Dissertations / Theses on the topic 'Waveguide component'

Abstract The main objective of this thesis was to research the integration of novel materials and fabrication processes into Low Temperature Co-fired Ceramic (LTCC) technology; enabling fabrication of Radio Frequency (RF) and microwave components with advanced performance. The research focuses on two specific integration cases, which divide the thesis into two sections: the integration of tunable dielectric structures and the integration of air filled waveguides. The first section of the thesis describes the development and characterization of low sintering temperature Barium Strontium Titanate (BST) thick film paste. Sintering temperature of BST is decreased from approximately 1350 °C down to 900 °C by lithium doping and pre-reaction of the doped composition. This allows the co-sintering of the developed BST paste with commercial LTCC materials. Additionally two integration techniques to embed tunable components in an LTCC substrate using the developed BST paste are also presented and the electrical performance of the components is evaluated. The highest measured tunability value was 44% with a bias field of 5.7 V/µm. The permittivity of the films varied between 790 and 190, and the loss tangent varied between 0.004 and 0.005, all measured unbiased at 10 kHz. The developed LTCC compatible BST paste and the presented integration techniques for tunable components have not been previously published. In the second section of the thesis, a fabrication method for the LTCC integrated air-filled rectangular waveguides with solid metallic walls is presented. The fabrication method is described in detail and implemented in a set of waveguides used for characterization. A total loss of 0.1–0.2 dB/mm was measured over a frequency band of 140–200 GHz. The electrical performance of the waveguides is evaluated and their use demonstrated in an integrated LTCC antenna operating at 160 GHz.

Thesis (Ph.D.)--City University of Hong Kong, 2006.
"Submitted to Department of Electronic Engineering in partial fulfillment of the requirements for the degree of Doctor of Philosophy" Includes bibliographical references.

[ES] La presente tesis doctoral tiene como objetivo principal el estudio, desarrollo, diseño y fabricación de nuevos componentes pasivos de microondas, tales como filtros y multiplexores que operen en las bandas de alta frecuencia de los actuales y futuros satélites de telecomunicación (bandas Ku, K y Ka) entre 12 y 40 GHz. Dichos componentes deben ser capaces de ofrecer tanto respuestas clásicas sencillas como avanzadas (elípticas), y presentar una capacidad de resintonización (tanto en términos de frecuencia central como de ancho de banda). Estos componentes darán solución a las necesidades actuales de los sistemas de comunicaciones espaciales, que requieren de mayores tasas de transmisión de datos (señales de mayor ancho de banda), así como de mayor flexibilidad en las frecuencias de operación, para ofrecer con un mismo dispositivo distintos servicios y prestaciones. Para ello, se proponen tanto modificaciones a las estructuras de filtros clásicos de microondas actuales, como la introducción de nuevas estructuras. Asimismo, también se investigará el uso de los tornillos de ajuste post-fabricación de los filtros como tornillos de sintonía metálicos, así como la posible introducción de tornillos de sintonía realizados con distintos materiales dieléctricos. Se pretende, de esta forma, mejorar las respuestas de los dispositivos actuales; reduciendo su tamaño y costes de producción (debido a la relajación de las tolerancias de fabricación), abaratando de esta forma la fabricación y futura operación de los mismos. Aprovechando estos nuevos dispositivos, se abordará también el diseño, fabricación y medida de componentes más complejos, como pueden ser los los diplexores de canal o los conmutadores con respuesta selectiva en frecuencia, todos ellos necesarios en los sistemas de comunicaciones espaciales y en íntima relación con los filtros previamente mencionados. Por último, el desarrollo de todos estos nuevos dispositivos vendrá acompañado de una metodología de diseño basado en el uso del Mapeo Espacial Agresivo (Aggressive Space Mapping, ASM) especialmente adaptado a los filtros en guía de onda.
[CA] La present tesis doctoral té com a objectiu el estudi, desenvolupament, diseny i fabricació de nous components pasius de microones, tals com els filtres i multiplexors que operen en les bandes d'alta freqüencia dels actuals i futurs satèl.lits de telecomunicació (bandes Ku, K i Ka) entre 12 i 40 GHz, Aquests components han de ser capaços d'oferir tant, respostes clàsiques sencilles com avançades (eliptiques), i que a més a més presenten una capacitat de resintonització (tant en termes de freqüència central com d'amplada de banda). Aquestos nous components pasius donaràn solució a les necesitats dels actuals sistemes espacials, que requereixen de majors taxes de transmissió de dades (senyals de major amplada de banda), així com de major flexibilitat en les frequencies de operació, per oferir en un mateix dispositiu distints serveis i prestacions. Per aquesta raó, es proposen tant modificacions a les estructures del filtres clàsics de microones actuals, com la introducció de noves estructures. Així mateix, també s'investigarà l'us dels tornells d'ajustament post-fabricació dels filtres com a tornells de sintonía metàl.lica i la introducció de tornells de sintonía realitzats amb diferents materials dielèctrics Es pretén, d'aquesta forma, la millora de les respostes del dispositius actuals; reduint la envergadura i els costos de producció (gràcies a la relaxació de les toleràncies de fabricació), abaratint d'aquesta forma la fabricació i futura operació dels filtres mateixos. Aprofitant aquestos nous dispositius es treballarà també en el disseny, fabricaçió i mesura de components més complexes, com poden ser els multiplexors de canal i els commutadors amb resposta selectiva en freqüencia, tots ells necessaris en els sistemes de comunicacions espacials i en íntima relació amb els filtres abans esmenats. Per analitzar, el desenvolupament de tots aquestos dispositius vindrà acompanyat d'una metodologia de disseny basada en l'us del Mapatge Espacial Agressiu (Aggressive Space Mapping, ASM), especialment adaptat als filtres en guia d'ona.
[EN] The main objective of this doctoral thesis is the study, development, design and manufacture of new passive microwave components in waveguide technology, such as filters and multiplexers, that operate in the high frequency bands of current and future telecommunication satellite payloads between 12 and 40 GHz (Ku, K and Ka bands). The new solutions developed must other both classic and advanced (elliptical) responses, as well as the possibility of being reconfigured both in terms of center frequency and bandwidth. The motivation for this research is to address the current and future needs of space communication systems which require higher data rate transmission (that is larger bandwidths), as well as flexibility with respect to the operating frequency to dynamic adaptation to possible changes in user demands. In this context, we propose in this thesis alternative microwave filter structures in metallic waveguide, as well as novel solutions. We explore different approaches to adjust the filter performance, using both traditional metallic tuning screws as well as tuning elements made with dierent dielectric materials. We also advance the state-of-the-art by developing more performing Space Mapping procedures for the design, optimization and tuning of the filter structures that we propose. The objective is to improve the response of the devices and reduce, at the same time, their manufacturing time and costs. As a fundamental element of our work, in addition to theoretical developments, we also apply the findings of our research to the design, manufacture and measurement of a number of more complex components, such as diplexers and integrated switches and filters. They are practical devices to demonstrate the ability of the novel filters that we propose to satisfy the requirements of current and future advanced satellite payloads.
Ossorio García, J. (2021). Development of New Tunable Passive Microwave Components in Waveguide Technology [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/166100
TESIS

In questo lavoro presento lo studio di fattibilità riguardo la realizzazione di una classe di dispositivi in tecnologia SIW (Substrate Integrated Waveguide) per applicazioni ICT alle frequenze delle microonde. Con questa tecnologia è possibile ottenere, attraverso i processi tradizionali per la realizzazione di circuiti stampati, componenti integrati nel substrato con fattori di qualità più alti rispetto alla microstriscia e la stripline. La tecnologia SIW è molto promettente in quanto permette di ottenere strutture guidanti, e quindi componenti, compatti, a basso costo e auto-schermanti. Sebbene siano presenti in letteratura molti articoli che esaltino queste qualità, questa tecnologia non è sfociata al momento in una produzione industriale, nemmeno su bassi volumi. Questo lavoro è parte del progetto di formazione annesso al progetto di ricerca, intitolato “Sviluppo di tecnologie in guida d’onda integrata (SIW) per applicazioni ICT a microonde” in collaborazione con il Politecnico di Bari, Università Politecnica delle Marche e SOMACIS SpA, un produttore internazionale di circuiti stampati con quarant’anni di esperienza in settori altamente tecnologici. Questa promettente tecnologia permette una drastica riduzione di costi e dimensioni, qualità che si adattano bene alle crescenti esigenze del mercato; il progetto prevede lo sviluppo e la realizzazione di una classe di dispositivi come filtri, ibridi, accoppiatori e antenne. La tecnologia SIW potrebbe permettere di produrre in larga scala prodotti complicati e costosi così come i radar per la difesa e l’automotive. Inoltre, nel mercato delle telecomunicazioni, potrebbe essere possibile sostituire le tradizionali e ingombranti parabole con schiere di antenne planari che sono più competitive e potrebbero avere una grande diffusione. Tali schiere potrebbero essere addirittura integrate al di sopra dei tetti come avviene per i pannelli solari, questo vantaggio potrebbe portare le persone ad optare per questo nuovo concetto di antenne satellitari. Quindi, sembra realistico prevedere un mercato di migliaia di componenti che forniscano le giuste motivazioni al successo del progetto. La tecnologia SIW permette di riprodurre in forma planare, attraverso file di fori metallizzati su di un substrato dielettrico, una guida d’onda tradizionale. Ovviamente in queste strutture, il campo elettromagnetico viaggia all’interno del dielettrico e non in aria. È chiaro che questo comporta un sensibile aumento delle perdite. Anche se le perdite dielettriche rappresentano la parte dominante, queste sono aumentate dalle perdite ohmiche dovute all’alta densità di corrente localizzata nei fori metallizzati che costituiscono le pareti laterali. Negli ultimi anni molti dispositivi in guida SIW sono stati riportati in letteratura, come antenne [1-2], filtri, and accoppiatori [3-4, 5-6]. La tecnologia SIW rappresenta una buona scelta di progettazione di circuiti e dispositivi a microonde e onde millimetriche [7-21]. Comunque, un uso industriale dei componenti SIW richiede ancora una fase essenziale di studio sistematico. Perciò il primo obiettivo di questo studio consiste nell’ottimizzazione di tecnologie appropriate per la realizzazione di questi componenti.
In this research work I present the feasibility study on the realization of a class of devices in SIW (Substrate Integrated Waveguide) technology for ICT application at microwave frequencies. With this technology it is possible to obtain, by the traditional processes for the printed circuits manufacturing, integrated components with quality factors greater than the microstrip and the stripline. SIW technology is very promising because it permits to obtain compact, low cost and self-shielding guiding structures and hence, guides components. Although many papers, presented in literature, strengthen these qualities, this technology did not lead to an industrial production today, even at low volumes. This work is part of the formation project annexed to its research project, entitled “Integrated Waveguide (SIW) technologies development for microwave ICT applications” in collaboration with the Politecnico of Bari, Università Politecnica delle Marche and SOMACIS SpA, a worldwide PCB (Printed Circuit Board) industry with forty years of experience in the highly technological sector of high-mix and low-volume. As this hopeful technology allows a drastic reduction in size and costs, qualities that are well suited to the increasing market needs, the project aims to design and realize a class of product ranging from filter, hybrids, “frequency-shaping” components and antenna. SIW technology could also permit to produce in a large scale expensive and complicated products like the automotive and defense radars. Moreover, in the market of civil telecommunication, it could be possible to replace the standard and bulky TV dishes with planar array of antenna that are more competitive and could have a wide spread. Such array could also be fully integrated in the roof like it happens for the solar panels, this advantage could drive people to opt for these new concept of satellite antennas. Indeed, it seems to be realistic to foresee a market of thousands of components overlooking the proper motivation to the success of the project. The SIW technology permits to reproduce in a planar form, through rows of metallic holes, a traditional waveguide. Obviously, in these structures, the electromagnetic field travels into the dielectric and not in air. It is clear that this involves a sensible increase of the losses. Even if the dielectric losses are the dominant part, these are still enhanced from a high density of current localized in the metallic holes that constitute the lateral sidewalls. In recent years several Substrate Integrated Waveguide devices such as antennas [1-2], filters, and couplers [3-4, 5-6] have been reported in literature. SIW technology is a good technique for designing and fabricating microwave and millimeter-wave devices and circuits [7-21]. However, an industrial use of SIW components still requires an essential phase of systematic study. Therefore the first objective of this study consists in optimization of technologies most suitable for the realization of this components.

This thesis presents a solution to the issue of integrating incompatible materials and material processing. In photonics, which is the focus of this thesis, this issue is manifested by the inability to integrate many active materials within silica, which is the mainstream photonics medium, due to the high-temperature processing methods. This problem is solved by the use of room-temperature convective self-assembly method to grow novel photonic structures, such as high aspect ratio microwire waveguides, from silica nanoparticles. A room-temperature method allows the integration of various dopants within silica for the first time. Two of the examples that are presented in this thesis in detail are rhodamine B (organic molecule) and nanodiamonds (nanoparticles), which are integrated within silica microwire waveguides. Rhodamine B absorption and fluorescence within the silica microwire was measured. Single and two photons emission from nanodiamonds incorporated within the silica microwires waveguides were also detected. The physical and optical properties of the microwire were characterised using a number of different methods and techniques. The microwires were found to have relatively low optical loss and robust enough to be handled and manipulated according to need.

This work discusses both the theoretical and experimental guidance of low-loss single-mode millimetre-wave (mmW) and terahertz (THz) waves within microstructured photonic crystal fibre or waveguides, as well as functional components which can be built upon them. The aim of this work is to provide good interconnects for mmW and THz system. The interconnects are desired to be low loss, single mode, low dispersion, as well as easy to fabricate and integrate. In this work, photonic crystal structures, which can easily manipulate the wave-behaving photons by artificially changing its geometrical and material properties, are used in the proposed mmW and THz waveguides. The proposed photonic crystal waveguides includes cylindrical Bragg fibres and flat hollow photonic crystal integrated waveguides. The geometrical differences between Bragg fibres and photonic crystal integrated waveguides make them work better for different challenges. The former are promising for long distance guidance of signals due to its ultra-low loss, while the latter are strong candidates for compact and multilayer packaging applications since its flatness and other exceptional properties. The thesis has three primary themes. The first them is about the design principles, analysis, and fabrication and measurement of low-loss asymptotically single-mode THz Bragg fibres. A design principle for manipulating the photonic bandgap of Bragg fibres, which is called as the generalized half-wavelength condition, is proposed. Based on the design principle, an ultra-low loss THz Bragg fibre with single mode and low dispersion is proposed, verified by the simulation. Considering practical fabrication challenges, a sub-THz Bragg fibre is fabricated using 3D printing technology and characterized to be one of the lowest loss waveguide at around 300 GHz. The mode transition and filtering in the fabricated sub-THz Bragg fibre is investigated, disclosing the mechanisms of asymptotically single-mode operation pattern of Bragg fibres. The second theme is about the design, fabrication and measurement of single-mode mmW flat and hollow photonic crystal integrated waveguides with low loss and zero group velocity dispersion. The hollow photonic crystal integrated waveguides comprise of air-core line-defect photonic crystal structures sandwiched by a pair of metallic parallel plates. Two different types of photonic crystals are used in the designs, namely hexagonal lattice array of air holes in dielectric slab and Bragg reflectors that consist of periodic arrangement of dielectric layers and air layers. Therefore, two types of hollow photonic crystal integrated waveguides are designed. The designs are fabricated and verified at Ka-band by measurements. The hollow photonic crystal integrated waveguides possess the merits of both substrate integrated waveguide and photonic crystal waveguide, but eliminates their drawbacks, making them strong candidates for compact and multilayer mmW and THz system-in-package applications. The third theme is about the design and simulation of mmW and THz functional components built upon the previously designed microstructured photonic crystal fibres and flat waveguides. The functional components that have been designed include waveguide bends, power splitters or combiners, cavity, h-plane horn antenna, and circular Bragg fibre horn antenna. This theme aims to demonstrate the expansibility and flexibility of the proposed microstructured photonic crystal fibres and flat waveguides as promising platforms for designing mmW and THz functional components. Though each theme discusses the theoretical analysis and/or experimental measurements of distinct phenomena, they are deeply related within the overall theme of engineering low-loss single-mode fibres or waveguides and their integration into mmW or THz systems.

The main objectives of this thesis were to develop a lowtemperature PECVD process suitable for optoelectronicintegration, and to optimize silica glass composition forUV-induced modifications of a refractive index in PECVDfabricated planar devices. The most important achievement isthe successful development of a low temperature silicadeposition, which for the first time makes it is possible tofabricate good quality low loss integrated components whilekeeping the temperature below 250oC during the entirefabrication process. Two strong absorption peaks thatappear at1.5 mm communication window due to N-H and Si-H bonds have beencompletely eliminated by process optimization. This openspossibilities for monolithic integration with other,temperature sensitive devices, such as semiconductor lasers anddetectors, or polymer-based structures on the common siliconplatform. PECVD technology for low loss amorphous silicon inapplication to SiO2/Si based photonic crystal structures hasbeen also optimized to remove hydrogen incorporated during thedeposition process, responsible for the porosity of thedeposited material and creation of similar to silica absorptionbands.

Change of the refractive index of germanium doped silicaunder UV irradiation is commonly used for fabrication of UVinduced fiber Bragg gratings. Here we describe our achievementsin fabrication of fiber Bragg gratings and their application todistributed sensor systems. Recently we have built up a laserlab for UV treatment in application to planar technology. Wehave demonstrated the high photosensitivity of PECVD depositedGe-doped glasses (not thermally annealed) even without hydrogenloading, leading to a record transmission suppression of 47dBin a Bragg grating photoinduced in a straight buried channelwaveguide. We have also used a UV induced refractive indexchange to introduce other device modifications or functions,such as phase shift, wavelength trimming and control ofpolarization birefringence.The developed low temperature technology and the UVprocessing form a unique technology platform for development ofnovel integrated functional devices for optical communicationsystems.

A substantial part of the thesis has been devoted tostudying different plasma deposition parameters and theirinfluence on the optical characteristics of fabricatedwaveguides to find the processing window giving the besttrade-off between the deposition rate,chamber temperatureduring the process, optical losses and presence of absorptionbands within the interesting wavelength range. The optimalconditions identified in this study are low pressure (300-400mTorr), high dilution of silane in nitrous oxide and high totalflow (2000 sccm), low frequency (380 KHz) RF source and high RFpower levels (800-1000 W).

The thesis provides better understanding of the plasmareactions during the deposition process. RF Power is the keyparameter for increasing the rate of surface processes so as toaccommodate each atomic layer in the lowest energy statepossible. All the process conditions which favor a moreenergetic ion bombardment (i.e. low pressure, low frequency andhigh power) improve the quality of the material, making it moredense and similar to thermal oxide, but after a certain pointthe positive trend with increasing power saturates. As theenergy of the incoming ion increases, a competing effect setsin at the surface: ion induced damage and resputtering.

Finally, the developed technologies were applied for thefabrication of some test and new concept devices for opticalcommunication systems including multimode interference (MMI)-based couplers/splitters, state-of-the-art arrayed waveguidegrating-based multi/ demultiplexers, the first Bragg gratingassisted MMI-based add-drop multiplexer, as well as moreresearch oriented devices such as a Mach-Zehnder switch basedon silica poling and a Photonic Crystal-based coupler.

Keywords:silica-on-silicon technology, PECVD, plasmadeposition, photonic integrated circuits, planar waveguidedevices, UV Bragg gratings, photosensitivity, arrayed waveguidegratings, multimode interference couplers, add-dropmultiplexers.

Optical waveguides, quantum dot emitters, and flat top beam shapers were designed and fabricated by two soft lithographic techniques; micro transfer molding (microTM) and vacuum assisted microfluidics (VAM). Optical waveguides were fabricated through a microTM technique that utilizes a poly dimethylsiloxane (PDMS) stamp. Generation of the flexible stamp required development of a channel waveguide pattern mask, defined by maskless lithography, and followed by construction of a three dimensional channel waveguide master, acquired through contact lithography on a glass substrate coated with SU-8 photoresist. Creation of a positive imprint replicating mold was accomplished through prepolymer PDMS solution settling and curing around the master. Waveguide fabrication was achieved through PDMS conformal contact on, and subsequent curing of, ultraviolet (UV) polymer resins on a silicon substrate. A slight modification of the microTM PDMS stamp, whereby inlet and outlet tunnels were incorporated, resulted in a novel VAM structure and correspondingly waveguides. Waveguide propagation losses were determined to be 1.14 dB/cm and 0.68 dB/cm for the microTM and VAM fabricated waveguides, respectively. A lithographic approach employing quantum dots doped in SU-8 photoresist has led to the realization of a new quantum dot emitter. Uniform coating of a doped material on a silver coated substrate was followed by contact mask lithography. Evaporation of a thin silver layer, upon development of the resultant quantum dot doped channel waveguide structure, facilitates confined emission. Successful edge emitting was demonstrated with blue laser pumping. The lithographic fabrication of such quantum dot emitter is successfully replaced by soft lithographic VAM technique. A flat top beam shaper, whose profile was developed on cured UV polymer resins, was fabricated by microTM technique. The master used for the development of the PDMS stamp was produced through an iterative wet etching process capable of achieving etching depths as small as a few nanometers. Comparisons between the reference wet etched beam shaper and the microTM based beam shaper produced near identical output flat top beams from incident Gaussian beams. Through this research work, successful soft lithographic fabrication of optical waveguides, quantum dot emitters, and flat top beam shapers were demonstrated. The vast potential exhibited by these and other related technologies show great promise for cost-effective mass production of various micro optics and integrated photonic components.

This report presents a method for fabrication of ridge-type waveguide electro-optic modulators in 500 nm thick, c-oriented, epitaxial, (Pb0.92,La0.08)(Zr0.4,Ti0.6)O3 thin films on a MgO substrate. The method is based on ordinary photolitography and wet etching techniques with lift-off metallisation of gold electrodes. To achieve good input coupling of light the device end faces were polished using diamond lapping film swith grain sizes as small as 0.5 um. Several devices with both Mach-Zehnder electro-optic modulators and phase modulators with co-planar gold electrodes and an interaction length of L = 3 mm were fabricated using this method. These modulators were used to examine the electro-optic efect in the thin films at the wavelength 1.55 um. Coherent, linearly polarised light was coupled into the waveguide end face using tapered fibres while a modulation voltage was applied to the electrodes. The phase modulators were used as intensity modulators by exciting them with light polarised 45 degrees on the optical axis and placing a linear polariser at the output. Practical modulation was achieved using voltages as low as 46 V with the phase modulators and 80 V with the Mach-Zehnder modulators. Using a numerical curve fitting technique, the measured data was fitted to a proposed theoretical model for the modulators. The model was based on Jones matrix formalism and the assumption that the electro-optic effect in the thin films corresponds with the Pockels effect. Good fits were achieved indicating that the effect is indeed a Pockels effect and estimates of the Pockels coecient r51 ranged from 4.4 pm/V to 11 pm/V depending on the device. These values were obtained under the uncertain assumption that the birefringence of (Pb,La)(Zr,Ti)O3 is 0.005. It is found that if the actual value of the birefringence is lower, then r51 will also be lower than estimated. Based on previous works the Pockels coeficient was expected to be on the order or ~102 pm/V. The low measured values of r51 and the variation between films is believed to be due to the thin films being multi domain with a domain structure created by a stochastic process.

Optical polymers are a subject of research and industry implementation for many decades. Optical polymers are inexpensive, easy to process and flexible enough to meet a broad range of application-specific requirements. These advantages allow a development of cost-efficient polymer photonic integrated circuits for on-chip optical communications. However, low refractive index contrast between core and cladding limits light confinement in a core and, consequently, integrated polymer device miniaturization. Also, polymers lack active functionality like light emission, amplification, modulation, etc. In this work, we improved a performance of integrated polymer waveguides and demonstrated active waveguide devices. Also, we present novel Si QD/polymer optical materials. In the integrated device part, we demonstrate optical waveguides with enhanced performance. Decreased radiation losses in air-suspended curved waveguides allow low-loss bending with radii of only 15 µm, which is far better than >100 µm for typical polymer waveguides. Another study shows a positive effect of thermal treatment on acrylate waveguides. By heating higher than polymer glass transition temperature, surface roughness is reflown, minimizing scattering losses. This treatment method enhances microring resonator Q factor more than 2 times. We also fabricated and evaluated all-optical intensity modulator based on PMMA waveguides doped with Si QDs. We developed novel hybrid optical materials. Si QDs are encapsulated into PMMA and OSTE polymers. Obtained materials show stable photoluminescence with high quantum yield. We achieved the highest up to date ~65% QY for solid-state Si QD composites. Demonstrated materials are a step towards Si light sources and active devices. Integrated devices and materials presented in this work enhance the performance and expand functionality of polymer PICs. The components described here can also serve as building blocks for on-chip sensing applications, microfluidics, etc.

QC 20171207

"Thèse en cotutelle, Doctorat en physique; Université Laval, Québec, Canada et Université de Bordeaux, Talence, France"
L'inscription laser directe est un domaine de recherche en croissance depuis ces deux dernières décennies, fournissant un moyen efficace et robuste pour inscrire directement des structures en trois dimensions (3D) dans des matériaux transparents tels que des verres en utilisant des impulsions laser femtosecondes. Cette technique présente de nombreux avantages par rapport à la technique de lithographie, qui se limite à la structuration en deux dimensions (2D) et implique de nombreuses étapes de fabrication. Cela rend la technique d’inscription laser directe bien adaptée aux nouveaux procédés de fabrication. Généralement, l’inscription laser dans les verres induit des changements physiques tels qu'un changement permanent de l'indice de réfraction localisé. Ces modifications ont été classées en trois types distincts:(type I, type II et type III). Dans ce travail, nous présentons un nouveau type de changement d'indice de réfraction, appelé type A qui est basé sur la création d’agrégats d'argent photo-induits. En effet, dans des verres dans lesquels sont incorporés des ions argent Ag+, lors de leur synthèse, l’inscription laser directe induit la création d’agrégats d’argent fluorescents Agmx+ au voisinage du voxel d’interaction. Ces agrégats modifient localement les propriétés optiques comme la fluorescence, la non-linéarité et la réponse plasmonique du verre. Ainsi, différents guides d'ondes, un séparateur de faisceau 50-50, ainsi que des coupleurs optiques ont été inscrits en se basant sur ce nouveau type A et complétement caractérisés. D'autre part, une étude comparative entre les deux types de guides d'ondes (type A et type I) est présentée, tout en montrant qu’en ajustant les paramètres laser, il est possible de déclencher soit le type I soit le type A. Enfin, en se basant sur des guides d’ondes de type A inscrits proche de la surface du verre, un capteur d'indice de réfraction hautement sensible a été inscrit dans une lame de verre de 1 cm de long. Ce capteur miniaturisé peut présenter deux fenêtres de détection d’indice, ce qui constitue une première mondiale. Les propriétés des guides d'ondes inscrits dans ces verres massifs ont été transposées à des fibres en forme de ruban, du même matériau contenant de l'argent. Les résultats obtenus dans ce travail de thèse ouvrent la voie à la fabrication de circuits intégrés en 3D et de capteurs à fibre basés sur des propriétés optiques originales inaccessibles avec des guides d’onde de type I standard.
Direct Laser Writing (DLW) has been an exponentially growing research field during the last two decades, by providing an efficient and robust way to directly fabricate three dimensional (3D) structures in transparent materials such as glasses using femtosecond laser pulses. It exhibits many advantages over the lithography technique, which is mostly limited to two dimensional (2D) structuring and involves many fabrication steps. This competitive aspect makes the DLW technique suitable for future technological transfer to advanced industrial manufacturing. Generally, DLW in glasses induces physical changes such as permanent local refractive index modifications that have been classified under three distinct types: (Type I, Type II & Type III). In silver containing glasses with embedded silver ions Ag+, DLW induces the creation of fluorescent silver clusters Agmx+ at the vicinity of the interaction voxel. In this work, we present a new type of refractive index change, called type A occurring in the low pulse energy regime that is based on the creation of the photo-induced silver clusters allowing the creation of new linear and nonlinear optical waveguides in silver containing glasses. Various waveguides, a 50- 50 Y beam splitter, as well as optical couplers, were written based on type A modification inside bulk glasses and further characterized. In addition, a comparitive study between type A and type I waveguides is presented, showing that finely tuning the laser parameters allows the creation of either type A or type I modifications inside silver containing glasses. Finally, based on type A near-surface waveguides, a highly sensitive refractive index sensor is created in a 1 cm glass chip, which could exhibit a pioneer demonstration of double sensing refractive ranges. The waveguiding properties observed and reported in the bulk of such silver containing glasses were transposed to ribbon shaped fibers of the same material. Those results pave the way towards the fabrication of 3D integrated circuits and fiber sensors with original fluorescent, nonlinear and plasmonic properties that are not accessible using the standard type I modification.

L'inscription laser directe est un domaine de recherche en croissance depuis ces deux dernières décennies, fournissant un moyen efficace et robuste pour inscrire directement des structures en trois dimensions (3D) dans des matériaux transparents tels que des verres en utilisant des impulsions laser femtosecondes. Cette technique présente de nombreux avantages par rapport à la technique de lithographie, qui se limite à la structuration en deux dimensions (2D) et implique de nombreuses étapes de fabrication. Cela rend la technique d’inscription laser direct bien adaptée aux nouveaux procédés de fabrication. Généralement, l’inscription laser dans les verres induit des changements physiques tels qu'un changement permanent de l'indice de réfraction localisé. Ces modifications ont été classés en trois types distincts : (Type I, Type II et Type III). Dans ce travail, nous présentons un nouveau type de changement d'indice de réfraction, appelé type A qui est basé sur la création d’agrégats d'argent photo-induit. En effet, dans des verres dans lesquels sont incorporés des ions argent Ag+, lors de leurs synthèses, l’inscription laser directe induit la création d’agrégats d’argent fluorescents Agmx+ au voisinage du voxel d’interaction. Ces agrégats modifient localement les propriétés optiques comme : la fluorescence, la non-linéarité et la réponse plasmonique du verre. Ainsi, différents guides d'ondes, un séparateur de faisceau 50-50, ainsi que des coupleurs optiques ont été inscrits en se basant sur ce nouveau Type A et complétement caractérisés. D'autre part, une étude comparative entre les deux types de guides d'ondes (type A et type I) est présentée, tout en montrant qu’en ajustant les paramètres laser, il est possible de déclencher soit le Type I soit le Type A. Enfin, en se basant sur des guides d’ondes de type A inscrits proche de la surface du verre, un capteur d'indice de réfraction hautement sensible a été inscrit dans une lame de verre de 1 cm de long. Ce capteur miniaturisé peut présenter deux fenêtres de détection d’indice, ce qui constitue une première mondiale. Les propriétés des guides d'ondes inscrits dans ces verres massifs ont été transposées à des fibres en forme de ruban, du même matériau contenant de l'argent. Les résultats obtenus dans ce travail de thèse ouvrent la voie à la fabrication de circuits intégrés en 3D et de capteurs à fibre basés sur des propriétés optiques originales inaccessibles avec des guides d’onde de Type I standard
Direct Laser Writing (DLW) has been an exponentially growing research field during the last two decades, by providing an efficient and robust way to directly address three dimensional (3D) structures in transparent materials such as glasses using femtosecond laser pulses. It exhibits many advantages over lithography technique which is mostly limited to two dimensional (2D) structuring and involves many fabrication steps. This competitive aspect makes the DLW technique suitable for future technological transfer to advanced industrial manufacturing. Generally, DLW in glasses induces physical changes such as permanent local refractive index modifications that have been classified under three distinct types: (Type I, Type II & Type III). In silver containing glasses with embedded silver ions Ag+, DLW induces the creation of fluorescent silver clusters Agmx+ at the vicinity of the interaction voxel. In this work, we present a new type of refractive index change, called type A that is based on the creation of the photo-induced silver clusters allowing the creation of new linear and nonlinear optical waveguides in silver containing glasses. Various waveguides, a 50-50 Y beam splitter, as well as optical couplers, were written based on type A modification inside bulk glasses and further characterized. On the other hand, a comparison study between type A and type I waveguides is presented, showing that finely tuning the laser parameters allows the creation of either type A or type I modification inside silver containing glasses. Finally, based on type A near-surface waveguides, a highly sensitive refractive index sensor is created in a 1 cm glass chip, which could exhibit a pioneer demonstration of double sensing refractive ranges. The waveguiding properties observed and reported in the bulk of such silver containing glasses were transposed to ribbon shaped fibers of the same material. Those results pave the way towards the fabrication of 3D integrated circuits and fiber sensors with original fluorescent, nonlinear and plasmonic properties that are not accessible using the standard type I modification

[EN] Modern communications systems impose stringent requirements on the equipment that operates at microwave frequency, especially in the case of wireless communications. The design of passive components for these applications is contingent upon the availability of accurate electromagnetic (EM) modeling tools that can efficiently handle the complex geometry of these components. Despite the widespread use of mesh-based general-purpose computer-aided engineering (CAE) tools to perform final design verifications, their application during the optimization process is limited. Optimum designs require a large number of simulations, which are computationally expensive when performed by general purpose tools. Instead, microwave designers prefer to employ faster software tools tailored to specific geometries, such as waveguide components, multilayered structures, etc. Therefore, the development of faster and more efficient specialized EM tools has a direct impact on the design of microwave components, both quantitatively and qualitatively. Increasingly complex geometries are modeled more accurately, and may be incorporated into novel designs without penalizing development time and its associated costs. By doing so, passive components become more advanced and are able to fulfill stricter requirements. At the same time, new research and development opportunities arise in order to address the challenges posed by these advanced structures. The present thesis is focused on a specific type of waveguide cavity geometry: bi-dimensional structures of arbitrary shape. Most microwave components based on rectangular waveguides include these elements (bends, T-junctions, tapers, power-dividers, etc.), thus the scope of this work is wide. To characterize these structures, an efficient full-wave modal formulation is developed. Taking into account common properties of bi-dimensional structures, such as its electromagnetic symmetry, the resulting technique is very efficient and accurate. Thanks to the integration of this formulation into a CAE tool, a designer is able to solve complex systems that combine this type of element with components of vastly different shapes. The developed formulation is first applied to the analysis and design of passive components, such as filters, multiplexers and orthomode transducers. These examples are employed to validate the results, as well as to demonstrate the improvement that the proposed analysis technique represents over well-known commercial EM packages. Likewise, this formulation is combined with the tool SPARK3D to predict RF breakdown (multipactor and corona) in selected bi-dimensional structures. Then, novel implementations of waveguide quasi-elliptic filters, based on the interconnection of bi-dimensional cavities, are proposed. Special attention is paid to the realization of multiple transmission zeros (TZs) with tuning-less compact structures. First, a novel family of filters, known as hybrid-folded rectangular waveguide structures, is studied. Simple and flexible methods to prescribe the location of the transmission zeros realized by these structures are presented. Practical aspects related to their physical implementation are also discussed. Secondly, a compact and purely capacitive obstacle, capable of realizing multiple TZs, is presented and discussed. In both cases, multiple examples are given to illustrate the step-by-step process involved in the design of these structures. Finally, a systematic procedure for the design of wideband manifold-coupled multiplexers is proposed. To preven the generation of undesired resonances, stubs that connect the filters to the manifold are removed. Likewise, the manifold length is kept as short as possible. Following a simple procedure, based on analytical formulas and EM simulations, a good starting point for the final optimization of these structures is obtained. It has been applied to a wideband quadruplexer for passive intermodulation measurement at C-band.
[ES] Actualmente, los sistemas de comunicaciones imponen unos requisitos muy estrictos sobre el equipamiento en la banda de microondas. El diseño de estos componentes está supeditado, frecuentemente, a la disponibilidad de herramientas de modelado electromagnético (EM) que sean capaces de analizar geometrías complejas. A pesar del amplio uso de herramientas CAE (computer-aided engineering) de propósito general para la verificación final de prototipos, su potencial aplicación durante el proceso de diseño es limitada. Los diseños óptimos exigen realizar una gran cantidad de simulaciones EM. Dado que las simulaciones con estas técnicas tienen un alto coste computacional, los diseñadores suelen optar por emplear herramientas software especializadas en las estructuras que diseñan. Por tanto, el desarrollo de nuevas herramientas más precisas y eficientes ayudará a reducir el tiempo de diseño de estos productos, y con ello los costes asociados. Además, permitirá abrir nuevas líneas de investigación para responder a los retos que plantean geometrías cada vez más complejas. Esta tesis se centra en el desarrollo de una herramienta de análisis EM para un tipo concreto de estructuras: cavidades bidimensionales de sección arbitraria. Es habitual encontrar este tipo de estructuras en la mayoría de componentes implementados en guía rectangular. Por tanto, el rango de aplicación de la teoría desarrollada en esta tesis es muy amplio. En concreto, se ha desarrollado una nueva formulación basada en métodos modales que permite realizar una caracterización de onda completa de estas estructuras de forma eficiente y precisa. Al aprovechar su simetría geométrica y electromagnética, la herramienta desarrollada puede minimizar los cálculos a realizar, consiguiendo grandes velocidades de computación pero manteniendo una alta precisión. Gracias a la integración de esta formulación dentro de una herramienta CAE basada en métodos modales, se ofrece la posibilidad a los diseñadores de resolver sistemas muy complejos que combinan este tipo de cavidades con otros componentes de geometrías distintas. Esta formulación se aplica, en primer lugar, al análisis y diseño de componentes pasivos comunes, tales como filtros, multiplexores y OMTs. Estos ejemplo validan la herramienta desarrollada, y demuestran la significativa mejora que supone el uso de esta nueva técnica con respecto a otros paquetes software de análisis electromagnético. Asimismo, al combinar esta formulación con la herramienta SPARK3D se abre la posibilidad de predecir la aparición de fenómenos de descarga de alta potencia en determinadas estructuras bidimensionales. A continuación, se proponen nuevas formas de implementar filtros cuasi-elípticos basados en la interconexión de cavidades bi-dimensionales. Se hace especial hincapié en la realización de múltiples ceros de transmisión mediante estructuras compactas que no requieran sintonía. Por una parte se estudian los filtros hybrid-folded rectangular waveguide. Este trabajo incluye una discusión en profundidad sobre distintas implementaciones de este tipo de filtros. En ella se consideran aspectos prácticos relacionados con su uso e implementación física, que ofrecen al diseñador unos criterios claros para elegir la estructura que más se ajuste a sus especificaciones. Por otra parte se presenta un nuevo obstáculo de naturaleza capacitiva muy compacto, que permite la realización de múltiples ceros de transmisión incluso en estructuras en línea. En ambos casos se incluyen ejemplos de aplicación y se describe la metodología seguida para su diseño. Finalmente, se expone un procedimiento sistemático para diseñar multiplexores de banda ancha. Para prevenir la generación de resonancias indeseadas se evitan, en la medida de lo posible, las interconexiones mediante tramos cortos de guía. Siguiendo una metodología simple se consigue un excelente punto inicial para su optimización. La te
[CAT] Els actuals sistemes de comunicacions sense fils imposen uns requisits molt estrictes sobre l'equipament de la banda de microones. El disseny d'aquests components està supeditat, frequentment, a la disponibilitat de ferramentes de modelatge electromagèntic (EM) que siguen capaços de gestionar geometries complexes. Tot i l'ampli ús de ferramentes CAE (computer-aided engineering) de propòsit general per a la verificació final de prototips, la seua aplicació durant el procés de disseny és limitada. Els dissenys òptims exigeixen realitzar una gran quantitat de simulacions. Les simulacions amb aquestes tècniques tenen un alt cost computacional, per tant els dissenyadors solen optar per utilitzar ferramentes software especialitzades en les estructures que dissenyen. Per tant, el desenvolupament de noves tècniques d'anàlisi més precises i eficients ajudarà a reduir el temps de desenvolupament d'aquests productes, i dels seus costos associats. A més permetrà obrir noves línies d'investigació per respondre els reptes que plantegen geometries cada vegada més complexes. Aquesta tesi es centra en el desenvolupament d'una ferramenta d'anàlisi EM per a un tipus concret d'estructures: cavitats bidimensionals de forma arbitraria. És habitual trobar aquestes estructures en la majoria de components implementats en guia rectangular. Per tant, l'àmbit d'aplicació de la teoria presentada en esta tesi és molt ampli. En concret, s'ha desenvolupat una nova formulació basada en mètodes modals que permet realitzar una caracterització d'ona completa d'aquestes estructures de forma eficient i precisa. Aprofitant la seua simetria geomètrica i electromagnètica, la ferramenta desenvolupada pot minimitzar els càlculs a realitzar, aconseguint grans velocitats de càlcul mantenint una alta precisió. Gràcies a la integració d'aquesta formulació dins d'una ferramenta CAE basada en mètodes modals, s'ofereix la possibilitat als dissenyadors de resoldre sistemes molt complexos que combinen aquest tipus de cavitats amb altres components de diferent geometria. Aquesta formulació s'aplica, en primer lloc, a l'anàlisi i disseny de components passius comuns: filtres, multiplexors i OMTs. Aquests exemples serveixen per a validar la ferramenta desenvolupada, així com demostrar la significativa millora que suposa l'ús d'aquesta nova tècnica respecte d'altres paquets software d'anàlisi electromagnètic. Així mateix, mitjançant la combinació d'aquesta formulació amb la ferramenta SPARK3D s'obri la possibilitat de predir l'aparició de fenòmens de descàrrega d'alta potència en estructures bidimensionals. A continuació, es proposen noves formes d'implementar filtres quasi el-líptics en guia d'ona basats en la interconnexió de cavitats bidimensionals. Es fa especial èmfasi en la realització de múltiples zeros de transmissió mitjançant estructures compactes que no requereixen de sintonia. D'una banda s'estudien els filtres hybrid folded rectangular waveguide. Aquest treball inclou una discussió en profunditat sobre diferents implementacions d'aquest tipus de filtres. S'hi consideren aspectes pràctics relacionats amb el seu ús i implementació física, que ofereixen al dissenyador uns criteris clars per triar l'estructura que més s'ajuste a les seues especificacions. D'altra banda es presenta un nou obstacle de naturalesa capacitiva extremadament compacte, que permet la realització de múltiples zeros de transmissió fins i tot en estructures en línia. En els dos casos s'inclouen exemples d'aplicació i es descriu la metodologia seguida per al seu disseny. Finalment, s'exposa un procediment sistemàtic per dissenyar multiplexors de banda ampla. Per prevenir la generació de ressonàncies no desitjades s'eviten les interconnexions amb trams de guia curts. Seguint una metodologia simple, basada en fórmules analítiques i simulacions electromagnètiques, s'aconsegueix un excel-lent punt inicial per a l'optimització.
Carceller Candau, C. (2016). Full-wave characterization of bi-dimensional cavities and its application to the design of waveguide filters and multiplexers [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/64089
TESIS

This dissertation proposes three novel bandpass filter structures to protect systems exposed to damaging levels of electromagnetic (EM) radiation from intentional and unintentional high-power microwave (HPM) sources. This is of interest because many commercial microwave communications and sensor systems are unprotected from high power levels. Novel technologies to harden front-end components must maintain existing system performance and cost. The proposed concepts all use low-cost printed circuit board (PCB) fabrication to create compact solutions that support high integration.

The first proposed filter achieves size reduction of 46% using a technology that is suitable for low-loss, narrowband filters that can handle high power levels. This is accomplished by reducing a substrate-integrated waveguide (SIW) loaded evanescent-mode bandpass filter to a half-mode SIW (HMSIW) structure. Demonstrated third-order SIW and HMSIW filters have 1.7 GHz center frequency and 0.2 GHz bandwidth. Simulation and measurements of the filters utilizing combline resonators prove the underlying principles.

The second proposed device combines a traditional microstrip bent hairpin filter with encapsulated gas plasma elements to create a filter-limiter: a novel narrowband filter with integral HPM limiter behavior. An equivalent circuit model is presented for the ac coupled plasma-shell components used in this dissertation, and parameter values were extracted from measured results and EM simulation. The theory of operation of the proposed filter-limiter was experimentally validated and key predictions were demonstrated including two modes of operation in the on state: a constant output power mode and constant attenuation mode at high power. A third-order filter-limiter with center frequency of 870 MHz was demonstrated. It operates passively from incident microwave energy, and can be primed with an external voltage source to reduce both limiter turn-on threshold power and output power variation during limiting. Limiter functionality has minimal impact on filter size, weight, performance, and cost.

The third proposed device demonstrates a large-area, light-weight plasma device that interacts with propagating X-band (8-12 GHz) microwave energy. The structure acts as a switchable EM aperture that can be integrated into a radome structure that shields enclosed antenna(s) from incident energy. Active elements are plasma-shells that are electrically excited by frequency selective surfaces (FSS) that are transparent to the frequency band of interest. The result is equivalent to large-area free-space plasma confined in a discrete layer. A novel structure was designed with the aid of full-wave simulation and was fabricated as a 76.2 mm square array. Transmission performance was tested across different drive voltages and incidence angles. Switchable attenuation of 7 dB was measured across the passband when driven with 1400 V_pp at 1 MHz. Plasma electron density was estimated to be 3.6 × 10 ¹² cm^-3 from theory and full-wave simulation. The proposed structure has potential for use on mobile platforms.

This thesis tackles issues of particular interest regarding analysis and design of passive components at the mm-wave and Terahertz (THz) bands. Innovative analysis techniques and modeling of complex structures, design procedures, and practical implementation of advanced passive devices are presented. The first part of the thesis is dedicated to THz passive components. These days, THz technology suffers from the lack of suitable waveguiding structures since both, metals and dielectric, are lossy at THz frequencies. This implies that neither conventional closed metallic structures used at microwave frequencies, nor dielectric waveguides used in the optical regime, are adequate solutions. Among a variety of new proposals, the Single Wire Waveguide (SWW) stands out due to its low attenuation and dispersion. However, this surface waveguide presents difficult excitation and strong radiation on bends. A Dielectric-Coated Single Wire Waveguide (DCSWW) can be used to alleviate these problems, but advantages of the SWW are lost and new problems arise. Until now, literature has not given proper solution to radiation on bends and, on the other hand, rigorous characterization of these waveguides lacks these days. This thesis provides, for the first time, a complete modal analysis of both waveguides, appropriated for THz frequencies. This analysis is later applied to solve the problem of radiation on bends. Several structures and design procedures to alleviate radiation losses are presented and experimentally validated. The second part of the thesis is dedicated to mm-wave passive components. These days, when implementing passive components to operate at such small, millimetric wavelengths, to ensure proper metallic contact and alignment between parts results challenging. In addition, dielectric absorption becomes significant at mm-wave frequencies. Consequently, conventional hollow metallic waveguides and planar transmission lines present high attenuation so that new topologies are being considered. Gap Waveguides (GWs), based on a periodic structure introducing an Electromagnetic Bandgap effect, result very suitable since they do not require metallic contacts and avoid dielectric losses. However, although GWs have great potential, several issues prevent GW technology from becoming consolidated and universally used. On the one hand, the topological complexity of GWs difficulties the design process since full-wave simulations are time-costly and there is a lack of appropriate analysis methods and suitable synthesis procedures. On the other hand, benefits of using GWs instead of conventional structures are required to be more clearly evidenced with high-performance GW components and proper comparatives with conventional structures. This thesis introduces several efficient analysis methods, models, and synthesis techniques that will allow engineers without significant background in GWs to straightforwardly implement GW devices. In addition, several high-performance narrow-band filters operating at Ka-band and V-band, as well as a rigorous comparative with rectangular waveguide topology, are presented.
Esta tesis aborda problemas actuales en el análisis y diseño de componentes pasivos en las bandas de onda milimétrica y Terahercios (THz). Se presentan nuevas técnicas de análisis y modelado de estructuras complejas, procedimientos de diseño, e implementación práctica de dispositivos pasivos avanzados. La primera parte de la tesis se dedica a componentes pasivos de THz. Actualmente no se disponen de guías de onda adecuadas a THz debido a que ambos, metales y dieléctricos, introducen grandes pérdidas. En consecuencia, no es adecuado escalar las estructuras metálicas cerradas usadas en microondas, ni las guías dieléctricas usadas a frecuencias ópticas. Entre un gran número de recientes propuestas, la Single Wire Waveguide (SWW) destaca por su baja atenuación y casi nula dispersión. No obstante, como guía superficial, la SWW presenta difícil excitación y radiación en curvas. El uso de un recubrimiento dieléctrico, creando la Dielecric-Coated Single Wire Waveguide (DCSWW), alivia estos inconvenientes, pero las ventajas anteriores se pierden y nuevos problemas aparecen. Hasta la fecha, no se han encontrado soluciones adecuadas para la radiación en curvas de la SWW. Además, se echa en falta una caracterización rigurosa de ambas guías. Esta tesis presenta, por primera vez, un análisis modal completo de SWW y DCSWW, adecuado a la banda de THz. Este análisis es aplicado posteriormente para evitar el problema de la radiación en curvas. Se presentan y validan experimentalmente diversas estructuras y procedimientos de diseño. La segunda parte de la tesis abarca componentes pasivos de ondas milimétricas. Actualmente, estos componentes sufren una importante degradación de su respuesta debido a que resulta difícil asegurar contacto metálico y alineamiento adecuados para la operación a longitudes de onda tan pequeñas. Además, la absorción dieléctrica incrementa notablemente a estas frecuencias. En consecuencia, tanto guías metálicas huecas como líneas de transmisión planares convencionales presentan gran atenuación, siendo necesario considerar topologías alternativas. Las Gap Waveguides (GWs), basadas en una estructura periódica que introduce un efecto de Electromagnetic Bandgap, resultan muy adecuadas puesto que no requieren contacto entre partes metálicas y evitan las pérdidas en dieléctricos. No obstante, a pesar del potencial de las GWs, varias barreras impiden la consolidación y uso universal de esta tecnología. Por una parte, la compleja topología de las GWs dificulta el proceso de diseño dado que las simulaciones de onda completa consumen mucho tiempo y no existen actualmente métodos de análisis y diseño apropiados. Por otra parte, es necesario evidenciar el beneficio de usar GWs mediante dispositivos GW de altas prestaciones y comparativas adecuadas con estructuras convencionales. Esta tesis presenta diversos métodos de análisis eficientes, modelos, y técnicas de diseño que permitirán la síntesis de dispositivos GW sin necesidad de un conocimiento profundo de esta tecnología. Asimismo, se presentan varios filtros de banda estrecha operando en las bandas Ka y V con altas prestaciones, así como una comparativa rigurosa con la guía rectangular.
Aquesta tesi aborda problemes actuals en relació a l'anàlisi i disseny de components passius en les bandes d'ona mil·limètrica i Terahercis. Es presenten noves tècniques d'anàlisi i modelatge d'estructures complexes, procediments de disseny, i implementació pràctica de dispositius passius avançats. La primera part de la tesi es focalitza en components passius de THz. Actualment no es disposen de guies d'ona adequades a THz causa que tots dos, metalls i dielèctrics, introdueixen grans pèrdues. En conseqüència, no és adequat escalar les estructures metál·liques tancades usades en microones, ni les guies dielèctriques usades a freqüències òptiques. Entre un gran nombre de propostes recents, la Single Wire Waveguide (SWW) destaca per la seua baixa atenuació i quasi nul·la dispersió. No obstant això, com a guia superficial, la SWW presenta difícil excitació i radiació en corbes. L'ús d'un recobriment dielèctric, creant la Dielecric-Coated Single Wire Waveguide (DCSWW), alleuja aquests inconvenients, però els avantatges anteriors es perden i nous problemes apareixen. Fins a la data, no s'han trobat solucions adequades per a la radiació en corbes de la SWW. A més, es troba a faltar una caracterització rigorosa d'ambdues guies. Aquesta tesi presenta, per primera vegada, un anàlisi modal complet de SWW i DCSWW, adequat a la banda de THz. Aquest anàlisi és aplicat posteriorment per evitar el problema de la radiació en corbes. Es presenten i validen experimentalment diverses estructures i procediments de disseny. La segona part de la tesi es centra en components passius d'ones mil·limètriques. Actualment, aquests components pateixen una important degradació de la seua resposta a causa de que resulta difícil assegurar contacte metàl·lic i alineament adequats per a l'operació a longituds d'ona tan menudes. A més, l'absorció dielèctrica incrementa notablement a aquestes freqüències. En conseqüència, tant guies metàl·liques buides com línies de transmissió planars convencionals presenten gran atenuació, sent necessari considerar topologies alternatives. Les Gap Waveguides (GWs), basades en una estructura periòdica que introdueix un efecte de Electromagnetic Bandgap, resulten molt adequades ja que no requereixen contacte entre parts metàl·liques i eviten les pèrdues en dielèctrics. No obstant, tot i el potencial de les GWs, diverses barreres impedixen la consolidació i ús universal d'aquesta tecnologia. D'una banda, la complexa topologia de les GWs dificulta el procés de disseny atés que les simulacions d'ona completa consumeixen molt de temps i no existeixen actualment mètodes d'anàlisi i disseny apropiats. D'altra banda, és necessari evidenciar el benefici d'utilitzar GWs mitjançant dispositius GW d'altes prestacions i comparatives adequades amb estructures convencionals. Aquesta tesi presenta diversos mètodes d'anàlisi eficients, models, i tècniques de disseny que permetran la síntesi de dispositius GW sense necessitat d'un coneixement profund d'aquesta tecnologia. Així mateix, es presenten diversos filtres de banda estreta operant en les bandes Ka i V amb altes prestacions, així com una comparativa rigorosa amb la guia rectangular.
Berenguer Verdú, AJ. (2017). Analysis and design of efficient passive components for the millimeter-wave and THz bands [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/84004
TESIS

The recent developments in Low Temperature Co-fired Ceramic (LTCC) as a substrate material enable it to be used in the micro and millimetre wave range providing low dissipation factors at high frequencies, good dielectric properties and a high degree of integration for further miniaturised devices. The most common metallisation method used in LTCC technology is screen printing with high cost noble metals such as silver and gold that are compatible with the high sintering temperatures (850°C). However, these techniques require high capital cost and maintenance cost. As the commercial world requires convenient and low cost process technologies for mass production, alternative metallisation methods should be considered. As a result, electroless copper plating of fired LTCC was mainly investigated in this research. The main goals of this project were to carry out electroless plating of fired LTCC with sufficient adhesion and to extend the process to metallise closed LTCC channel structures to manufacture Substrate Integrated Waveguide (SIW) components. The objectives were focused on electroless copper deposition on fired LTCC with improved adhesion. Electroless deposits on the Sn/Pd activated LTCC surface showed poor adhesion without any surface pre-treatments. Hence, chemical etching of fired LTCC was carried out using concentrated NaOH solution. NaOH pre-treatment of LTCC led to the formation of flake like structures on the LTCC surface. A number of surface and chemical analysis techniques and weight measurements were used to investigate the mechanism of the modification of the LTCC surface. The results showed that the flake like structures were dispersed in the LTCC material and a material model for the LTCC structure was proposed. SEM EDX elemental mapping showed that the flake like structure consisted of aluminium, calcium, boron and oxygen. Further experiments showed that both the concentration of NaOH and the immersion time affect the surface morphology and the roughness of fired LTCC. The measured Ra values were 0.6 μm for untreated LTCC and 1.1 μm for the LTCC sample treated with 4M NaOH for 270 minutes. Adhesion tests including peel test and scratch test were carried out to examine the adhesion strength of the deposited copper and both tests indicated that the NaOH pre-treatment led to an improvement, with the best results achieved for samples treated with 4M NaOH. A second aspect of the research focused on the selective metallisation of fired LTCC. Excimer laser machining was used to pattern a resist film laminated on the LTCC surface. This process also roughened the substrate and created channels that were characterised with respect to the laser operating parameters. After patterning the resist layer, samples were activated using Sn/Pd catalyst solution followed by the electroless copper deposition. Electroless copper was selectively deposited only on the patterned LTCC surface. Laser parameters clearly affected the copper plating rate. Even with a similar number of shots per area, the tracks machined with higher repetition rate showed relatively more machining depth as well as good plating conditions with low resistance values. The process was further implemented to realize a complete working circuit on fired LTCC. Passive components including a capacitor and an inductor were also fabricated on LTCC using the mask projection technique of the excimer laser system. This was successful for many designs, but when the separation between conductor lines dropped below 18 μm, electroless copper started to deposit on the areas between them. Finally, a method to deposit copper films on the internal walls of closed channel structures was developed. The method was first demonstrated by flowing electroless copper solutions through silane treated glass capillaries. A thin layer (approx. 60 nm) of electroless copper was deposited only on the internal walls of the glass capillaries. The flow rate of the electroless copper solution had to be maintained at a low level as the copper deposits tended to wash away with higher flow rates. The structures were tested for transmission losses and showed low (<10dB) transmission losses in the terahertz region of the electromagnetic spectrum. The process was further applied to deposit electroless copper on the internal walls of the LTCC closed channel structures to manufacture a LTCC Substrate Integrated Waveguide (SIW).

The widespread adoption of photonic circuits requires the economics of volume manufacturing offered by integration technology. A Complementary Metal-Oxide Semiconductor compatible silicon material platform is particularly attractive because it leverages the huge investment that has been made in silicon electronics and its high index contrast enables tight confinement of light which decreases component footprint and energy consumption. Nevertheless, there remain challenges to the development of photonic integrated circuits. Although the density of integration is advancing steady and the integration of the principal components – waveguides, optical sources and amplifiers, modulators, and photodetectors – have all been demonstrated, the integration density is low and the device library far from complete. The integration density is low primarily because of the difficulty of confining light in structures small compared to the wavelength which measured in micrometers. The device library is incomplete because of the immaturity of hybridisation on silicon of other materials required by active devices such as III-V semiconductor alloys and ferroelectric oxides and the difficulty of controlling the coupling of light between disparate material platforms. Metamaterials are nanocomposite materials which have optical properties not readily found in Nature that are defined as much by their geometry as their constituent materials. This offers the prospect of the engineering of materials to achieve integrated components with enhanced functionality. Metamaterials are a class of photonic crystals includes subwavelength grating waveguides, which have already provided breakthroughs in component performance yet require a simpler fabrication process compatible with current minimum feature size limitations. The research reported in this PhD thesis advances our understanding of the structure-property relations of key planar light circuit components and the metamaterial engineering of these properties. The analysis and simulation of components featuring structures that are only just subwavelength is complicated and consumes large computer resources especially when a three dimensional analysis of components structured over a scale larger than the wavelength is desired. This obstructs the iterative design-simulate cycle. An abstraction is required that summarises the properties of the metamaterial pertinent to the larger scale while neglecting the microscopic detail. That abstraction is known as homogenisation. It is possible to extend homogenisation from the long-wavelength limit up to the Bragg resonance (band edge). It is found that a metamaterial waveguide is accurately modeled as a continuous medium waveguide provided proper account is taken of the emergent properties of the homogenised metamaterial. A homogenised subwavelength grating waveguide structure behaves as a strongly anisotropic and spatially dispersive material with a c-axis normal to the layers of a one dimensional multi-layer structure (Kronig-Penney) or along the axis of uniformity for a two dimensional photonic crystal in three dimensional structure. Issues with boundary effects in the near Bragg resonance subwavelength are avoided either by ensuring the averaging is over an extensive path parallel to boundary or the sharp boundary is removed by graded structures. A procedure is described that enables the local homogenised index of a graded structure to be determined. These finding are confirmed by simulations and experiments on test circuits composed of Mach-Zehnder interferometers and individual components composed of regular nanostructured waveguide segments with different lengths and widths; and graded adiabatic waveguide tapers. The test chip included Lüneburg micro-lenses, which have application to Fourier optics on a chip. The measured loss of each lens is 0.72 dB. Photonic integrated circuits featuring a network of waveguides, modulators and couplers are important to applications in RF photonics, optical communications and quantum optics. Modal phase error is one of the significant limitations to the scaling of multimode interference coupler port dimension. Multimode interference couplers rely on the Talbot effect and offer the best in-class performance. Anisotropy helps reduce the Talbot length but temporal and spatial dispersion is necessary to control the modal phase error and wavelength dependence of the Talbot length. The Talbot effect in a Kronig-Penny metamaterial is analysed. It is shown that the metamaterial may be engineered to provide a close approximation to the parabolic dispersion relation required by the Talbot effect for perfect imaging. These findings are then applied to the multimode region and access waveguide tapers of a multi-slotted waveguide multimode interference coupler with slots either in the transverse direction or longitudinal direction. A novel polarisation beam splitter exploiting the anisotropy provided by a longitudinally slotted structure is demonstrated by simulation. The thesis describes the design, verification by simulation and layout of a photonic integrated circuit containing metamaterial waveguide test structures. The test and measurement of the fabricated chip and the analysis of the data is described in detail. The experimental results show good agreement with the theory, with the expected errors due to fabrication process limitations. From the Scanning Electron Microscope images and the measurements, it is clear that at the boundary of the minimum feature size limit, the error increases but still the devices can function.

Les systèmes de communications sans fils actuels imposent des contraintes très sévères en termes de la capacité du canal, la qualité de transmission tout en gardant les niveaux d'interférences et multi-trajets assez faibles. De telles contraintes ont rendu les antennes multifaisceaux un élément essentiel dans ces systèmes. Parmi les techniques permettant de réaliser une antenne multifaisceaux (sans avoir recours aux systèmes à balayages électroniques), un réseau d'antennes élémentaires est associé à un réseau d'alimentation (une matrice) à formation de faisceau (Beam Forming Network-BFN). Parmi les différents types de ces matrices, la matrice de Butler a reçu une attention particulière. Ceci est dû au fait qu'elle est théoriquement sans pertes et qu'elle emploie un nombre minimum de composants (coupleurs et déphaseurs) afin de générer l'ensemble de faisceaux orthogonaux demandé (avec l'hypothèse que le nombre de faisceau est une puissance de 2). Néanmoins, la matrice de Butler a un problème de conception majeur. Ce problème réside dans la structure de la matrice qui renferme des croisements ce qui a été adressé par différents travaux de recherches dans la littérature. Les Guide Intégré au Substrat (GIS) offrent des caractéristiques intéressants pour la conception des composants microondes et millimétriques faciles à intégrer sur un même support avec d'autres composants planaires. Les composants à base de GIS combinent les avantages des guides d'ondes rectangulaires, comme leur grand facteur de qualité Q, leur faibles pertes tout en étant compatible avec les technologies à faibles coûts comme le PCB et le LTCC. Vus ses caractéristiques attrayants, la technologie GIS devient un bon candidat pour la réalisation des matrices multifaisceaux faciles à intégrer avec d'autres systèmes en technologies planaires ou à base de guide GIS. Dans cette thèse, de nouveaux composants passifs sont développés en exploitant la technologie GIS en multicouches en vue de la réalisation d'une matrice de Butler 4x4 compacte et large bande. Les composants recherchés sont donc des coupleurs et des déphaseurs ayant des performances large bande en termes des amplitudes des coefficients de transmissions et les phases associés tout en gardant de faibles niveaux de pertes et de bonnes isolations. Différents techniques pour l'implémentation de déphaseurs large bande en technologie GIS sont présentés. Une nouvelle structure à base d'une propagation composite : main gauche main droite (Composite Right/Left- Handed, CRLH) dans un guide d'onde est proposée. La structure consiste d'un guide d'onde monocouche ayant des fenêtres inductives et des fentes transversales à réactances capacitives pour synthétiser l'inductance parallèle et la capacité série main gauche, respectivement. La structure est adaptée pour les réalisations de déphaseurs compacts en technologie GIS. Bien que les pertes d'insertions restent dans le même ordre de grandeur de celles des structures CRLH à base d'éléments non-localisés, ces niveaux de pertes restent relativement grands par rapport aux applications nécessitant plusieurs déphaseurs. Les déphaseurs à bases de GIS ayant des longueurs égales et des largeurs variables sont ensuite abordés. Ce type de déphaseur est effectivement très adapté à la technologie GIS qui permet des réalisations de parcours avec différentes formes (parcours droits, courbés, coudés, ..) tout en assurant des différences de phase large bande. Afin de satisfaire de faibles pertes d'insertions pour une large dynamique de phase, la longueur de ces déphaseurs est en compromis avec les variations progressives des différentes largeurs associées aux valeurs de déphasages requises. Une transition large bande, double couche et à faible perte est ainsi proposée. La transition est analysée à partir de son circuit électrique équivalent afin d'étudier les performances en termes de l'amplitude et la phase du coefficient de transmission par rapport aux différents paramètres structurels de la transition. Cette transition est ensuite exploitée pour développer un déphaseur à trois couches, large bande, en GIS. La structure consiste effectivement d'un guide d'onde replié à plusieurs reprises sur luimême selon la longueur dans une topologie trois couches à faibles pertes. De nouveaux coupleurs double couche en GIS sont également proposés. Pour les applications BFNs, une structure originale d'un coupleur large bande est développée. La structure consiste de deux guides d'onde parallèles qui partagent leur grand mur ayant une paire de fentes inclinées et décalées par rapport au centre de la structure. Une étude paramétrique détaillée est faite pour étudier l'impact des différents paramètres des fentes sur l'amplitude et la phase du coefficient de transmission. Le coupleur proposé a l'avantage d'assurer une large dynamique de couplage ayant des performances larges bandes en termes des amplitudes et les phases des coefficients de transmission avec de faibles pertes et de bonnes isolations entre le port d'entré et celui isolé. D'autre part, contrairement à d'autres travaux antérieurs et récents qui souffraient d'une corrélation directe entre la phase en transmission et le niveau de couplage, la structure proposée permet de contrôler le niveau de couplage en maintenant presque les mêmes valeurs de phase en transmission pour différents niveaux de couplage. Ceci le rend un bon candidat pour les BFNs déployant différents coupleurs telle la matrice de Nolen. Une deuxième structure originale d’un coupleur bibande est également proposée. La structure consiste de deux coupleurs concentriques en guide nervuré intégré au substrat avec un motif innovant de démultiplexage à base de GIS. Ce coupleur a été développé conjointement avec M. Tarek Djerafi de l’Ecole Polytechnique de Montréal dans un cadre de collaboration avec le Prof. Ke Wu. Finalement, pour l'implémentation de la matrice de Butler, la topologie double couche est explorée à deux niveaux. Le premier consiste à optimiser les caractéristiques électriques de la matrice, tandis que le second concerne l'optimisation de la surface occupée afin de rendre la matrice la plus compacte possible sans dégrader ses performances électriques. D'une part, la structure double couche présente une solution intrinsèque au problème de croisement permettant ainsi une plus grande flexibilité pour la compensation de phase sur une large bande de fréquence. Ceci est réalisé par une conception adéquate de la surface géométrique sur chaque couche de substrat et optimiser les différentes sections de GIS avec les différents parcours adoptés. La deuxième étape consiste effectivement à optimiser la surface sur chaque couche en profitant de la technologie GIS. Ceci consiste à réaliser des murs latéraux communs entre différents chemin électrique de la matrice en vue d'une compacité optimale. Les deux prototypes de matrices de Butler 4x4 sont optimisés, fabriqués et mesurés. Les résultats de mesures sont en bon accord avec ceux de la simulation. Des niveaux d'isolations mieux que - 15 dB avec des niveaux de réflexions inférieurs à -12 dB sont validés expérimentalement sur plus de 24% de bande autour de 12.5 GHz. Les coefficients de transmission montrent de faibles dispersions d'environ 1 dB avec une moyenne de -6.8 dB, et 10° par rapport aux valeurs théoriques, respectivement, sur toute la bande de fréquence
Multibeam antennas have become a key element in nowadays wireless communication systems where increased channel capacity, improved transmission quality with minimum interference and multipath phenomena are severe design constraints. These antennas are classified in two main categories namely adaptive smart antennas and switched-beam antennas. Switched-beam antennas consist of an elementary antenna array connected to a Multiple Beam Forming Network (M-BFN). Among the different M-BFNs, the Butler matrix has received particular attention as it is theoretically lossless and employs the minimum number of components to generate a given set of orthogonal beams (provided that the number of beams is a power of 2). However, the Butler matrix has a main design problem which is the presence of path crossings that has been previously addressed in different research works. Substrate Integrated Waveguide (SIW) features interesting characteristics for the design of microwave and millimetre-wave integrated circuits. SIW based components combine the advantages of the rectangular waveguide, such as the high Q factor (low insertion loss) and high power capability while being compatible with low-cost PCB and LTCC technologies. Owing to its attractive features, the use of SIW technology appears as a good candidate for the implementation of BFNs. The resulting structure is therefore suitable for both waveguide-like and planar structures. In this thesis, different novel passive components (couplers and phase shifters) have been developed exploring the multi-layer SIW technology towards the implementation of a two-layer compact 4×4 Butler matrix offering wideband performances for both transmission magnitudes and phases with good isolation and input reflection characteristics. Different techniques for the implementation of wideband fixed phase shifters in SIW technology are presented. First, a novel waveguide-based CRLH structure is proposed. The structure is based on a single-layer waveguide with shunt inductive windows (irises) and series transverse capacitive slots, suitable for SIW implementations for compact phase shifters. The structure suffers relatively large insertion loss which remains however within the typical range of non-lumped elements based CRLH implementations. Second, the well-known equal length, unequal width SIW phase shifters is discussed. These phase shifters are very adapted for SIW implementations as they fully exploit the flexibility of the SIW technology in different path shapes while offering wideband phase characteristics. To satisfy good return loss characteristics with this type of phase shifters, the length has to be compromised with respect to the progressive width variations associated with the required phase shift values. A twolayer, wideband low-loss SIW transition is then proposed. The transition is analyzed using its equivalent circuit model bringing a deeper understanding of its transmission characteristics for both amplitude and phase providing therefore the basic guidelines for electromagnetic optimization. Based on its equivalent circuit model, the transition can be optimized within the well equal-length SIW phase shifters in order to compensate its additional phase shift within the frequency band of interest. This twolayer wideband phase shifter scheme has been adopted in the final developed matrix architecture.This transition is then exploited to develop a three-layer, multiply-folded waveguide structure as a good candidate for compensated-length, variable width, low-loss, compact wideband phase shifters in SIW technology. Novel two-layer SIW couplers are also addressed. For BFNs applications, an original structure for a two-layer 90° broadband coupler is developed. The proposed coupler consists of two parallel waveguides coupled together by means of two parallel inclined-offset resonant slots in their common broad wall. A complete parametric study of the coupler is carried out including the effect of the slot length, inclination angle and offset on both the coupling level and the transmission phase. The first advantage of the proposed coupler is providing a wide coupling dynamic range by varying the slot parameters allowing the design of wideband SIW Butler matrix in two-layer topology. In addition, previously published SIW couplers suffer from direct correlation between the transmission phase and the coupling level, while the coupler, hereby proposed, allows controlling the transmission phase without significantly affecting the coupling level, making it a good candidate for BFNs employing different couplers, such as, the Nolen matrix. A novel dual-band hybrid ring coupler is also developed in multi-layer Ridged SIW (RSIW) technology. This coupler has been jointly developed with Tarek Djerafi in a collaboration scenario with Prof. Ke Wu from the Ecole Polytechnique de Montréal. The coupler has an original structure based on two concentric rings in RSIW topology with the outer ring periodically loaded with radial, stub-loaded transverse slots. A design procedure is presented based on the Transverse Resonance Method (TRM) of the ridged waveguide together with the simple design rules of the hybrid ring coupler. A C/K dual band coupler with bandwidths of 8.5% and 14.6% centered at 7.2 GHz and 20.5 GHz, respectively, is presented. The coupler provides independent dual band operation with low-dispersive wideband operation. Finally, for the Butler matrix design, the two-layer SIW implementation is explored through a two-fold enhancement approach for both the matrix electrical and physical characteristics. On the one hand, the two-layer topology allows an inherent solution for the crossing problem allowing therefore more flexibility for phase compensation over a wide frequency band. This is achieved by proper geometrical optimization of the surface on each layer and exploiting the SIW technology in the realization of variable width waveguides sections with the corresponding SIW bends. On the other hand, the two-layer SIW technology is exploited for an optimized space saving design by implementing common SIW lateral walls for the matrix adjacent components seeking maximum size reduction. The two corresponding 4×4 Butler matrix prototypes are optimized, fabricated and measured. Measured results are in good agreement with the simulated ones. Isolation characteristics better than -15 dB with input reflection levels lower than -12 dB are experimentally validated over 24% frequency bandwidth centered at 12.5 GHz. Measured transmission magnitudes and phases exhibit good dispersive characteristics of 1dB, around an average value of -6.8 dB, and 10° with respect to the theoretical phase values, respectively, over the entire frequency band

碩士
國立中央大學
光電科學研究所
93
In this work, we have performed the simulation, fabrication and characterization of the silicon on insulator (SOI). 1×8 power splitters, Array Waveguide Grating(AWG), taper waveguides and comb drive attenuators are studied. Three types of 1×8 power splitters are investigated, including 1×8 multi-mode interference(MMI) splitters, 1×2×2×2 MMI splitters and 1×8 Y-branch splitters. Losses, uniformity and device sizes are compared for different splitters. Among these three kinds of structures, 1×8 power MMI splitters possess the best performance. For the results of AWG, the accurate distance control of array waveguides, output waveguides and length of star coupler can ameliorate the performance of the AWG. We also propose a taper structure attached to waveguides to reduce the coupling losses. In the comb drive attenuator, the component is fabricated in SOI wafer. Novel comb drive attenuator structures are proposed to solve the sticking problem.

碩士
南台科技大學
電子工程系
95
In this thesis, we created an unique process combining with soft molding, photolithography and holography interference to fabricate an polymer Bragg reflection waveguide component. First we made a waveguide component through photolithography and then combined with micro-contact printing of non-photolithography, micro-molding in capillaries and replica molding to fabricate the molding of the polymer waveguide component. Afterwards, we utilized formed polymer OG waveguide molding along with different diffraction rates of polymer materials to perform the optical transmission layer Finally, we used the process of thick layer photo-resist of photolithography associated with holography interference to implement a polymer Bragg reflective waveguide component. The molding of this waveguide component is reproducible and is able used for mass production. It has some advantages including easy production, lowest optical loss and low cost. The experiment results are measured and observed by AFM and SEM. Whereas the optical transmitting features are measured through the OSA.

THz and mm-wave technology has become increasingly significant in a very diverse range of applications such as spectroscopy, imaging, and communication as a consequence of a plethora of significant advances in this field. However to achieve a mass production of THz systems, all the commercial aspects should be considered. The main concerns are attributed to the robustness, compactness, and a low cost device. In this regard, research efforts should be focused on the elimination of obstacles standing in the way of commercializing the THz technology. To this end, in this study, low cost fabrication technologies for various parts of mm-wave/THz systems are investigated and explored to realize compact, integrated, and rugged components. This task is divided into four phases. In the first phase, a robust fiber-based beam delivery configuration is deployed instead of the free beam optics which is essential to operate the low cost THz photomixers and photoconductive antennas. The compensation of different effects on propagation of the optical pulse along the optical fiber is achieved through all-fiber system to eliminate any bulky and unstable optical components from the system. THz measurements on fiber-coupled systems exhibit the same performance and even better compared to the free beam system. In the next phase, the generated THz wave is coupled to a rectangular dielectric waveguide through design of a novel transition with low insertion loss. The structure dimensions are reported for various range of frequencies up to 650GHz with insertion loss less than 1dB. The structure is fabricated through a standard recipe. In third phase, as consequence of the advent of high performance active device at mm-wave and THz frequency, a transition is proposed for coupling the electromagnetic wave to the active devices with CPW ports. Different approaches are devised for different frequencies as at higher frequencies any kind of metallic structure can introduce a considerable amount of loss to the system. The optimized structures show minimum insertion loss as low as 1dB and operate over 10% bandwidth. The various configurations are fabricated for lower frequencies to verify the transition performance. The last phase focuses on the design, optimization, fabrication and measurements of a new dielectric side-grating antenna for frequency scanning applications. The radiation mechanism is extensively studied using two different commercial full-wave solvers as well as the measured data from the fabricated samples. The optimized antenna achieves a radiation efficiency of 90% and a gain of 18dB. The measured return loss and radiation pattern show a good agreement with the simulation results.

碩士
國立臺灣大學
光電工程學研究所
99
THz technology has been proved to have high potential in a variety of fields such as high-speed telecommunications, bio imaging, molecular detection, material property study, anti-terrorism applications, and astronomical remote sensing. To facilitate THz technology, various kinds of THz fibers and waveguides have been extensively investigated in the past decade. Two years ago, we previously proposed a circular pipe waveguide for low-loss THz waveguiding. With commercial Teflon pipes, an attenuation constant lower than 0.001 cm-1 had been achieved. In this thesis, we proposed several kinds of THz pipe-waveguide-based components for the purpose of constructing compact and flexible THz systems. We first investigated the bending loss characteristics of the pipe waveguides. It is found that the circular pipe waveguides possess magnificent flexibility and unexpected low bending loss. In order to construct THz polarization controllers and directional couplers, we modified the circular pipe waveguides into square and rectangular ones. The proposed rectangular waveguides not only suffer low attenuation (~0.002 cm-1), but also possess polarization-sensitivity to guided THz waves. Moreover, we established a THz leaky mode directional coupler with two square pipe waveguides. The proposed directional coupler is polarization-sensitive. Because of the　anti-resonant reflecting guiding principle of the pipe waveguides, the directional coupler works most efficiently in the minimal-attenuation wavelength regime. We further devised a simple butt coupler setup to combine circular pipe waveguides and rectangular ones. With butt coupling method, square and rectangular pipe waveguides can be high-efficiently (almost 100%) coupled with circular ones. It is expected that these low loss, polarization-sensitive waveguide-based components have high potential in future THz applications.

碩士
國立臺灣科技大學
電子工程系
106
Based on the prior work developed in our group, this thesis presents the improved design of the silicon photonic components realized with both silicon on insulator (SOI) and standard bulk CMOS platforms. The simulation methods for investigating the mode evolution and performance of photonic integrated circuits (PICs) will be introduced. The design process leads to the improvement of the devices on silicon-on-insulator (SOI) platforms including optical filters based on Mach-Zehnder interferometers and sub-wavelength gratings, as well as the grating coupler, ring resonators, and sub-wavelength grating waveguide on the standard 28-nm CMOS platform. The design rules for each platform are adopted in the design processes. The design of optical waveguide devices using the standard 28-nm CMOS process provided by a semiconductor foundry is demonstrated for the first time in this work. The optical waveguide is fabricated using the thin polysilicon layer in the CMOS process without modifying any standard process conditions. Because of the very thin waveguide layer, the motivations here are to investigate the performance of waveguides with very-low confinement factor and to reduce the optical loss of the polysilicon layer. However, the pitch of the grating coupler in the layout is actually twice the original design value. This causes the difficulty in device characterization. We verify the grating design and correct the angle for fiber coupling. Preliminary results are obtained for subsequent design and optimization.

Due to high demand for planar structures with low loss, a considerable amount of research has been done to the design of substrate integrated waveguide (SIW) components in the mm-wave and microwave range. SIW has many advantages in comparison to conventional waveguides and microstrip lines, such as compact and planar structure, ease of fabrication, low radiation loss, high power handling ability and low cost which makes it a very promising technology for current and future systems operating in K-band and above. Therefore, all the work presented in this dissertation focuses on SIW technology. Five di erent antenna systems are proposed to verify the advantages of using SIW technology. First, a novel K-band end- re SIW circularly polarized (CP) antenna system on a single layer printed-circuit board is proposed. A high gain SIW H-plane horn and a Vivaldi antenna are developed to produce two orthogonal polarizations in the plane of the substrate. CP antennas have become very popular because of their unique characteristics and their applications in satellites, radars and wireless communications. Second, a K-band front-end system for tracking applications is presented. The circuit comprises an antenna array of two Vivaldi antennas, a frequency-selective power combiner, and two frequency-selective SIW crossovers, which eliminate the need for subsequent ltering. The integration of monopulse systems in planar, printed circuit SIW technology combined with the added bene ts of ltering functions is of great importance to the antennas and propagation community. Third, a phased array antenna system consisting of 24 radiating element is designed as feed system for reflector antennas in radio astronomy applications. A Ku-band antipodal dipole antenna with wide bandwidth, low cross-polarization and wide beamwidth is suggested as the radiating element. Forth, four di erent right-angled power dividers including in-phase and out-of-phase dividers as feed systems for antenna arrays are introduced. TE10 - to - TEq0 mode transducers are used for obtaining two, three, and four output dividers with phase control ability at K- and Ka-band. This feature is practical, for instance, when designing tracking systems since they are employed to obtain controllable phase distributions over the output ports. Fifth, a Ku-band beam steering antenna system which is applicable to use for wireless communications, radar systems, and also 5G applications is proposed. This antenna system uses variable reflection-type phase shifters which electrically steer the beam over a 50-degree scan range. Therefore, the SIW technology's reliability and also promising behavior in the microwave frequency range is proven for di erent applications.
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