A major focus is on integrated Silicon-based optoelectronics for the creation of low-cost photonics for mass-market applications. Especially, the growing demand for sensitive and portable optical sensors in the environmental control and medicine follows in the development of integrated high resolution sensors [1]. In particular, since 2013 the quick onsite verification of pathogens, like legionella in drinking water pipes, is becoming increasingly important [2, 3]. The essential questions regarding the establishment of portable biochemical sensors are the incorporation of electronic and optical devices as well as the implementations of fundamental cross-innovations between biotechnology and microelectronics. This thesis describes the design, fabrication and analysis of high-refractive-index-contrast photonic structures. Besides silicon nitride (Si3N4) strip waveguides, lateral tapers, bended waveguides, two-dimensional photonic crystals (PhCs) the focus lies on monolithically integrated waveguide butt-coupled Silicon-based light emitting devices (Sibased LEDs) [4, 5] for use as bioanalytical sensor components. Firstly, the design and performance characteristics as single mode regime, confinement factor and propagation losses due to the geometry and operation wavelength (1550 nm, 541 nm) of single mode (SM), multi mode (MM) waveguides and bends are studied and simulated. As a result, SM operation is obtained for 1550 nm by limiting the waveguide cross-section to 0.5 μm x 1 μm resulting in modal confinement factors of 87 %. In contrast, for shorter wavelengths as 541 nm SM propagation is excluded if the core height is not further decreased. Moreover, the obtained theoretical propagation losses for the lowestorder TE/TM mode are in the range of 0.3 - 1.3 dB/cm for an interface roughness of 1 nm. The lower silicon dioxide (SiO2) waveguide cladding should be at least 1 μm to avoid substrate radiations. These results are in a good correlation to the known values for common dielectric structures. In the case of bended waveguides, an idealized device with a radius of 10 μm was developed which shows a reflection minimum (S11 = - 22 dB) at 1550 nm resulting in almost perfect transmission of the signal. Additionally, tapered waveguides were investigated for an optimized light coupling between high-aspect-ratio devices. Here, adiabatic down-tapered waveguides were designed for the elimination of higher-order modes and perfect signal transmission. Secondly, fabrication lines including Electron-beam (E-beam) lithography and reactive ion etching (RIE) with an Aluminum (Al) mask were developed and lead to well fabricated optical devices in the (sub)micrometer range. The usage of focused ion beam (FIB) milling is invented for smoother front faces which were analyzed by scanning electron microscopy (SEM) and atomic force microscopy (AFM). As a result, the anisotropy of the RIE process was increased, but the obtained surface roughness parameters are still too high (10 – 20 nm) demonstrating a more advanced lithography technique is needed for higher quality structures. Moreover, this study presents an alternative fabrication pathway for novel designed waveguides with free-edge overlapping endfaces for improving fiber-chipcoupling. Thirdly, the main focus lies on the development of a monolithic integration circuit consisting of the Si-based LED coupled to an integrated waveguide. The light propagation between high-aspect-ratio devices is enabled through low-loss adiabatic tapers. This study shows, that the usage of CMOS-related fabrication technologies result in a monolithic manufacturing pathway for the successful implementation of fully integrated Si-based photonic circuits. Fourth, transmission loss measurements of the fabricated photonic structures as well as the waveguide butt-coupled Si-based LEDs were performed with a generated setup. As a result, free-edge overlapping MM waveguides show propagation loss coefficients of ~ 65 dB/cm in the range of the telecommunication wavelength. The high surface roughness parameters (~ 150 nm) and the modal dispersion in the core are one of the key driving factors. These facts clearly underline the improvement potential of the used fabrication processes. However, electroluminescence (EL) measurements of waveguide butt-coupled Si-based LEDs due to the implanted rare earth (RE) ion (Tb3+, Er3+) and the host material (SiO2/SiNx) were carried out. The detected transmission spectra of the coupled Tb:SiO2 systems show a weak EL signal at the main transition line of the Tb3+-ion (538 nm). A second emission line was detected in the red region of the spectrum either corresponding to a further optical transition of Tb3+ or a Non Bridging Oxygen Hole Center (NBOHC) in SiO2. Unfortunately, no light emission in the infrared range was established for the Er3+-doped photonic circuits caused by the low external quantum efficiencies (EQE) of the Er3+ implanted Si-based LEDs. Nevertheless, transmission measurements between 450 nm – 800 nm lead again to the result that an emission at 650 nm is either caused by an optical transition of the Er3+-ion or initialized by the NBOHC in the host. Overall, it is difficult to assess whether or not these EL signals are generated from the implanted ions, thus detailed statements about the coupling efficiency between the LED and the integrated waveguide are quite inadequate. Nevertheless, the principle of a fully monolithically integrated photonic circuit consisting of a Si-based LED and a waveguide has been successfully proven in this study.

Inkjet printing has emerged from a digital graphic arts printing technology to become a versatile tool for the patterned deposition of functional materials. This thesis contributes to the research in the area of functional inkjet printing by focusing on two different topics: (i) inkjet printing of colloidal suspensions to study the principles of deposit formation and to develop deposits with photonic properties based on self-assembly, and (ii) the development of a reliable manufacturing process for all-inkjet-printed thin-film transistors, highlighting the importance of selection of materials and inks, print pattern generation, and the interplay between ink, substrate and printing conditions. (i) Colloidal suspensions containing nanospheres were applied as ink formulation in order to study the fundamental processes of layer formation and to develop structures with periodically arranged nanospheres allowing the modulation of electromagnetic waves. Evaporation-driven self-assembly was found to be the main driver for the formation of the final deposit morphology. Fine-tuning of inkjet process parameters allows the deposition of highly ordered structures of nanospheres to be arranged as monolayer, multilayer or even three-dimensional assemblies with a microscopic spherical shape. (ii) This thesis demonstrates the development of a manufacturing process for thin-film transistors based on inkjet printing. The knowledge obtained from the study with the colloidal nanospheres is used to generate homogeneous and continuous thin films that are stacked well-aligned to each other to form transistors. Industrial printheads were applied in the manufacturing process, allowing for the up-scaling of the manufacturing by printing of several thousands of devices, and thus the possibility to study the process yield as a function of printing parameters. The discrete droplet-by-droplet nature of the inkjet printing process imposes challenges on the control of printed patterns. Inkjet printing of electronic devices requires a detailed understanding about the process and all of the parameters that influence morphological or functional characteristics of the deposits, such as the selection of appropriate inks and materials, the orientation of the print pattern layout to the deposition process and the reliability of the inkjet process.

A major focus is on integrated Silicon-based optoelectronics for the creation of low-cost photonics for mass-market applications. Especially, the growing demand for sensitive and portable optical sensors in the environmental control and medicine follows in the development of integrated high resolution sensors [1]. In particular, since 2013 the quick onsite verification of pathogens, like legionella in drinking water pipes, is becoming increasingly important [2, 3]. The essential questions regarding the establishment of portable biochemical sensors are the incorporation of electronic and optical devices as well as the implementations of fundamental cross-innovations between biotechnology and microelectronics. This thesis describes the design, fabrication and analysis of high-refractive-index-contrast photonic structures. Besides silicon nitride (Si3N4) strip waveguides, lateral tapers, bended waveguides, two-dimensional photonic crystals (PhCs) the focus lies on monolithically integrated waveguide butt-coupled Silicon-based light emitting devices (Sibased LEDs) [4, 5] for use as bioanalytical sensor components. Firstly, the design and performance characteristics as single mode regime, confinement factor and propagation losses due to the geometry and operation wavelength (1550 nm, 541 nm) of single mode (SM), multi mode (MM) waveguides and bends are studied and simulated. As a result, SM operation is obtained for 1550 nm by limiting the waveguide cross-section to 0.5 μm x 1 μm resulting in modal confinement factors of 87 %. In contrast, for shorter wavelengths as 541 nm SM propagation is excluded if the core height is not further decreased. Moreover, the obtained theoretical propagation losses for the lowestorder TE/TM mode are in the range of 0.3 - 1.3 dB/cm for an interface roughness of 1 nm. The lower silicon dioxide (SiO2) waveguide cladding should be at least 1 μm to avoid substrate radiations. These results are in a good correlation to the known values for common dielectric structures. In the case of bended waveguides, an idealized device with a radius of 10 μm was developed which shows a reflection minimum (S11 = - 22 dB) at 1550 nm resulting in almost perfect transmission of the signal. Additionally, tapered waveguides were investigated for an optimized light coupling between high-aspect-ratio devices. Here, adiabatic down-tapered waveguides were designed for the elimination of higher-order modes and perfect signal transmission. Secondly, fabrication lines including Electron-beam (E-beam) lithography and reactive ion etching (RIE) with an Aluminum (Al) mask were developed and lead to well fabricated optical devices in the (sub)micrometer range. The usage of focused ion beam (FIB) milling is invented for smoother front faces which were analyzed by scanning electron microscopy (SEM) and atomic force microscopy (AFM). As a result, the anisotropy of the RIE process was increased, but the obtained surface roughness parameters are still too high (10 – 20 nm) demonstrating a more advanced lithography technique is needed for higher quality structures. Moreover, this study presents an alternative fabrication pathway for novel designed waveguides with free-edge overlapping endfaces for improving fiber-chipcoupling. Thirdly, the main focus lies on the development of a monolithic integration circuit consisting of the Si-based LED coupled to an integrated waveguide. The light propagation between high-aspect-ratio devices is enabled through low-loss adiabatic tapers. This study shows, that the usage of CMOS-related fabrication technologies result in a monolithic manufacturing pathway for the successful implementation of fully integrated Si-based photonic circuits. Fourth, transmission loss measurements of the fabricated photonic structures as well as the waveguide butt-coupled Si-based LEDs were performed with a generated setup. As a result, free-edge overlapping MM waveguides show propagation loss coefficients of ~ 65 dB/cm in the range of the telecommunication wavelength. The high surface roughness parameters (~ 150 nm) and the modal dispersion in the core are one of the key driving factors. These facts clearly underline the improvement potential of the used fabrication processes. However, electroluminescence (EL) measurements of waveguide butt-coupled Si-based LEDs due to the implanted rare earth (RE) ion (Tb3+, Er3+) and the host material (SiO2/SiNx) were carried out. The detected transmission spectra of the coupled Tb:SiO2 systems show a weak EL signal at the main transition line of the Tb3+-ion (538 nm). A second emission line was detected in the red region of the spectrum either corresponding to a further optical transition of Tb3+ or a Non Bridging Oxygen Hole Center (NBOHC) in SiO2. Unfortunately, no light emission in the infrared range was established for the Er3+-doped photonic circuits caused by the low external quantum efficiencies (EQE) of the Er3+ implanted Si-based LEDs. Nevertheless, transmission measurements between 450 nm – 800 nm lead again to the result that an emission at 650 nm is either caused by an optical transition of the Er3+-ion or initialized by the NBOHC in the host. Overall, it is difficult to assess whether or not these EL signals are generated from the implanted ions, thus detailed statements about the coupling efficiency between the LED and the integrated waveguide are quite inadequate. Nevertheless, the principle of a fully monolithically integrated photonic circuit consisting of a Si-based LED and a waveguide has been successfully proven in this study.

Inkjet printing has emerged from a digital graphic arts printing technology to become a versatile tool for the patterned deposition of functional materials. This thesis contributes to the research in the area of functional inkjet printing by focusing on two different topics: (i) inkjet printing of colloidal suspensions to study the principles of deposit formation and to develop deposits with photonic properties based on self-assembly, and (ii) the development of a reliable manufacturing process for all-inkjet-printed thin-film transistors, highlighting the importance of selection of materials and inks, print pattern generation, and the interplay between ink, substrate and printing conditions. (i) Colloidal suspensions containing nanospheres were applied as ink formulation in order to study the fundamental processes of layer formation and to develop structures with periodically arranged nanospheres allowing the modulation of electromagnetic waves. Evaporation-driven self-assembly was found to be the main driver for the formation of the final deposit morphology. Fine-tuning of inkjet process parameters allows the deposition of highly ordered structures of nanospheres to be arranged as monolayer, multilayer or even three-dimensional assemblies with a microscopic spherical shape. (ii) This thesis demonstrates the development of a manufacturing process for thin-film transistors based on inkjet printing. The knowledge obtained from the study with the colloidal nanospheres is used to generate homogeneous and continuous thin films that are stacked well-aligned to each other to form transistors. Industrial printheads were applied in the manufacturing process, allowing for the up-scaling of the manufacturing by printing of several thousands of devices, and thus the possibility to study the process yield as a function of printing parameters. The discrete droplet-by-droplet nature of the inkjet printing process imposes challenges on the control of printed patterns. Inkjet printing of electronic devices requires a detailed understanding about the process and all of the parameters that influence morphological or functional characteristics of the deposits, such as the selection of appropriate inks and materials, the orientation of the print pattern layout to the deposition process and the reliability of the inkjet process.:Bibliography II Abstract III Preface and acknowledgements IV On the major results and novelty of the thesis VII Table of contents VIII List of abbreviations and symbols X List of figures XII List of tables XX 1 Introduction 1 2 Fundamentals 6 2.1 Inkjet printing – an overview 6 2.2 Piezoelectric inkjet technology and a historical overview of inkjet printing 10 2.3 Pattern and film formation in inkjet printing under the scheme of self-assembly 20 2.4 Inkjet printing of colloidal nanospheres 27 2.5 Spherical colloidal assemblies 29 2.6 All-inkjet-printed thin film transistors 31 3 Experimental section 35 3.1 Inkjet printing systems and accessories 35 3.2 Inks and substrates 38 3.3 Print patterns 43 3.4 Post-processing 46 3.5 Optical, morphological and functional characterization 47 4 Inkjet printing of colloidal nanospheres: Evaporation-driven self-assembly based on ink-substrate interaction 49 4.1 Single droplet deposit morphology: Interaction of substrate and ink 49 4.2 Optical properties of inkjet-printed single droplet monolayers and multilayers 54 5 Inkjet printing of colloidal nanospheres: Evaporation-driven self-assembly of SCAs independent on substrate properties 58 5.1 Inkjet printing of spherical colloidal assemblies and their identification 58 5.2 Fine-tuning of the waveform applied to the printhead 60 5.3 Interaction of substrate and ink 66 5.4 Structures, morphologies and materials of SCAs 68 5.5 Optical properties of SCAs 76 6 Inkjet printing of TFTs: Process development and process reliability 80 6.1 Influence of print layout design 80 6.2 Selection of materials and inks 91 6.3 Manufacturing workflow and electrical TFT parameters 108 6.4 Manufacturing yields and failure origins 113 7 Summary and conclusion 124 References 127 Documentation of authorship and contribution of third persons 149 List of publications 151 APPENDIX A Formation of colloidal hemispheres on hydrophobic PTFE substrates 161 APPENDIX B Inkjet-printed higher-order cluster with N < 100 using BL280 162 APPENDIX C Inkjet-printed SCAs based on BS305 with similar sizes and inkjet-printed SCA based on PSC221 163 APPENDIX D Microreflectance spectra of SCAs and the processing of the spectra using the Savitzky-Golay filter with a second-order polynomial and a moving window of 100 data points 164 APPENDIX E Waveform, drop ejection and photographs of the printed patterns of Sun Chemical EMD5603 and UTDots UTDAgIJ1 165 APPENDIX F Smoothening of profiles obtained by profilometry of EMD5603 and UTDAgIJ1 and dependency of print resolution of layer height 166 APPENDIX G Percentage of area increase based on a 4 mm x 4 mm digital print pattern using the ink Harima NPS-JL and influence of print resolution and post-treatment temperature on sheets resistance 168 APPENDIX H Cross-sectional view of a TFT stack printed with the dielectric Sun Chemical EMD6415 that shows high layer thickness due to ink contraction after the deposition as presented in Figure 46 169 APPENDIX I Influence of printing parameters on the dielectric layer applied in the TFT 170 APPENDIX J Reduction of channel length by decreasing the S-D electrode channel length in the print pattern layout 171

The work provides an overview of different integrated optical amplifiers. Semiconductor optical amplifiers and fiber amplifiers are described, as well as devices that utilize non-linear effects, nanocrystalline materials, or photonic crystals. Dielectric materials that are doped with rare-earth ions are considered more thoroughly. After a review of the principles of their optical activity the general mechanisms of excitation and emission are described. Materials aspects regarding the spectral range, their fabrication and the solubility of the dopants follow. An erbium-doped alumina waveguide amplifier, reported earlier in the literature, is chosen as an example to demonstrate the feasibility of such components. A theoretical model of the population densities of the energy levels is derived for the simulation. By numerical methods the non-linear system of the rate equations is solved and the stability of the steady state is shown. The simulation of the amplifier demonstrates the dependence of the gain of both the excitation energy and the z-coordinate. Moreover, the superiority of an excitation wavelength of 980 nm compared to 1530 nm is shown. With the model the literature data could be reproduced. / Die Arbeit gibt einen Überblick über verschiedene Möglichkeiten der Realisierung integriert-optischer Wellenleiterverstärker. Ausgehend von optischen Halbleiter- und Faserverstärkern werden einführend ebenso Anordnungen beschrieben, die nichtlineare Effekte sowie nanokristalline Materialien und photonische Kristalle nutzen. Besondere Bedeutung kommt dielektrischen Materialien zu, die mit optisch aktiven Dotanden, bevorzugt Seltenerdionen, versehen sind. Hierbei werden die Ursachen für die optische Aktivität der Lanthanide sowie die generellen Mechanismen der Anregungs- und Emissionsprozesse beschrieben. Aspekte der Materialauswahl, vor allem hinsichtlich des verwendeten Spektralbereiches sowie bezüglich ihrer Herstellung und der Löslichkeit der Dotanden schließen sich an. Anhand eines Literaturbeispiels wird die Realisierbarkeit eines erbiumdotierten Aluminiumoxid-Wellenleiterverstärkers demonstriert. Hierfür wird ein Modell zur Simulation der Besetzungsdichten der angeregten Energieniveaus abgeleitet und mittels numerischer Methoden das sich ergebende, nichtlineare System der Ratengleichungen gelöst, wobei besonders die Stabilität des stationären Besetzungszustandes herausgearbeitet wird. Die Simulation der Verstärkeranordnung zeigt zum einen die Abhängigkeit der Verstärkung von der z-Koordinate sowie der Pumpleistung; zum anderen wird deutlich, dass die Anregung bei 980 nm der Variante bei 1530 nm überlegen ist. Mit dem verwendeten Modell konnten die Literaturdaten reproduziert werden.

In dieser Arbeit werden verschiedene Methoden zur Erhöhung der Systemtoleranz optischer Übertragungssysteme theoretisch analysiert, durch numerische Simulationen untersucht und in Experimenten und Feldversuchen praktisch überprüft. Der Schwerpunkt lag dabei auf empfängerseitigen elektronischen sowie optischen Entzerrern. Diese Entzerrer verbessern die Signalübertragung, in dem sie die Augenöffnung des Signals am Empfänger vergrößern oder in dem sie durch digitale Logikschaltungen das gesendete Signal aus einem gestörten Signal rekonstruieren. Der Schwerpunkt dieser Arbeit liegt jedoch auf der Untersuchung der Entzerrer auf Systemebene, d.h. es wird das Verhalten in einem kompletten optischen Übertragungssystem bestehend aus Sender, Glasfaserstrecke und Empfänger bewertet. Zur Untersuchung wurde eine Simulationsumgebung in der Programmiersprache FORTRAN erstellt, in der die unterschiedlichen Entzerrer in verschiedenen Netz-Szenarien untersucht wurden. Zur praktischen Untersuchung wurde außerdem eine Testumgebung im verlegten Glasfasernetz aufgebaut und eine Realisierung eines Entzerrers experimentell untersucht. / In this thesis, several methods for the enhancement of the tolerance of optical transmission systems are analyzed theoretically, investigated in numerical simulations and evaluated in experiments and field trials. The investigations were thereby focused on receiver sided electronic and optical equalizers. Those devices improve the signal transmission by increasing the eye-opening at the receiver or by reconstructing the original signal from the distorted received signal by the use of digital signal processing. However, this thesis is focused on the investigation of different equalizers on a system level where the performance of a complete transmission system consisting of a transmitter, transmission fiber and receiver is evaluated. For those studies a simulation environment was created using the programming language FORTRAN where the different equalizers were evaluated in different network scenarios. For practical investigations, a test environment was created using the deployed fiber infrastructure and specific equalizer realization were evaluated experimentally.

The scope of this work is an in-depth investigation of dielectric mirror microcavities with central organic dye layers, which are preferably modified in at least one lateral dimension. The large quality factor of the planar resonator in conjunction with comparatively stable and spectrally broad emitting molecules allows for a detailed analysis of several aspects of microresonator systems. Their optical properties are analyzed both with transmission and luminescence measurements as well as in the lasing regime. The first part presents the resonant mode properties of planar and laterally structured microcavities. With the help of a high-resolution imaging micro-photoluminescence setup, working either in the spatial (near field) or vectorial (far field) regime, the polarization splitting is studied in a detuned microcavity, containing the dye 4,4'-bis[(N-carbazole)styryl]biphenyl (BSB-Cz) in a matrix of 4,4'-di(N-carbazolyl)- biphenyl (CBP). With the help of a thickness gradient, a relation between the large spectral distance of the cross-polarized states and the mode position within the stop band is investigated. In shadow-mask prepared, laterally restricted devices (5x5 µm2 square boxes), the three-dimensional confinement introduces sets of discrete modes, which experience a similar polarization splitting. The origin in this case is a different phase shift of electromagnetic waves during internal total reflection at a boundary. By using a concentration gradient planar microcavity sample of the dye 4-(dicyanomethylene)-2-methyl-6-(4-(dimethylamino)styryl)-4H-pyran (DCM) in a tris-(8-hydroxyquinoline)aluminum (Alq3) matrix, the influence of the number of emitters on the lasing characteristics is subsequently analyzed. Depending on the pumping conditions, and thus the involvement of the Förster resonant energy transfer, an optimal composition is identified. After a qualitative evaluation of the long-term stability upon various excitation energies, the attention is focussed to the modification of the stimulated emission properties of photonic boxes. The stronger field concentration and altered density of states leads to a significant improvement of the values for the coupling factor fi and the threshold levels. Furthermore, new properties arise, namely simultaneous multimode and off-axis laser emission. With an inhomogeneous excitation of the box, it is possible to selectively excite single modes above the threshold. The work ends with experimental results of metal structures as additional optical element in the organic microcavity layer. Here, the aim is is to understand the passive influence of these possible contact- devices on the lasing performance. For this purpose, the lasing is studied at an interface of an areal thin metal layer, which is incorporated in the organic layer.

In dieser Arbeit werden verschiedene Methoden zur Erhöhung der Systemtoleranz optischer Übertragungssysteme theoretisch analysiert, durch numerische Simulationen untersucht und in Experimenten und Feldversuchen praktisch überprüft. Der Schwerpunkt lag dabei auf empfängerseitigen elektronischen sowie optischen Entzerrern. Diese Entzerrer verbessern die Signalübertragung, in dem sie die Augenöffnung des Signals am Empfänger vergrößern oder in dem sie durch digitale Logikschaltungen das gesendete Signal aus einem gestörten Signal rekonstruieren. Der Schwerpunkt dieser Arbeit liegt jedoch auf der Untersuchung der Entzerrer auf Systemebene, d.h. es wird das Verhalten in einem kompletten optischen Übertragungssystem bestehend aus Sender, Glasfaserstrecke und Empfänger bewertet. Zur Untersuchung wurde eine Simulationsumgebung in der Programmiersprache FORTRAN erstellt, in der die unterschiedlichen Entzerrer in verschiedenen Netz-Szenarien untersucht wurden. Zur praktischen Untersuchung wurde außerdem eine Testumgebung im verlegten Glasfasernetz aufgebaut und eine Realisierung eines Entzerrers experimentell untersucht.:Inhaltsverzeichnis 1 Einleitung 1 2 Grundaufbau und Komponenten optischer Übertragungssysteme 3 2.1 Optische Sender 4 2.2 Das Übertragungsmedium Glasfaser 9 2.3 Optische Faserverstärker 22 2.4 Optische Empfänger und Signalauswertung 24 3 Filterstrukturen und Polynomsysteme 29 3.1 Digitalfilter 29 3.2 Optische Filter 30 3.3 Volterra-Systeme 33 4 Elektronische Entzerrung zur Erhöhung der Systemtoleranz 35 4.1 Klassische Entzerrer 35 4.2 Nichtlineare Entzerrer basierend auf Volterra-Systemen 41 4.3 Maximum Likelihood Sequence Estimation 45 5 Optische Entzerrung und Kompensation 49 5.1 Dispersionskompensationsfasern 49 5.2 Optische FIR-Filter 50 6 Entzerrung in unkompensierten Übertragungssystemen 61 6.1 Prinzipieller Vergleich der Entzerrer bei linearer Übertragung 61 6.2 Entzerrung unter Berücksichtigung nichtlinearer Fasereffekte 78 7 Entzerrung in dispersionskompensierten Übertragungssystemen 87 7.1 Ausgleich einer DCF-Fehlanpassung 87 7.2 Entzerrung von Restdispersion 93 8 Gleichzeitige Entzerrung mehrerer Fasereffekte 97 8.1 Simulation der Entzerrung durch MLSE-Entzerrer 97 8.2 Experimentelle Untersuchung von MLSE-Entzerrern im Feldversuch 99 9 Alternative Verfahren zur Erhöhung der Systemtoleranz 113 9.1 Optisches Subcarrier-Multiplexing 113 9.2 Gezielter Austausch von Glasfasern mit hoher PMD 117 10 Zusammenfassung und Schlussfolgerung 121 Literaturverzeichnis 123 Verzeichnis der im Rahmen dieser Arbeit entstandenen Veröffentlichungen 133 Anhang A 137 Anhang B 138 / In this thesis, several methods for the enhancement of the tolerance of optical transmission systems are analyzed theoretically, investigated in numerical simulations and evaluated in experiments and field trials. The investigations were thereby focused on receiver sided electronic and optical equalizers. Those devices improve the signal transmission by increasing the eye-opening at the receiver or by reconstructing the original signal from the distorted received signal by the use of digital signal processing. However, this thesis is focused on the investigation of different equalizers on a system level where the performance of a complete transmission system consisting of a transmitter, transmission fiber and receiver is evaluated. For those studies a simulation environment was created using the programming language FORTRAN where the different equalizers were evaluated in different network scenarios. For practical investigations, a test environment was created using the deployed fiber infrastructure and specific equalizer realization were evaluated experimentally.:Inhaltsverzeichnis 1 Einleitung 1 2 Grundaufbau und Komponenten optischer Übertragungssysteme 3 2.1 Optische Sender 4 2.2 Das Übertragungsmedium Glasfaser 9 2.3 Optische Faserverstärker 22 2.4 Optische Empfänger und Signalauswertung 24 3 Filterstrukturen und Polynomsysteme 29 3.1 Digitalfilter 29 3.2 Optische Filter 30 3.3 Volterra-Systeme 33 4 Elektronische Entzerrung zur Erhöhung der Systemtoleranz 35 4.1 Klassische Entzerrer 35 4.2 Nichtlineare Entzerrer basierend auf Volterra-Systemen 41 4.3 Maximum Likelihood Sequence Estimation 45 5 Optische Entzerrung und Kompensation 49 5.1 Dispersionskompensationsfasern 49 5.2 Optische FIR-Filter 50 6 Entzerrung in unkompensierten Übertragungssystemen 61 6.1 Prinzipieller Vergleich der Entzerrer bei linearer Übertragung 61 6.2 Entzerrung unter Berücksichtigung nichtlinearer Fasereffekte 78 7 Entzerrung in dispersionskompensierten Übertragungssystemen 87 7.1 Ausgleich einer DCF-Fehlanpassung 87 7.2 Entzerrung von Restdispersion 93 8 Gleichzeitige Entzerrung mehrerer Fasereffekte 97 8.1 Simulation der Entzerrung durch MLSE-Entzerrer 97 8.2 Experimentelle Untersuchung von MLSE-Entzerrern im Feldversuch 99 9 Alternative Verfahren zur Erhöhung der Systemtoleranz 113 9.1 Optisches Subcarrier-Multiplexing 113 9.2 Gezielter Austausch von Glasfasern mit hoher PMD 117 10 Zusammenfassung und Schlussfolgerung 121 Literaturverzeichnis 123 Verzeichnis der im Rahmen dieser Arbeit entstandenen Veröffentlichungen 133 Anhang A 137 Anhang B 138

In dieser Arbeit wird das Design und die Präparation von nicht-klassischen Zuständen von Licht in verschiedenen Szenarien untersucht. Zunächst wird die theoretische Beschreibung eines Interferometers entwickelt, welches für die Messung der Teilchenaustauschphase von Photonen entworfen wurde. Die Analyse der experimentellen Daten offenbart den bosonischen Charakter von Photonen, sowie die geometrische Phase, welche mit dem physischen Austausch zweier Quantenzustände assoziiert ist. Nach dieser Feststellung der Austauschsymmetrie von Zweiphotonenzuständen folgt die Ausarbeitung der Theorie über die Propagation von Mehrphotonenzuständen in Multiportsystemen. Dabei offenbaren sich hoch-dimensionale, synthetische, gekoppelte Strukturen die sich aus der Mehrphotonenanregung von diskreten Systemen ergeben. Basierend auf diesen Resultaten wird eine konkrete Anwendung der Theorie im Kontext von nicht-hermitischen Systemen formuliert. Dabei ergeben sich sogenannte “exceptional points” höherer Ordnung, welche Anwendungen im Bereich der Sensorik finden und ferner nur im Raum der Photonenanzahlzustände von diskreten Systemen realisiert werden können. Neben der Sensorik ist der Transport von Lichtzuständen ein wichtiger Aspekt in der Verarbeitung von Quanteninformationen. In dieser Hinsicht werden hier Photonische Topologische Isolatoren untersucht, welche eine rückstreuungsfreie Propagation entlang ihrer Ränder erlauben. Es wird gezeigt, dass partiell kohärentes Licht, Gaussisch und Nicht-Gaussisch verschränkte Zweiphotonenzustände einen solchen topologischen Schutz genießen können. Dies gilt unter der Vorraussetzung, dass die Anfangsanregung in einem wohldefinierten Bereich des topologischen Schutzes liegt, wodurch das “klassische” Bandlücken-kriterium erweitert und gestärkt wird. / In this work we study the design and preparation of non-classical states of light in several scenarios. We begin by developing the theoretical description of an interferometer, which is designed to measure the particle exchange phase of photons. The analysis of the experimental data reveals the bosonic nature of photons, as well as the geometric phase associated with the physical exchange of the quantum states of two photons. Having established the exchange symmetry of two-photon states, we proceed to develop the theory of multi-photon states propagating in multi-port systems. We unveil the high- dimensional synthetic coupled structures that arise via the multi-photon excitation of discrete systems. Using these results, we formulate an application of the theory in the context of non-hermitian systems. We find so-called high-order exceptional points, which find applications in sensing and can only be achieved in the photon-number space of discrete systems. Apart from sensing, an important ingredient for the processing of quantum information is the transport of light states. In this regard, we consider photonic topological insulators, which allow the back-scattering-free propagation along their edges. We show that partially coherent light, Gaussian- as well as non-Gaussian two-photon entangled states can enjoy such a topological protection, provided that the initial excitations fit inside a well defined topological window of protection, which strengthens the “classical” band-gap protection criterion.

In dieser Arbeit werden einzelne atomare Defekte in hexagonalem Bornitrid (hBN) charakterisiert und mögliche Anwendungen aufgezeigt, welche die gefundenen herausragenden optischen Eigenschaften ausnutzen. Solche optisch aktiven Punktdefekte in Halbleitern bergen das Versprechen von skalierbaren und stabilen Einzelphotonenquellen, welche für eine Vielzahl von zukünftigen Anwendungen im Bereich der Quanteninformationstechnologie oder für Präzisionsmessungen benötigt werden. Dementsprechend groß ist das Interesse der Wissenschaftsgemeinde, was sich auch in der Anzahl der untersuchten Defektsysteme widerspiegelt. Das Besondere an dem hier vorliegenden System ist zum einen die Zweidimensonalität des Halbleiter-Wirtskristalls und zum anderen die enorme Helligkeit des Emitters, welche sich in bis zu sechs Millionen mit einem Mikroskop detektierten Photonen pro Sekunde niederschlägt. Darüber hinaus motivieren die Stabilität des Emitters bei Raumtemperatur und die schmale spektrale Linienbreite eine tiefgreifende Analyse dieses Neuzugangs zum Emitterzoo. / In this thesis, single atomic defects in hexagonal boron nitride (hBN) are characterized and possible applications are shown, which take advantage of the outstanding optical properties found. Such optically active point defects in semiconductors hold the promise of scalable and stable single-photon sources, which are needed for a variety of future applications in quantum information technology or for precision measurements. The interest of the scientific community is correspondingly high, which is also reflected in the number of defect systems investigated. The special feature of the system presented here is on the one hand the two-dimensionality of the semiconductor host crystal and on the other hand the enormous brightness of the emitter, which is reflected in up to six million photons per second detected with a microscope. In addition, the stability of the emitter at room temperature and the narrow spectral width motivate a profound analysis of this new addition to the emitter zoo.