De nos jours, la croissance du trafic d’informations entraine un développement technologique spectaculaire dans le domaine des télécommunications, qu'il s'agisse de réseau cellulaire, télévision, satellite, WIFI ou autres applications. Cette révolution a engendré d'énormes besoins et suscite une évolution technologique prodigieuse dans le domaine de la conception des antennes. Ces dernières se doivent de répondre aux différentes exigences, telles que la diminution de l’encombrement et des interférences électromagnétiques, la robustesse à l’environnement proche, l'augmentation du gain, l'élargissement de la bande passante, l’intelligence, etc. Les travaux menés dans cette thèse s’orientent surtout vers la conception de nouvelles topologies d’antennes simples, à faible encombrement, intelligentes, insensibles à l’environnement, large et ultra large bande… Notre intérêt s’est porté sur les antennes à résonateurs diélectriques (ARD). Dans le domaine de l’internet des objets, nous avons conçu et réalisé une antenne filtre, à base d’une jonction fente-résonateur diélectrique de forme rectangulaire en vue d’une intégration dans les dispositifs dédiés à ces applications. Pour des applications liées à la télémétrie, et plus précisément les compteurs intelligents, nous avons conçu et réalisé une antenne à base d’un résonateur diélectrique de forme cylindrique. Ces antennes intégrées dans des dispositifs où les sources de perturbations sont très présentes, ont montré une grande robustesse et une insensibilité à leur proche environnement. Par ailleurs, nous avons proposé deux nouvelles topologies d’antennes larges et ultra larges bandes. La première est un anneau cylindrique, constitué de quatre quartiers avec deux permittivités différentes. Un gap d’air a été introduit séparant le résonateur en deux. Cette structure innovante, confère à notre antenne une large bande et des caractéristiques de rayonnement stables. Cette antenne a servi comme élément de base pour proposer une antenne réseau agile en diagramme de rayonnement. La seconde, est dans la continuité de la première structure pour laquelle nous avons adopté une nouvelle technique d’alimentation ainsi qu’une diminution des dimensions du plan de masse. L’antenne obtenue propose alors des caractéristiques adaptées à des applications ultra large bande. / Nowadays, the constant increase of information traffic leads to a spectacular technological development in the field of telecommunications, whether it is cellular network, television, satellite, WIFI or other applications. This revolution is creating new needs and is inspiring a phenomenal technological evolution in the field of antenna design. Modern antennas in fact must meet increasingly harder requirements in terms of compactness, electromagnetic interference reduction, robustness to environment, increased gain, broadband bandwidth, intelligence, etc. The work carried out in this thesis mainly focuses on the design of new simple antenna topologies of small size, intelligent, insensitive to environment, broad and ultra-wide band. In particular, our interest focused on antennas based on Dielectric Resonators (DRs). In the field of the Internet of Things (IoT), we designed and realized a high-Q filter antenna based on a slot loaded rectangular dielectric resonator suitable for integration in compact IoT devices. We also designed and characterized an antenna based on a cylindrical shaped dielectric resonator (CDR). This antenna, which has been proposed to be integrated in smart meter devices, where interference sources are very present, has shown a great robustness to the surrounding environment. In addition, we proposed two new broadband and ultra-wideband antenna topologies. The first one is based on a cylindrical ring resonator, divided in four quarters characterized by two different permittivities. An air gap was inserted separating the resonator in two parts. This innovative structure gives our antenna a wide band behavior and stability in terms of radiation pattern. This structure has been used in an array configuration to achieve a reconfigurable radiation pattern. Starting from this work, the second antenna achieves an ultra-wideband behavior by adopting a new feeding technique as well as a reduced ground plane.

Optoplasmonic microtube cavities, the combination of dielectric microcavities and noble metal layers, allow for the interactions between photonic modes and surface plasmons, leading to several novel phenomena and promising applications. In this thesis, the hybrid modes with different plasmon-types of evanescent field in the optoplasmonic microtube cavities are discussed. The basic physical mechanism for the generation of plasmon-type field is comprehensively investigated based on an effective potential approach. In particular, when the cavity wall becomes ultra-thin, the plasmon-type field can be greatly enhanced, and the hybrid modes are identified as strong photon-plasmon hybrid modes which are experimentally demonstrated in the metal-coated rolled-up microtube cavities. By designing a metal nanocap onto microtube cavities, angle-dependent tuning of hybrid photon-plasmon modes are realized, in which TE and TM polarized modes exhibit inverse tuning trends due to the polarization match/mismatch. And a novel sensing scheme is proposed relying on the intensity ratio change of TE and TM modes instead of conventionally used mode shift. In addition, localized surface plasmon resonances coupled to resonant light is explored by designing a vertical metal nanogap on microtube cavities. Selective coupling of high-order axial modes is demonstrated depending on spatial-location of the metal nanogap. A modified quasi-potential well model based on perturbation theory is developed to explain the selective coupling mechanism. These researches systematically explore the design of optoplasmonic microtube cavities and the mechanism of photon-plasmon coupling therein, which provide a novel platform for the study of both fundamental and applied physics such as the enhanced light-matter interactions and label-free sensing.

This report collects selected outstanding scientific and technological results obtained within the frame of the European project "FLASiC" (Flash LAmp Supported Deposition of 3C-SiC) but also other work performed in adjacent fields. Goal of the project was the production of large-area epitaxial 3C-SiC layers grown on Si, where in an early stage of SiC deposition the SiC/Si interface is rigorously improved by energetic electromagnetic radiation from purpose-built flash lamp equipment developed at Forschungszentrum Rossendorf. Background of this work is the challenging task for areas like microelectronics, biotechnology, or biomedicine to meet the growing demands for high-quality electronic sensors to work at high temperatures and under extreme environmental conditions. First results in continuation of the project work – for example, the deposition of the topical semiconductor material zinc oxide (ZnO) on epitaxial 3C-SiC/Si layers – are reported too.

At the Forschungszentrum Rossendorf the build-up of the superconducting 1.3 GHz accelerator ELBE is still in progress. Furthermore a new sc photo injector (SRF gun) is under development, which should accelerate electrons up to 10 MeV at 1.3 GHz frequency. The use of electron accelerators is also more and more interesting for applications where the destructive potential of the electrons are used like sterilization of medical waste and medical products, food irradiation or decontamination of sewage. For these processes a high power is required to achieve a high product throughput in a plant. The aim is therefore to use beam powers of around 100 kW or more. Since the applications of electron accelerators in industrial environments are steadily increasing one can speculate about transferring the above named state of the arte technology to industrial electron accelerators. At the FZR a feasibility study of such a table top electron accelerator (TTE) has been performed to investigate its technical limits and marketabilitys.

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The presence of photonic band gap in an arbitrarily shaped photonic structure, particularly structures that are fabricated by exploiting rolled-up nanotechnology, can be understood from the density of optical states. In this thesis, the density of optical states and the local density of optical states in finite-sized photonic structures are calculated using the finite difference time domain method together with a parallelized message passing interface. With this approach, a software package suitable for high-performance computing on multi-platform was published under GNU GPL license. When light is guided to propagate along a rolled-up thin film, whispering gallery mode resonances can be formed in a microtubular structure. Dynamic probing and tuning via a plasmonic nanoparticle-coated glass tip are investigated to demonstrate the transition from dielectric-dielectric to dielectric-plasmonic coupling in the tubular microcavity. The competition of these two coupling mechanisms allow the tuning of the optical cavity modes towards lower and then higher energies in a single coupling system. Moreover, three dimensionally confined higher order axial modes can be selectively coupled and tuned by the glass tip due to their unique spatial distribution of the optical field along the tube axis. In addition, the interaction between sharp optical cavity modes and broad plasmonic modes supported by silver nanoparticles leads to the occurrence of Fano resonance. In particular, Fano resonances occurring at higher-order axial modes has been observed as well. The experimental results are supported by numerical simulations based on the finite difference time domain method. In photonic lattice structures, light propagation behavior can be influenced and defined by the photonic band structure. By designing the unit cell with glide mirror symmetry, topologically protected edge states operating in the visible spectral range have been proposed in two dimensional photonic crystals which can be made of feasible materials. Topological phenomena such as unidirectional waveguiding and/or effective zero refractive index are presented. In addition, a scheme to study topological phase transition in a single photonic crystal device is proposed and studied via unevenly stretching photonic lattice. Moreover, a new method is explored to distinguish the topological phase from the bulk modes. The research presented in this thesis concerns molding the flow of light in specially designed photonic devices for various potential applications. The software package can be used to design and investigate finite-sized photonic structures with an arbitrary shape, which is much faster in terms of computation than other reported techniques and software packages. The rolled-up microcavities can be employed to trap and store light in the way of whispering gallery mode resonances, and the resonant light can be tuned and modulated by a plasmonic nanoparticles-coated glass tip. This research is particularly interesting for optical signal processing, slowing light via Fano resonances, and high sensitive sensing. In addition, the topological photonic crystal design and examination scheme presented in this thesis provide a simplified yet more efficient way to obtain non-trivial topological phase from a tunable photonic crystal that can be verified not only by edge modes but also by bulk modes.:Bibliographic record 1 Abstract 1 LIST OF ABBREVIATIONS and Symbols 3 1 Introduction 9 1.1 Introduction and Motivation 9 1.2 Objectives 11 1.3 Organization of the thesis 12 2 Density of optical states in rolled-up photonic crystals and quasi crystals 15 2.1 Introduction 15 2.1.1 background 17 2.1.2 Infinitely extended ideal photonic crystal 17 2.2 Finite-sized photonic crystal, photonic quasicrystal, and arbitrary photonics structures 20 2.2.1 Numerical algorithm 25 2.2.2 Rolled-up photonic crystals and quasi crystals 30 2.3 Software package 33 2.3.1 Computational performance 33 2.3.2 FPS User interface 35 2.3.3 Detailed tutorial 37 2.3.4 Alternative rolled-up photonic crystals 47 2.3.5 Beyond 3D photonic crystals. 48 2.4 Conclusion 49 3 Rolled-up microesonator 51 3.1 Introduction 51 3.2 Rolled-up microresonators 52 4 Tip-assisted photon-plasmon coupling in three-dimensionally confined microtube cavities 57 4.1 Introduction 57 4.2 Tube and plasmonic particle preparation and characterization 60 4.3 Results and discussion 62 4.4 Axial mode tuning 64 4.5 Fano resonance 65 4.5.1 Background 65 4.5.2 Fano resonance in the tip assisted coupling setup 68 4.6 Conclusion 71 5 Topological photonics 73 5.1 Introduction and motivation 73 5.2 Topological phase transition point 77 5.2.1 Fundamental phase transition point 77 5.2.2 Zero refractive index material 79 5.3 Non-trivial topology in realistic materials 80 6 Topological phase transition in stretchable photonic crystals 85 6.1 Introduction and motivation 85 6.2 SSH model 88 6.3 Photonic crystal 91 6.4 Band structure and end modes of the photonic crystal 99 6.5 Conclusion 101 7 Summary and outlook 103 7.1 Summary 103 7.2 Outlook 104 Bibliography 111 List of figures 127 Publications 133 Acknowledgments 136 Selbständigkeitserklärung 137 Curriculum Vitae 138

The thesis discusses the dynamic electromagnetic field on periodic structures. The author focuses on three principal types of resonant structures, considering their application possibilities. In general, these types can be individually defined as follows: materials exhibiting a negative refractive index of the incident electromagnetic wave; structures with gradual changes in impedance, characterised by their usability as reflectionless surfaces; and periodic structures able to conveniently shape the magnetic field distribution. Materials of the third group within the above-shown short list facilitate the fabrication of magnetoinductive lenses for nuclear magnetic resonance. The presented analysis of the properties of periodic resonant structures is mainly based on numerical models utilising the finite element method, and this approach is combined with both the derivation of the corresponding analytical relations and an experimental measurement of the non-radiating component of the electromagnetic field. The thesis includes a physical description of the basic elements of periodic resonant structures. Physical properties of the elements were examined in detail via numerical analysis. In the course of the research, the data acquired through this analysis and the related experimental measurement enabled the author to propose a method for optimising the most widely used resonant structures. Moreover, several new versions of resonant elements, structures, and fabrication techniques were also designed. The results obtained from the numerical analyses carried out to examine the central physical properties of the fabricated structure samples were all verified via the designed method for measuring the non-radiating component of the magnetic field.

Existing unified numerical electromagnetic methods are often unable to analyze electrically large structures due to the amount of memory and processing power required, necessitating approximate analyses with limited applicability. In this research a hybrid modeling methodology is adopted to solve these complex problems more efficiently than unified numerical methods and more accurately than analytical methods. Electromagnetic modeling problems are divided into two or more levels of scale. Each level analyzes a specific level of detail and only promotes the required information to the next level. The method is demonstrated by successful application to three important problems: (1) remote sensing of snow, (2) modeling an optical Bragg resonator, and (3) modeling the MIMO wireless channel. First, complex snow media is analyzed with a hybrid FDTD/radiative transfer model. FDTD is used to compute phase matrices and extinction coefficients required for radiative transfer. Comparison with exact analytical methods proves the validity of the FDTD method for modest domain sizes ([5λ^3]) and number of Monte Carlo realizations (32). The method is used to illustrate a penetrating sphere model, which is not possible with existing analysis techniques. Backscatter from the resulting model is about 3 times higher than that of existing dense-medium theories, underlying the importance of exact characterization of the media. Second, a hybrid FD/FDTD/S-parameter analysis is developed to model a large (10^4 section) optical Bragg resonator: a simple FD method computes propagation constants and field profiles, FDTD analysis provides reflection and transmission coefficients for the single section, and S-parameter analysis combines the sections to obtain the complete device response. A detailed study on error suggests that the method provides better than 2% accuracy in reflection and transmission response. Third, a hybrid electromagnetic/SVA model is developed to study the indoor MIMO wireless channel. A MIMO measurement platform is discussed for simultaneous probing of up to 16 transmit and receive antennas, which was required to assess the validity of later modeling. FDTD or MOM antenna analysis coupled with the SVA model gives capacity predictions which match measured data. The model is used to explore the impact of antenna spacing, directivity, and polarization on channel capacity. Closely spaced antennas lead to an approximate halving of receive power. Directivity effectively doubles receive power for aligned transmit and receive. Dual polarization increases system capacity anywhere from 10% to 70%, depending on the spacing of elements and the amount of multipath richness. This analysis of MIMO systems underlines the need for models that describe both multipath richness and average receive power.

Advancements in photonic integrated circuits, so-called PICs, have progressed fast in the last decades. More complex PICs are getting developed, which are promising in possibly offering advantages like low power consumption and high-performance computing. Re-programmable photonic FPGAs are one of these candidates. To make these PICs viable, fundamental building blocks based on photonics need to be developed. Some of those fundamental building blocks are tunable silicon ring resonators, which can be used to filter signals in the transmission of light through photonic circuits. Fabrication of PICs is developing and those components are getting smaller, which leads to a strong sensitivity of their behavior to nanometer-scale variations. That has created a need for active tuning of those devices to recuperate those variances. One promising way to tune silicon ring resonator devices is to integrate microelectromechanical systems (MEMS) into the tuning section of the devices, because of their local and low power actuation. They are prospective to eliminate drawbacks from usual actuation methods like thermal actuation, which comes with high power consumption and cross talk while heating the functional sections of the ring. In this thesis, we have measured and analyzed MEMS-tunable silicon ring resonators, featuring two different designs, being an all-pass ring resonator and an add-drop ring resonator. The MEMS in the design are used to change the gap between the waveguides in their directional coupler and phase shifter section to control the position and extinction ratios of the ring resonance dips, which has been successfully demonstrated for the all-pass ring resonator. For the add-drop ring resonators, we have obtained performance parameters of their resonances with an average Q-factor of 3000 over the measured wavelength ranged from 1460nm to 1580nm and the characteristic behavior of their transmission has been shown without actuation. Further investigation with MEMS actuation of add-drop ring resonators and passive measurements on all-pass ring resonators can be done for a better understanding of their behavior and functionality. This can be achieved by characterizing all-pass ring resonators in terms of obtained performance parameters and by active measurements on add-drop ring resonators, as we expect that their MEMS could enable similar functionalities as all-pass ring resonators. Our first characterization results confirm the potential of MEMS for ring resonator tuning and could enable future circuits based on ring resonators with low power consumption. / Framsteg inom fotoniska integrerade kretsar, så kallade PIC, har utvecklats snabbt under de senaste decennierna. Mer komplexa PIC utvecklas, vilket lovar att möjligen erbjuda fördelar som låg strömförbrukning och högpresterande datorer. Omprogrammerbara fotoniska FPGA är en av dessa kandidater. För att göra dessa PICs livskraftiga måste grundläggande byggstenar baserade på fotonik utvecklas. Några av dessa grundläggande byggstenar är avstämningsbara kiselringresonatorer, som kan användas för att filtrera signaler vid överföring av ljus genom fotoniska kretsar. Tillverkning av PIC utvecklas och dessa komponenter blir mindre, vilket leder till en stark känslighet för variationer, även på nanometer skala. Det har skapat ett behov av aktiv inställning av dessa enheter för att återhämta dessa avvikelser. Ett lovande sätt att ställa in kiselringresonatoranordningar är att integrera mikroelektromekaniska system (MEMS) i enhetens stämningsdel på grund av deras lokala och lågeffektaktivering. De kan eliminera nackdelar med vanliga manövreringsmetoder som termisk aktivering, som kommer med hög strömförbrukning och termisk överhöring. I denna avhandling har vi mätt och analyserat MEMS-avstämbara kiselringresonatorer, med två olika designer, som är en all-pass ringres-onator och en add-drop ringresonator. MEMS i konstruktionen används för att ändra gapet mellan vågledarna i deras kopplare och fasskiftarsektion för att styra positionen och djupet på ringresonaserna, vilket har visats framgångsrikt för allpassningsresonatorn. För add-dropringresonatorer har vi erhållit prestandaparametrar för deras resonanser med en genomsnittlig Q-faktor på 3000 över den uppmätta våglängden som varierar från 1460 nm till 1580 nm och det karakteristiska beteendet för deras överföring har visats utan aktivering. Ytterligare undersökning med MEMS-aktivering av add-drop-ringresonatorer och passiva mätningar på all-pass-ringresonatorer kan göras för en bättre förståelse av deras beteende och funktionalitet. Detta kan uppnås genom att karakterisera allpassningsresonatorer i termer av erhållna prestandaparametrar och genom aktiva mätningar på add-drop-ringresonatorer, eftersom vi förväntar oss att deras MEMS kan möjliggöra liknande funktioner som all-pass-ringresonatorer. Våra första karakteriseringsresultat bekräftar MEMS potential för ringresonatorinställning och kan möjliggöra framtida kretsar baserade på ringresonatorer med låg strömförbrukning.

<p>The thesis intends to explain in full detail the developed techniques and approaches for the modeling, design, and sensitivity analysis of nano-plasmoic structures. However, some examples are included for audiences of general microwave background. Although the thesis is mainly focused on simulation-based techniques, analytical and convex optimization approaches are also demonstrated. The thesis is organized into two parts. Part 1 includes Chapters 2-4, which cover the simulation-based modeling and sensitivity analysis approaches and their applications. Part 2 includes Chapters 5 and 6, which cover the analytical optimization approaches.</p> / <p>We propose novel techniques for modeling, adjoint sensitivity analysis, and optimization of photonic and nano-plasmonic devices. The scope of our work is generalized to cover microwave, terahertz and optical regimes. It contains original approaches developed for different categories of materials including dispersive and plasmonic materials. Artificial materials (metamaterials) are also investigated and modeled. The modeling technique exploits the time-domain transmission line modeling (TD-TLM) technique. Generalized adjoint variable method (AVM) techniques are developed for sensitivity analysis of the modeled devices. Although TLM-based, they can be generalized to other time-domain modeling techniques like finite difference time-domain method (FDTD) and time-domain finite element method (FEM).</p> <p>We propose to extend the application of TLM-based AVM to photonic devices. We develop memory efficient approaches that overcome the limitation of excessive memory requirement in TLM-based AVM. A memory reduction of 90% can be achieved without loss of accuracy and at a more efficient calculation procedure. The developed technique is applied to slot waveguide Bragg gratings and a challenging dielectric resonator antenna problem.</p> <p>We also introduce a novel sensitivity analysis approach for materials with dispersive constitutive parameters. To our knowledge, this is the first wide-band AVM approach that takes into consideration the dependence of material properties on the frequency. The approach can be utilized for design optimization of innovative nano-plasmonic structures. The design of engineered metamaterial is systematic and efficient. Beside working with engineered new designs, dispersive AVM can be utilized in bio-imaging applications. The sensitivity of the objective function with respect to dispersive material properties enables the exploitation of parameter and gradient based optimization for imaging in the terahertz and optical regimes. Material resonance interaction can be easily investigated by the provided sensitivity information.</p> <p>In addition to the developed techniques for simulation-based optimization, several analytical optimization algorithms are proposed to foster the parameter extraction and design optimization in terahertz and optical regimes. In terahertz time-domain spectroscopy, we have developed an efficient parameter based approach that utilizes the pre-known information about the material. The algorithm allows for the estimation of the optical properties of sample materials of unknown thicknesses. The approach has been developed based on physical analytical dispersive models. It has been applied with the Debye, Lorentz, Cole-Cole, and Drude model.</p> <p>Furthermore, we propose various algorithms for design optimization of coupled resonators. The proposed algorithms are utilized to transform a highly non-linear optimization problem into a linear one. They exploit an approximate transfer function of the coupled resonators that avoids negligible multiple reflections among them. The algorithms are successful for the optimization of very large-scale coupled microcavities (150 coupled ring resonators).</p> / Doctor of Philosophy (PhD)