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Engineering Phonon, Photon, Electron and Plasmon Interactions in Silicon - Metal Nanocavitiies for Silicon Photonics and Thermoplasmonics University of Pennsylvania ScholarlyCommons Publicly Accessible Penn Dissertations 2016 Engineering Phonon, Photon, Electron and Plasmon interactions in Silicon - Metal Nanocavitiies for Silicon Photonics and Thermoplasmonics Daksh Agarwal University of Pennsylvania, [email protected] Follow this and additional works at: https://repository.upenn.edu/edissertations Part of the Mechanics of Materials Commons Recommended Citation Agarwal, Daksh, "Engineering Phonon, Photon, Electron and Plasmon interactions in Silicon - Metal Nanocavitiies for Silicon Photonics and Thermoplasmonics" (2016). Publicly Accessible Penn Dissertations. 1576. https://repository.upenn.edu/edissertations/1576 This paper is posted at ScholarlyCommons. https://repository.upenn.edu/edissertations/1576 For more information, please contact [email protected]. Engineering Phonon, Photon, Electron and Plasmon interactions in Silicon - Metal Nanocavitiies for Silicon Photonics and Thermoplasmonics Abstract ENGINEERING PHONON, PHOTON, ELECTRON AND PLASMON INTERACTIONS IN SILICON - METAL NANOCAVITIIES FOR SILICON PHOTONICS AND THERMOPLASMONICS Daksh Agarwal Ritesh Agarwal, PhD Silicon photonics offers a cost effective solution to achieve ultrafast data processing speeds. But due to its indirect bandgap structure, making lasers from silicon is extremely difficult. Thusesear r ch has focused on nonlinear Raman processes in silicon as a method to achieve optical gain. Silicon nanowires provide an interesting platform for enhancing these nonlinearities because of their small size, geometry and relevant length scales. In the current work Raman measurements done on silicon nanowires reveal that up to twelvefold enhancement in Stokes scattering intensity and fourfold enhancement in anti Stokes scattering intensity can be attained depending on cavity structure and size, and excitation wavelength. In some cavities Stokes intensity depends on the sixth power of pump intensity, indicating extreme nonlinearity. Numerical calculations, done to understand the mechanism of these results indicate that silicon nanowires confine light to highly intense electric field modes inside the cavity which lead to stimulated Stokes and anti Stokes Raman scattering. Cavity modes can also be tuned to enhance the relative emission of either one of anti Stokes or Stokes photons which could enhance cavity cooling. These results would enable the development of smallest monolithically integratable silicon laser with extremely low lasing threshold and could lead to the development of next generation of high speed and energy efficient ocessors.pr The intense electric field inside the nanowire could also be used to enhance the degree of plasmon excitation in metallic nanoparticles. Silicon nanowires coated with a 10 nm thick gold film lead to strong plasmon excitation in gold and high cavity absorption which enable the cavity to heat up to temperatures of 1000K at relatively low pump powers. The cavities also give the ability to measure temperature attained during plasmon excitation and control the plasmon resonance wavelength. Because of the strong heating and plasmonic effects, these cavities show enhanced evolution rates of hydrogen, a crucial industrial building block and a promising fuel, in photoreforming reactions of alcohols. Degree Type Dissertation Degree Name Doctor of Philosophy (PhD) Graduate Group Materials Science & Engineering First Advisor Ritesh Agarwal Keywords optics, plasmonics, semiconductor, silicon photonics Subject Categories Mechanics of Materials This dissertation is available at ScholarlyCommons: https://repository.upenn.edu/edissertations/1576 ENGINEERING PHONON, PHOTON, ELECTRON AND PLASMON INTERACTIONS IN SILICON - METAL NANOCAVITIIES FOR SILICON PHOTONICS AND THERMOPLASMONICS Daksh Agarwal A DISSERTATION in Materials Science and Engineering Presented to the Faculties of the University of Pennsylvania in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy 2016 Supervisor of Dissertation _____________________ Ritesh Agarwal, PhD Professor of Materials Science and Engineering Graduate Group Chairperson _______________________ Shu Yang, PhD, Professor of Materials Science and Engineering Dissertation Committee Nader Engheta, PhD, H. Nedwill Ramsey Professor of Electrical and Systems Engineering, Physics and Astronomy and Materials Science and Engineering and Bioengineering Christopher B. Murray, PhD, Richard Perry University Professor of Chemistry, and Materials Science and Engineering Cherie R. Kagan, PhD, Stephen J. Angello Professor of Electrical and Systems Engineering, Materials Science and Engineering, and Chemistry ENGINEERING PHONON, PHOTON, ELECTRON AND PLASMON INTERACTIONS IN SILICON - METAL NANOCAVITIIES FOR SILICON PHOTONICS AND THERMOPLASMONICS COPYRIGHT 2016 Daksh Agarwal This work is licensed under the Creative Commons Attribution- NonCommercial-ShareAlike 3.0 License To view a copy of this license, visit https://creativecommons.org/licenses/by-nc-sa/3.0/us/ To my dad, for his unconditional love and for his smiles no matter what. iii ACKNOWLEDGMENT I would like to take this opportunity to first thank my supervisor Dr. Ritesh Agarwal, whose esteemed guidance and support has helped me tremendously in these past five years. I would also like to thank my thesis committee members (past and present) Dr. Nader Engheta, Dr. Cherie Kagan, Dr. Chris Murray and Dr. Ertugrul Cubukcu for providing valuable counsel and insights. I would like to thank Dr. Carlos Aspetti, former member of the Agarwal group for his guidance early on in my PhD; and Jacob Berger and Rob Middleton for helping me navigate difficult times. The current and former members of the Agarwal group have made these years truly transformative and memorable; I would like to thank Dr. Joohee Park, Dr. Mingliang Ren, Dr. Pavan Nukala, Wenjing Liu, Dr. Liaoxin Sun, Dr. Bumsu Lee, Dr. Sajal Dhara, Dr. Rahul Agarwal, Stephanie Malek and Gerui Liu, for all their insightful scientific discussions. I must not forget to mention other members of my PhD cohort- Dan, Frank and Nick, and friends from Penn Taekwondo- Becky, Jessie, Tom, Robin and Kevin for enriching my life these past five years. Lastly, and most importantly, I want to thank my family especially my father who always strived to bring happiness in my life, my mother for always standing beside me, my sisters for make me believe in me, my brother in laws for supporting me in the most difficult times of my life, and my wife for being there for me no matter what. iv ABSTRACT ENGINEERING PHONON, PHOTON, ELECTRON AND PLASMON INTERACTIONS IN SILICON - METAL NANOCAVITIIES FOR SILICON PHOTONICS AND THERMOPLASMONICS Daksh Agarwal Ritesh Agarwal, PhD Silicon photonics offers a cost effective solution to achieve ultrafast data processing speeds. But due to its indirect bandgap structure, making lasers from silicon is extremely difficult. Thus research has focused on nonlinear Raman processes in silicon as a method to achieve optical gain. Silicon nanowires provide an interesting platform for enhancing these nonlinearities because of their small size, geometry and relevant length scales. In the current work Raman measurements done on silicon nanowires reveal that up to twelvefold enhancement in Stokes scattering intensity and fourfold enhancement in anti Stokes scattering intensity can be attained depending on cavity structure and size, and excitation wavelength. In some cavities Stokes intensity depends on the sixth power of pump intensity, indicating extreme nonlinearity. Numerical calculations, done to understand the mechanism of these results indicate that silicon nanowires confine light to highly intense electric field modes inside the cavity which lead to stimulated Stokes and anti Stokes Raman scattering. Cavity modes can also be tuned to enhance the relative emission of either one of anti Stokes or Stokes photons which could enhance cavity cooling. These results would enable the development of smallest monolithically integratable silicon laser with extremely low lasing threshold and could lead to the v development of next generation of high speed and energy efficient processors. The intense electric field inside the nanowire could also be used to enhance the degree of plasmon excitation in metallic nanoparticles. Silicon nanowires coated with a 10 nm thick gold film lead to strong plasmon excitation in gold and high cavity absorption which enable the cavity to heat up to temperatures of 1000K at relatively low pump powers. The cavities also give the ability to measure temperature attained during plasmon excitation and control the plasmon resonance wavelength. Because of the strong heating and plasmonic effects, these cavities show enhanced evolution rates of hydrogen, a crucial industrial building block and a promising fuel, in photoreforming reactions of alcohols. vi TABLE OF CONTENTS ACKNOWLEDGMENT ......................................................................................................... IV LIST OF TABLES .................................................................................................................... IX LIST OF FIGURES/ILLUSTRATIONS ............................................................................... X CHAPTER 1. INTRODUCTION ........................................................................................... 1 1.1 Case for nanoscale silicon photonics ................................................................................................. 1 1.2 Recent
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