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La plasmónica es la ciencia que estudia la interacción, a escala nanométrica, entre la luz y los electrones libres de los metales, dando lugar a la propagación de ondas altamente confinadas a su superficie. La plasmónica tiene multitud de aplicaciones en nanotecnología, como son el sensado biológico y químico, espectroscopía, nanolitografía, comunicaciones de banda ultra ancha integradas en chips, nanoantenas para luz, filtrado, y manipulación de señales ópticas, entre muchas otras. Una de las aplicaciones más novedosas es la creación de metamateriales: estructuras artificiales diseñadas para controlar la propagación de la luz, con aplicaciones fascinantes como la lente perfecta o la capa de invisibilidad. La plasmónica y los metamateriales están al frente de la investigación actual en fotónica, gracias al auge de la nanotecnología y la nanociencia, que abre las puertas a una gran cantidad de nuevas aplicaciones. Esta tesis, desarrollada en el Centro de Tecnología Nanofotónica de Valencia de la UPV, en colaboración con la University of Pennsylvania y King's College London, trata de aportar nuevas ideas, estructuras y dispositivos a los campos de la plasmónica y los metamateriales, tratando de realizar su fabricación y medida experimental cuando sea posible. La tesis no se ciñe a una única aplicación o dispositivo, sino que realiza una extensiva exploración de los diversos sub-campos de la plasmónica en busca de fenómenos novedosos. Los resultados descritos son los siguientes: En el campo de los metamateriales de índice negativo se presentan dos estructuras: nanocables en forma de U, y guías coaxiales plasmónicas. En el campo del sensado plasmónico se presenta el diseño y la prueba experimental de un sensor se sustancias químicas de altas prestaciones con nanocruces metálicas. También se detallan teóricamente: un novedoso dispositivo para luz lenta e inversión temporal de pulsos basada en metamateriales y cristales fotónicos, un metamaterial para conversión de polarización sintonizable mediante pérdidas, un análogo plasmónico al efecto de levitación Meissner en superconductores y un método de reducción de pérdidas en guías plasmónicas mediante interferencia en guías multimodo. Por último se presenta teórica y experimentalmente un nuevo ejemplo fundamental de interferencia de campo cercano, logrando la excitación unidireccional de modos fotónicos ---ya sean plasmónicos o no--- mediante los campos cercanos de un dipolo circularmente polarizado. / Rodríguez Fortuño, FJ. (2013). Design and implementation of plasmonic metamaterials and devices [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/31207 / Premios Extraordinarios de tesis doctorales

Thesis (DEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2009. / The Finite Element Method (FEM) as applied to Computational Electromagnetics (CEM), can beused to solve a large class of Electromagnetics problems with high accuracy and good computational efficiency. For solving wide-band problems time domain solutions are often preferred; while time domain FEM methods are feasible, the Finite Difference Time Domain (FDTD) method is more commonly applied. The FDTD is popular both for its efficiency and its simplicity. The efficiency of the FDTD stems from the fact that it is both explicit (i.e. no matrices need to be solved) and second order accurate in both time and space. The FDTD has limitations when dealing with certain geometrical shapes and when electrically large structures are analysed. The former limitation is caused by stair-casing in the geometrical modelling, the latter by accumulated dispersion error throughout the mesh. The FEM can be seen as a general mathematical framework describing families of concrete numerical method implementations; in fact the FDTD can be described as a particular FETD (Finite Element Time Domain) method. To date the most commonly described FETD CEM methods make use of unstructured, conforming meshes and implicit time stepping schemes. Such meshes deal well with complex geometries while implicit time stepping is required for practical numerical stability. Compared to the FDTD, these methods have the advantages of computational efficiency when dealing with complex geometries and the conceptually straight forward extension to higher orders of accuracy. On the downside, they are much more complicated to implement and less computationally efficient when dealing with regular geometries. The FDTD and implicit FETD have been combined in an implicit/explicit hybrid. By using the implicit FETD in regions of complex geometry and the FDTD elsewhere the advantages of both are combined. However, previous work only addressed mixed first order (i.e. second order accurate) methods. For electrically large problems or when very accurate solutions are required, higher order methods are attractive. In this thesis a novel higher order implicit/explicit FETD method of arbitrary order in space is presented. A higher order explicit FETD method is implemented using Gauss-Lobatto lumping on regular Cartesian hexahedra with central differencing in time applied to a coupled Maxwell’s equation FEM formulation. This can be seen as a spatially higher order generalisation of the FDTD. A convolution-free perfectly matched layer (PML) method is adapted from the FDTD literature to provide mesh termination. A curl conforming hybrid mesh allowing the interconnection of arbitrary order tetrahedra and hexahedra without using intermediate pyramidal or prismatic elements is presented. An unconditionally stable implicit FETD method is implemented using Newmark-Beta time integration and the standard curl-curl FEM formulation. The implicit/explicit hybrid is constructed on the hybrid hexahedral/tetrahedral mesh using the equivalence between the coupled Maxwell’s formulation with central differences and the Newmark-Beta method with Beta = 0 and the element-wise implicitness method. The accuracy and efficiency of this hybrid is numerically demonstrated using several test-problems.

Thesis (PhD)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: The parallel FDTD method as used in computational electromagnetics is implemented on a variety of different high performance computing platforms. These parallel FDTD implementations have regularly been compared in terms of performance or purchase cost, but very little systematic consideration has been given to how much effort has been used to create the parallel FDTD for a specific computing architecture. The deployment effort for these platforms has changed dramatically with time, the deployment time span used to create FDTD implementations in 1980 ranging from months, to the contemporary scenario where parallel FDTD methods can be implemented on a supercomputer in a matter of hours. This thesis compares the effort required to deploy the parallel FDTD on selected computing platforms from the constituents that make up the deployment effort, such as coding complexity and time of coding. It uses the deployment and performance of the serial FDTD method on a single personal computer as a benchmark and examines the deployments of the parallel FDTD using different parallelisation techniques. These FDTD deployments are then analysed and compared against one another in order to determine the common characteristics between the FDTD implementations on various computing platforms with differing parallelisation techniques. Although subjective in some instances, these characteristics are quantified and compared in tabular form, by using the research information created by the parallel FDTD implementations. The deployment effort is of interest to scientists and engineers considering the creation or purchase of an FDTD-like solution on a high performance computing platform. Although the FDTD method has been considered to be a brute force approach to solving computational electromagnetic problems in the past, this was very probably a factor of the relatively weak computing platforms which took very long periods to process small model sizes. This thesis will describe the current implementations of the parallel FDTD method, made up of a combination of several techniques. These techniques can be easily deployed in a relatively quick time frame on computing architectures ranging from IBM’s Bluegene/P to the amalgamation of multicore processor and graphics processing unit, known as an accelerated processing unit. / AFRIKAANSE OPSOMMING: Die parallel Eindige Verskil Tyd Domein (Eng: FDTD) metode word gebruik in numeriese elektromagnetika en kan op verskeie hoë werkverrigting rekenaars geïmplementeer word. Hierdie parallele FDTD implementasies word gereeld in terme van werkverrigting of aankoop koste vergelyk, maar word bitter min sistematies oorweeg in terme van die hoeveelheid moeite wat dit geverg het om die parallele FDTD vir 'n spesifieke rekenaar argitektuur te skep. Mettertyd het die moeite om die platforms te ontplooi dramaties verander, in the 1980's het die ontplooings tyd tipies maande beloop waarteenoor dit vandag binne 'n kwessie van ure gedoen kan word. Hierdie tesis vergelyk die inspanning wat nodig is om die parallelle FDTD op geselekteerde rekenaar platforms te ontplooi deur te kyk na faktore soos die kompleksiteit van kodering en die tyd wat dit vat om 'n kode te implementeer. Die werkverrigting van die serie FDTD metode, geïmplementeer op 'n enkele persoonlike rekenaar word gebruik as 'n maatstaf om die ontplooing van die parallel FDTD met verskeie parallelisasie tegnieke te evalueer. Deur hierdie FDTD ontplooiings met verskillende parallelisasie tegnieke te ontleed en te vergelyk word die gemeenskaplike eienskappe bepaal vir verskeie rekenaar platforms. Alhoewel sommige gevalle subjektief is, is hierdie eienskappe gekwantifiseer en vergelyk in tabelvorm deur gebruik te maak van die navorsings inligting geskep deur die parallel FDTD implementasies. Die ontplooiings moeite is belangrik vir wetenskaplikes en ingenieurs wat moet besluit tussen die ontwikkeling of aankoop van 'n FDTD tipe oplossing op 'n höe werkverrigting rekenaar. Hoewel die FDTD metode in die verlede beskou was as 'n brute krag benadering tot die oplossing van elektromagnetiese probleme was dit waarskynlik weens die relatiewe swak rekenaar platforms wat lank gevat het om klein modelle te verwerk. Hierdie tesis beskryf die moderne implementering van die parallele FDTD metode, bestaande uit 'n kombinasie van verskeie tegnieke. Hierdie tegnieke kan maklik in 'n relatiewe kort tydsbestek ontplooi word op rekenaar argitekture wat wissel van IBM se BlueGene / P tot die samesmelting van multikern verwerkers en grafiese verwerkings eenhede, beter bekend as 'n versnelde verwerkings eenheid.

Thesis (PhD (Electrical and Electronic Engineering))--University of Stellenbosch, 2011. / ENGLISH ABSTRACT: This work considers the acceleration of matrix-based computational electromagnetic (CEM) techniques using graphics processing units (GPUs). These massively parallel processors have gained much support since late 2006, with software tools such as CUDA and OpenCL greatly simplifying the process of harnessing the computational power of these devices. As with any advances in computation, the use of these devices enables the modelling of more complex problems, which in turn should give rise to better solutions to a number of global challenges faced at present. For the purpose of this dissertation, CUDA is used in an investigation of the acceleration of two methods in CEM that are used to tackle a variety of problems. The first of these is the Method of Moments (MOM) which is typically used to model radiation and scattering problems, with the latter begin considered here. For the CUDA acceleration of the MOM presented here, the assembly and subsequent solution of the matrix equation associated with the method are considered. This is done for both single and double precision oating point matrices. For the solution of the matrix equation, general dense linear algebra techniques are used, which allow for the use of a vast expanse of existing knowledge on the subject. This also means that implementations developed here along with the results presented are immediately applicable to the same wide array of applications where these methods are employed. Both the assembly and solution of the matrix equation implementations presented result in signi cant speedups over multi-core CPU implementations, with speedups of up to 300x and 10x, respectively, being measured. The implementations presented also overcome one of the major limitations in the use of GPUs as accelerators (that of limited memory capacity) with problems up to 16 times larger than would normally be possible being solved. The second matrix-based technique considered is the Finite Element Method (FEM), which allows for the accurate modelling of complex geometric structures including non-uniform dielectric and magnetic properties of materials, and is particularly well suited to handling bounded structures such as waveguide. In this work the CUDA acceleration of the cutoff and dispersion analysis of three waveguide configurations is presented. The modelling of these problems using an open-source software package, FEniCS, is also discussed. Once again, the problem can be approached from a linear algebra perspective, with the formulation in this case resulting in a generalised eigenvalue (GEV) problem. For the problems considered, a total solution speedup of up to 7x is measured for the solution of the generalised eigenvalue problem, with up to 22x being attained for the solution of the standard eigenvalue problem that forms part of the GEV problem. / AFRIKAANSE OPSOMMING: In hierdie werkstuk word die versnelling van matriksmetodes in numeriese elektromagnetika (NEM) deur die gebruik van grafiese verwerkingseenhede (GVEe) oorweeg. Die gebruik van hierdie verwerkingseenhede is aansienlik vergemaklik in 2006 deur sagteware pakette soos CUDA en OpenCL. Hierdie toestelle, soos ander verbeterings in verwerkings vermoe, maak dit moontlik om meer komplekse probleme op te los. Hierdie stel wetenskaplikes weer in staat om globale uitdagings beter aan te pak. In hierdie proefskrif word CUDA gebruik om ondersoek in te stel na die versnelling van twee metodes in NEM, naamlik die Moment Metode (MOM) en die Eindige Element Metode (EEM). Die MOM word tipies gebruik om stralings- en weerkaatsingsprobleme op te los. Hier word slegs na die weerkaatsingsprobleme gekyk. CUDA word gebruik om die opstel van die MOM matriks en ook die daaropvolgende oplossing van die matriksvergelyking wat met die metode gepaard gaan te bespoedig. Algemene digte lineere algebra tegnieke word benut om die matriksvergelykings op te los. Dit stel die magdom bestaande kennis in die vagebied beskikbaar vir die oplossing, en gee ook aanleiding daartoe dat enige implementasies wat ontwikkel word en resultate wat verkry word ook betrekking het tot 'n wye verskeidenheid probleme wat die lineere algebra metodes gebruik. Daar is gevind dat beide die opstelling van die matriks en die oplossing van die matriksvergelyking aansienlik vinniger is as veelverwerker SVE implementasies. 'n Verselling van tot 300x en 10x onderkeidelik is gemeet vir die opstel en oplos fases. Die hoeveelheid geheue beskikbaar tot die GVE is een van die belangrike beperkinge vir die gebruik van GVEe vir groot probleme. Hierdie beperking word hierin oorkom en probleme wat selfs 16 keer groter is as die GVE se beskikbare geheue word geakkommodeer en suksesvol opgelos. Die Eindige Element Metode word op sy beurt gebruik om komplekse geometriee asook nieuniforme materiaaleienskappe te modelleer. Die EEM is ook baie geskik om begrensde strukture soos golfgeleiers te hanteer. Hier word CUDA gebruik of om die afsny- en dispersieanalise van drie gol eierkonfigurasies te versnel. Die implementasie van hierdie probleme word gedoen deur 'n versameling oopbronkode wat bekend staan as FEniCS, wat ook hierin bespreek word. Die probleme wat ontstaan in die EEM kan weereens vanaf 'n lineere algebra uitganspunt benader word. In hierdie geval lei die formulering tot 'n algemene eiewaardeprobleem. Vir die gol eier probleme wat ondersoek word is gevind dat die algemene eiewaardeprobleem met tot 7x versnel word. Die standaard eiewaardeprobleem wat 'n stap is in die oplossing van die algemene eiewaardeprobleem is met tot 22x versnel.

Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2007. / The finite element tearing and interconnect(FETI) domain decomposition(DD) method is investigated in terms of the 2D transverse electric(TEz) finite element method(FEM). The FETI is for the first time rigorously derived using the weighted residual framework from which important insights are gained. The FETI is used in a novel way to implement a total-/scattered field decomposition and is shown to give excellent results. The FETI is newly formulated for the time domain(FETI-TD), its feasibility is tested and it is further formulated and tested for implementation on a distributed computer architecture.

Cette thèse concerne la modélisation numérique de Chambres Réverbérantes à Brassage de Modes (CRBM). Cet outil est utilisé pour les tests en Compatibilité ElectroMagnétique (CEM) de systèmes électroniques variés. L'utilisation de modèles temporel, géométrique et électronique particuliers a été motivée en s'appuyant sur un maximun de paramètres réels. La prise en compte naturelle par la méthode des Volumes Finis dans le Domaine Temporel (VFDT) de géométries complexes autorise la modélisation conforme des équipements rencontrés en CRBM. L'intégration réaliste des pertes est assurée via un filtre temporel spécifique. Ces travaux ont permis de quantifier au mieux les effets de la dissipation numérique VFDT : une technique temporelle hybride Différences Finies/ Volumes Finis adaptée est ainsi proposée. Enfin, différentes améliorations numériques permettent d'optimiser les développements actuels des simulations temporelles en chambre réverbérante sont présentées.