Clemson University TigerPrints All Dissertations Dissertations 5-2018 Molten Core Fabrication of Bismuth-Containing Optical Fibers Benoit Faugas Clemson University Follow this and additional works at: https://tigerprints.clemson.edu/all_dissertations Recommended Citation Faugas, Benoit, "Molten Core Fabrication of Bismuth-Containing Optical Fibers" (2018). All Dissertations. 2166. https://tigerprints.clemson.edu/all_dissertations/2166 This Dissertation is brought to you for free and open access by the Dissertations at TigerPrints. It has been accepted for inclusion in All Dissertations by an authorized administrator of TigerPrints. For more information, please contact [email protected]. MOLTEN CORE FABRICATION OF BISMUTH- CONTAINING OPTICAL FIBERS A Dissertation Presented to the Graduate School of Clemson University In Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy Materials Science and Engineering by Benoit Faugas May 2018 Accepted by: Prof. John Ballato, Committee Chair Prof. Stephen Foulger Prof. Liang Dong Prof. Philip Brown ABSTRACT Glass optical fibers have generated significant commercial and research interest in the fields of communications, lasers and sensors since their successful development in the 1970s. Since then, higher performing optical fibers have arisen due to new and evolving demands necessitating the community to occasionally rethink the materials from which optical fibers are made. Although chemical vapor deposition (CVD)- based methods dominate due to their ability to make extremely low loss optical fiber, it is limited in the range of materials, hence properties, that can be brought to bear on modern problems. Accordingly, the method for fiber fabrication has proven to be a very useful technology from which fruitful knowledge and fiber performance has emerged. Not only does this technique allow the study of new and unusual glass optical fibers but it has also provided the opportunity of fabricating crystalline core analogs as well. Crystals, because of their regular structure, are very attractive fiber waveguide materials; particularly for electro-optic functionalities. The fabrication of crystalline oxide core phases using the molten core method is further intriguing because of the high quench speed (~m/min compared to mm/h for standard conventional crystal fiber growth techniques), which usually leads to amorphous phases. The possibility of fabricating both phases (crystals and glasses) whilst using conventional optical fiber drawing techniques is thus an attractive feature of the molten core method. The thermodynamic-kinetic interplay offered by said method is the central topic of this dissertation. The questions of where does the thermodynamic takes over the kinetics when one draws fibers using the molten core method? and can one control crystal formation during fiber draw? will be investigated. For that purpose, the bismuth germanate and bismuth silicate system will be explored for their ii interesting electro-optic and nonlinear optic phases (Bi4Ge3O12/Bi4Si3O12 crystals and bismuth oxide glass). Chapter I provides a background on optical fiber history and the principal optical fiber fabrication techniques. Additionally, the fundamental origin of nonlinearities in materials are described as are a few nonlinear applications. Chapter II investigates the fabrication of Bi4Ge3O12 (BGO) crystalline core fibers in borosilicate glass cladding. Phase pure BGO crystalline core fibers were demonstrated. It is shown that one needs to control the inherent core-clad interaction, which incorporates glass cladding compounds and prevents one to retain a stoichiometric melt in order to obtain a single phase. Nonetheless, the glass cladding compounds (SiO2 notably) are found incorporated into the crystal structure and do not prevent the crystallization processes from taking place. Chapter III explores the understanding of eulytine crystal formation during fiber draw in borosilicate and soda-lime silicate glass claddings. Homogeneous nucleation is investigated and refuted as a crystallization mechanism. Instead, heterogeneous nucleation is demonstrated as a pathway for crystal growth. The reaction 2Bi2SiO5 + SiO2 → Bi4Si3O12 for crystal growth is also considered but could not be identified as the mechanism. Chapter IV studies the necessary processing conditions using the molten core method in order to fabricate bismuth-containing glass optical fibers. The materials’ processing conditions are shown to affect the fiber core structure, where a low density precursor powder is necessary to achieve a glass core phase as a result of a volume expansion effect. Furthermore, it is found that fibers fabricated from a borosilicate iii glass cladding are impractical due to cracks as a result of the CTE mismatch between core and cladding, and, soda-lime silicate glass cladding provides a better match. Finally, the thermo-reduction behavior of bismuth oxide is studied and it is shown that bismuth metallic nanoparticles are formed during fiber draw. The use of an oxidizing agent such as CeO2 is shown to have no relevant impact on the formation of these nanoparticles. iv DEDICATIONS Pour ma famille et mes parents, Catherine et François. v ACKNOWLEDGEMENTS First, I would like to thank my advisor and mentor Prof. John Ballato for awarding me a place in his group and giving me this challenging and futuristic project to work my mind around. Thank you also for sharing and translating your passion about optical fibers and glass/crystal science! Finally, thank you for providing me support and guidance with an ever-ending happiness and easy-going way, and, for the laughter’s about the French way. I would also like to thank Dr. Klaus Böhnert, who initiated and funded the project, for the discussion and support about the project itself and also for understanding the challenge. Also, thank you for receiving me at the ABB Company while I was visiting Switzerland. I also show my gratitude to my committee members Prof. Stephen Foulger, Prof. Liang Dong and Prof. Philip Brown. Thank you for agreeing to be part of my committee and taking your time to serve in my committee. Big thanks to Courtney Kucera for all the guidance throughout my years within the group. You have been of tremendous help! Thank you also for all your generosity (e.g., cooking) and for bringing a family ambiance to the group! I will always be beholden to T. Wade Hawkins, Maxwell Jones and Kenneth Peters for drawing the optical fibers. Thank you also for the engineering discussion and the will to draw optical fibers, sometimes, within the limits of the materials. Furthermore, I would kindly acknowledge the MS&E and COMSET staff members for providing me help within the university. Thank you Ms. Heather Cox, Ms. Sheryl Gonzalez and Ms. Sandra Bradberry. Thanks also goes to Mr. Donald vi Mulwee for all his support and teaching at the electron microscope facilities, as well as for his (contagious) happiness. Moreover, I am thankful for my group members for the science discussion and, everyday laughter’s in the office: Laura, Josh, Matt, David, Amber, Baris, Ronaldo. A special thanks to my dear work colleague and friend of all time Maxime Cavillon for all the never-ending discussions about the molten core method, optical fibers, soccer, wine and, philosophy of life… T’es vraiment un mec à la cool. Of course, my time through my PhD required more friends, and I would like to thank all my friends who have made this journey wonderful. The list is too long to detail but if you have crossed my path then you know your name belongs here. Special thanks to Jake Townsend, Bradley Schultz and Erica Linard (and their respective families) whom I am forever grateful for their friendship, incommensurable varieties of unpredictable discussions, and wonderful memories we have built. It would not have been the same without you! Finally, it is my pleasure to acknowledge the friendship of Robert Bowen and his family for the tailgates, Sunday barbeques and, laughter’s and caring at all times. Financial support is acknowledged from the Department of Materials Science and Engineering and the ABB company (grant #2009842). vii TABLE OF CONTENTS Page ABSTRACT .................................................................................................................. ii DEDICATIONS ............................................................................................................ v ACKNOWLEDGEMENTS .......................................................................................... vi TABLE OF CONTENTS ........................................................................................... viii LIST OF FIGURES .................................................................................................... xiii LIST OF TABLES ....................................................................................................... xx Chapter I INTRODUCTION ......................................................................................... 1 I.1. A (short) history of glass fiber optics .................................................................. 1 I.2. Optical fiber fabrication technologies ................................................................. 7 I.3. Nonlinearities in optical fibers and their applications ....................................... 17 I.3.1. Introduction to nonlinear optics .................................................................. 18 I.3.1.1. Electronic polarization ...............................................................................