuations which propagate through a bulk metal with an eigenfrequency of �� called the plasma frequency. 2. Localized surface plasmons are non-propagating excitations of the conduction electrons of a metallic nanoparticle coupled to an electromagnetic field. 3. Surface plasmon polaritons are evanescent, dispersive propagating electromagnetic waves formed by a coupled state between a photon and the excitation of the surface plasmons. They propagate along the surface of a metal-dielectric interface with a broad spectrum of eigenfrequencies from � = 0 to � = ��⁄√2. iv Plasmonics is a subfield of photonics which focuses on the study of surface plasmons and the optical properties that result from light interacting with metal films and nanostructures on the deep subwavelength scale. In this thesis, plasmonic nanostructures are investigated for optical waveguides and other nanophotonic applications through computational simulations primarily base on electrodynamic theory. The theory was formulated by several key figures and established by James Clerk Maxwell after he published a set of relations which describe all classical electromagnetic phenomena, known as Maxwell’s equations. Using methods based on Maxwell’s equations, the optical properties of metallic nanostructures utilizing surface plasmons is explored. In Chapter 3, light propagation of bright and dark modes of a partially and fully illuminated silver nanorod is investigated for waveguide applications. Then, the origin of the Fano resonance line shape in the scattering spectra of a silver nanorod is investigated. Next, in Chapter 4, the reflection and transmission of a multilayer silver film is simulated to observe the effects of varying the dielectric media between the layers on light propagation. Building on the multilayer film work, metal-insulator-metal waveguides are explored by perforating holes in the bottom layer of a two layer a silver film to investigate the limits of subwavelength light trapping, confinement, and propagation. Lastly, in Chapter 5, the effect of surface plasmons on the propagation direction of electromagnetic wave around a spherical silver nanoparticle which shows an effective negative index of refraction is examined. In addition, light manipulation using a film of silver prisms with an effective negative index of refraction is also investigated. The silver prisms demonstrate v polarization selective propagation for waveguide and optical filter applications. These studies provide insight into plasmonic mechanisms utilized to overcome the diffraction limit of light. Through better understanding of how to manipulating light with plasmonic nanostructures, further advancements in nanophotonic technologies for applications such as extremely subwavelength waveguides, sensitive optical detection, optical filters, polarizers, beam splitters, optical data storage devices, high speed data transmission, and integrated subwavelength photonic circuits can be achieved.

I denna avhandling studeras elektromagnetisk vågutbredning i graderade materialkompositer med extraordinära egenskaper. Två sådana materialkompositsystem studeras särskilt, med hjälp av både analytiska och beräkningstekniska elektromagnetiska metoder. Det första systemet används för utvecklingen av en lovande icke-invasiv metod för cancerbehandling, som bygger på att tumören med insatta guldnanopartiklar värms upp med hjälp av mikrovågsstrålning. En vågledarstruktur föreslås bestående av ett tunt dielektriskt skikt med en kontinuerlig graderad materialövergång till dess omgivande material till vardera sidan av skiktet. Det tunna lagret består av cancervävnad med insatta guldnanopartiklar som drivs in i elektroforetisk svängning med hjälp av elektromagnetisk strålning. Analytiska lösningar för det givna vågledarproblemet erhålls, vilket möjliggör beräkning av absorptionskoefficienterna endast inom det tunna skiktet, vilket är viktigt för bedömning av genomförbarheten av den tänkta medicinska tillämpningen. De dispersiva dielektriska modellerna som beskriver de elektromagnetiska egenskaperna hos de relevanta biologiska vävnaderna föreslås och diskuteras. Numeriska simuleringar gjorda i COMSOL Multiphysics är i utmärkt överensstämmelse med och validerar de analytiska resultaten. Det andra systemet involverar vågutbredning från ett högerhänt material till ett vänsterhänt metamaterial i fri rymd. De två materialen är impedansmatchade, vilket säkerställer ingen reflektion, och det graderade gränssnittet mellan dem beskrivs av en kontinuerlig funktion. Metamaterialkompositer med rumsligt varierande materialparametrar har fått ett ökande teoretiskt och experimentellt intresse de senaste två decennierna. De är användbara för ett antal tillämpningar, såsom transformationsoptik. I denna uppsats diskuteras egenskaperna hos vänsterhänta material. Fältlösningarna till det impedansmatchade graderade gränssnittet härleds, och en numerisk modell utvecklas i COMSOL. Resultaten bekräftar de extraordinära egenskaperna hos vänsterhänta material. / In this thesis, electromagnetic wave propagation in graded material composites with extraordinary properties are studied. Two such material composite systems are studied in particular, using both analytical and computational electromagnetic methods. The first system is used for the development of a promising non-invasive method of cancer treatment based on heating the tumors with inserted gold nanoparticles by means of microwave radiation. A waveguide structure is proposed consisting of a thin dielectric layer with a continuous graded material transition to its surrounding materials to either side of the layer. The thin layer consists of cancer tissue with inserted gold nanoparticles that are driven into electrophoretic oscillation by means of electromagnetic radiation. Analytical solutions for the given waveguide problem are obtained, allowing the calculation of the absorption coefficients within the thin layer only, which is important for assessment of the feasibility of the envisioned medical application. The dispersive dielectric models describing the electromagnetic properties of the relevant biological tissues are proposed and discussed. Numerical simulations done in COMSOL Multiphysics are in excellent agreement with and validate the analytical results. The second system involves wave propagation from a right-handed material to a left-handed metamaterial in an open boundary system. The two materials are impedance-matched, thus ensuring no reflection, and the graded interface between them is described by a continuous function. Metamaterial composites with spatially varying material parameters have been given an increasing theoretical and experimental interest the last two decades. They are useful for a number of applications, such as transformation optics. In this thesis, the properties of left-handed media are discussed. The field solutions to the impedance-matched graded interface are derived, and a numerical model is developed in COMSOL. The results confirm the extraordinary properties of left-handed media. / <p>QC 20221129</p>