Fully Quantum Mechanical Description of Ultrashort Time Dynamics of Semiconductor Quantum Dots

Abstract

In this thesis, the quantum kinetics of semiconductor quantum dots coupled to the radiation field, the vibrational modes of the crystalline lattice, and another quantum confined electron are studied using the density matrix formalism in the full quantization regime. To address and characterize the influence of the environment on the optical properties of quantum dots, the experimentally observable quantities in quantum optics are described by the radiation field correlation functions which are coupled to quantum confined electrons and phonons via the electron-photon and -phonon interaction. The influence of dispersive, absorbing, and inhomogeneous media on the local photon density of quantum dots is investigated by a quantized radiation field with the Green function formalism. The influence of the electron-phonon interaction on the quantum dot interband coherence, which consequently yields incoherent photon emission, is explained by the ratio of the electron-phonon scattering time to the duration of the coherent laser pulse. As another aspect of the electron-phonon interaction, the radiation induced by coherent acoustic waves in the intersubband region of quantum dots is investigated. This is a highly off-resonant nonlinear excitation due to the energetically large discrepancy between the acoustic waves and the electronic intersubband transition. As a basic building block for quantum information processes, the excitation energy transfer in a coupled quantum dot system is investigated. Here, the dipole-dipole interaction, where the longitudinal and the transversal electric field couplings are given by the Coulomb and the radiation field coupling, respectively, is a main energy exchange mechanism. Using 8 band kptheory wave functions of self-growth semiconductor quantum dots, all coupling constants are calculated. In linear optics and local excitation regime, quantum kinetic equations of motion for the electrons are analytically solved by using the Hartree-Fock approximation, and its validity is verified. The absorption and the resonance fluorescence spectrum are given in an analytical form. In nonlinear optics, each coupling and dephasing mechanism influencing the energy transfer between the two quantum dots is discussed in the differential transmission spectrum, the resonance fluorescence spectrum, and the joint counting rate of two photons.