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Physics Vivien SERIES IN OPTICS AND OPTOELECTRONICS SERIES IN OPTICS AND OPTOELECTRONICS Pavesi SERIES EDITORS: E ROY PIKE AND ROBERT G W BROWN H Handbook of Handbook of a Silicon Photonics n Silicon Photonics d b The development of integrated silicon photonic circuits has recently been o driven by the Internet and the push for high bandwidth as well as the need to reduce power dissipation induced by high data-rate signal transmission. o To reach these goals, efficient passive and active silicon photonic devices, k including waveguide, modulators, photodetectors, multiplexers, light sources, and various subsystems, have been developed that take advantage of state- o of-the-art silicon technology. f Suitable for both specialists and newcomers, Handbook of Silicon Photonics presents a coherent and comprehensive overview of this field from the S fundamentals to integrated systems and applications. It covers a broad i spectrum of materials and applications, emphasizing passive and active l i photonic devices, fabrication, integration, and the convergence with CMOS c technology. The book’s self-contained chapters are written by international experts from academia and various photonics-related industries. o The handbook starts with the basics of silicon as an optical material. It then n describes the building blocks needed to drive integrated silicon photonic circuits and explains how these building blocks are incorporated in complex P photonic/electronic circuits. The book also presents applications of silicon photonics in numerous fields, including biophotonics and photovoltaics. h o With many illustrations, including some in color, this handbook provides an up- to-date reference to the broad and rapidly changing area of silicon photonics. t It shows how basic science and innovative technological applications are o pushing the field forward. n i c s Edited by K11631 Laurent Vivien • Lorenzo Pavesi ISBN 978-1-4398-3610-1 90000 9 781439 836101 K11631_COVER_final.indd 1 3/25/13 11:02 AM Handbook of Silicon Photonics SerieS in OpticS and OptOelectrOnicS Series Editors: E Roy Pike, Kings College, London, UK Robert G W Brown, University of California, Irvine, USA Recent titles in the series Handbook of Silicon Photonics Laurent Vivien and Lorenzo Pavesi (Eds.) Microlenses: Properties, Fabrication and Liquid Lenses Hongrui Jiang and Xuefeng Zeng Laser-Based Measurements for Time and Frequency Domain Applications: A Handbook Pasquale Maddaloni, Marco Bellini, and Paolo De Natale Handbook of 3D Machine Vision: Optical Metrology and Imaging Song Zhang (Ed.) Handbook of Optical Dimensional Metrology Kevin Harding (Ed.) Biomimetics in Photonics Olaf Karthaus (Ed.) Optical Properties of Photonic Structures: Interplay of Order and Disorder Mikhail F Limonov and Richard De La Rue (Eds.) Nitride Phosphors and Solid-State Lighting Rong-Jun Xie, Yuan Qiang Li, Naoto Hirosaki, and Hajime Yamamoto Molded Optics: Design and Manufacture Michael Schaub, Jim Schwiegerling, Eric Fest, R Hamilton Shepard, and Alan Symmons An Introduction to Quantum Optics: Photon and Biphoton Physics Yanhua Shih Principles of Adaptive Optics, Third Edition Robert Tyson Optical Tweezers: Methods and Applications Miles J Padgett, Justin Molloy, and David McGloin (Eds.) Thin-Film Optical Filters, Fourth Edition H Angus Macleod Laser Induced Damage of Optical Materials R M Wood Principles of Nanophotonics Motoichi Ohtsu, Kiyoshi Kobayashi, Tadashi Kawazoe, Tadashi Yatsui, and Makoto Naruse Handbook of Silicon Photonics Edited by Laurent Vivien Lorenzo Pavesi Cover Image: Various silicon photonics devices realized within the HELIOS consortium of the European Commission and fabricated by CEA-Leti. LED plots are courtesy of Eveline Rigo. Taylor & Francis Taylor & Francis Group 6000 Broken Sound Parkway NW, Suite 300 Boca Raton, FL 33487-2742 © 2013 by Taylor & Francis Group, LLC Taylor & Francis is an Informa business No claim to original U.S. Government works Version Date: 20130214 International Standard Book Number-13: 978-1-4398-3611-8 (eBook - PDF) This book contains information obtained from authentic and highly regarded sources. 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Visit the Taylor & Francis Web site at http://www.taylorandfrancis.com and the CRC Press Web site at http://www.crcpress.com Contents Preface ............................................................................................................................................vii Contributors ....................................................................................................................................xi 1. Group IV Materials ................................................................................................................1 Erich Kasper, Michael Oehme, Matthias Bauer, Martin Kittler, Manfred Reiche, Osamu Nakatsuka, and Shigeaki Zaima 2. Guided Light in Silicon-Based Materials ........................................................................55 Koji Yamada, Tai Tsuchizawa, Hiroshi Fukuda, Christian Koos, Joerg Pfeifle, Jens H. Schmid, Pavel Cheben, Przemek J. Bock, and Andrew P. Knights 3. Off-Chip Coupling ...............................................................................................................97 Wim Bogaerts and Diedrik Vermeulen 4. Multichannel Silicon Photonic Devices.........................................................................139 Ting Lei, Shaoqi Feng, Aimé Sayarath, Jun-Feng Song, Xianshu Luo, Guo-Qiang Lo, and Andrew W. Poon 5. Nonlinear Optics in Silicon ..............................................................................................197 Ozdal Boyraz, Xinzhu Sang, Massimo Cazzanelli, and Yuewang Huang 6. Long-Wavelength Photonic Circuits ...............................................................................249 Goran Z. Mashanovich, Milan M. Milošević, Sanja Zlatanovic, Faezeh Gholami, Nikola Alic, Stojan Radic, Zoran Ikonic, Robert W. Kelsall, and Gunther Roelkens 7. Photonic Crystals ................................................................................................................287 Masaya Notomi, Kengo Nozaki, Shinji Matsuo, and Toshihiko Baba 8. Silicon-Based Light Sources .............................................................................................333 Aleksei Anopchenko, Alexei Prokofiev, Irina N. Yassievich, Stefano Ossicini, Leonid Tsybeskov, David J. Lockwood, Saba Saeed, Tom Gregorkiewicz, Maciek Wojdak, Jifeng Liu, and Al Meldrum 9. Optical Modulation ............................................................................................................439 Delphine Marris-Morini, Richard A. Soref, David J. Thomson, Graham T. Reed, Rebecca K. Schaevitz, and David A. B. Miller 10. Photodetectors .....................................................................................................................479 Jurgen Michel, Steven J. Koester, Jifeng Liu, Xiaoxin Wang, Michael W. Geis, Steven J. Spector, Matthew E. Grein, Jung U. Yoon, Theodore M. Lyszczarz, and Ning- Ning Feng 11. Hybrid and Heterogeneous Photonic Integration .......................................................553 Martijn J. R. Heck and John E. Bowers © 2008 Taylor & Francis Group, LLC v vi Contents 12. Fabrication of Silicon Photonics Devices ......................................................................611 Francisco López Royo 13. Convergence between Photonics and CMOS ...............................................................679 Thierry Pinguet and Jean-Marc Fedeli 14. Silicon Photonics for Biology ...........................................................................................707 Dan-Xia Xu, Siegfried Janz, Adam Densmore, André Delâge, Pavel Cheben, Jens H. Schmid, Ryan C. Bailey, Adam T. Heiniger, Qiang Lin, Philippe M. Fauchet, Qi Wang, and Yimin Chao 15. Silicon-Based Photovoltaics .............................................................................................749 Mario Tucci, Massimo Izzi, Radovan Kopecek, Michelle McCann, Alessia Le Donne, Simona Binetti, Shujuan Huang, and Gavin Conibeer © 2008 Taylor & Francis Group, LLC Preface In 1965, Gordon Moore announced his famous law that the number of transistors per chip will double every 19 months.1 Since then, Moore’s law has driven the development of microelectronics. Microelectronic evolution has followed the motto “smaller, cheaper, faster” by using very-large-scale integration of a basic building block, the transistor. Today, there are processors that contain billions of transistors, each one with dimensions of a few tenths of nanometers. It is interesting to note that in 1969, S. T. Miller from Bell Labs already suggested that integration should drive the development of photonics as well.2 However, the number of photonic components for optical integrated circuits has not grown as for microelectronics over the years. Current integrated photonic circuits contain only a hun- dred different components with the burden of a high production cost. Instead of look- ing for performance improvements by increasing the integration level, photonic research was concentrated on single device scale refinements. What is the reason for this? Table P.1 shows a comparison between microelectronic and photonic in term of building blocks, materials, and technology. While for microelectronics the key feature is standard (a single building block is repetitively manufactured with a single material and a single production process), for photonics, there is a diversity of materials, elementary devices, and manufacturing processes. This is the main reason why microelectronics kept pace with integration while photonics did so with isolated device optimization. The rationale of silicon photonics is to apply the paradigm of microelectronics to photonics by manufacturing various devices in a single material—silicon—and using a single manufacturing process—the CMOS process (see Table P.1). In this way, the level of integration of photonic devices can be increased, which in turn is reflected in an increase in the performance of the photonic integrated circuit. At the same time, mass manufacturing of integrated photonic circuits yields a low price of production per unit.3 During recent years, additional materials, mainly germanium and III–V semiconductors, have been introduced in silicon photonics to reach efficient building blocks. The com- plexity of each device has gotten higher and higher to take into account light polarization and performance independence in a broad wavelength range. Manufacturing technology has shifted from a pure CMOS process, still keeping in mind CMOS process compatibility. This was achieved by producing the photonic devices using typical CMOS manufacturing tools and trying to depart at least from standard CMOS processes. In fact, most of microelectronics industries are now developing programs on silicon photonics within their production line using 200- and 300-mm CMOS tools. The development of silicon photonics is also driven by other strong pushes: on one hand, the Internet and the move of high bandwidth as close as possible to the user; on the other hand, the need to control power dissipation (i.e., heat) induced by the long-distance high- data-rate transmission of digital signals. Currently, in high-performance computers, there is already a need to manage both the exchange of data between hundreds of thousands of cores in the multiprocessors (aggregate data rate of the order of 1 Tbps) and the exchange of information between the multiprocessor and the other boards (memories, peripherals, etc.) at a rate in excess of 40 Gbps. In addition, these developments spawn other applications for silicon photonics in technologies as diverse as telecommunications, information processing, displays, sensing, metrology, medicine, consumer electronics, and energetics. The richness of applications will continuously push silicon photonics to new innovative © 2008 Taylor & Francis Group, LLC vii viii Preface TABLE P.1 Comparison of Various Technologies Microelectronics Photonics Silicon Photonics Building blocks Transistor Laser, photodetector, Laser, waveguides, photodetectors, modulator, optical fiber, modulator, microresonators, etc. waveguide, DWDM, etc. Material Silicona Semiconductors, glasses, Silicona polymers, insulators, etc. Manufacturing CMOS Epitaxy, deposition, glass CMOS compatible processb technology drawing, ionic diffusion, etc. a In microelectronics and silicon photonics, the substrate material is silicon. Many other materials are used as well, for example, Germanium, III–V semiconductors, rare earths, metals, etc. See, e.g., M. Heyns and W. Tsai, Ultimate scaling of CMOS logic devices with Ge and III–V materials, MRS Bulletin, vol. 34 (2009), pp. 485–492. b Use of CMOS tools to fabricate photonic device with a maximum emphasis to adjust the technology to the CMOS process. concepts. One can also notice that the opposite is also true: the richness of silicon photonics will push more and more applications. It is interesting to note that these developments occurred in only a few years. Indeed, in many semiconductors textbooks, silicon is introduced as an indirect band-gap semicon- ductor that is important only for electronic applications.4 For this reason, we think that this is the right time to step back and present a coherent and comprehensive overview of silicon photonics from the basics and fundamentals to integrated systems and applications. This handbook covers a broad spectrum from the material to applications, emphasizing passive and active photonic devices, fabrication, integration, and the convergence with CMOS technology. Each chapter is written by world experts in the field. Authors come from both academia as well as industries. Specifically, the handbook starts with a set of chapters (Chapters 1 to 7) where the basics of silicon as an optical material are introduced. In Chapter 1, the basic properties and the growth mechanisms of group IV materials are reviewed. After a detailed introduction on the various growth methods, the growth of silicon and silicon/germanium alloys is discussed. Then the main properties of group IV elements are reported, with a specific emphasis on silicon and germanium. The chapter ends with a section on the strain control and engineering in Si/Ge and Ge/Sn heterostructures. Chapter 2 introduces silicon-based waveguides. First, it presents a narrow submicrometer cross-section photonic wire waveguide and discusses the problem of losses and polarization control. Then, nanostructured silicon waveguides are considered both in a slot waveguide geometry and in a subwave- length grating waveguide geometry. The chapter ends with a discussion of micrometer- sized waveguides, which are silicon- or medium index silica–based. Chapter 3 addresses the problem of light coupling from optical fiber to waveguide. After defining the problem and the proper metrics, edge-coupling solutions are discussed. Then, surface cou- plers based on waveguide gratings are described. Finally, free space coupling is presented. Chapter 4 is about multichannel silicon photonic devices: integrated grating technologies, waveguide-coupled microring resonator–based multiplexers and demultiplexers, and interferometric-based structures. Chapter 5 deals with nonlinear optics in silicon. Since silicon is a centrosymmetric material, most nonlinear effects are based on third-order optical nonlinearities: four-wave mixing, two-photon absorption, self- and cross-phase © 2008 Taylor & Francis Group, LLC Preface ix modulation, stimulated Raman scattering. In this chapter, there is also a review of the various approaches to generate second-order nonlinear effects. The last part of the chapter is dedicated to the applications derived from third-order nonlinear effects. Chapter 6 is about long-wavelength, i.e., medium infrared, silicon photonic circuits. The chapter covers all the associated topics, from waveguiding to light generation, from nonlinear optical properties in the long wavelength region to detectors, and from the different material platforms (silicon on insulator, silicon on sapphire, silicon on porous silicon, silicon on air) to the heterogeneous integration of III–V and silicon. Chapter 7 introduces silicon-based photonic crystals and metamaterials and motivates their use in future on-chip optical interconnects. First, a discussion of all optical switches and memories based on photonic crystal nanocavities is presented. Then, photonic crystal lasers where active III–V materials are optically coupled to silicon are reviewed. Finally, slow light generation and applications are discussed. These chapters are followed by Chapters 8 to 10, where the different building blocks needed to drive silicon photonic integrated circuits are presented. Chapter 8 treats silicon-based light sources. An exhaustive discussion of the light emission processes in indirect gap semiconductors is followed by a review of the physics of low-dimensional silicon structures. Then, two alternative systems are introduced: Si/Ge alloys or Si/SiGe nanostructures and rare earth-doped silicon or silicon nanostructures. This is followed by a discussion of band-engineered Ge on Si lasers. The chapter ends with a review of Purcell effects in silicon nanocrystals as a way to enhance radiative recombination rates. Chapter 9 discusses the physics and device applications of silicon-based optical modulators. First, the physical mechanisms to obtain optical modulation in silicon are presented: carrier accumulation, injection, or depletion-based devices are detailed and compared. Then, Franz–Keldysh and quantum-confined Stark effects in Ge and SiGe materials are discussed. Chapter 10 reports on photodetectors suitable to be integrated in silicon photonics. It traces the development of Ge photodetectors, their performance and integration into Si photonics circuits. Si-based photodetectors developed for near-IR applications are also discussed. Through the chapter, a sensitive issue is the design, modeling, and fabrication of waveguide integrated photodetectors. Once the building blocks are available, the next issue is their integration in complex photonic integrated circuits. This is the subject of Chapters 11 to 13. Chapter 11 deals with hybrid and heterogeneous integrations of III–V active materials in silicon photonics. First, the integration schemes and their fabrication technologies are introduced. Then, an overview of the various demonstrated devices that make a complete photonic toolbox is addressed. Chapter 12 discusses the fabrication of silicon photonic devices by providing a basic foundation on micro- and nano-fabrication technologies from photonic perspectives. Cleanrooms, lithography, depositions, etching, microfabrication tools, processes, and materials are discussed. Also, issues such as parameter variations on wafers and dimensional control in CMOS processing are presented. Chapter 13 attacks the problem of the convergence between photonics and CMOS at the single-wafer level. The various alterna- tives are introduced and critically discussed. Both die-to-die integration via wire bonding or flip-chip, wafer-to-wafer bonding, and single-wafer fabrication are presented. Applications of silicon photonics in different fields from data communication or optical interconnects are reported in Chapters 14 and 15. Chapter 14 shows the different kinds of devices when silicon photonics is applied to biology or life science. Planar silicon waveguide molecular affinity sensors and the strategies of surface functionalization and bioconjuga- tion are discussed. The manipulation and transport of biomolecules using silicon nanostructures is reviewed. The status of bioimaging using silicon nanoparticles is reported as well. Chapter 15 describes silicon-based photovoltaics. High-efficiency monocrystalline © 2008 Taylor & Francis Group, LLC