Master’s thesis deals with the issue of electronic filtering circuits with arbitrary frequency characteristics. First part of the thesis describes theoretical basis. Second part explores the possibilities of design procedures for filters with arbitrary frequency characteristics. Design procedures are demonstrated on examples accordingly to the presented methods, including their circuit implementation and computer simulation to verify the correctness of theoretical assumptions. Thesis also explores the possibilities of tuning circuit structures and electronic setting for characteristics using controllable active elements.

This work deals with the most famous constructions of planar antennas. The work analyses selected methods of connecting planar antennas' charging with the possibility of impedance adaptation. An important part of the work consists of description of techniques for increasing bandwidth and conversely techniques for reducing the dimensions which are important for the design of planar antennas for mobile devices. The antennas were designed by means of theoretical basis and their properties were examined in the electromagnetic field simulator. The selected antenna model was constructed and its parameters were measured experimentally. The matching circuit for the antenna to tune it to different resonant frequencies was designed and constructed.

Rolled-up nanotechnology based on strain-engineering is a powerful tool to manufacture three-dimensional hollow structures made of virtually any kind of material on a large variety of substrates. The aim of this thesis is to address the key features of different on- and off-chip applications of rolled-up microtubes through modification of their basic framework. The modification of the framework pertains to the tubular structure, in particular the diameter of the microtube, and the material which it is made of, hence achieving different functionalities of the final rolled-up structure. The tuning of the microtube diameter which is adjusted to the individual size of an object allows on-chip studies of single cells in artificial narrow cavities, for example. Another modification of the framework is the addition of a catalytic layer which turns the microtube into a self-propelled catalytic micro-engine. Furthermore, the tuneability of the diameter can have applications ranging from nanotools for drilling into cells, to cargo transporters in microfluidic channels. Especially rolled-up microtubes based on low-cost and easy to deposit materials, such as silicon oxides, can enable the exploration of novel systems for several scientific topics. The main objective of this thesis is to combine microfluidic features of rolled-up structures with optical sensor capabilities of silicon oxide microtubes acting as optical ring resonators, and to integrate these into a Lab-on-a-Chip system. Therefore, a new concept of microfluidic integration is developed in order to establish an inexpensive, reliable and reproducible fabrication process which also sustains the optical capabilities of the microtubes. These integrated microtubes act as optofluidic refractrometric sensors which detect changes in the refractive index of analytes using photoluminescence spectroscopy. The thesis concludes with a demonstration of a functional portable sensor device with several integrated optofluidic sensors. / Die auf verspannten Dünnschichten basierende „rolled-up nanotechnologie“ ist eine leistungsfähige Methode um dreidimensionale hohle Strukturen (Mikroröhrchen) aus nahezu jeder Art von Material auf einer großen Vielfalt von Substraten herzustellen. Ausgehend von der Möglichkeit der Skalierung des Röhrchendurchmessers und der Modifikation der Funktionalität des Röhrchens durch Einsatz verschiedener Materialien und Oberflächenfunktionalisierungen kann eine große Anzahl an verschiedenen Anwendungen ermöglicht werden. Eine Anwendung behandelt unter anderem on-chip Studien einzelner Zellen wobei die Mikroröhrchen, an die Größe der Zelle angepasste, Reaktionscontainer darstellen. Eine weitere Modifikation der Funktionalität der Mikroröhrchen kann durch das Aufbringen einer katalytischen Schicht realisiert werden, wodurch das Mikroröhrchen zu einem selbstangetriebenen katalytischen Mikro-Motor wird. Hauptziel dieser Arbeit ist es Mikrometer große optisch aktive Glasröhrchen herzustellen, diese mikrofluidisch zu kontaktieren und als Sensoren in Lab-on-a-Chip Systeme zu integrieren. Die integrierten Glasröhrchen arbeiten als optofluidische Ringresonatoren, welche die Veränderungen des Brechungsindex von Fluiden im inneren des Röhrchens durch Änderungen im Evaneszenzfeld detektieren können. Die Funktionsfähigkeit eines Demonstrators wird mit verschiedenen Flüssigkeiten gezeigt, dabei kommt ein Fotolumineszenz Spektrometer zum Anregen des Evaneszenzfeldes und Auslesen des Signals zum Einsatz. Die entwickelte Integrationsmethode ist eine Basis für ein kostengünstiges, zuverlässiges und reproduzierbares Herstellungsverfahren von optofluidischen Mikrochips basierend auf optisch aktiven Mikroröhrchen.

Um der Mikrowellenerwärmung als Single- oder Hybridanwendung im industriellen Ofenbau ein weiteres Anwendungsspektrum zu eröffnen, wird dem Anlagenkonstrukteur im Rahmen dieser Arbeit eine Aufstellung von Entwicklungsprioritäten und Konstruktionshinweisen übergeben. Für eine energieeffiziente Ausnutzung des technologischen Potenzials wird hierbei nicht - wie in der Vergangenheit - die Feldstärkenverteilung, sondern das Reflexionsverhalten in den Vordergrund gestellt. Durch die Entwicklung und den Aufbau eines Messplatzes zur Bestimmung temperaturspezifischer Dielektrizitätsparameter konnte die Realitätsnähe der Simulation für die anwendungsorientierte Applikatorentwicklung gesteigert werden. Die Anwendbarkeit der Auslegungskriterien wird im Rahmen der Projektierung und des Aufbaus einer Beispielanlage zur Entbinderung von keramischen Grünkörpern und bei der Entwicklung zahlreicher mikrowellenspezifischer Anlagenbauteile verifiziert.

Vertically rolled-up microcavities are fabricated using differentially strained nanomembranes by employing rate and temperature gradients during electron beam evaporation of SiO2. The geometry of the rolled-up tubes is defined by a photo-lithographically patterned polymer sacrificial layer beneath the SiO2 layers that is dissolved to start the rolling. Rolled-up tubes support resonances formed by constructive interference of light propagating along the circumference. Optical studies are performed in the visible spectral range using a micro-photoluminescence (µPL) setup to excite and detect optical modes. Record high quality factors (Q factors) of 5400 for rolled-up resonators probed in PL-emission mode are found and their limits are theoretically investigated. Axial modes can also be supported when an increased winding number in the center is realized by appropriate pattern designs. In addition, higher order radial modes can be confined when atomic layer deposition (ALD) coatings are applied. Both types of modes are identified using polarization and spatially resolved µPL maps. Evanescent-wave coupling by tapered fibers and tubes on substrates is the second method used to study light confinement and to demonstrate frequency filtering in ALD coated rolled-up microcavities. Scans are performed by monitoring light from a tunable laser in the range of 1520-1570 nm after transmission through the tapered fiber. Dips in the spectrum are found and attributed to fundamental and axial resonant modes. Moreover, by coupling two tapered fibers to a lifted rolled-up microcavity, a four-port add-drop filter is demonstrated as a future component for vertical resonant light transfer in on-chip optical networks. Simulations show that the subwavelength tube wall thickness limits the Q factor at infrared wavelengths and ALD coatings are necessary to enhance the light confinement. After coating, two linear polarization states are found in experiment and fundamental and axial modes can be selectively excited by coupling the fiber to different positions along the tube axis. Spatially and polarization resolved transmission maps reveal a polarization dependent axial mode distribution which is verified theoretically. The results of this thesis are important for lab-on-chip applications where rolled-up microcavities are employed as high resolution optofluidic sensors as well as for future uses as waveguide coupled components in three-dimensional multi-level optical data processing units to provide resonant interlayer signal transfer.

This work is devoted to investigate light confinement in rolled-up microtubular cavities and their optofluidic applications. The microcavities are fabricated by a roll-up mechanism based on releasing pre-strained silicon-oxide nanomembranes. By defining the shape and thickness of the nanomembranes, the geometrical tube structure is well controlled. Micro-photoluminescence spectroscopy at room temperature is employed to study the optical modes and their dependence on the structural characteristics of the microtubes. Finite-difference-time-domain simulations are performed to elucidate the experimental results. In addition, a theoretical model (based on a wave description) is applied to describe the optical modes in the tubular microcavities, supporting quantitatively and qualitatively the experimental findings. Precise spectral tuning of the optical modes is achieved by two post-fabrication methods. One method employs conformal coating of the tube wall with Al2O3 monolayers by atomic-layer-deposition, which permits a mode tuning over a wide spectral range (larger than one free-spectral-range). An average mode tuning to longer wavelengths of 0.11nm/ Al2O3-monolayer is obtained. The other method consists in asymmetric material deposition onto the tube surface. Besides the possibility of mode tuning, this method permits to detect small shape deformations (at the nanometer scale) of an optical microcavity. Controlled confinement of resonant light is demonstrated by using an asymmetric cone-like microtube, which is fabricated by unevenly rolling-up circular-shaped nanomembranes. Localized three-dimensional optical modes are obtained due to an axial confinement mechanism that is defined by the variation of the tube radius and wall windings along the tube axis. Optofluidic functions of the rolled-up microtubes are explored by immersing the tubes or filling their core with a liquid medium. Refractive index sensing of liquids is demonstrated by correlating spectral shift of the optical modes when a liquid interacts with the resonant light of the microtube. In addition, a novel sensing methodology is proposed by monitoring axial mode spacing changes. Lab-on-a-chip methods are employed to fabricate an optofluidic chip device, allowing a high degree of liquid handling. A maximum sensitivity of 880 nm/refractive-index-unit is achieved. The developed optofluidic sensors show high potential for lab-on-a-chip applications, such as real-time bio/chemical analytic systems.

La sensibilité des détecteurs d’ondes gravitationnelles de LIGO (Laser Interferometer Gravitational-Wave Observatory) est limité par les fluctuations thermiques dues à la dissipation mécanique dans les couches de Ta2O5 amorphe, qui est une composante des miroirs des interféromètres. Le paramètre d’angle de perte ( ) permet de quantifié l’ampleur de la dissipation et est obtenu en étudiant l’absorption d’énergie mécanique par la couche de matériau. Ce paramètre est généralement caractérisé expérimentalement à des fréquences d’excitations allant de 1-30 KHz près de celle qui nous intéresse pour la détection d’onde gravitationnelle (10-100 Hz) et par des simulations de dynamique moléculaire pour des fréquences très élevées (GHz). Notre recherche vise à caractériser l’angle de perte pour ce matériau pour des fréquences intermédiaires, soit dans la gamme des MHz. Afin d’obtenir une meilleure précision sur les résultats, on utilise les ondes acoustiques de surface qui donne un plus grand poids à la couche mince lors du calcul de l’angle de perte. Deux méthodes sont utilisées pour tenter d’obtenir l’angle de perte des couches ( c) de Ta2O5 de 1 μm déposées sur des substrats, d’une part, composé de SiO2 B270 d’épaisseur 2 mm, et d’autre part, de LiNbO3 d’épaisseur 1 mm. La première se fait à l’aide d’un transmetteur piézoélectrique amovible qui génère les ondes de surface et d’un vibromètre laser qui détecte l’amplitude des vibrations à différentes positions sur l’échantillon. Malgré un précision limitée, il est possible d’obtenir l’angle de perte des couches minces à une fréquence d’excitation de 9.08 MHz. Les résultats les plus fiables de c sont dans l’intervalle 2−7×10−2 avec des incertitudes de 1−3×10−2, ce qui représente de 15 à 50% des valeurs selon le cas. On obtient donc des résultats plus élevés que ce qui est attendu pour cette gamme de fréquence, même avec une précision limitée, ce qui nous porte à penser que certains mécanismes peuvent affecter l’angle de perte à plus hautes fréquences. Pour la deuxième méthode, on place directement sur l’échantillon des transmetteurs interdigitaux qui servent à la fois d’émetteur et de récepteur et une cavité résonante qui permet de contenir les ondes d’une certaine longueur d’onde sur l’échantillon. Les fréquences d’excitations des ondes de surface générés sont de 19.89 MHz et 33.15 MHz. Nos échantillons ne nous permettent pas de calculer c, mais la technique de mesure nous permet d’avoir une précision au moins plus élevée que la première méthode soit 1 × 10−2 pour un échantillon et 4 × 10−3 pour l’autre. On peut facilement améliorer la méthode, notamment en augmentant la réflectivité de la cavité résonante, ce qui permettrait d’obtenir des résultats précis avec des échantillons qui comprennent la couche mince. / Limitations to the sensitivity of LIGO’s (Laser Interferometer Gravitational-Wave Observatory) gravitational wave detectors is due to thermal fluctation induced by mechanical dissipation in the amorphous Ta2O5 thin films composing the interferometer’s mirrors. The loss angle parameter ( ) describes the magnitude of the dissipation that occurs in the material and is obtained by studying the mechanical energy absorption of the thin film. This parameter is usually measured for a range of frequencies going from 1 to 30 KHz, which is near the expected frequencies for gravitational wave detection (10-100 Hz). Molecular dynamics simulations also calculate the loss angle for very high frequencies (GHz). Our research aim to caracterise the loss angle of Ta2O5 thin films in the MHz mid-range frequencies. We use surface acoustic waves for the thin film to have a greater weight in the caculation of the loss angle to help us get a higher precision. Two methods are used to obtain the loss angle of the film ( c) of Ta2O5 (1 μm thick) which, for the first method, is deposited on a 2 mm thick SiO2 B270 substrates, and, for the second method, on a 1mm thick LiNbO3 substrates. The first one uses a movable piezoelectric transducer that generates the surface waves and a laser vibrometer to mesure the amplitude of the vibration along the sample. Though the precision is not very good, we were able to calculate the loss angle of thin films for a surface wave frequency of 9.08 MHz. The best results for c are within the range of 2 − 7 × 10−2 with uncertainties ranging from 1−3×10−2, which represent 15 to 50% of values by case. We get higher loss angles than what was expected for this frequency range, even with a low precision, so we suspect that some loss mechanisms might affect the loss angle at higher frequency. The second method uses a resonator that is place directly on the samples with interdigital transducers that generate the surface waves and acoustical mirrors that form the resonator (acoustical cavity). Wave are excited at two different frequencies, 19.89 MHz and 33.15 MHz, and are contained in the resonator to study their propagation on the sample. Althouth we do not have c results for coated sample, we were able to evaluate the precision of such measuments and we have uncertainties of 1 × 10−2 for a sample and 4 × 10−3 for the other. The samples used with this method could easily be improve, by increasing the reflecitvity of the resonator mirrors, to obtain a higher precision and get better results for sample coated with a thin film.

Micro-technology relies on a highly parallel fabrication of 2D electronic and/or microelectromechanical devices, where in most cases silicon wafers are used as substrates. In contrast 3D fabrication shows unique advantages, such as footprint reduction or the possibility to obtain additional functionalities. For example, in the case of a sensor, knowledge of the acceleration in all possible directions, the surrounding electric or magnetic field among other quantities can help to determine the exact position of an object in 3D space. To do that it is crucial to retrieve all components of a vector field, which requires at least one out of plane component. In other fields like integrated optics three dimensional structures can enhance the coupling efficiency with free space interactions. As such 3D micro-structures will be crucial for upcoming products and devices. A highly parallel fabrication is required to enable mass-adaption, self-assembly is an emerging technology that could deliver this purpose. Examples of 3D structures created by self-assembly include polyhedrons like cubes, pyramids or micro tubular structures such as tubes or spirals. Following a self assembly scheme, 3D devices would be created through the fabrication of standard 2D structures that are reshaped through a self-assembly step into a 3D object. In this thesis a novel dry release protocol was developed to roll-up strained nanomembranes from a silicon sacrificial layer employing dry fluorine chemistry. This way a wet release is totally circumvented thus preventing damage of the created structures due to turbulent flow or capillary forces. Additionally the developed process enabled the use of standard CMOS deposition and processing tools, leading to a high increase in yield and quality, with yields exceeding 99% for microtubes. Building on the developed technology various devices where fabricated, for example rolled-up micro capacitors at a wafer scale with an increased yield and a low spread of electrical characteristics. For the E12 industrial standard more than 90% of devices behaved within the required performance characteristics. Furthermore the yield and Q-factor of roll-up whispering gallery mode resonators was strongly improved, making it possible to self assemble 3D coupled photonic molecules, which showed a mode splitting exceeding the FSR, as well as hybrid supermodes at points of energy degeneracy.:Contents Bibliographic Record i List of Abbreviations vii List of Chemical Substances ix 1 Introduction 1 1.1 Microelectromechanical Systems 1 1.2 Strain Engineering 2 1.3 Rolled - Up Nanotechnology 3 1.4 Objective and Structure of the Thesis 5 2 Materials and Methods 9 2.1 Fabrication Techniques 9 2.1.1 Substrates 9 2.1.2 Plasma Enhanced Chemical Vapor Deposition 9 2.1.3 Dry Etching12 2.1.4 Deep Reactive Ion Etching 18 2.1.5 Atomic Layer Deposition 19 2.1.6 Lithography 20 2.2 Characterization Techniques 22 2.2.1 Strain Measurement 22 2.2.2 Ellipsometry 23 3 Dry Roll-Up of Strained Nanomembranes 25 3.1 Rolled - Up Nanotechnology 25 3.2 Fabrication 26 3.2.1 Release 29 3.3 Conclusions 33 4 Rolled-UpMicro Capacitors 35 4.1 Micro Capacitors 35 4.2 Fabrication 38 4.3 Characterization 39 4.4 Conclusion 41 5 Optical Micro-Cavities 43 5.1 Optical Micro Cavities 43 5.2 Theorectical Background 45 5.2.1 Quality - factor 49 5.2.2 FDTD 52 6 Optical Microtube Resonators 55 6.1 Optical Whispering Gallery Mode Microtube Resonators 55 6.2 Fabrication 57 6.3 Active Characterization 60 6.4 Conclusions 64 7 Photonic Molecules 65 7.1 Coupled Photonic Systems 65 7.2 Fabrication 68 7.3 Device Characterization 71 7.4 Multimode Waveguides 84 7.5 Conclusions 85 8 Conclusions and Outlook 87 8.1 Conclusions 87 8.2 Outlook 88 Bibliography 91 List of Figures 109 List of Tables 117 A Equipment 119 Cover Pages 121 Selbstständigkeitserklärung 123 Acknowledgements 125 List of Publications 127 List of Presentations 129 Curriculum Vitae 131

[ES] La presente tesis doctoral tiene como objetivo fundamental desarrollar nuevas estructuras capacitivas de filtrado en guía de ondas rectangular que sean capaces de proporcionar mayores ancho de banda en la banda de paso y, al mismo tiempo, mejorar la respuesta fuera de banda. Estas nuevas estructuras guiadas han sido pensadas para ofrecer nuevas soluciones tecnológicas para los filtros de microondas de alta frecuencia, con una variedad de diferentes funciones de transferencia, abordando específicamente las necesidades de los futuros sistemas de telecomunicaciones para aplicaciones terrestres y espaciales. En este contexto, por lo tanto, discutimos en este documento el estudio, diseño y fabricación de varios tipos de filtros de microondas en guía de ondas rectangular que muestran una mejora significativa con respecto al estado del arte. Las soluciones que discutimos se obtienen introduciendo modificaciones simples en la estructura de los filtros de microondas clásicos. Varias técnicas que emplean iris híbridos, resonadores con salto de impedancia, configuración en escalera y uniones T en plano E con conexiones en cortocircuito o manifold, se utilizan con éxito para cumplir con las exigentes especificaciones de los futuros sistemas para aplicaciones terrestres y espaciales. Además, un desafío actual adicional al que se enfrentan todos los diseñadores de equipos y componentes de microondas es la necesidad de reducir tanto su tamaño físico como su masa (o peso). Para abordar este problema, discutimos en este documento el uso de aperturas resonantes en guías de ondas rectangulares, presentando una nueva familia de filtros que se pueden usar para implementar funciones complejas de transferencia de banda única y banda doble con una reducción significativa de tamaño y masa. En los siguientes capítulos de esta tesis doctoral, cada tema se analiza en detalle, incluyendo las formulaciones teóricas básicas, los procedimientos de diseño, los resultados de las simulaciones electromagnéticas de onda completa, las consideraciones de fabricación y el rendimiento medido de una serie de prototipos. En todos los casos se ha encontrado una excelente concordancia entre las mediciones y las simulaciones realizadas, validando así completamente tanto las estructuras novedosas propuestas como sus procedimientos de diseño. / [CA] La present tesi doctoral té com a objectiu fonamental el desenvolupament de noves estructures capacitives de filtrat en guia d'ones rectangular que siguen capaços de proporcionar major ample de banda en la banda de pas i millorar, al mateix temps, la resposta fora de banda. Aquestes noves estructures guiades han sigut pensades per a oferir noves solucions tecnològiques per a filtres de microones d'alta freqüència, amb una varietat de diferents funcions de transferència, abordant específicament les necessitats dels futurs sistemes de telecomunicacions per a aplicacions terrestres i espacials. En aquest context, per tant, discutim en aquest document l'estudi, disseny i fabricació de diversos tipus de filtres de microones en guia d'ones rectangular que mostren una millora significativa respecte a l'estat de l'art. Les solucions que discutim s'obtenen introduint modificacions simples en l'estructura dels filtres de microones clàssics. Diverses tècniques que fan ús d'iris híbrids, ressonadors amb salt d'impedància, configuració en escala i unions T en plànol E amb connexions en curtcircuit o col·lector, s'utilitzen amb èxit per a complir amb les exigents especificacions dels sistemes futurs per a aplicacions terrestres i espacials. A més, un desafiament actual addicional al qual s'enfronten tots els dissenyadors d'equips i components de microones és la necessitat de reduir tant la seua grandària física com la seua massa (o pes). Per a abordar aquest problema, discutim en aquest document l'ús d'obertures ressonants en guies d'ones rectangulars, presentant una nova família de filtres que es poden usar per a implementar funcions complexes de transferència de banda única i doble banda amb una reducció significativa de grandària i massa. En els següents capítols d'aquesta tesi doctoral, cada tema s'analitza detalladament, incloent les formulacions teòriques bàsiques, els procediments de disseny, els resultats de les simulacions electromagnètiques d'ona completa, les consideracions de fabricació i el rendiment mesurat d'una sèrie de prototips. En tots els casos s'ha trobat una excel·lent concordança entre el mesurament i les simulacions realitzades, validant així completament tant les estructures noves propostes com els seus procediments de disseny. / [EN] The main objective of this doctoral thesis is the development of new capacitive filtering structures in rectangular waveguide that are able to provide wide bandwidths in the pass-band and improve, at the same time, the out-of-band response. These new guided structures have been developed in order to offer new technological solutions for high-frequency microwave filters, with a variety of different transfer functions, addressing specifically the needs of future telecommunication systems for both ground and space applications. In this context, therefore, we discuss in this document the study, design and manufacture of several types of microwave filter in rectangular waveguide that show a significant improvement with respect to the state-of-the-art. The new solutions that we propose are obtained by introducing simple modifications in the structure of classic microwave filters. Several techniques based on hybrid irises, stepped impedance resonators, staircase configuration and E-plane T-junctions with shorted stubs or manifold connections, are successfully used in order to meet the very demanding specifications of future systems for both ground and space applications. Furthermore, an additional current challenge faced by all designers of microwave components is the need to reduce both their physical size and mass (or weight). To address this issue, we discuss in this document the use of resonant apertures in rectangular waveguide, introducing a new family of filters which can be used to implement complex single and dual-band transfer functions with significant size and mass reduction. In the following chapters of this doctoral thesis, each subject is discussed in detail including the basic theoretical formulations, design procedures, the results of full-wave electromagnetic simulations, manufacturing considerations, and the measured performance of a number of prototypes. Excellent agreement is found in all cases between measurement and simulations, thereby fully validating both the novel structures discussed and their design procedures. / Valencia Sullca, JF. (2021). New Wide-Band Capacitive Filter Structures in Rectangular Waveguide Technology With Enhanced Out-of-Band Response [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/180198

Mitt-Infrarot-Technologie (mid-IR) ist ein äußerst leistungsfähiges Werkzeug für die Anwendung in der Molekülspektroskopie, da die Schwingungsmoden vieler Moleküle in diesem Wellenlängenbereich liegen. Der Quantenkaskadenlaser mit externem Resonator (EC-QCL) kann alle Bereiche dieses Spektrums abdecken. Das Hauptanliegen dieser Arbeit ist die Verbesserung der Leistung des EC-QCL im Hinblick auf die Breite des Wellenlängen-Durchstimmbereichs und die Laserleistung. Theoretische Untersuchungen bestätigen zunächst, dass der QCL die Schlüsselrolle bei EC-Systemen einnimmt: Die Effizienz des EC wird bestimmt durch die Effizienz des QCL und die Güte der Antireflex-Schicht (ARC) der Laserfacette. Die Breite des Durchstimmbereichs wird bestimmt durch das Gain-Spektrum des QCL. Im Rahmen dieser Arbeit wurden die QCL in unserer Gruppe hergestellt und vom QCL-Wachstum selbst bis hin zur Facettenbeschichtung optimiert. Eine der größten Herausforderungen in der Herstellung des EC-Systems ist die Reduktion des Reflexionsvermögens innerhalb der Facetten des Laserchips. Dafür haben wir ein neues ARC-Konzept entwickelt und auf dem beschichteten Substrat demonstriert, dass innerhalb des gesamten, sehr breiten Wellenlängenbereichs von 7–12 μm die Reflexion auf unter 1% reduziert wird. Das Beschichtungsmodell wurde außerdem auf „broad-gain“-QCL-Facetten angewendet, wodurch die Reflexion auf 0,75% über den gesamten Emissions-Wellenlängenbereich reduziert werden konnte. Ein weiterer Schwerpunkt dieser Arbeit ist die Entwicklung und Konstruktion von EC-Lasersystemen. Es wurden zwei kompakte Laser vom Littrow-Typ entwickelt, die von 920 cm-1 bis 1190 cm-1 durchstimmbar sind und die eine Pulsleitung von 0.45 W erreichen. Außerdem wurde eine neue optische Konfiguration des EC-Systems vorgeschlagen um eine höhere Ausgangsleistung zu erzielen. Dieser „Intra-cavity Out-coupling Laser“ erreicht eine Pulsleistung von 1 W und den gleichen Emissionbereich wie die beiden Littrow-Laser. / Mid-infrared (mid-IR) technology is a very powerful tool for molecular spectroscopy since vibration modes of many molecules lie in this wavelength range. The External-Cavity Quantum Cascade Laser (EC-QCL) can cover any part of this spectral range. The main goal of this study is to improve EC-QCL performance in terms of wavelength tunability and laser power. The theoretical study about Quantum Cascade Laser (QCL) and EC systems has confirmed that the QCL plays the core role of EC-QCL systems; the power efficiency of an EC system is determined by the combination of the power efficiency of QCL and AR-coating of the laser facet. The width of the tuning range is determined by the gain spectrum of QCL. During this work, QCLs have been fabricated in our group and the optimization of these factors were carried out with various approaches, from QCL growth to facet coatings. One of the major challenges in making EC systems is to reduce the intra-facet reflectivity of the laser chip, and we first proposed a new anti-reflection (AR) coating concept and demonstrated its performance for the first time to the community, achieving good reduction of reflection of the AR-coated substrate over 7-12 μm range, keeping below R < 1% reflection over the entire spectrum. The coating model was applied on broad-gain QCL facets, and the reflection was reduced to 0.75% over the entire emission wavelength range. Furthermore, this work focused on the development and engineering of laser systems, and two compact Littrow-type lasers and an EC system with a new optical configuration have been developed, achieving good performances; tunable from 920 cm-1 to 1190 cm-1 and 0.45 W pulse power. The new type of laser, an Intra-cavity out-coupling EC laser, was also proposed to enhance the power output and achieved over 1 W pulse power with keeping the same tuning range as the Littrow-type. / 中赤外分光の技術は非常に有用である。これはとりわけ多くの分子振動モードがこの波長帯域に存在しているためである。可変長レーザーである外部共振器量子カスケードレーザー(External cavity quantum cascade laser, EC-QCL)は、これらスペクトル領域を網羅することが可能で、したがって、EC-QCLは産業スケールを含めた、標準的な光源として非常に潜在的である。商品化のフェーズをさらに推し進めるため、このレーザー性能におけるボトムアップの技術が求められてる。 多くの中赤外光のアプリケーションには広帯域の光源が求められている。この研究はおもにそうした性能を最大化することを背景としている。具体的な目的としては、波長の変調性および光源の強度の向上である。これらの目的に取り組むため、我々はいくつかの段階にステージ化して研究を進めてきた。まず初めに、QCLおよびEC-QCLの基本的な特性の追求から始めた。QCLおよびEC-QCLの物理機構の理論的な考察を行い、これらからEC-QCL形態における要素の最適条件もしくは要請を求めた。QCL素子が、その主要な部位であり、EC系におけるほとんどの性能特性である量子効率、変調領域幅、増幅器の光学損失を決定する。 さまざまなアプローチによりこれら緒特性の最適化が行われた。 この研究のなかで、我々グループ内でシステムの心臓となるQCL素子の全製造プロセス(結晶成長から素子コーティングに至るまで)をおこなった。これら製造手順および性能特性の詳細もまた本論文に記す。 ECレーザーにおける要請特性の中で特に困難な課題として、レーザー素子の内部断面(intra-facet)の反射率の低減があげられる。これに応じるものとして、我々は新たな反射防止膜のコンセプトで、特に中赤外光領域に有益なものを提案した。この実現のために、様々な誘電体物質の光学特性を調べ、中赤外光の応用に最適なものを選択し、実際のコーティングに応用した。ここで提案されたモデル``quasi-Lockhart'' (疑ロックハート)のコーティングは、実験によりその高い性能が実証された。波長7–12 μmの領域をカバーし、かつその全領域内で反射率を1%以下に抑えることができた。またこのコーティングは広帯域ゲインのチップにも施され、その反射率を全体域をカバーしながら、0.75%まで低減させた。この成果はEC-QCLだけでなく、一般の中赤外光の光学コーティングにおいても大いに有用であろう。 さらに、我々は本研究の中でレーザーシステムの構築にも取り組んだ。この研究のなかで、二台のLittrow型レーザーと、新たな光学系をもつECレーザーを構築し、その高性能性を実証した。Littrow型では920 cm-1-1190 cm-1の帯域とパルス強0.45 Wを達成。新たなレーザーシステムであるIntra-cavity out-coupling系は従来の系にくらべ高出力することを目的とされ、その帯域を維持しながら、パルス強1~Wの出力を達成した。またこれら新たなシステムを用いて、またプロジェクトバートナーとの食道癌の細胞イメージングも試験、およびグループにおいてアンモニアの吸光度測定を実施した。