京都大学 / 0048 / 新制・課程博士 / 博士(情報学) / 甲第21216号 / 情博第669号 / 新制||情||115(附属図書館) / 京都大学大学院情報学研究科通信情報システム専攻 / (主査)教授 守倉 正博, 教授 大木 英司, 教授 梅野 健 / 学位規則第4条第1項該当 / Doctor of Informatics / Kyoto University / DFAM

The objective of this dissertation is to generate high power ultrashort optical pulses from an all-semiconductor mode-locked laser system. The limitations of semiconductor optical amplifier in high energy, ultrashort pulse amplification are reviewed. A method to overcome the fundamental limit of small stored energy inside semiconductor optical amplifier called "eXtreme Chirped Pulse Amplification (X-CPA)" is proposed and studied theoretically and experimentally. The key benefits of the concept of X-CPA are addressed. Based on theoretical and experimental study, an all-semiconductor mode-locked X-CPA system consisting of a mode-locked master oscillator, an optical pulse pre-stretcher, a semiconductor optical amplifier (SOA) pulse picker, an extreme pulse stretcher/compressor, cascaded optical amplifiers, and a bulk grating compressor is successfully demonstrated and generates >kW record peak power. A potential candidate for generating high average power from an X-CPA system, novel grating coupled surface emitting semiconductor laser (GCSEL) devices, are studied experimentally. The first demonstration of mode-locking with GCSELs and associated amplification characteristics of grating coupled surface emitting SOAs will be presented. In an effort to go beyond the record setting results of the X-CPA system, a passive optical cavity amplification technique in conjunction with the X-CPA system is constructed, and studied experimentally and theoretically.

Silicon photonics (SiP) has become a cornerstone technology of the modern age by leveraging the mature fabrication processes and infrastructure of the microelectronics industry for the cost-effective and high-volume production of compact and power-efficient photonic integrated circuits (PICs). The impact that silicon (Si)-based PICs have had on data communications, particularly data center interconnection and optical transceiver technologies, has encouraged SiP chip development and their use in other applications such as artificial intelligence, biomedical sensing and engineering, displays for augmented/virtual reality, free-space communications, light detection and ranging, medical diagnostics, optical spectroscopy, and quantum computing and optics. To expand the functionality and improve the performance of SiP circuits for these surging applications, subwavelength grating (SWG) metamaterials have been thoroughly investigated and implemented in various passive integrated photonic components fabricated on the silicon-on-insulator (SOI) platform. SWG metamaterials are periodic structures composed of two materials with different permittivities that exhibit unnatural properties by using a period shorter than the guided wavelength of light propagating through them. The ability to synthesize the constituent SiP materials without any need to alter standard fabrication procedures enables precise, flexible control over the electromagnetic field and sophisticated selectively over anisotropy, dispersion, polarization, and the mode effective index in these metastructures. This provides significant benefits to SOI devices, such as low loss mode conversion and propagation, greater coupling efficiencies and alignment tolerances for fiber-chip interfaces, ultrabroadband operation in on-chip couplers, and improved sensitivities and limits of detection in integrated photonic sensors. Parallel to the rise of SiP technology is the development of other materials compatible with mature PIC fabrication methods both in the foundry (e.g., silicon nitride (Si3N4)) and outside the foundry (e.g., high-index oxide glasses such as aluminum oxide (Al2O3) and tellurium oxide (TeO2)). Si3N4 offsets the pitfalls of Si as a passive waveguiding material, providing lower scattering and polarization-dependent losses, optical transparency throughout the visible spectrum, increased tolerance to fabrication error, and better handling of high-power optical signals. Meanwhile, Al2O3 and TeO2 both serve as excellent host materials for rare-earth ions, and TeO2 possesses strong nonlinear optical properties. Using a single-step post-fabrication thin film deposition process, these materials can be monolithically integrated onto Si PICs at a wafer scale, enabling the realization of complementary-metal-oxide-semiconductor (CMOS)-compatible, hybrid SiP devices for linear, nonlinear, and active functionalities in integrated optics. While SWG metamaterials have widely impacted the design space and applicability of integrated photonic devices in SOI, they have not yet made their mark in other material systems outside of Si. Furthermore, demonstrations of their capabilities in active processes, including optical amplification, are still missing. In this thesis, we present a process for developing various SWG metamaterial-engineered integrated photonic devices in different material systems both within and beyond SOI. The demonstrations in this thesis emphasize the benefits of SWG metamaterials in these devices and realize their potential for enhancing functionality in applications such as sensing and optical amplification. The objective of the thesis is to highlight the prospects of SWG metamaterial implementation in different media used in integrated optics. This is accomplished by experimentally demonstrating SWG metamaterial waveguides, ring resonators and other components composed of different hybrid core-cladding material systems, including Si-TeO2 and Si3N4-Al2O3. Chapter 1 introduces the background and motivation for integrated optics and SWG metamaterials and provides an overview and comparison of the different materials explored in this work. Chapter 2 presents an initial experimental demonstration of TeO2-coated SOI SWG metamaterial waveguides and mode converters. It also details the design of fishbone-style SWG waveguides aimed at lowering loss and enhancing mode overlap with the active TeO2 cladding material in the hybrid SiP platform. Chapter 3 details an open-access Canadian foundry process for rapid prototyping of Si3N4 PICs, emphasizing the Si3N4 material and waveguide fabrication methods, as well as the design and characterization of various integrated photonic components included in a process design kit. The platform is compared against other Si3N4 foundries, and plans for further development are also discussed. Chapter 4 reports the first demonstration of SWG metamaterial waveguides and ring resonators fabricated using a Si3N4 foundry platform. The measured devices have a propagation loss of ∼1.5 dB/cm, an internal quality factor of 2.11·10^5, and a bulk sensitivity of ∼285 nm/RIU in the C-band, showcasing competitive metrics with conventional Si3N4 waveguides and SWG ring resonators and sensors reported in SOI. Chapter 5 presents work towards an SWG metamaterial-engineered waveguide amplifier. The fabricated device, based in Si3N4 and functionalized by an atomic layer deposited, erbium-doped Al2O3 thin film cladding, exhibited a signal enhancement of ∼8.6 dB, highlighting its potential for on-chip optical amplification. Methods to reduce the loss within the material system are proposed to achieve net gain in future devices. Chapter 6 summarizes the thesis and discusses pathways for optimizing the current devices as well as avenues for exploring new and intriguing materials and devices for future applications in integrated photonics. / Thesis / Doctor of Philosophy (PhD)

Le travail de thèse porte sur une étude d'impact de différentes structures SOA sur la transmission optique de signaux OFDM modulés en intensité et reçus en détection directe (IMDD-OOFDM), dans le cadre des réseaux d'accès de nouvelle génération (σGPτσ). Dans la première partie du travail, nous avons d’abord validé expérimentalement la modélisation d’un RSτA sur une large plage d’utilisation. Ce modèle a ensuite été implémenté dans le cadre d'une plate-forme de co-simulation pour les systèmes de transmission IMDD-OOFDM et pour la conversion en longueur d'onde de signaux OOFDM avec une validation expérimentale. Une analyse approfondie des performances de transmission a été ensuite menée en termes de puissance optique et de longueur d’onde injectées, de longueur de fibre, de l’émission spontanée amplifiée (ASE), de la bande passante électrique et des non-linéarités du RSτA. Nous avons notamment montré théoriquement qu’une capacité minimale de transmission de 8,9 Gb/s sur 100 km pouvait être atteinte sur une plage de 100 nm avec le RSOA utilisé et avec l’aide d’une modulation adaptative (AMττFDM). Nous avons également démontré expérimentalement, pour la première fois à notre connaissance, la conversion de longueur d'onde de signaux optiques OOFDM-16QAM sur une plage de 70 nm en utilisant l'effet XGM du RSOA. Dans la seconde partie, nous avons développé la modélisation de plusieurs structures de SOA : un SOA à îlots quantiques (QD SOA), un SOA bi-électrodes et deux SOA cascadés en configuration contra-propagative. Nous avons étudiés leurs performances en transmission à l’aide de la modulation AMττFDM. Nous avons montré que ces structures présentent une capacité de transmission allant jusqu’à 30 Gb/s avec des distances de transmission jusqu'à 60 km. Nous avons montré également que le QD-SOA présente de meilleures performances en termes de capacité de transmission pour des distances allant jusqu'à 140 km en comparaison avec les deux autres configurations. / The thesis work deals with study of different SOA structures impact on the transmission of intensity modulation and direct detection OFDM signals in the context of the next generation access networks. In the first part of the work, we have experimentally validated a comprehensive wideband RSOA field model. It was the nused as part of a co-simulation platform for IMDD-OOFDM and OOFDM wavelength conversion transmission systems. Thanks to this co-simulation platform that presents good agreement with the measurement, and our experimental setup, we analyze the transmission performance in terms of optical input power, fiber length, ASEnoise, electrical bandwidth and RSOA nonlinearities. We showed by simulation that an AMOOFDM signal transmission over a 100 nm wavelength range with a minimum transmission capacity of 8.9 Gb/s for fiber lengths up to 100 km can be reached. Finally, we experimentally demonstrated, for the first time to the best of our knowledge, the feasibility of performing wave length conversion over 70 nm of OOFDM-16QAM optical signals using the XGM effect in an RSOA. In the second part of this work we develop a simplified quantum dot –SOA and two electrode SOAintensity modulator models and study their effect on a numerical OFDM IMDD transmission system, we also study a two cascaded SOA in a counter propagating configuration as an intensity modulator. We find that for the three configurations we can achieve a high transmission capacity of around 30 Gb/s for transmission distances up to 60 Km, we also find that the QD-SOA will have the best performance in terms of transmission capacity for distances up to 140 Km in comparison with the two other SOA configurations.

The aim of this thesis is to introduce to reader the application and use of optical EDFA amplifiers in optical transmission and to show wiring and practical test, including measurements on amplifier. The aim of this thesis is to propose the use of optical amplifier in laboratory practice for subject Optical networks. The thesis briefly introduces the problems of data transmissions through optical fibers with a focus on the use of optical amplifiers. The basic characteristic of optical transmission paths and the reasons for the use of optical amplifiers are described here. One entire chapter is devoted to distinction of optical amplifiers. Amplifiers can be divided according to location in the transmission path to the booster, in-line and pre-amplifiers and according to the used of amplifying technology to optical amplifiers with subsidies, semiconductor optical amplifiers and Raman optical amplifiers. The factors affecting the efficiency of optical amplifiers, such as noise and the level of saturated power are mentioned here too. The different types of optical amplifiers from the two producers are also described. From these amplifiers was chosen EDFA CzechLight Amplifier from Optokon to be used for the laboratory exercise in the subject of Optical networks. The use of EDFA optical amplifiers in optical transmission lines is mentioned here too. These amplifiers can be used in telecommunications transmission systems and for data transmission over long distances. They will find use in WDM transmission systems and cable TV distribution through the optical fiber to the end users. Practical measurements were performed on optical amplifier CLA-PB01F. In the transmission route was located attenuator and the dependence of output power to input signal power was measured. The amplification course was linear in the range of input values provided by the manufacturer. Laboratory exercise for the subject of Optical networks is aimed at preacquaintance of students with problems EDFA optical amplifiers and practical measurements with the optical amplifier CLA-PB01F. Students acquire basic theoretical knowledge of the issue and verify the functionality of optical amplifiers on a specific exercise. This work is destined for all who wish to get basic knowledge of optical amplifiers, their characteristics and possibilities of their use in optical transmission lines.

The main goal of this diploma thesis is to design of high-speed optical network. The first part deals with theoretical knowledge in the field of optical transmissions, especially principle of wavelength division multiplexing. Generally speaking, this part is dedicated to optical connections over long distances. It will concentrate on different types of wavelength division multiplexing, optical fiber amplifiers and other basic optical components. Then it discusses influence of negative effects acting on optical transmission and discusses how to reduce or suppress their influence. Subsequently, there is designed backbone network in the Czech Republic in OptiSystem 7.0 software and are verified some mentioned theoretical knowledge. One of chapters also presents results of measurements of real optical routes in our state. The second part of the diploma thesis moves its attention on that part of optical network, which provides data connectivity to end users, that means it is focused on optical access network. There are described the most common topologies, standards and components. Based on these findings, in the last chapter, there is worked out design of optical access network FTTH (more precisely FTTD) in the selected location. Afterwards, the design is transferred to the OptiSystem 7.0 software, where is verified its functionality.

Le futur système de transmission multicanaux (WDM) pourrait mettre à profit l'utilisation d'amplificateurs optiques à semi-conducteurs (SOA), pour bénéficier notamment de leur grande bande passante optique pour l'amplification du signal. Dans ce travail, nous étudions l’influence des SOA sur la transmission cohérente de signaux OFDM optiques (CO OFDM). Cette technique, récemment proposée, permet à la fois d’augmenter l'efficacité spectrale de la transmission et de compenser les imperfections linéaires du canal optique. Nous avons développé, dans ce travail, une chaîne expérimentale de transmission de signaux à formats de modulation complexes tout-optiques et une plateforme de simulation au niveau système. Les résultats obtenus par simulation, au niveau composant et au niveau système, sont en très bon accord avec ceux obtenus par les mesures expérimentales à la fois pour des formats de modulation QPSK et QPSK CO-OFDM. À travers différentes mesures et simulations, l’étude a permis de cerner clairement l’influence des paramètres du SOA sur la qualité de transmission des données. Les non-linéarités induites par le SOA, telles que le couplage phase amplitude, l’auto modulation du gain et de la phase (SGM et SPM), la modulation croisée du gain et de la phase (XGM et XPM) et le mélange à quatre ondes (FWM), jouent de façon importante sur les performances de ce format de modulation multi-porteuses ; leur influence a donc été analysée avec précision. Les connaissances acquises permettront à l’avenir d’une part de mieux définir les conditions d’utilisation des SOA dans les réseaux de transmission et d’autre part aideront à l’optimisation de nouvelles structures de SOA conçues pour la transmission de données à très haut débit utilisant des formats de modulation complexes. / Future wavelength division multiplexing (WDM) systems might take advantage from the use of semiconductor optical amplifiers (SOA), especially to benefit from their large optical bandwidth for signal amplification. In this work, we study the influence of SOAs on the coherent optical-OFDM (CO OFDM) transmission system. This recently proposed technique allows both to increase the spectral efficiency of the transmission and to compensate the linear imperfections of the optical channel. In this work, we have developed an experimental setup for signal transmission operating with advanced optical modulation formats and a system level simulation platform. Simulation results, both at the component level and at the system level, are in very good agreement with those obtained from experimental measurements in the case of both QPSK and QPSK CO-OFDM signals. The study has clearly identified, through various measurements and simulations, the influence of SOA parameters on the quality of data transmission. Nonlinearities induced by the SOA, such as phase-amplitude coupling, self gain and phase modulation (SGM and SPM), cross gain and phase modulation (XGM and XPM) and the four-wave mixing (FWM) affect the performances of this multicarrier modulation format. Their influence is studied very precisely in this work. This acquired knowledge will allow, on the one hand, better defining the conditions of use of SOAs in the transmission networks and, on the other hand, helping to optimize new structures of SOA designed for very high bit rate data transmissions using complex modulation formats.

Les techniques permettant de maitriser la vitesse de la lumière, au-delà de l'intérêt scientifique qu'elles suscitent, peuvent être appliquées au domaine radar. Elles permettent, ainsi, de remplacer avantageusement les retards optiques, jusqu'alors réalisés par des modifications géométriques du chemin optique. L’objectif de la thèse est d’étudier la lumière lente et rapide créée par oscillations cohérentes de population dans les amplificateurs à semi-conducteurs.Nous avons évalué théoriquement et expérimentalement les performances d’une ligne à retards accordables, en termes d’amplitude des retards et déphasages accordables, et de bandes passantes. Nous avons aussi étudié l’impact des oscillations cohérentes de population sur les facteurs de mérite de la liaison opto-électronique. La compréhension des mécanismes physiques mis en jeu nous a amenés à proposer des solutions pour contourner les limites identifiées du composant. Nous avons montré qu’il était possible d’utiliser les lignes à retards accordables au delà de l’inverse du temps de vie des porteurs (500 MHz) en utilisant la montée en fréquence des oscillations cohérentes de population par modulation croisée de gain. Nous avons ainsi obtenu des retards accordables de 389 ps à 16 GHz, sur une bande passante instantanée de 360 MHz. Enfin nous avons proposé une architecture permettant d’obtenir des déphasages accordables proches de 180 degrés à haute fréquence, en substituant l’effet du couplage gain-indice, révélé par l’utilisation d’un filtre optique, par l’excitation paramétrique des oscillations cohérentes de population. Nous avons utilisé ce principe, qui permet par exemple d’atteindre un déphasage accordable de 162 degrés à 2,2 GHz, pour concevoir un oscillateur optoélectronique fonctionnant à 2,2 GHz. La fréquence de ce dernier est rapidement accordable sur 6 MHz à l’aide du courant d’injection de l’amplificateur à semi-conducteur. / Slow and fast light is becoming a wide research field driven by an extensive effort to implement this new technology in real applications. Coherent population oscillations in semiconductor optical amplifiers constitute one of the most promising approaches, in particular for the processing of optically carried microwave signals, which includes the control of tunable true time delays and RF phase shifts.We studied theoretically and experimentally the available tunable delays and phase shifts and the associated bandwidths for a microwave photonics link including a semiconductor optical amplifier. We analyzed the influence of the coherent population oscillations on the dynamic range of the link.The understanding of the underlying physical mechanisms led us to propose new architectures in order to overcome the identified limitations of the components. We show how up-converted coherent population oscillations enable to get rid of the intrinsic limitation of the carrier lifetime (500 MHz), leading to the generation of true time delays at any high frequencies in a single semiconductor device. We demonstrated tunable delays up to 389 ps at 16 GHz, with an instantaneous bandwidth of 360 MHz.Lastly we demonstrate how to conceive a RF phase shifter up to 180 degrees at high frequency by forced coherent population oscillations. This effect replaces the enhancement of the coherent population oscillations by gain-index coupling effect, revealed by an optical filter. We used this principle, which enables to achieve a tunable phase shift up to 162 degrees at 2,2 GHz, in order to conceive an optoelectronic oscillator at 2,2 GHz. The frequency of this oscillator is fast tunable over 6 MHz by changing the current of the semiconductor amplifier.

L’amplification optique large bande à base de SOA est devenue indispensable pour la montée en débit des systèmes de transmissions optiques et pour pouvoir exploiter au mieux la bande optique des fibres optiques. Ce travail présente une étude théorique et expérimentale d’un SOA large bande passante développé par Alcatel Thales III-V Lab dans le cadre des projets ANR AROME et UltraWIDE. Dans cette thèse, nous avons d’abord effectué une modélisation semi-phénoménologique du gain matériau et du coefficient de gain d’une structure à base de multi-puits quantiques avec un nombre réduit de paramètres. L’intégration de notre modèle dans un modèle de SOA déjà développé au laboratoire a montré son efficacité pour restituer quantitativement le comportement statiques (gain, facteur de bruit) des nouvelles structures SOA large bande sur une large plage de longueurs d’onde (> 110 nm), de courants d’alimentation et de puissances optiques. A l’aide de ce modèle, nous avons étudié l’influence de la structure du SOA sur la bande passante pour un gain cible en jouant sur la longueur, le nombre d’électrode et le courant d’alimentation du SOA. Nous avons mis en évidence qu’une structure bi-électrodes n’apportait pas d’amélioration de la bande passante optimisée par rapport au cas mono-électrode. En revanche, la structure bi-électrode permet d’optimiser la puissance de saturation et le facteur de bruit du SOA, sans sacrifier ni le gain maximal ni la bande passante optique. Nous avons aussi montré que, pour ce type de composants, une augmentation de la puissance optique injectée pouvait être compensée par une augmentation du courant d’alimentation pour maintenir une large bande passante optique. Nous avons également mis en place deux techniques d’élargissement de la bande passante optique de SOA à large bande. La première technique est fondée sur le filtrage en réflexion spectralement sélectif (ESOA). Le dispositif expérimental a permis d’amplifier simultanément 8 canaux CWDM dans une bande passante (définie à −1 dB) de 140 nm. La deuxième technique, basée sur un amplificateur hybride Raman-SOA, a fourni une bande passante optique (définie à −1 dB) de 89 nm avec un gain de 17 dB. Nous avons ainsi pu réaliser une transmission simultanée de 5 canaux CWDM allant jusqu’à 10 Gb/s sur 100 km. / SOA-based optical amplification became crucial for increasing optical system capacity and to benefit from the broad bandwidth of optical fibers. In this work we present both theoretical and experimental studies for a new broadband SOA developed by Alcatel Thales III-V lab in the framework of AROME and UltraWIDE ANR projects.We developed firstly a semi-phenomenological model for both the material gain and the gain coefficient of a multi-quantum well -based SOA structure with a reduced set of parameters. This material gain model has been integrated in an existing SOA model and proved its performance in reproducing steady state behavior of this new broadband SOA (gain and noise figure) for a wide range of wavelengths, input powers and bias currents. Thanks to this model, we studied the influence of the SOA geometrical structure on the optical bandwidth for a given target gain, by varying length, number of electrodes and bias current. We showed that two-electrode SOA structures do not provide any improvement of the bandwidth compared to the one-electrode case. However, the two-electrode structure allows the optimization of both the SOA saturation power and the noise figure, without sacrificing neither the maximum gain nor the optical bandwidth. We have also shown that for this kind of component, an increase in the injected optical power could be compensated by an increase in the supply current to maintain a wide optical bandwidth.We have also investigated two techniques to widen the optical bandwidth of our broadband SOA. The first one is based on a modification of the SOA structure by introducing a selective reflection filter (ESOA). Its experimental implementation allowed the amplification of an 8-CWDM-channel comb in a bandwidth (defined at -1 dB) of 140 nm. The second one, based on a hybrid Raman-SOA amplifier, provided an optical bandwidth (defined at -1 dB) of 89 nm with a gain of 17 dB. With this last technique, we were able to achieve a 5-CWDM-channel comb transmission up to 10 Gb/s over 100 km.

Chalcogenide glasses are highly nonlinear optical materials which can be used for fabricating active and passive photonic devices. This thesis work deals with the fabrication of buried, three dimensional, channel waveguides in chalcogenide glasses, using ultrafast laser inscription technique. The femtosecond laser pulses are focused into rare earth ions doped and undoped chalcogenide glasses, few hundred microns below from the surface to modify the physical properties such as refractive index, density, etc. These changes are made use in the fabrication of active and passive photonic waveguides which have applications in integrated optics. The first chapter provides an introduction to the fundamental aspects of femtosecond laser inscription, laser interaction with matter and chalcogenide glasses for photonic applications. The advantages and applications of chalcogenide glasses are also described. Motivation and overview of the present thesis work have been discussed at the end. The methods of chalcogenide glass preparation, waveguide fabrication and characterization of the glasses investigated are described in the second chapter. Also, the details of the experiments undertaken, namely, loss (passive insertion loss) and gain measurements (active) and nanoindentation studies are outlined. Chapter three presents a study on the effect of net fluence on waveguide formation. A heat diffusion model has been used to solve the waveguide cross-section. The waveguide formation in GeGaS chalcogenide glasses using the ultrafast laser, has been analyzed in the light of a finite element thermal diffusion model. The relation between the net fluence and waveguide cross section diameter has been verified using the experimentally measured properties and theoretically predicted values. Chapter four presents a study on waveguide fabrication on Er doped Chalcogenide glass. The active and passive characterization is done and the optimal waveguide fabrication parameters are given, along with gain properties for Er doped GeGaS glass. A C-band waveguide amplifier has been demonstrated on Chalcogenide glasses using ultrafast laser inscription technique. A study on the mechanical properties of the waveguide, undertaken using the nanoindentation technique, is presented in the fifth chapter. This work brings out the close relation between the change in mechanical properties such as elastic modulus and hardness of the material under the irradiation of ultrafast laser after the waveguide formation. Also, a threshold value of the modulus and hardness for characterizing the modes of the waveguide is suggested. Finally, the chapter six provides a summary of work undertaken and also discusses the future work to be carried out.