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On-Chip Generation of Non-Classical States of Light Via Quantum Dots Coupled to Photonic Crystal Nanocavities

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On-Chip Generation of Non-Classical States of Light Via Quantum Dots Coupled to Photonic Crystal Nanocavities ON-CHIP GENERATION OF NON-CLASSICAL STATES OF LIGHT VIA QUANTUM DOTS COUPLED TO PHOTONIC CRYSTAL NANOCAVITIES A DISSERTATION SUBMITTED TO THE DEPARTMENT OF ELECTRICAL ENGINEERING AND THE COMMITTEE ON GRADUATE STUDIES OF STANFORD UNIVERSITY IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY Armand Rundquist June 2015 © 2015 by Armand Rundquist. All Rights Reserved. Re-distributed by Stanford University under license with the author. This dissertation is online at: http://purl.stanford.edu/sd515wp4826 ii I certify that I have read this dissertation and that, in my opinion, it is fully adequate in scope and quality as a dissertation for the degree of Doctor of Philosophy. Jelena Vuckovic, Primary Adviser I certify that I have read this dissertation and that, in my opinion, it is fully adequate in scope and quality as a dissertation for the degree of Doctor of Philosophy. Hideo Mabuchi I certify that I have read this dissertation and that, in my opinion, it is fully adequate in scope and quality as a dissertation for the degree of Doctor of Philosophy. David Miller Approved for the Stanford University Committee on Graduate Studies. Patricia J. Gumport, Vice Provost for Graduate Education This signature page was generated electronically upon submission of this dissertation in electronic format. An original signed hard copy of the signature page is on file in University Archives. iii Abstract Cavity quantum electrodynamics has enabled unprecedented control over the funda- mental interaction of matter and light|the coupling between individual atoms and single photons. At the same time, semiconductor electronics is quickly approaching a regime in which the strange effects of quantum mechanics can no longer be ignored. New types of on-chip optical technologies that exploit the quantum mechanical na- ture of light have the potential to open up an entirely new direction for semiconductor devices, combining the fine control of cavity quantum electrodynamics with the con- venience of the semiconductor platform. However, the practical implementation of quantum technologies on a chip will require an on-demand source of non-classical states of light, such as pulses with a well-defined number of photons. In this dissertation, I will present the development of a semiconductor non-classical light source based on coupling artificial atoms (quantum dots) to small mode-volume optical resonators (photonic crystal nanocavities). The strong coupling we achieve between a quantum dot and a photonic crystal nanocavity produces a hybridization of the quantum dot excitation with the optical field confined inside the cavity. I will demonstrate how the rich energy structure exhibited by this system enables us to control the statistics of photons in a transmitted laser beam, moving between sub-Poissonian (in which photons are more evenly spaced in each pulse) and super- Poissonian (in which photons are more likely to arrive bunched together) on demand. I will further discuss how these non-classical states of light can be characterized by examining the higher-order photon correlations measured via a generalized Hanbury Brown and Twiss type interferometer. In addition, I will show that by detuning the quantum dot resonance away from the cavity resonance, we can improve both the iv purity and the efficiency of single-photon generation in this system. This approach allows us to combine the high fidelity of single quantum emitters with the high repe- tition rate and accessibility of optical cavities. Finally, I will explore methods for scaling up this system by fabricating multiple photonic crystal nanocavities in such a way that they couple to each other. I will present the experimental realization of a photonic molecule|two coupled photonic crystal nanocavities|that is strongly coupled to a quantum dot contained inside one of the component cavities. I will also examine the fabrication of coupled optical cavity arrays in this photonic crystal platform. Our experimental findings demonstrate that the coupling between the cavities is significantly larger than the fabrication-induced disorder in the cavity frequencies. Satisfying this condition is necessary for using such cavity arrays to generate strongly correlated photons, which could potentially be used for the quantum simulation of many-body systems. These on-chip sources of non-classical light represent a significant step in the ad- vancement of semiconductor quantum optical systems. Their capability to produce single photons of high purity at high repetition rate is essential for quantum key distribution and for generating highly-entangled states in quantum metrology. Fur- thermore, the photonic crystal platform represents an ideal way to move beyond the single resonator and begin the development of integrated quantum optical networks. v Acknowledgements First, I would like to thank my advisor Prof. Jelena Vuˇckovi´cfor all of her incredible support. When she brought me into her lab during my first year, I had no idea how lucky I was to find such an excellent supervisor and mentor. I particularly appreciate the way in which she supports her students' independence and capacity to grow while still providing feedback to guide their development. I've learned so much from arguing about technical points and scientific ideas with her, even when I eventually come around to her point of view in the end. In addition to her invaluable research experience, Jelena is also an incredible teacher; I want to thank her for giving me the opportunity to TA so many of her classes and learn from her expertise. I also want to thank my reading and defense committee, Prof. David A. B. Miller, Prof. Hideo Mabuchi, and Prof. Shanhui Fan for their guidance and advice. I've taken classes from each of them that have left their mark not only on my knowledge of the field but also on the way I look at science. In addition, I'm grateful to Prof. Monika Schleier-Smith for chairing my defense. Science is a highly collaborative enterprise, and none of this work would have been possible without the constant support and friendship of the other members of the Nanoscale and Quantum Photonics Laboratory. Before I even came to Stanford, Prof. Edo Waks (a former Vuˇckovi´cgroup member) sparked my interest in nanopho- tonics through a summer research program I participated in at the University of Maryland. Then, during my first year at Stanford, I took a lab class in which Kelley Rivoire recommended to Jelena that I join their lab, so I am especially grateful for her willingness to take a chance on me. At first, I worked closely with Yiyang Gong, and I greatly appreciate his patience for putting up with my near-constant confusion. vi I later worked primarily with Arka Majumdar and Michal Bajcsy, both of whom shaped my scientific development immensely. I'm also thankful for the mentorship and support of the other senior members of the lab: Bryan Ellis, Erik Kim, Jesse Lu, and Gary Shambat. Along the way, Sonia Buckley was an unforgettable friend and colleague, and I benefited so much from her valuable help, hard work, and infectious laughter. I've learned an incredible amount from working with our current post-docs Tom Babinec, Konstantinos Lagoudakis, Kai M¨uller,and Tomas Sarmiento, each of whom I've collaborated with on one project or another. And I've been extremely fortunate these past few years to enjoy the camaraderie and scientific insight of Jan Petykiewicz, Marina Radulaski, Kevin Fischer, Yousif Kelaita, and Alex Piggott. Even as we move on to other endeavors, I know the future of these projects is in the capable hands of Tori Borish, Constantin Dory, Vincent Sebag, and Linda Zhang, and I'm excited to see what brilliant ideas they'll come up with in the years to come. I'm also very grateful for the tireless work of our administrative assistant Ingrid Tarien, without whom life in graduate school would have been a lot more painful and bureaucratic. Of course, this work depends a great deal on the quantum dot material provided by Hyochul Kim and Prof. Pierre Petroff at UC Santa Barbara, by Vaishno Dasika and Prof. Seth Bank at UT Austin, and by our own Tomas Sarmiento originally from Prof. Jim Harris's group here at Stanford. We've also had a variety of collaborators from other universities whose skills and expertise have expanded what our group was capable of: Per Kaer at TU Denmark; Kassem Alassaad and Prof. Gabriel Ferro at the Universite de Lyon; Carlos S´anchez-Mu~noz,Elena del Valle, and Fabrice P. Laussy at the Universidad Aut´onomade Madrid; and Prof. Jonathan Finley at TU M¨unchen, who was kind enough to invite me to visit his lab and has been incredibly supportive of my research efforts. Much of this research involved a great deal of time in the cleanrooms of the Stanford Nanofabrication Facility (SNF) and the Stanford Nano Center, and I want to express my gratitude to the many staff members who helped me out: James Conway for first introducing me to the pleasures of e-beam lithography; the whole etcher team|Jim Kruger, Elmer Enriquez, Nancy Latta, and Jim McVittie|for keeping vii those machines running throughout the years; Uli Thumser who is the true heart of the SNF even when she has a funny way of showing it; J Provine and Tom Carver who have been indispensable on a variety of projects; and Rich Tiberio for working with us to bring the new JEOL e-beam system to bear on our designs. I also want to thank the entire Stanford photonics community, from the Stanford Optical Society and Stanford Photonics Research Center for running so many fun and useful events (in particular, the Stanford University Photonics Retreat that I've enjoyed for the past five years) to all the groups in the Ginzton Laboratory for their support, advice, and willingness to help when needed.
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