Three Essays on Time-Varying Risk Aversion and Investor Sentiment

Abstract

Light-matter interactions in semiconductor nanostructures have attracted significant research interest because of both fundamental physics questions and practical concerns. Epitaxially grown quantum dots (QDs), with their narrow emission linewidths and atom-like density of states in a solid state system, are archetypical elements of study and are potentially useful for many applications, such as on-demand single photon emitters [1,2], efficient entangled photon-pair sources [3,4], and cavity quantum electrodynamics (QED) research [5-11]. Most experiments employ resonant or near-resonant excitation to directly interact with the bound states, which enables high excitation efficiency, precise control of quantum states, and minimal disturbance of the local environment. However, the inevitable doping of the material in growth introduces an intrinsic free charge carrier reservoir that enables charge fluctuations of the QD and defects in its surrounding local environment. The direct consequences are fluorescent intermittency (or blinking) in a QD's emission, and spectral diffusion of the QD's energy level. Both effects pose challenges for using these photons as flying qubits to realize a quantum network or linear optical quantum computing. Blinking compromises the properties of these QDs useful for generating on-demand single photons. Characterizing these charge dynamics and understanding the underlying physics is critical for hunting potential methods to suppress them. In this dissertation, by examining the excitation spectra of the QD and the photon statistics of its emission, we are able to determine the possible trap locations and the time scale of these charge dynamics. In fact, the temporal correlation measurement captures both the non-classical nature of these quantum emitters and the charge dynamics of both the QD and nearby defects. This information helps identify the nature of these charge traps, and provides the clues for suppressing these electric fluctuations; for example, by modifying the sample growth parameters or fabricating additional nano-structures on the sample to deplete the free charge carriers. I would like to express my sincere gratitude to my advisor, Prof. Dr. Edward B. Flagg, for his patient guidance, amiable encouragement, intellectual enlightenment and generous advice throughout my time as his student. As a professor, he showed me the path and prospects of being a scientific researcher with constant passion, curiosity, and dedication, which motivates me to master the physics and tackle the unknown. As a supervisor, he devoted considerate care on not only the academic job of his students, but also their future career as a person. These interactions alleviate the stress of being a Ph.D. candidate and make the pursuing journey more enjoyable and pleasant. I have been extremely lucky to have a supervisor who values the teaching and educating of new generation of physicists appreciably, and who engages in the commitments with substantial efforts. I deeply appreciate these practice since it not o...