Theory and space-time simulations of dipole-dipole interactions in the presence of mechanical oscillations
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Authors
Chang, Yi-Ming
Date
2024-04-26
Type
thesis
Language
eng
Keyword
Mechanical perturbation , Lorentz Oscillators , Floquet theory of Coupled atoms , Dipole-dipole interaction with Mechanical oscillations
Alternative Title
Abstract
We study the spontaneous emission dynamics of coupled electric dipoles, modelled as Lorentz oscillators (LOs), in the presence of real-time mechanical motion. The dipoles are treated in a self-consistent way through a direct electromagnetic simulation approach that fully includes the movement of the charges, radiation reaction, as well as the emitted radiation. This allows for a powerful numerical solution of optomechanical resonances without any perturbative approximations for the mechanical motion.
The scaled population (excitation) dynamics of the LOs are investigated as well as the emitted radiation and emitted spectra, which demonstrates how the usual dipole-dipole resonances couple to the underlying Floquet states, yielding multiple spectral peaks that are separated from the superradiant and subradiant states by an integer number of the mechanical oscillation frequency. Moreover, we observe that when the mechanical amplitude and frequency are sufficiently large, these additional spectral peaks undergo further modification, including spectral splitting, squeezing, or shifting. These observations are corroborated by a theoretical Floquet analysis conducted on two coupled two-level systems (TLSs). We find a rich dependence of population of excited states, emitted spectra (including the spatial dependence) as well as coupling strength on the dipole-dipole separation and on the oscillating amplitude and driving frequency of the moving atom. Additionally, we also study the near-field energy transfer rates between two finite size dipoles, generalizing the result of Forster coupling between two point-dipole LOs. We also demonstrate how the Forster interaction is screened as the size of the LOs become comparable to the dipole-dipole separation. This regime also leads to the emergence of non-rotating wave approximation (non-RWA) and multi-pole effects, resulting in spectral redshifts, a breakdown of the point dipole approximation, and the appearance of extra spectral peaks separated by odd integers of the frequency shift. Finally, we extend our findings to three coupled dipoles in free space, and study the dynamics with and without mechanical motion on these systems.
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ProQuest PhD and Master's Theses International Dissemination Agreement
Intellectual Property Guidelines at Queen's University
Copying and Preserving Your Thesis
This publication is made available by the authority of the copyright owner solely for the purpose of private study and research and may not be copied or reproduced except as permitted by the copyright laws without written authority from the copyright owner.