The growing speed and bandwidth requirements of telecommunication systems demand all-optical on-chip solutions. Microphotonic devices can deliver low power nonlinear signal processing solutions. This thesis looks at the slow light photonic crystals in chalcogenide glasses to enhance low power nonlinear operation. I demonstrate the development of new fabrication techniques for this delicate class of materials. Both, reactive ion etching and chemically assisted ion beam etching are investigated for high quality photonic crystal fabrication. A new resist-removal technique was developed for the chemical, mechanical and light sensitive thin films. I have developed a membraning method based on vapor phase etching in combination with the development of a save and economical etching tool that can be used for a variety of vapour phase processes. Dispersion engineered slow light photonic crystals in Ge₃₃As₁₂Se₅₅ are designed and fabricated. The demonstration of low losses down to 21±8dB/cm is a prerequisite for the successful demonstration of dispersion engineered slow light waveguides up to a group index of around n[subscript(g)] ≈ 40. The slow light waveguides are used to demonstrate highly efficient third harmonic generation and the first advantages of a pure chalcogenide system over the commonly used silicon. Ge₁₁.₅As₂₄24Se₆₄.₅ is used for the fabrication of photonic crystal cavities. Quality factors of up to 13000 are demonstrated. The low nonlinear losses have enabled the demonstration of second and third harmonic generation in those cavities with powers up to twice as high as possible in silicon. A computationally efficient model for designing coupled resonator bandpass filters is used to design bandpass filters. Single ring resonators are fabricated using a novel method to define the circular shape of the rings to improve the fabrication quality. The spectral responses of the ring resonators are used to determine the coupling coefficient needed for the design and fabrication of the bandpass filters. A flat top bandpass filter is fabricated and characterized as demonstration of this method. A passive all-optical regenerator is proposed, by integrating a slow-light photonic crystal waveguide with a band-pass filter based on coupled ring resonators. A route of designing the regenerator is proposed by first using the dispersion engineering results for nonlinear pulse propagation and then using the filter responses to calculate the nonlinear transfer function.

The field of nanophotonics is a major research topic, as it offers potential solutions to important challenges, such as the creation of low power, high bandwidth interconnects or optical sensors. Within this field, resonant structures and slow light waveguides are used to improve device performance further. Photonic crystals are of particular interest, as they allow the fabrication of a wide variety of structures, including high Q-factor cavities and slow light waveguides. The high scattering loss of photonic crystal waveguides, caused by fabrication disorder, however, has so far proven to be the limiting factor for device applications. In this thesis, I present a detailed study of propagation loss in slow light photonic crystal waveguides. I examine the dependence of propagation loss on the group index, and on disorder, in more depth than previous work by other authors. I present a detailed study of the relative importance of different components of the propagation loss, as well as a calculation method for the average device properties. A new calculation method is introduced to study different device designs and to show that photonic crystal waveguide propagation loss can be reduced by device design alone. These “loss engineered” waveguides have been used to demonstrate the lowest loss photonic crystal based delay line (35 dB/ns) with further improvements being predicted (< 20 dB/ns). Novel fabrication techniques were investigated, with the aim of reducing fabrication disorder. Initial results showed the feasibility of a silicon anneal in a nitrogen atmosphere, however poor process control led to repeatability issues. The use of a slow-fast-slow light interface allowed for the fabrication of waveguides spanning multiple writefields of the electron-beam lithography tool, overcoming the problem of stitching errors. The slow-fast-slow light interfaces were combined with loss engineering waveguide designs, to achieve an order of magnitude reduction in the propagation loss compared to a W1 waveguide, with values as low as 130 dB/cm being achieved for a group index around 60.

"Optical vortices are singularities in phase fronts of laser beams. They are characterized by a dark core whose size may dramatically affect their behavior upon propagation. Previously, only large-core vortices have been extensively studied. The object of the research presented in this dissertation was to explore ways of generating small-core optical vortices (also called optical vortex filaments), and to examine their propagation using analytical, numerical and experimental methods. Computer-generated holography enabled us to create arbitrary distributions of optical vortex filaments for experimental exploration. We used hydrodynamic paradigms to develop an heuristic model which described the dependence of vortex motion on other vortices and the background beam, both qualitatively and quantitatively. We predicted that pair of optical vortex filaments will rotate with angular rates inversely proportional to their separation distance (just like vortices in a fluid). We also reported the first experimental observation of this novel fluid-like effect. It was found, however, that upon propagation in linear media, the fluid-like rotation was not sustained owing to the overlap of diffracting vortex cores. Further numerical studies and experiments showed that rotation angle may be enhanced in nonlinear self-defocusing media. The results presented in this thesis offer us a better understanding of dynamics of propagating vortices which may result in applications in optical switching, manipulation of micro-particles and optical limiting."

"Photonic crystals have recently been the subject of studies for use in optical signal processing. In particular, a Coupled Resonator Optical Waveguide (CROW) structure has been considered by M. F. Yanik and S. Fan in “Stopping Light All Optically” for use in a time-varying optical system for the storage of light in order to mitigate the effects of waveguide dispersion. In this thesis, the effects of the thermal field on the state stored in such a structure is studied. Through simulation, this thesis finds that when this structure is constructed of gallium arsenide cylinders in air, loss of the signal was found to be caused by free-carrier absorption, and the decay of the signal dominates over thermal spreading of the optical signal’s spectrum."

Cette thèse est consacrée à l’étude du dépôt uniforme et de l’alignement à haute densité en nanotubes de carbone monoparois (NTCMP) sur différents substrats, à l’analyse qualitative des propriétés optiques excitoniques et aux modes de vibration des échantillons à NTCMP, et à la fabrication de guides d’onde optiques à base de NTCMP, en vue de composants photoniques pour les télécoms, autour de 1550 nm. Deux types de NTCMP ont été étudiés durant cette thèse : des NTCMP « HiPCO » (« high pressure carbon monoxide ») issus de la décomposition du monoxyde de carbone à haute pression, et des NTCMP « LV » (« laser vaporization ») provenant de l’ablation laser d’une cible en graphite. Plusieurs méthodes de dépôt de ces NTCMP ont été développées, telles que la méthode de dépôt assistée-par-tube, la méthode de dépôt en sillon, la méthode par pulvérisation, la méthode par centrifugation à grande vitesse, la méthode optimisée par centrifugation à vitesse réduite (MOCVR) et la méthode à jet d’encre. La qualité, l’épaisseur et l’uniformité des films de NTCMP sont caractérisées par observations au microscope électronique à balayage (MEB). Il est montré ici que l’uniformité des films à base de NTCMP HiPCO dépend fortement de la concentration en surfactants de la dispersion à base de NTCMP déposée. Des films uniformes de NTCMP LV ont été obtenus par la MOCVR et leur épaisseur couvre une gamme de 600nm à 900nm (avec une erreur <10%), qui dépend de la nature du substrat. L’alignement par diélectrophorèse (DEP) de NTCMP HiPCO et LV a été développé et optimisé. Ainsi, une nouvelle méthode (DEP « assistée-parchauffage ») est proposée afin d’obtenir un alignement à très haute densité en NTCMP. Cette méthode d’alignement par DEP assistée-par-chauffage a fait l’objet de travaux de simulation pour comprendre l’effet de la température. Les propriétés optiques excitoniques et les modes de vibration des NTCMP en solution et en film sur substrat ont été caractérisés par spectroscopies d’absorption, de photoluminescence (PL), d’excitation de la PL et Raman. Les niveaux de défauts et d’isolement des NTCMP HiPCO, les distributions en diamètre et en chiralité, les cartographies de l’uniformité et de l’épaisseur des films à base de NTCMP, et l’effet du laser à forte puissance, ont été qualitativement étudiés par spectroscopie Raman. Le rendement quantique interne en PL de NTCMP HiPCO en film est estimée à une valeur de 5%. Le transfert d’exciton entre NTCMP HiPCO individualisés, le rôle du polymère environnant sur les propriétés excitoniques des NTCMP LV, et les excitons sombres sont discutés dans cette thèse. Le design et la fabrication de guides optiques hybrides à une dimension, contenant une ou trois couches de NTCMP HiPCO, et de guides optiques à deux dimensions à base de NTCMP LV ont été menés. Les étapes de fabrication des guides optiques sont ici examinées en détails. La propagation à 1550nm de ces guides d’onde à base de NTCMP est observée. La propagation de la lumière dans les guides d’onde à base de NTCMP LV est une caractéristique préliminaire pour toute cavité optique et confère un fort potentiel aux NTCMP LV pour les composants photoniques de la future génération. / This thesis concentrates on the uniform deposition and highdensity alignment of single-walled carbon nanotubes (SWCNTs) on various substrates, the qualitative analysis of optical and excitonic properties, as well as vibrational modes of SWCNTbased samples by absorption, photoluminescence (PL) and Raman spectroscopies, and the fabrication of SWCNT-based optical waveguides towards photonics devices in the 1.55μm telecom window. Two types of SWCNT were studied during this thesis: “HiPCO” SWCNT from high pressure carbon monoxide conversion process (HiPCO) and “LV” SWCNT from catalytic growth of SWCNT assisted by laser vaporization (LV) of graphite. Several methods for the deposition of these SWCNTs were investigated and performed, including tube-assisted deposition method, groove deposition method, spraying method, high-speed spin coating method, improved low-speed spin coating method (ILSSCM) and inkjet printing method. The quality, thickness and uniformity of SWCNT films are characterized by scanning electron microscopy (SEM). The uniformity of HiPCO SWCNT-based film is shown to depend strongly on the surfactants concentration in deposited SWCNTbased dispersion. Uniform LV SWCNTbased films using ILSSCM were obtained with thicknesses ranging from 600nm to 900nm (with thickness error <10%), depending on substrates nature. Alignment of HiPCO and LV- SWCNTs using a dielectrophoresis method, combining microtechnological processes and SEM observations, is investigated and optimized. Thus, a new method (“heating-enhanced DEP”) for ultra-high alignment density of HiPCO SWCNTs is proposed. The effect of temperature in this heating-enhanced DEP process is further explained by simulation works. Optical and excitonic properties, vibrational modes of SWCNT solutions and films are characterized by absorption, PL and PL excitation, Raman spectroscopies. The defects and the isolation levels of HiPCO SWCNT, the chirality- and diameterdistributions of SWCNT, the uniformity and the thickness mapping of SWCNT-based films, and the effect of high energy laser are qualitatively analyzed by Raman spectra. We estimated the PL quantum efficiency value of HiPCO SWCNT film of around 5%. The exciton energy transfer between individualized HiPCO SWCNTs, the role of polymer environment on excitonic properties of LV SWCNTs, and the dark excitons are discussed in this thesis. One-layer and three-layers of HiPCO SWCNT-based onedimensional slab optical waveguides of hybrid core structures, and LV SWCNT-based twodimensional optical waveguides are designed and fabricated. The fabrication process steps of the optical waveguides are investigated in details. 1.55μm propagation in these SWCNT-based waveguides is highlighted. Single- or multi-mode emissions around 1.5μm and 1.6μm are observed in LV SWCNTbased optical waveguides. The light propagation in the LV SWCNT-based optical waveguide is the preliminary characteristic of an optical cavity, which confers great potential for future generation LV SWCNT-based photonics devices.

This thesis aims to determine the distribution of the relative permittivity for random mixtures of material using electromagnetic simulations. The algorithm used in the simulations is the FDTD method which solves Maxwell's equations numerically in the time-domain. The material is modeled as randomly shaped particles with radius 12 ± 10 micrometre in x- and y-direction and radius 3 ± 1 micrometre in zdirection. The scattering parameters from the transmitted and reflected electric field when a plane wave interacts with the material are measured. The relative permittivity is determined from the scattering parameters using the iterative Baker-Jarvis method. The simulations shows that both the distribution and the value of the relative permittivity is low when the particles have non conducting layers to force interruptions to prevent percolation, a conducting path between the particles. The most important result is of the kind where the simulations do not have any boundaries to prevent percolation. These simulations reflects how the relative permittivity distributes in real measurements. It is established that the value of the relative permittivity has a large distribution and also that percolation occurs because of the periodic structures.

Abstract not available

Optical traveling-wave resonator architectures have shown promise for the realization of many compact photonic functionalities in different research disciplines. Realizing these resonator structures in high-index contrast silicon enables dense and large scale integration of large arrays of functionalized resonators in a CMOS-compatible technology platform. Based on these motivations, the main focus of this Ph.D. research has been on the device physics, modeling, implementations, and applications of planar ultra-high Q silicon traveling-wave microresonators in a silicon-on-insulator (SOI) platform. Microdisk, microring, and racetrack resonators are the three general traveling-wave resonator architectures of interests that I have investigated in this thesis, with greater emphasis on microdisks. I have developed efficient tools for the accurate modeling of these resonators. The coupling to these resonators has been through a nano-waveguide side coupled to them. For this purpose, I have developed a systematic method for engineering a waveguide-resonator structure for optimum coupling. I have addressed the development of nanofabrication techniques for these resonators with efficient interaction with a nano-waveguide and fully compatible with active electronic integration. The outcome of the theoretical design, fabrication, and characterization of these resonators is a world-record ultra-high Q (3×10[superscript 6]) with optimum waveguide-resonator interaction. I have investigated the scaling of these resonators toward the ultimate miniaturization and its impact on different physical properties of the resonators. As a result of these investigations, I have demonstrated miniaturized Si microdisk resonators with radii of ~ 1.5 micron and Q > 10⁵ with single-mode operation over the entire large free-spectral range. This is the highest Q (~ one order more than that in previously reported data) that has been obtained for a Si microdisk resonator with this size on a SiO₂ substrate. I have employed these resonators for more advanced functionalities such as large-scale integration of resonators for spectroscopic and filtering applications, as well as the design of flat-band coupled-resonator filter structures. By proposing a systematic method of design, I have shown ultra-compact coupled-resonator filters with bandwidths ranging from 0.4 to 1 nm. I have theoretically and experimentally investigated the performance of ultra-high Q resonators at high powers and in the presence of nonlinearities. At high powers, the presence of two-photon absorption, free-carrier generation, and thermo-optic properties of silicon results in a rich dynamic in the response of the resonator. In both theory and experiment, I have predicted and demonstrated self-sustained GHz oscillation on the amplitude of an ultra-high Q resonator pumped with a continuous-wave laser.

Optical biosensors are increasingly being considered for lab-on-a-chip applications due to their benefits such as small size, biocompatibility, passive behaviour and lack of the need for fluorescent labels. The light guiding mechanisms used by many of them result in poor overlap of the optical field with the target molecules, reducing the maximum sensitivity achievable. This thesis presents a new platform for optical biosensors, namely slotted photonic crystals, which engender higher sensitivities due to their ability to confine, spatially and temporally, the peak of optical mode within the analyte itself. Loss measurements showed values comparable to standard photonic crystals, confirming their ability to be used in real devices. A novel resonant coupler was designed, simulated, and experimentally tested, and was found to perform better than other solutions within the literature. Combining with cavities, microfluidics and biological functionalization allowed proof-of-principle demonstrations of protein binding to be carried out. High sensitivities were observed in smaller structures than most competing devices in the literature. Initial tests with cellular material for real applications was also performed, and shown to be of promise. In addition, groundwork to make an integrated device that includes the spectrometer function was also carried out showing that slotted photonic crystals themselves can be used for on-chip wavelength specific filtering and spectroscopy, whilst gas-free microvalves for automation were also developed. This body of work presents slotted photonic crystals as a realistic platform for complete on-chip biosensing; addressing key design, performance and application issues, whilst also opening up exciting new ideas for future study.

Microelectromechanical resonators have found widespread applications in timing, sensing and spectral processing. One of the important performance metrics of MEMS resonators is the temperature sensitivity of their frequency. The main objective of this dissertation is the compensation and control of the temperature sensitivity of silicon resonators through engineering of device geometry and structural composition. This has been accomplished through formation of composite platforms or novel geometries based on dispersion characteristics of guided acoustic waves in single crystalline silicon (SCS) microstructures. Furthermore, another objective of this dissertation is to develop efficient longitudinal piezoelectric transduction for in-plane resonance modes of SCS resonators that have lithographically-defined frequencies, to reduce their motional resistance (Rm). A uniformly distributed matrix of silicon dioxide pillars is embedded inside the silicon substrate to form a homogenous composite silicon-oxide platform (SilOx) with nearly perfect temperature-compensated stiffness moduli. Temperature-stable micro-resonators implemented in SilOx platform operating in any desired in- and out-of-plane resonance modes show full compensation of linear temperature coefficient of frequency (TCF). Overall frequency drifts as small as 80 ppm has been achieved over the industrial temperature range (-40°C to 80°C) showing a 40x improvement compared to uncompensated native silicon resonators. A 27 MHz temperature-compensated MEMS oscillator implemented using SilOx resonator demonstrated sub-ppm instability over the industrial temperature range. Besides this, a new formulation of different resonance modes of SCS resonators based on their constituent acoustic waves is presented in this dissertation. This enables engineering of the acoustic resonator to provide several resonance modes with mechanical energy trapped in central part of the resonator, thus obviating narrow tethers traditionally used for anchoring the cavity to the substrate. This facilitates simultaneous piezoelectric-transduction of multiple modes with different TCFs through independent electrical ports, which can realize highly accurate self-temperature sensing of the device using a beat frequency (fb) generated from linear combination of different modes. Piezoelectrically-transduced multi-port silicon resonators implemented using this technique provide highly temperature-sensitive fb with a large TCF of ~8500 ppm/°C showing 100x improvement compared to other Quartz/MEMS counterparts, suggesting these devices as highly sensitive temperature sensors for environmental sensing and temperature-compensated/oven-controlled crystal oscillator (TCXO/OCXO) applications. Another part of this dissertation introduces a novel longitudinal piezoelectric transduction technique developed for implementation of low Rm silicon resonators operating in lithographically defined in-plane modes. Aluminum nitride films deposited on the sidewalls of thick silicon microstructures provides efficient electromechanical transduction required to achieve low Rm. 100 MHz SCS bulk acoustic resonators implemented using this transduction technique demonstrates Rm of 33Ω showing a 100x improvement compared to electrostatically transduced counterparts. Low-loss narrow-band filters with tunable bandwidth and frequency have been implemented by electrical coupling of these devices, showing their potential for realization of truly reconfigurable and programmable filter arrays required for software-defined radios.