<p>The development of silicon photonics, driven by the increasing demand for bandwidth from data centre applications, is receiving growing attention. As a result of the indirect bandgap of Si material, it is more practical to heterogeneously incorporate the laser source than fabricate directly on Si. Of all the approaches, an external cavity laser (ECL) approach which consists of III-V gain material and Si photonic integrated circuit (SiPIC), is a flexible and cost effective solution. This thesis captures theoretical and experimental work on the design of SiPIC ECLs. In addition, a four wavelength laser source using an SiPIC ECL scheme is proposed and studied.</p> <p>The theoretical tool is first introduced on the traveling wave model (TWM) and it is numerically solved with FDTD in Matlab. A digital filter approach is used to describe the feedback from an SiPIC external cavity, where the phase delay of the digital filter is investigated and utilized to set the cavity length.</p> <p>The III-V gain chip and SiPIC are then examined separately for their characterization, along with the coupling and feedback requirements in an ECL design.</p> <p>Lastly, experiments are conducted to demonstrate the feasibility of four wavelength ECLs and SiPIC ECLs.</p> / Master of Applied Science (MASc)

<p>A glass-clad, slow-light photonic-crystal waveguide is proposed as a solution to sub-bandgap light detection in silicon photonic circuits. Such detection in silicon is perceived as a challenge owing to silicon's indirect band gap and transparency to 1550nm wavelengths, yet is essential for achieving low-cost, high-yield integration with today's microelectronics industry. Photonic crystals can be engineered in such a way as to enhance light-matter interaction over a specific bandwidth via the reduction of the group velocity of the propagating wave (i.e. the slowing of light). The interaction enhanced for light detection in the present work is electron-hole pair generation at defect sites. The intrinsic electric field of a p-i-n junction enables light detection by separating the electron-hole pairs as a form of measurable current. The photonic-crystal waveguides are designed to have bandwidths in the proximity of a wavelength of 1550nm. Refractive indices of over 80 near the photonic-crystal waveguide's Brillouin zone boundary are measured using Fourier transform spectral interferometry and are found to correspond to numerical simulations. Defect-induced propagation loss was seen to scale with group index, from 400dB/cm at a group index of 8 to 1200dB/cm at a group index of 88. Scaling was sublinear, which is believed to be due to the spreading of modal volume at large group index values. Photodetectors were measured to have responsivities as high as 34mA/W near the photonic-crystal waveguide's Brillouin zone boundary for a reverse bias of 20V and a remarkably short detector length of 80um. The fabrication of each device is fully CMOS-compatible for the sake of cost-effective integration with silicon microelectronics.</p> / Master of Applied Science (MASc)

This thesis presents studies on light management in optoelectronic devices. The broad aim of the thesis is to improve the efficiency of optoelectronic devices by optimised light usage. The studies emphasise the design and fabrication of nanostructures for optimised photon control. A key hypothesis guiding the research is that better designs can be achieved by ab initio identification of their desired Fourier properties. The specific devices studied are organic Distributed Feedback (DFB) lasers, organic solar cells and silicon solar cells. The impact of a substructured grating design capable of affording unprecedented control over the balance between feedback and output coupling in DFB organic lasers was investigated both experimentally and theoretically. It was found experimentally that such gratings can halve the threshold of organic DFB lasers. The reduction in the laser threshold is associated with reduced output coupling and higher feedback provided by the substructured gratings. The possibility of improving the efficiency of organic solar cells by trapping light into the absorbing medium was investigated. It was found that the low refractive index of the organic gain medium compromises the light trapping performance. It was found that strong absorption enhancement, however, can be achieved using plasmonic nanostructures. Finally, a novel design concept for light trapping in silicon solar cells is proposed. This design takes advantage of grating structures with long periods that are capable of providing broad-band light trapping, which is an important requirement for silicon solar cells. The design is based on a supercell that enables better light injection through manipulation of the grating's Fourier properties. The design idea leads to the formation of quasi-random nanostructures that afford great versatility for photon control. Strong light trapping was achieved and characterised both theoretically and experimentally.

<p>Developing an automatic control system from original stage is quite time consuming, a lot of works must be done before the final result, in order to save designing time and money, a systematic way to carry through development is necessary. This project will give an experience about using a systemic method to develop an automatic control system for metal dosing and transfer from original stage. The project will be divided into several different phases, and each phase focuses on some different important tasks. In this project a research of PLCs and stepper motors and then give suitable suggestions of selection of them have been done. One of important roles for this project is to develop a prototype machine and use computer to model and simulate prototype and whole machine, therefore, in this project, using SDL assistant with Matlab to model and simulate both prototype and whole machine have been processed. Because of some unexpected condition, this project doesn’t include real PLC programming.</p>

This work presents recent progress in the area of organic photorefractive polymer composites. These materials have been previously shown to be a suitable medium for dynamic holographic displays, with multiple colors and single frame writing times on the order of seconds. However, these materials still require large electric fields and high intensity lasers to function effectively. Recent advancements in improving these areas are discussed, including a review of the history and state-of-the-art in photorefractive polymer composites.The addition of electron traps via low loading of the electron-transporting molecule Alq3 is shown to dramatically improve the diffraction efficiency and reduce the required field. The grating formation also proceeds faster by more than one order of magnitude, leading to an increase in sensitivity by a factor of 3. The dynamics of these materials also show evidence of competing gratings indicative of bipolar charge transport and trapping.The addition of an amorphous polycarbonate (APC) buffer layer is reported to have a similar effect on the steady-state diffraction efficiency, and the further doping with a fullerene derivative (PCBM) allows a 3x increase in the efficiency in the reflection geometry, which is normally poor due to the small grating spacing. These composites reveal the fundamental limits of the reflection geometry, based on the physics of high frequency gratings. A reversal in the direction and increase in the magnitude of the two-beam coupling energy transfer is also observed.The use of interdigitated coplanar electrodes, instead of the standard uniform electrodes in a parallel-plate geometry, is shown to result in large diffraction efficiency with symmetric writing beams due to the increased projection field. The efficiency is similar to that achieved in the standard samples with large slant angles and much better than those geometries typically used in applications, with the benefit that the writing beams do not have to be slanted with respect to the sample normal. Different electrode widths are examined and the trade-offs discussed. This device makes beam injection simpler and allows one to bring the benefits of highly slanted geometries, common to small area setups, to the large-area applications.

Plasmonics is the branch of photonics that is concerned with the interactions which take place between metallic structures and incident electromagnetic radiation. It is a field which has seen a recent resurgence of interest, predominantly due to the emerging fields of metamaterials and sub-wavelength optics. The original work contained within this thesis is concerned with the plasmonic resonances of metallic nanoparticles which can be excited with visible light. These structures have been placed in a variety of configurations, and the optical response of each of these configurations has been probed both experimentally, and with numerical simulations. The first chapter contains some background and describes some recent advances in the literature, set against the broad background of more general concepts which are important in plasmonics. The best starting point in describing the response of plasmonic systems is to consider individual metallic particles and this is the subject of the second chapter. Three separate modelling techniques are described and compared, and dark-field spectroscopy is used to produce experimental scattering spectra of single particles which support dipolar and higher order modes. Mie theory is used as a starting point in understanding these modes, and finite element method (FEM) modelling is used to make numerical comparisons with dark-field data. When two plasmonic particles are placed close to each other, interactions take place between them and their response is modified, sometimes considerably. This effect can be even stronger if particles are placed in large arrays. Interactions between the dipolar modes of gold particles form the basis of the third chapter. The discussion begins with pairs of particles, and the coupled dipole approximation (CDA) is introduced to describe the response. Ordered square arrays are considered and different modelling techniques are compared to experimental data. Also, random arrays have been investigated with a view to inferring the extinction spectrum of a single particle from a carefully chosen array of particles in which the inter-particle interactions are suppressed. The fourth chapter continues the theme of particles interacting in arrays, but the particles considered support quadrupolar modes (and they are silver instead of gold). The optical response is strongly modified, and an explanation is provided which overturns the accepted explanation. The final chapter of new results is somewhat different to the others in that a very different structure is considered and different parameters are extracted. Instead of far-field quantities, here, near-fields of composite structures are of interest; they can generate greatly enhanced fields in the vicinity of the structure. These enhanced fields, in turn, enhance the fluorescence and Raman emission of nearby dye molecules. A novel field integration technique is proposed which aims to mimic the experiments which were carried out using fluorescence confocal microscopy.

Dans cette thèse, trois approches différentes ont été étudiées pour des dispositifs photoniques accordables basés sur la technologie MEMS. Premièrement, la structure à double barrière optique a été étudiée numériquement et expérimentalement, sous forme de commutateur thermo-optique, polariseur commutable et de jonctions tunnel optiques intégrées en tant que système WDM reconfigurable. Le dispositif est fabriqué sur substrat silicium SOI utilisant le procédé de gravure profonde. Les dispositifs optiques tunnel sont contrôlés électro-thermiquement, le temps de commutation mesuré correspondant est de plusieurs microsecondes. Deuxièmement, des structures de propagation de lumière lente à base de méta matériaux constitués de cellules unitaires sous forme d’anneaux fendus couplés, sont numériquement analysés. Les résultats des simulations montrent que la conception de SRRs (Split Ring Resonator) couplés améliore l'accordabilité de la permittivité et de la perméabilité effectives de 70 et 200 fois, respectivement. On peut trouver des applications potentielles dans le stockage de données, des circuits photoniques, les communications optiques et les biocapteurs. Enfin, un méta matériau accordable magnétique est démontré en utilisant la technologie MEMS. Il démontre une approche unique pour contrôler les propriétés optiques des méta matériaux par l'évolution des dimensions géométriques et les formes des cellules unitaires / In this PhD project, three different approaches have been studied for tunable photonic devices based on MEMS technology. First, the optical double barrier structure has been numerically studied and experimentally demonstrated as the thermo-optical switch, switchable polarizer and optical tunneling junctions integrated as reconfigurable WDM system. Second, the slow light structure using metamaterial with coupled split ring unit cells is numerically analyzed. Finally, a tunable magnetic metamaterial is demonstrated using MEMS technology. The first major work is to use the optical tunneling effects to design MEMS based photonic devices. Three different tunable photonic devices has been demonstrated using thermo-optical tuning. a thermo-optic switch is realized using MEMS technology. The device is fabricated on silicon-on-isolator wafer using deep etching process. The transmission of the optical switch is controlled by the optical length of the central rib which is thermally controlled by the external pumping current. In experiment, it measures a switching speed of 1 us and an extinction ratio of 30 dB. A switchable polarizer is demonstrated using the double optical barrier structure which transmit the light with one polarization state and filter out the others. In experiment it measures a PER of lager than 23 dB when the pumping current is above 60mA. The switching time is shorter than 125 us which is limited by the polarization analyzer used in the experiment. A MEMS reconfigurable add-drop multiplexer is realized by applied the optical tunneling structure to the ribbed waveguide. The tunable add-drop multiplexer is based on Y-shape optical double barriers tunneling junction which are realized by MEMS technology

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.

In this paper, we propose a rate-compatible forward error-correcting (FEC) scheme based on low-density-parity check (LDPC) codes together with its software reconfigurable unified field-programmable gate array (FPGA) architecture. By FPGA emulation, we demonstrate that the proposed class of rate-compatible LDPC codes based on puncturing and generalized LDPC coding with an overhead from 25% to 46% provides a coding gain ranging from 12.67 to 13.8 dB at a post-FEC bit-error rate (BER) of 10(-15). As a result, the proposed rate-compatible codes represent one of the strong FEC candidates of soft-decision FEC for both short-haul and long-haul optical transmission systems.

Wireless Sensor Networks appear as a technology, which provides the basisfor a broad field of applications, drawing interest in various areas. On theone hand, they appear to allow the next step in computer networks, buildinglarge collections of simple objects, exchanging information with respect totheir environment or their own state. On the other hand, their ability tosense and communicate without a fixed physical infrastructure makes theman attractive technology to be used for measurement systems.Although the interest inWireless Sensor Network research is increasing,and new concepts and applications are being demonstrated, several fundamentalissues remain unsolved. While many of these issues do not requireto be solved for proof-of-concept designs, they are important issues to beaddressed when referring to the long-term operation of these systems. Oneof these issues is the system’s lifetime, which relates to the lifetime of thenodes, upon which the system is composed.This thesis focuses on node lifetime extension based on energy management.While some constraints and results might hold true from a moregeneral perspective, the main application target involves environmental measurementsystems based onWireless Sensor Networks. Lifetime extensionpossibilities, which are the result of application characteristics, by (i) reducingenergy consumption and (ii) utilizing energy harvesting are to be presented.For energy consumption, we show howprecise task scheduling due to nodesynchronization, combined with methods such as duty cycling and powerdomains, can optimize the overall energy use. With reference to the energysupply, the focus lies on solar-based solutions with special attentionplaced on their feasibility at locations with limited solar radiation. Furtherdimensioning of these systems is addressed.It will be shown, that for the presented application scenarios, near-perpetualnode lifetime can be obtained. This is achieved by focusing on efficient resourceusage and by means of a carefully designed energy supply.