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High Contrast Gratings for Integrated Optoelectronics High Contrast Gratings for Integrated Optoelectronics Weijian Yang Electrical Engineering and Computer Sciences University of California at Berkeley Technical Report No. UCB/EECS-2014-197 http://www.eecs.berkeley.edu/Pubs/TechRpts/2014/EECS-2014-197.html December 1, 2014 Copyright © 2014, by the author(s). All rights reserved. Permission to make digital or hard copies of all or part of this work for personal or classroom use is granted without fee provided that copies are not made or distributed for profit or commercial advantage and that copies bear this notice and the full citation on the first page. To copy otherwise, to republish, to post on servers or to redistribute to lists, requires prior specific permission. High Contrast Gratings for Integrated Optoelectronics by Weijian Yang A dissertation submitted in partial satisfaction of the requirements for the degree of Doctor of Philosophy in Engineering-Electrical Engineering and Computer Sciences and the Designated Emphasis in Nanoscale Science and Engineering in the Graduate Division of the University of California, Berkeley Committee in charge: Professor Constance J. Chang-Hasnain, Chair Professor Ming C. Wu Professor Xiang Zhang Professor Eli Yablonovitch Fall 2013 High Contrast Gratings for Integrated Optoelectronics © 2013 by Weijian Yang Abstract High Contrast Gratings for Integrated Optoelectronics by Weijian Yang Doctor of Philosophy in Engineering-Electrical Engineering and Computer Sciences and the Designated Emphasis in Nanoscale Science and Engineering University of California, Berkeley Professor Constance J. Chang-Hasnain, Chair Integrated optoelectronics has seen its rapid development in the past decade. From its original primary application in long-haul optical communications and access network, integrated optoelectronics has expanded itself to data center, consumer electronics, energy harness, environmental sensing, biological and medical imaging, industry manufacture control etc. This revolutionary progress benefits from the advancement in light generation, manipulation, detection and its interaction with other systems. Device innovation is the key in this advancement. Together they build up the component library for integrated optoelectronics, which facilities the system integration. High contrast grating (HCG) is an emerging element in integrated optoelectronics. Compared to the other elements, HCG has very rich properties and design flexibility. Some of them are fascinating and extraordinary, such as broadband high reflectivity, and high quality factor resonance – all it needs is a single thin-layer of HCG. Furthermore, it can be a microelectromechanical structure. These rich properties are readily to be harnessed and turned into novel devices. This dissertation is devoted to investigate the physical origins of the extraordinary features of HCG, and explore its applications in novel devices for integrated optoelectronics. An intuitive picture will be presented to explain the HCG physics. The essence of HCG lies in its superb manipulation of light, which can be coupled to applications in light generation and detection. Various device innovations, such as low- loss hollow-core waveguide, fast optical phased array, tunable VCSEL and detector are demonstrated with the HCG as a key element. This breadth of functionality of HCG suggests that HCG has reached beyond a single element in integrated optoelectronics; it has enabled a new platform for integrated optoelectronics. 1 To my parents TABLE OF CONTENTS TABLE OF CONTENTS ..................................................................................................... i LIST OF FIGURES ........................................................................................................... iii LIST OF TABLES ............................................................................................................. xi ACKNOWLEDGEMENTS .............................................................................................. xii Chapter 1 Introduction ........................................................................................................ 1 1.1 Introduction to high contrast grating .................................................................... 1 1.2 Dissertation Overview .......................................................................................... 3 Chapter 2 Physics of High Contrast Grating....................................................................... 5 2.1 Overview of the Underlying Principles ................................................................ 6 2.2 Analytical Formulation ........................................................................................... 10 2.2.1 TM-polarized Incidence ................................................................................... 10 2.2.2 TE-polarized incidence .................................................................................... 20 2.2.3 Comparison with Numerical Simulations ........................................................ 21 2.2.4 General Analytical Treatment – Transmission Matrix .................................... 21 2.2.5 Special case at surface normal incidence ......................................................... 25 2.3 HCG Supermodes and Their Interferences ............................................................. 27 2.3.1 The mechanism of high reflectivity and 100% reflectivity ............................. 29 2.3.2 The mechanism of 100% transmission ............................................................ 33 2.3.3 Crossings and Anti-crossings ........................................................................... 35 2.3.4 Resonator without mirrors ............................................................................... 38 2.4 HCG Band Diagram ................................................................................................ 39 2.5 Longitudinal HCG ................................................................................................... 44 2.6 Summary ................................................................................................................. 45 Chapter 3 High Contrast Grating based Hollow-core Waveguide and Its Application .... 46 3.1 High Contrast Grating Hollow-core Waveguide with Novel Lateral Confinement 47 3.1.1 Design .............................................................................................................. 47 3.1.2 Device Fabrication ........................................................................................... 52 3.1.3 Device Characterization ................................................................................... 52 3.1.4 Control of Lateral Confinement ....................................................................... 55 3.1.5 Light guiding in curved HCG Hollow-core Waveguides ................................ 57 3.1.6 Discussion ........................................................................................................ 59 3.2 HCG-DBR hybrid Hollow-core Waveguide ........................................................... 61 i 3.2.1 Design and fabrication ..................................................................................... 62 3.2.2 Characterization ............................................................................................... 62 3.3 Cage-like High Contrast Grating Hollow-core Waveguide .................................... 64 3.4 Optical Switch based on High Contrast Grating Hollow-core Waveguide ............. 65 3.5 Application of High Contrast Grating Hollow-core Waveguide in Gas sensing .... 73 3.6 Summary ................................................................................................................. 73 Chapter 4 High Contrast Grating Optical Phased Array ................................................... 74 4.1 HCG MEMS Mirror as a Phase Tuner .................................................................... 75 4.1.1 Piston Mirror Approach ................................................................................... 75 4.1.2 All-pass Filter Approach .................................................................................. 78 4.2 Device Characterization and Beam Steering Experiment ....................................... 83 4.2.1 Small Actuation Distance for Large Phase Shift ............................................. 83 4.2.2 High Speed Phase Tuning ................................................................................ 86 4.2.3 Beam Steering Experiment .............................................................................. 89 4.2.4 Two-dimensional HCG .................................................................................... 91 4.3 HCG Optical Phased Array on Silicon Platform ..................................................... 93 4.4 Summary ................................................................................................................. 93 Chapter 5 Tunable High Contrast Grating Detector ......................................................... 95 5.1 Tunable High Contrast Grating Detector ................................................................ 96 5.2 High Speed Tunable High Contrast Grating Detector and VCSEL ........................ 98 5.3 Tracking Detector .................................................................................................. 103 5.4 Chip-scale Optical spectrometer ........................................................................... 105 5.5 Summary
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