Over the past decades, integrated photonics has revolutionized the way we generate and manipulate light, employing micro- and nanoscale structures to shrink full optical systems into chips smaller than a fingernail. By leveraging the infrastructure of semiconductor foundries and fabrication processes, the development and deployment of integrated photonic technologies has been greatly accelerated. The main focus has been in applications for infrared light, such as optical interconnects and communication. Nevertheless, photonic integrated circuits (PICs) have quickly found applications in many other fields, including sensing, ranging, imaging, quantum technologies, biomedicine, spectroscopy, microwave generation, astrophysics, and displays. However, many of these technologies require light at visible wavelengths, where PIC technology is still in its infancy. Visible-light photonics presents several additional and stricter challenges when compared the infrared portion of the spectrum. First, laser sources are not as developed or available. Second, the sensitivity of devices to fabrication variations and the coupling losses are intensified. Third, the range of transparent materials available for waveguiding is more limited, and their technology is not as mature. Lastly, techniques that work well in the infrared spectrum are not as effective in the visible range due to the remarkably different material properties in this spectral window.In this thesis, we explore integrated photonics in the visible spectrum and focus on solving two of its main challenges: the lack of high-performance laser sources, and the high losses of PICs. We develop a low loss, high-confinement silicon nitride (SiN) platform and use it to demonstrate high-performance visible-light lasers from near-ultraviolet (near-UV) to near-infrared (near-IR), to probe the limits of absorption and scattering across the visible spectrum, and to generate multi-octave frequency combs with simultaneous infrared and visible light of all colors of the rainbow. Since our SiN platform is compatible with current photonic foundries, our work lays the foundation for fully-integrated, dense and scalable visible-light PIC systems that combine high-performance lasers and ultra-low loss devices. We envision such chip-scale platform to not only transform existing technologies, but to also enable a whole new generation of applications that have so far been impossible, causing tremendous impact in science, medicine and industry.

Using silicon based microfabrication and materials, a photonic platform, capable of single bioparticle analysis, has been developed. This platform combines liquid and hollow core waveguides on the micron-scale (5 µm x 12 µm) to isolate femtoliter sized sample volumes. Fluorescence excitation and signals in the visible range are directed into and out of the sample volume at an orthogonal angle to maximize signal-to-noise. In order to guide light in a low-index material antiresonant reflecting optical waveguides (ARROWs) were incorporated into the platform. This thesis reveals the development path of these structures over several device generations including innovations in material, geometries, and fabrication techniques to increase detection sensitivity. As a result of these developments, this photonic platform has shown to successfully detect virus samples and other particles. This thesis also presents a new idea for increasing the signal to noise ratio (SNR) by incorporating Y-splitter devices into the design. Specifically, the 1 x 2 and 1 x 4 splitter structures can be used as orthogonal excitation points to the liquid core waveguide. When fluorescently tagged particles are introduced into the hollow core, these points create an optical signal that is correlated in time and space. The data collected by a photodetector can then be processed by an algorithm to increase SNR. Such advancements have shown to increase the SNR by 175 times.

This dissertation investigates the monolithic integration of dual optical elements on high power semiconductor lasers for emission around 980nm wavelength. In the proposed configuration, light is coupled out of the AlGaAs/GaAs waveguide by a low reflectivity grating coupler towards the substrate where a second monolithic optical element is integrated to improve the device performance or functionality. A fabrication process based on electron beam lithography and plasma etching was developed to control the grating coupler duty cycle and shape. The near-field intensity profile outcoupled by the grating is modeled using a combination of finite-difference time domain (FDTD) analysis of the nonuniform grating and a self-consistent model of the broad area active region. Improvement of the near-field intensity profile in good agreement with the FDTD model is demonstrated by varying the duty cycle from 20% to 55% and including the aspect ratio dependent etching (ARDE) for sub-micron features. The grating diffraction efficiency is estimated to be higher than 95% using a detailed analysis of the losses mechanisms of the device. The grating reflectivity is estimated to be as low as 2.10-4. The low reflectivity of the light extraction process is shown to increase the device efficiency and efficiently suppress lasing oscillations if both cleaved facets are replaced by grating couplers to produce 1.5W QCW with 11nm bandwidth into a single spot a few mm above the device. Peak power in excess of 30W without visible COMD is achieved in this case. Having optimized, the light extraction process, we demonstrate the integration of three different optical functions on the substrate of the surface-emitting laser. First, a 40 level refractive microlens milled using focused ion beam shows a twofold reduction of the full-width half maximum 1mm above the device, showing potential for monolithic integration of coupling optics on the wafer. We then show that differential quantum efficiency of 65%, the highest reported for a grating-coupled device, can be achieved by lowering the substrate reflectivity using a 200nm period tapered subwavelength grating that has a grating wavevector oriented parallel to the electric field polarization. The low reflectivity structure shows trapezoidal sidewall profiles obtained using a soft mask erosion technique in a single etching step. Finally, we demonstrate that, unlike typical methods reported so far for in-plane beam-shaping of laser diodes, the integration of a beam-splitting element on the device substrate does not affect the device efficiency. The proposed device configuration can be tailored to satisfy a wide range of applications including high power pump lasers, superluminescent diodes, or optical amplifiers applications.

In recent years, there has been significant progress in the development of integrated photonic circuits (PICs). Matured fabrication and simulation techniques have enabled the development of novel devices and system architectures. Ideally, these newly developed technologies are put to test in the lab, both to verify that they perform as simulated and to demonstrate the viability of the technology. Testing the increasingly complex optical circuits brings various challenges. One of these challenges is the sensitivity to temperature changes of many optical circuits, especially micro ring and micro disk resonators (MRRs and MDRs). Due to the nature of these resonators, slight deviations in the material properties have a large impact on their resonant frequency. Despite this, their small footprint and wavelength selectivity makes them promising components for many future technologies, especially Dense Wavelength Division Multiplexed (DWDM) communication links. Multiple resonators cascaded on a single bus waveguide can operate on multiple wavelengths simultaneously with relatively few components and in a small combined area. Since every extra connection to a PIC has a footprint similar to that of a micro resonator, a packaging optimized thermal control scheme is needed to fully leverage all advantages of micro resonators. This work will focus on the thermal stabilization of cascaded micro resonators and how thermal control can be optimized to simplify the packaging of PIC prototypes. This simplification enables the demonstration of complex systems and more realistic scenarios for thermal control of both resonators and other circuits. It will first show how a number of PICs and their respective packages were built, keeping subsequent testing in mind. Then, it demonstrates automatic initialization of cascaded MRR and how stable operation, while undergoing large temperature swings, can be achieved using a minimum number of connections to the PIC. Next, it shows stable operation of an eight-wavelength receiver, operating uncooled at 16 Gb/s/?, over a record 75 °C. Finally, it presents how all the learned lessons are brought together to built a 2.5D integrated SiPh transceiver that is capable of transmitting 512 Gb/s bidirectionally. This transceiver can be plugged into Field Programmable Gate Arrays (FPGAs), which can then be used to implement accelerators for real computing problems, used as a PCIe bridge to a standard compute server, or both. The transceiver is also designed to work with many types of optical switches, allowing demonstrations of novel switching algorithms and network architectures. The contributions discussed in this thesis can assist in enabling future high bandwidth optical interfaces by optimizing the thermal control strategy and may be used at all stages of PIC design and packaging to facilitate the development of new technologies.

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Le laser est devenu un outil très riche depuis sa création en 1960. Ses applications sont très variées et il a intégré tous nos outils du quotidien. Décliné sous leur forme impulsionnelle, les lasers se sont encore ouverts d'autres champs d'application tels que l'usinage, la découpe, le marquage ou le nettoyage de matériaux; ou encore la médecine et le bien-être et également les capteurs et notamment les capteurs embarqués. Les lasers impulsionnels à déclenchement passif (Q-Switch) sont tout particulièrement adaptés à ce dernier champ d'application de par leur suffisance énergétique, utilisant l'énergie du laser lui-même pour créer des impulsions lasers très énergétiques dont la durée est de l'ordre de la nanoseconde. Les lasers réalisés sur substrat de verre se sont avérés également très adaptés à la fabrication de dispositifs de captation embarquée : ils montrent une grande stabilité, de fortes résistances mécanique et chimique les rendant utilisables dans un large panel de conditions environnementales. A l'IMEP-LaHC, des lasers réalisés par échange d'ions argent/sodium dans des substrats de verre phosphate dopés à l'erbium et à l'ytterbium ont été réalisés. Des lasers impulsionnels ont également été réalisés en utilisant cette technologie de guides d'ondes planaires en interaction avec des couches minces d'acétate de cellulose dopé à un colorant nommé BDN possédant les propriétés d'absorption saturable nécessaires à la naissance d'un comportement Q-Switch. Ces lasers permettent déjà de s’orienter vers la captation embarquée. Cependant, certaines applications nécessitent encore plus de puissance et surtout une meilleure résistance à l'environnement que celle proposée par l'acétate de cellulose. Afin de répondre à toutes ces attentes, nous présentons dans ce manuscrit la fabrication d’absorbants saturables à partir de matrices sol-gel et dopées au BDN afin de créer des guides d'ondes absorbants saturables. Des méthodes de caractérisation et des simulations spécifiques d’absorption saturable sont développés afin de décrire le comportement de tels dispositifs et d’évaluer la pertinence du choix de telles matrices alliées au colorant BDN afin de créer des lasers Q-Switch en optique intégrée sur verre. / Since its creation in 1960, laser has become a really useful tool. Lasers are very versatile and they has become part of many of our everyday life tools. Coming in their pulsed form, lasers have opened-up others fields of application such as machining, cutting, marking or cleaning materials; or medicine and well-being and also sensors and in particular embedded sensors. Passively Q-Switched lasers are particularly adapted to this last field of application thanks to their energetic self-sufficiency, using the energy of the laser itself to create very energetic laser pulses whose duration order is about the nanosecond. The lasers made on optical glass wafers have also proved very suitable for the manufacture of on-board sensing devices: they show great stability, strong mechanical and chemical resistance, making them usable in a wide range of environmental conditions. At IMEP-LaHC, lasers made by silver / sodium ion exchange in erbium and ytterbium doped phosphate glasses were made. Pulsed lasers have also been realized using this planar waveguide technology in interaction with thin films of cellulose acetate doped with a dye named BDN, having the saturable absorption properties needed for the emergence of Q –Switch operation. These lasers can already address on-board sensing applications. However, some applications require even more power and above all a better environmental resistance than that proposed by cellulose acetate. In order to meet all these expectations, we present in this manuscript the production of saturable absorbers from BDN-doped sol-gel matrices to create saturable absorber waveguides. Specific characterization methods and saturable absorption simulations are developed to describe the operation of such devices and to evaluate the relevance of the choice of such matrices allied with BDN dye in order to create glass integrated Q-Switched lasers.

La montée exponentielle du trafic de données liée au développement de l’interconnexion entre objets et personnes sur la toile nécessite de nouvelles technologies. Au cours de la dernière décennie, les peignes de fréquences optiques ont révolutionné le secteur des télécommunications, ouvrant la voie à une transmission de données à un débit de données auparavant inaccessible. Mis à part le domaine des télécommunications, les peignes de fréquences optiques ont été avantageusement exploités dans d’autres domaines comme la détection optique, la détection chimique, les horloges optiques… L'efficacité du phénomène de mélange à quatre ondes, qui sous-tend la génération des peignes de fréquences, dépend de manière significative des pertes par propagation dans les guides d’ondes optiques et, par conséquent, de la rugosité de ces derniers. De plus, l'absorption intrinsèque du matériau réduit l'efficacité des phénomènes non linéaires tout en contribuant à l’atténuation du signal lumineux dans le milieu optique de propagation. Grâce à la maturité des procédés de fabrication dits CMOS, la rugosité peut être réduite en optimisant la gravure, tandis que l’absorption peut être réduite par des traitements thermiques. L'utilisation d'un matériau CMOS permet donc une fabrication à faible coût et la co-intégration avec d’autres dispositifs optoélectroniques sur la même puce. Le nitrure de silicium sur isolant est une plateforme prometteuse pour la génération de peignes de fréquences optiques grâce à la faible absorption à deux photons dans ce matériau par rapport au silicium cristallin. Cependant, le nitrure présente une absorption dans la bande des télécommunications relié à la présence des liens moléculaires N-H. Tandis que des recuits à haute température ont été utilisés pour réduire le contenu en hydrogène du film et démontrer avec succès la génération de peignes de fréquence, ces procédés rendent la co-intégration monolithique de ces dispositifs en nitrure de silicium avec une optoélectronique à base de silicium très difficile, réduisant ainsi considérablement sa compatibilité avec les autres matériaux CMOS. Dans cette thèse, nous décrivons la conception, la fabrication et les caractérisations de circuits photoniques non-linéaires en nitrure de silicium sans recuit. En particulier, nous avons mis au point un procédé de fabrication de films de Si3N4 d'une épaisseur de 740 nm, sans utilisation de recuit et avec une maitrise de la gestion des contraintes typiquement associées à ce type de matériau pour l’optique non linéaire. Cette approche offre une compatibilité de fabrication technologique avec la photonique sur silicium. Des preuves expérimentales montrent que les micro-résonateurs utilisant de tels films de nitrure de silicium sans recuit sont capables de générer un peigne de fréquence s'étendant sur 1300-2100 nm via une oscillation paramétrique optique basée sur du mélange à quatre ondes. En allant encore plus loin, nous présentons également les travaux d’optimisation technologique portant sur des microrésonateurs en nitrure de silicium recuits avec des guides d’onde à fort confinement modal, qui nous ont permis d’atteindre des pertes de propagation record. Ces résultats ont été rendus possible grâce à une optimisation fine des étapes de gravure des guides d’onde ainsi qu’à l'utilisation de traitements thermiques-chimiques efficaces. Cette nouvelle approche nous a permis de démontrer par ailleurs des sources de peignes de fréquences intégrées sur puce utilisant des résonateurs en nitrure de silicium couplés par aboutement à un laser III-V DFB utilisé comme une pompe. Cette preuve de concept prouve la validité de notre plateforme de circuits photoniques non-linéaires en Si3N4 pour la réalisation de peignes de fréquences optiques ultra-compacts à faible consommation. / The data traffic need for ultra-high definition videos as well as for the mobile data continues to grow. Within the last decade, optical frequency combs have revolutionized the telecommunications field and paved the way for groundbreaking data transmission demonstrations at previously unattainable data rates. Beside the telecommunications field, optical frequency combs brought benefits also for many other applications such as precision spectroscopy, chemical and bio sensing, optical clocks, and quantum optics. The efficiency of the four-wave mixing phenomenon from which the optical frequency comb arises critically depends on the propagation losses and consequently on the device roughness induced by the lithography and the etching processes. In addition, the bulk material absorption reduces the efficiency of the nonlinear phenomena. By using state-of-the-art complementary metal oxide semiconductor processes, the roughness can be reduced thanks to the maturity of the manufacturing, while the material bulk absorption can be reduced by thermal treatments. In addition, using a CMOS material enables a low-cost fabrication and the co-integration with electronic devices into the same chip. Silicon-nitride-on-insulator is an attractive CMOS-compatible platform for optical frequency comb generation in the telecommunication band because of the low two-photon absorption of silicon nitride when compared with crystalline silicon. However, the as deposited silicon nitride has a hydrogen related absorption in the telecommunication band. Although high-temperature annealing has been traditionally used to reduce the hydrogen content and successfully demonstrate silicon nitride-based frequency combs, this approach made the co-integration with silicon-based optoelectronics elusive, thus reducing dramatically its effective complementary metal oxide semiconductor compatibility. In this thesis, we report on the fabrication and test of annealing-free silicon nitride nonlinear photonic circuits. In particular, we have developed a process to fabricate low-loss, annealing-free and crack–free Si3N4 740-nm-thick films for Kerr-based nonlinear photonics, featuring a full process compatibility with front-end silicon photonics. Experimental evidence shows that micro-resonators using such annealing-free silicon nitride films are able to generate a frequency comb spanning 1300-2100 nm via optical parametrical oscillation based on four-wave mixing. In addition, we present the further optimized technological process related to annealed silicon nitride optical devices using high-confinement waveguides, allowing us to achieve record-low losses. This was enabled via a carefully tailored patterning etching process and an annealing treatment particularly efficient due to the already low hydrogen content in our as-deposited silicon nitride. Such improved Si3N4 platform allowed us to demonstrate on-chip integrated Kerr frequency comb sources using silicon nitride resonators that were butt-coupled to a III-V DFB laser used as a pump source. This proof of concept proves the validity of our approach for realizing fully packaged compact optical frequency combs.

Photonic crystals, periodic dielectric structures that control photons in a similar way that atomic crystals control electrons, present opportunities for the unprecedented control of light. Photonic crystals display a wide gamut of properties, such as the photonic band gap, negative index of refraction, slow or stationary modes, and anomalous refraction and propagation effects. This thesis investigates the modeling, simulation, fabrication, and measurement of two-dimensional square lattice photonic crystals. An effective index model was developed to describe the propagation of electromagnetic waves in the media and applied to characterize the behavior of self-collimated beams to discern the effect of the photonic crystal on the evolution of the amplitude and phase of the propagating beam. Potential applications include optical interconnects and stand alone devices such as filters and lasers. Based on design parameters from the simulations, two dimensional photonic crystals were fabricated on amorphous and single crystal silicon-on-insulator substrates utilizing electron beam lithography and inductively coupled plasma etching. A unique etching process utilizing a combination of Cl2 and C4F6 gases was developed and characterized which displayed a vertical profile with a sidewall angle of under 1 degree from vertical and very smooth sidewalls for features as small as 150 nm. The high quality of the etching was the key to obtaining extremely low loss, low noise structures, making feasible the fabrication of large area photonic crystal devices that are necessary to measure propagation phenomena. Reflectivity measurements were used to directly observe the photonic band structure with excellent correlation with theory. A device was designed and fabricated which successfully verified the prediction of the simulations through measurements of the self-collimation effect across a broad range of infrared wavelengths. A solid foundation for the necessary components (simulation, modeling, design, fabrication, and measurement) of two-dimensional photonic crystal has been demonstrated. Elements from solid state physics, materials science, optics, and electromagnetics were incorporated to further the understanding of the mechanism of beam propagation in photonic crystals and illuminating the vast potential of research in periodic media.

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