In this research, we design and characterize thermally tuned hybrid tellurium ox- ide coated silicon (TeO2-Si) microdisk resonators for the development of tunable on chip lasers. Several heater designs are proposed that are compatible with stan- dard silicon photonics foundry processes and the requirement to deposit TeO2 onto the fabricated chips in post-processing. The devices are designed using simulation software packages such as Lumerical MODE and HEAT to simulate the mode profiles and thermo-optic coefficients of the microdisk resonators and the heating profiles of the various heater designs. The devices are laid out using the Luceda IPKISS Photonics Design Platform and fabricated at the AMF silicon photonics foundry. TeO2 is then deposited onto the fabricated chips at McMaster University in a single post-processing step via reactive radio frequency magnetron sputter- ing. Passive optical transmission measurements are performed to characterize the intrinsic Q-factors, loss and FSR of the microdisks. This is followed by resonance tuning measurements to characterize the tuning efficiencies of each of the heater designs presented in this thesis. The performances of each of the heater designs are then discussed and compared. / Thesis / Master of Applied Science (MASc)

The recent and rapid growth of silicon photonics is driven by the ever-increasing demand for bandwidth inside and between data centres. Silicon photonics can offer an unparalleled performance in terms of scalability and power consumption with low-cost fabrication through the leveraging of CMOS fabrication techniques. This thesis describes research on the silicon micro-ring resonator modulator, a device which combines energy-efficiency with a compact footprint that is ideal for data centre applications. Both theoretical and experimental work is described in the context of improving the reachability, capacity and stability of the silicon micro-ring resonator modulator for inter/intra-data centre communication. Chapter 2 presents modeling work using MATLAB® that provides predictive results for both device-level and system-level performance. Chapter 3 studies the chirp characteristic of an over-coupled silicon micro-ring resonator modulator and its capability of generating a negative-chirp modulation. The resulting chirp-induced power penalty is measured to be as low as 2.5 dB after 100 km transmission. Chapter 4 focuses on the advanced modulation techniques that can be efficiently exploited for increasing the spectral efficiency in the typically band-limited system. A record single-polarization 104 Gb/s data rate per wavelength (direct-detect) was achieved by using digital signal processing to alleviate the modulation deficiencies that are specific to the silicon micro-ring resonator modulator. In Chapter 5, a generic resonance control method using intrinsic defect-mediated photocurrent is described and experimentally demonstrated to provide stability for the silicon micro-ring resonator modulator during high-speed operation. This control method can also lead to an “all-silicon” system without the need for power detection using germanium. / Thesis / Doctor of Philosophy (PhD)

Atmospheric turbulence in free space optical satellite downlinks negatively impacts link availability and bit error rate. These effects can be mitigated using a compensation system capable of measuring the incoming wavefront distortion and applying a suitable correction to the received signal. The traditional solution based on adaptive optics and the Shack-Hartmann wavefront sensor has limitations in bandwidth, system complexity, size, weight, and power consumption. Signal correction can also be accomplished using a novel single-chip silicon photonic solution. This work introduces a four-arm grating coupler structure acting as a wavefront sensing element that emulates the performance of the Shack-Hartmann wavefront sensor by giving local tip and tilt estimation. FDTD simulations and measurements have confirmed the presence of a monotonic relationship between incident angle, polarization, and coupler output which can be converted to phase estimation through a reconstruction algorithm. An array of four-arm couplers on a silicon photonic chip provides enough sampling to fully reconstruct the wavefront, providing benefits over traditional solutions such as higher bandwidth, reduced size and weight, and reduced cost. Scaling up the results of this work to a full device could provide a solution for free space optical satellite to ground links in remote and rural communities across Canada and around the world. / Thesis / Master of Applied Science (MASc)

This thesis presents results on the applications and limitations of plasma enhanced chemical vapour deposition for silicon-based photonics, with an emphasis on optical microcavities for the control of light emission from silicon nanocrystals. ¶ Silicon nanocrystals were formed by precipitation and growth within Si-rich oxide layers (SiOx) deposited by plasma enhanced chemical vapour deposition. The films were found to exhibit strong room temperature photoluminescence, with the optimum emission depending on the composition and processing of the films. The strongest emission was achieved for films with a silicon content of ~40%, following hydrogen passivation. Hydrogen was introduced into the samples by two different methods: by annealing in forming gas (95% N2: 5% H2) or by annealing with a hydrogenated silicon nitride capping layer. Both methods caused an increase in photoluminescence intensity due to the passivation of defects. In contrast, the presence of low levels of iron and gold were shown to reduce the concentration of luminescent nanocrystals due to the creation of non-radiative centres. ¶ Optical microcavity structures containing silicon nanocrystals were also fabricated by Plasma enhanced chemical vapour deposition, using silicon dioxide, silicon nitride and silicon-rich oxide layers. The microcavities consisted of a silicon-rich oxide layer between two distributed Bragg reflectors formed of alternating silicon dioxide/nitride layers. The optical emission from these and related structures were examined and compared with that from individual layers in the structure. This revealed a complex interplay between defect and nanocrystal luminescence, hydrogen passivation and materials structure. The resulting microcavity structures were shown to be suitable for producing a stop-band over the wavelength range of interest for nanocrystal emission, 500-1000nm, and to produce significant intensity enhancement and spectral narrowing. Quality factors of 50-200 were demonstrated. ¶ The application of plasma deposited films was shown to be limited by stress-induced failure that resulted in cracking and delamination of the films during annealing. The SiOx films thicker than about 600nm failed predominantly by cracking. This was shown to be caused by tensile stress in the film caused by hydrogen desorption during high temperature annealing. The resulting cracks showed preferred alignment depending on the crystallographic orientation of the silicon substrate. For films deposited on (100) silicon, two modes of crack propagation were observed, straight cracks aligned along < 100> directions, and wavy cracks aligned along < 110> directions. For films deposited on (110) silicon, straight cracks were observed along [-1 10] directions, with a lesser number aligned along [001] directions. Cracks were also observed for films on (111) silicon. These showed 3-fold symmetry consistent with crack propagation along < 211> directions due to plastic deformation. Details of these crack geometries and their dependencies are discussed.

Optics and photonics enable important technological solutions for critical areas such as health, communications, energy, and manufacturing. Novel nanofabrication techniques, on the other hand, have enabled the realization of ever shirking devices. On-chip photonic micro-resonators, the fabrication of which was made possible in the recent decade thanks to the progress in nanofabrication, provide a sensitive and scalable transduction mechanism that can be used for biochemical sensing applications. The recognition and quantification of biological molecules is of great interest for a wide range of applications from environmental monitoring and hazard detection to early diagnosis of diseases such as cancer and heart failure. A sensitive and scalable biosensor platform based on an optimized array of silicon nitride microring resonators is proposed for multiplexed, rapid, and label-free detection of biomolecules. The miniature dimension of the proposed sensor allows for the realization of handheld detection devices for limited-resource and point-of-care applications. To realize these sensors, the design, fabrication, stabilization, and integration challenges are addressed. Especially, the focus is placed on solving a major problem in using resonancebased integrated photonic sensors (i.e., the insufficiency of wavelength scan accuracy in typical tunable lasers available) by using an interferometric referencing technique for accurate resonance tracking. This technique can improve the limit of detection of the proposed sensor by more than one order of magnitude. The method does not require any temperature control or cooling, and the biosensor platform does not require narrow linewidths necessary for the biosensors based on ultrahigh quality factor resonators, thus enabling low-cost and reliable integration on the biosensor platform.

Silicon with its mature integration platform has brought electronic circuits to mass-market applications; silicon photonics will most probably follow this evolution. However, there are still many technological challenges to be addressed in order to realize silicon photonics technology. One of the key challenges is building a complete design environment interfaced with standard EDA tools; as in microelectronics, this would enable the creation of photonic libraries and photonic IP blocks. In this study, we focus on developing a physical verification (PV) flow for the silicon photonics technology.There are a number of components from the traditional CMOS IC physical verification world that can be borrowed. All, however, will require some modification due to the distinct nature of photonic circuits. We study the photonic circuit PV requirements, in comparison with those for traditional IC designs. The most significant limitation of current PV tools is to handle non- Manhattan layout designs. We adapt industrial standard PV tools to perform efficient and reliable design rule checking (DRC) that validates non-Manhattan like layout. We also propose methodologies and develop a layout versus schematic (LVS) checking flow specific to the non- Manhattan characteristics and photonic circuit verification requirements. The flow is capable of verifying photonic circuit layout implementation (or even manufactured silicon) with regard to the intended design. The developed flows are demonstrated with Mentor Graphics Pyxis design environment and Calibre® PV tool suit. As generic methodologies, they can also be in principle adopted in other EDA tool environments in order to verify the physical implementation of the photonic designs. Such a PV flow is essential for bringing the silicon photonics technology onto the real CMOS streamline. / La plate-forme d'intégration silicium est arrivée à maturité, et a amené les circuits intégrés électroniques (IC) aux applications du marché de masse ; la photonique sur silicium va suivre probablement cette évolution. Pourtant, il y a encore de nombreux défis technologiques à relever pour réaliser la technologie photonique sur silicium. Parmi les principaux défis, il est essentiel de se concentrer sur la construction d'un environnement de conception complet interfacé avec les outils EDA standards ; comme dans la microélectronique, il permettrait la création de librairies photoniques et des blocs IP photoniques. Dans cette étude, nous nous concentrons sur l’adaptation et le développement du flot de vérification physique (PV, ou « physical verification ») pour la conception photonique sur silicium.Il y a un certain nombre de concepts de PV existant pour le CMOS traditionnel qui peuvent être empruntés. Tous, cependant, nécessiteront quelques modifications en raison de la nature distincte du circuit photonique. Nous étudions les exigences de PV pour les circuits photoniques, en comparaison avec celles de la conception de circuits intégrés traditionnels. La limitation la plus importante des outils de PV actuels est de traiter les layout « non-Manhattan ». Nousadaptons des outils industriels standards pour effectuer un « design rule checking » (DRC) efficace et fiable qui valide les layout non-Manhattan. Nous proposons également des méthodologies et développons un flot « layout versus schematic » (LVS) spécifique aux caractéristiques non-Manhattan et aux exigences de vérification de circuits photoniques. Le flot est capable de vérifier le layout du circuit photonique (ou même le silicium fabriqué du circuit) en ce qui concerne la conception cible. Les flots développés sont démontrées avec les outils de Mentor Graphics – Pyxis (l’environnement de dessin) et Calibre® (les outils de PV). Comme les méthodologies génériques, ils peuvent aussi être en principe adoptés dans d'autres outils EDA afin d'effectuer la vérification de la réalisation de la conception du circuit photonique. Un tel flot de PV est essentiel pour amener la technologie photonique sur silicium sur la ligne de production réelle de CMOS.

The American Institute for Manufacturing Integrated Photonics (AIM Photonics) is focused on developing an end- to- end integrated photonics ecosystem in the U.S., including domestic foundry access, integrated design tools, automated packaging, assembly and test, and workforce development. This paper describes how the institute has been structured to achieve these goals, with an emphasis on advancing the integrated photonics ecosystem. Additionally, it briefly highlights several of the technological development targets that have been identified to provide enabling advances in the manufacture and application of integrated photonics.

Silicon has been the material of choice of the photonics industry over the last decade due to its easy integration with silicon electronics as well as its optical transparency in the near-infrared telecom wavelengths. Besides these, it has very high refractive index, and also a broad optical transparency window over the entire mid-IR till about 8[Mu]m. Photonic crystal is well known that it can slow down the speed of light. It also can provide a universal platform for microcavity optical resonators with high quality factor Q and small modal volumes. The slow light effect, high Q and small modal volumes enhance light-matter interaction, together with high refractive index of silicon can be utilized to build a highly sensitive, high throughput sensor with small footprint. In this research, we have demonstrated highly compact and sensitive silicon based photonic crystal biosensor by engineering the photonic crystal microcavity in both cavity size and cavity-waveguide coupling condition. We have developed solutions to increase biosensor throughput by integrating multimode interference device and improving the coupling efficiency to a slow light photonic crystal waveguides. We have also performed detailed investigations on silicon based photonic devices at mid-infrared region to develop an ideal platform for highly sensitive optical absorption spectroscopy on chip. The studies have led to the demonstration of the first slot waveguide, the first photonic crystal waveguide, and the first holey photonic crystal waveguide and first slotted photonic crystal waveguide in silicon-on-sapphire at mid-infrared. The solutions and devices we developed in our research could be very useful for people to realize an integrated photonic circuit for biological and chemical sensing in the future. / text

Plasmonic resonances are characterized by enhanced optical near field and subwavelength power confinement. Light is not only scattered but also simultaneously absorbed in the metal nanostructures. With proper structural design, plasmonic-enhanced light absorption can generate nanoscopically confined heat power in metallic nanostructures, which can even be temporally modulated by varying the pump light. These intrinsic characters of plasmonic nanostructures are investigated in depth in this thesis for a range of materials and nanophotonic applications.   The theoretical basis for the photothermal phenomenon, including light absorption, heat generation, and heat conduction, is coherently summarized and implemented numerically based on finite-element method. Our analysis favours disk-pair and particle/dielectric-spacer/metal-film nanostructures for their high optical absorbance, originated from their antiparallel dipole resonances.   Experiments were done towards two specific application directions. First, the manipulation of the morphology and crystallinity of Au nanoparticles (NPs) in plasmonic absorbers by photothermal effect is demonstrated. In particular, with a nanosecond-pulsed light, brick-shaped Au NPs are reshaped to spherical NPs with a smooth surface; while with a 10-second continuous wave laser, similar brick-shaped NPs can be annealed to faceted nanocrystals. A comparison of the two cases reveals that pumping intensity and exposure time both play key roles in determining the morphology and crystallinity of the annealed NPs.   Second, the attempt is made to utilize the high absorbance and localized heat generation of the metal-insulator-metal (MIM) absorber in Si thermo-optic switches for achieving all-optical switching/routing with a small switching power and a fast transient response. For this purpose, a numerical study of a Mach-Zehnder interferometer integrated with MIM nanostrips is performed. Experimentally, a Si disk resonator and a ring-resonator-based add-drop filter, both integrated with MIM film absorbers, are fabricated and characterized. They show that good thermal conductance between the absorber and the Si light-guiding region is vital for a better switching performance.   Theoretical and experimental methodologies presented in the thesis show the physics principle and functionality of the photothermal effect in Au nanostructures, as well as its application in improving the morphology and crystallinity of Au NPs and miniaturized all-optical Si photonic switching devices. / <p>QC 20140331</p>

Quantum systems’ integration in chip-scale photonic circuits is the most promising way to succeed in scaling up complex systems for applications ranging from quantum computation to secure communications. Large systems with many components, especially for scaled all-optical quantum or classical processors, will require improved building blocks with greatly reduced loss, and enhanced bandwidth and robustness to fabrication uncertainties, temperature, etc. In this work, we introduce the concept of rapid adiabatic mode evolution that is the basis of a new family of passive devices with fundamentally improved performance, that we refer to as rapid adiabatic devices. In conventional adiabatic devices, a concept well known in photonics, the waveguide cross-section slowly evolves along the propagation direction, with no particular attention paid to transverse positioning of the cross-section. In contrast, in rapid adiabatic devices, we control the transverse position evolution (taking a tailored off-axis path while advancing along the direction of propagation). This has a major impact on the dominant crosstalk mechanism, the limiting factor to all performance metrics. By judicious synthesis and design, the dominant crosstalk coupling mechanism can be minimized or even set to zero everywhere along the structure. This concept brings a new paradigm to photonic passives that we stand the test of time as an important tool in the integrated photonics tool-box. We experimentally demonstrate a new integrated 2×2 beam splitter design we call a Rapid Adiabatic Coupler (RAC) in different fabrication platforms. The design is implemented in state-of-the art, field-leading CMOS photonics platforms pioneered in our group, taking into account foundry-imposed limitations on design. It nevertheless shows field-leading, very low-loss and extremely broadband 50:50 splitting ratio over hundreds of nanometers of optical bandwidth. In addition, we also demonstrate other photonic passives based on the concept – Rapid Adiabatic Crossings (RAX), a Rapid Adiabatic Mode Splitter (RAMS) as well as a Polarization Splitter Rotator based on the RAMS. These new high performance, compact components will enable larger-scale systems on chip with a higher number of components, not only for quantum photonics applications but also for other types of systems for sensing, optical AI accelerators, optical “FPGAs”, optical switches and routers, optical communication links and others. Another key building block for quantum photonic systems is integrated single photon sources. Following the first demonstration of a pair source integrated with pump filters by our group, here we demonstrate a monolithically integrated tunable photon pair source and pump filter on chip in a commercial, advanced 45nm CMOS microelectronics process. Next, we propose electronic-photonic quantum systems on chip, that contain monolithically integrated electronics and photonic components, as a platform to further scale up complexity in, and modularize, quantum systems on chip. As a first demonstration concept, we propose and demonstrate the first experimental step toward a “wall-plug” photon pair source implemented as an electronic-photonic monolithic chiplet. The idea is a CMOS die (or electronic-photonic block on the chip) that takes only electrical DC power, optical CW laser “DC power”, and control signals, and generates high quality photon pairs. The system contains a thermally tunable second-order filter with heater drivers integrated in the chiplet electronics to clean the input pump laser, a self-locking source ring with integrated electronic circuits that allow the ring resonance to automatically align to the pump laser and low-loss, high extinction, high-order thermally tunable filters. These results taken together show that monolithic integration in CMOS micro-electronics processes does allow high performance photonics, while also supporting scalable complex circuits with electronic control to account for the extreme sensitivity of photonic components and impart reconfigurability and tunability; showing it as a viable approach to build large-scale electronic-photonic systems with a realistic path to commercial technologies. This work was supported in part by the NSF RAISE-EQuIP program (Award 1842692) and by the Packard Foundation (Award 2012-38222). / 2023-05-23T00:00:00Z