Polymer Microring Coupled-Resonator Optical Waveguides

We present measurements of the transmission and dispersion properties of coupled-resonator optical waveguides (CROWs) consisting of weakly coupled polymer microring resonators. The fabrication and the measurement methods of the CROWs are discussed as well. The experimental results agree well with the theoretical loss, waveguide dispersion, group delay, group velocity, and group-velocity dispersion (GVD). The intrinsic quality factors of the microrings were about 1.5 times 10^4 to 1.8 times 10^4, and group delays greater than 100 ps were measured with a GVD between -70 and 100 ps/(nm x resonator). With clear and simple spectral responses and without a need for the tuning of the resonators, the polymer microring CROWs demonstrate the practicability of using a large number of microresonators to control the propagation of optical waves

Optical Power Splitting Techniques Using Photonic Crystal Line Defect Waveguides

“Photonic Crystals (PCs)” are dielectric or metallo-dielectric structures with periodic spatial alternations of refractive index on the scale of the wavelength of light. Many optical devices, based on PCs, have been proposed. There are multiple ways by which equal amount of power of incoming signals can be divided into two, three and four output channels; for example using multiple coupled photonic crystal waveguides, directional coupling and cascaded multimode PC waveguides. Ideally, the splitter should divide the input power equally into the output channels without significant reflection or radiation losses and should be compact in size. In this thesis we have proposed different techniques of optical power splitting using (a) Y-junction, (b) PC line defect waveguides integrated with multimode interference (MMI) block, and (c) multiple line defect PC waveguides. The optical modeling of these proposed structures were investigated by finite difference time domain (FDTD) simulation. The goal was to achieve equal power at each output channel with broad spectrum around the target wavelength with low loss. Using a new design of a 2-D slab based Y-junction scheme, we have achieved 84.4% power output from a 1×2 power splitter and 58.3% form a 1×4 power splitter configuration respectively. Then to improve the power transmission of 1×4 power splitter configuration, we have examined two more structures, one is 2-D slab PC line defect waveguides integrated with MMI block and another which is based on multiple line defect waveguides. The first structure transmits 75.7% power at the output with 46nm broad spectrum for a 2-D slab configuration whereas the second structure transmits 94.9% power at output with 32nm broad spectrum for 2-D configuration. The advantages of PC line defect waveguides integrated with MMI block for 1×4 power splitter configuration over the Y-junction are ease of fabrication, broad output spectrum and high transmission power. The only disadvantage is the size of the device. The device is somewhat larger than other devices but still compact enough to compete with commercial on chip optical power splitters. In future multiple line defect PC waveguides will probably be able to achieve both compact size and high power

Reconfigurable photonic crystal

Tunability and programmability are highly demanded for silicon photonic integrated circuits (PICs) to expand their applications in the next-generation photonics. The main objective of this thesis is to develop several reconfigurable and programmable photonic crystal (PC) devices. In Chapter 2, we developed a relatively general nanofabrication process for integrating PC devices with movable mechanical components on silicon-on-insulator (SOI) wafers. We also investigated grating coupling technology, to facilitate coupling lights into and out of PC devices. In Chapter 3, we developed an all-optical programmable PC device that integrates digital micromirror device (DMD), photo-responsive LC, and PC technologies. We demonstrated the functionality and programmability of the device, by forming a point-defect cavity, a straight waveguide, and a waveguide bend on the single device. In Chapter 4, we developed two types of reconfigurable PC devices by leveraging the strengths of optical nanobeam and nano-electro-mechanical systems (NEMS) technologies. The first device consists of an array of movable nanobeams. Each nanobeam is an electrostatically tunable photonic element in a PC waveguide. We demonstrated the capability of the device to engineer different photonic bandgaps, by tuning one unit in group of two neighboring nanobeam units, tuning one or two in group of three units, and forming two reconfigurable PCs, on the single device. To achieve a higher-level integration, we also theoretically studied another reconfigurable PC integrating an array of mechanical tunable nanobeams with an array of fixed pillars into the top silicon layer of a SOI wafer. In Chapter 5, we developed two tunable photonic crystal-cantilever cavity (PC3) resonators. The first device has an NEMS cantilever embedded into a L6 cavity in a PC slab. The second device has a similar cantilever to insert into a nanobeam-base waveguide. We studied bending characteristics of the cantilever and optical characteristics of these two devices at different applied voltages. In Chapter 6, we conducted theoretical investigation on a nano-opto-mechanical reconfigurable PIC device consisting of an array of silicon plugs and a 2D PC slab. We theoretically demonstrated that a point-defect cavity, a line-defect waveguide, and a waveguide bend can be configured in the PC slab, by inserting different plugs into an air hole, a straight line of holes, and an L-shape line of holes

Small Footprint Multilayered Millimeter-Wave Antennas and Feeding Networks for Multi-Dimensional Scanning and High-Density Integrated Systems

This paper overviews the state-of-the-art of substrate integrated waveguide (SIW) techniques in the design and realization of innovative low-cost, low-profile and low-loss (L3) millimeter-wave antenna elements, feeding networks and arrays for various wireless applications. Novel classes of multilayered antenna structures and systems are proposed and studied to exploit the vertical dimension of planar structures to overcome certain limita-tions in standard two-dimensional (2-D) topologies. The developed structures are based on two techniques, namely multi-layer stacked structures and E-plane corners. Differ-ent E-plane structures realised with SIW waveguide are presented, thereby demonstrating the potential of the proposed techniques as in multi-polarization antenna feeding. An array of 128 elements shows low SLL and height gain with just 200g of the total weight. Two versions of 2-D scanning multi-beam are presented, which effectively combine frequency scanning with beam forming networks. Adding the benefits of wide band performance to the multilayer structure, two bi-layer structures are investigated. Different stacked antennas and arrays are demonstrated to optimise the targeted antenna performances in the smallest footprint possible. These structures meet the requirement for developing inexpensive compact millimeter-wave antennas and antenna systems. Different structures and architectures are theoretically and experimentally studied and discussed for specific space- and ground-based appli-cations. Practical issues such as high-density integration and high-volume manufacturability are also addressed

Photonic crystal assisted L-shaped waveguide bend

Thesis (Master)--Izmir Institute of Technology, Physics, Izmir, 2009Includes bibliographical references (leaves: 79-82)Text in English; Abstract: Turkish and Englishxv, 88 leavesPhotonic crystals are periodic dielectric structures. This periodicity allow us to manipulate light in ways that have not been possible before. As a result, photonic crystal waveguide components play a significant role in integrated optical circuit design because waveguides allow only certain electromagnetic wave modes to propagate inside the structure. There are many corresponding applications that rely on total internal reflection. However, with total internal reflection, there is a problem in guiding light through sharp corners, large optical losses occur around tight curves with a small bending radius. A simple explanation for these losses is that the angle of the incident light too low for total internal reflection when wave turns through a sharp corner. Thus, an unacceptable fraction of the electromagnetic energy is radiated out of the waveguide. To overcome this difficulty, in this thesis, we demonstrate a novel method for guiding light through sharp corners, using a 1 photonic crystal slab waveguide for the straight sections, and assisted by 2D Line Defect Waveguide at the corners.Plane Wave Method and Supercell Method are used to Figure out parameters and obtain the guided mode for our proposed structure. Then, numerical simulations (FDTD) reveal nearly perfect transmission at certain frequency ranges. Also, in this thesis different corner elements are used to show highly efficient transmission of light through sharp corners. Thus, light can be guided through a 90. corner, almost without loss, by using different corner elements. "Crystals are like people, it is the defect in them which tend do make them interesting". Colin Humphreys

Novel Photostructurable Polymer for On-Board Optical Interconnects Enabled by Femtosecond Direct Laser Writing

Die integrierte Optik hat sich als vielversprechende Lösung für elektronische Verbindungen erwiesen, die eine hohe Bandbreitendichte und einen geringen Stromverbrauch ermöglicht. Seit kurzem ist es möglich photochemische und physikalische Reaktionen auf ein Mikrovolumen zu begrenzen. Dies hat der optischen Verbindungstechnik unter Verwendung von Glas oder Polymer eine zusätzliche Dimension verliehen. Dreidimensionale Wellenleiter können das optische Signal zwischen Blöcken aller Dimensionen verbinden, kombinieren oder aufteilen. Die Erhöhung des Brechungsindex ist jedoch immer noch eine Herausforderung für die Herstellung stabiler Freiform- und monomodaler Wellenleiter mit dreidimensionaler Ausdehnung, welche sich innerhalb der Platine befinden. Diese Dissertation stellt ein neues Konzept vor, um dieser Herausforderung zu begegnen, indem direktes Femtosekunden-Laserschreiben in Polymer und externe Diffusion eines gasförmigen Monomers verwendet wird. Direktes Laserschreiben mit Zwei-Photonen-Absorption wurde verwendet, um die Vernetzung entlang eines vorher definierten Pfades zur Bildung des Wellenleiterkerns zu initiieren. Es wurde ein ausreichender Brechungsindexkontrast erzeugt, um gaußförmige Strahlen mit einem Modus zu führen. Feature-Größen konnten durch Variieren der Scangeschwindigkeit und der Laserintensität linear angepasst werden. Dieses Herstellungsverfahren erfordert nur eine Schicht eines einzelnen Materials ohne Masken-, Kontakt- oder Nassbearbeitung. Durch Verwendung dieser neuartigen Methode wurden dreidimensionale optische Wellenleiter-Arrays, Fan-in/Fan-out- und Splitter-Strukturen hergestellt. Dreidimensionale freiforme Wellenleiter haben ein hohes Potential zur Verbesserung der Packungsdichte und Flexibilität optischer Verbindungen auf Platinenebene