Dissertation/Thesis Abstract

Microscopic Description of Quantum-Dot Vertical-Cavity Surface-Emitting Structures Using Maxwell-Bloch Equations
by Kim, Jeong Eun, Dr.Nat., Technische Universitaet Berlin (Germany), 2011, 142; 10712301
Abstract (Summary)

This work is focused on the optical properties of electrically pumped vertical-cavity surface-emitting structures which use self-assembled quantum dots (QDs) as an active medium. In order to investigate the electric field propagation and the carrier dynamics, we have proposed a model which is based on the self-consistent quantum dot-wetting layer Maxwell-Bloch equations incorporating microscopically calculated Coulomb and phonon-assisted scattering processes between the QD and the QD-embedding WL states. The scattering rates are calculated within a second order screened Born-Markov approximation and implemented as a function of the wetting layer carrier density. All numerical calculations for the carrier dynamics and the field propagation are performed using the finite-difference time-domain (FDTD) method for the full structure. Within this model, the normal mode coupling in the weak and strong coupling regime as well as the linear and nonlinear regime are studied on a microscopic level in dependence on the structural parameters, the QD properties, and the properties of the input pulse at the temperatures of 77 K and 300 K. A more detailed understanding of the light-matter interaction in the normal mode coupling is provided by the time dynamics of the electric field, the QD population inversion, and the scattering rates as well as the transmission spectra. Furthermore, the switch-on dynamics of QD vertical-cavity surface-emitting lasers (VCSELs) is microscopically investigated since the internal time scales of the switch-on delay time and the frequency and damping of relaxation oscillations of the lasers are important for high-speed optical systems. The obtained internal time scales in dependence on the strength of the injection current, the Bragg mirror reflectivity, and the number of QD layers are in agreement with experimental data. Summarizing, the work presented in this thesis provides a microscopic understanding of the light-matter interaction in confined nanostructures and further insight into other advanced techniques such as current modulation and modelocking.

Indexing (document details)
Advisor: Knorr, Andreas
School: Technische Universitaet Berlin (Germany)
School Location: Germany
Source: DAI-C 81/1(E), Dissertation Abstracts International
Subjects: Optics, Electrical engineering, Condensed matter physics
Keywords: Self-assembled quantum dots
Publication Number: 10712301
ISBN: 9781392605509
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