The work described in this thesis is a theoretical investigation of the properties of exciton-polaritons in quantum wells (QWs). The polariton effect is first studied in the case of a completely coherent interaction between QW excitons and bulk photons, i.e. in the so called strong coupling limit. Then, an incoherent damping rate for the exciton states is included and the resulting modifications in the polariton dispersion are analyzed. A microscopic model which accounts for the scattering of QW excitons by random impurities is also proposed. In the strong coupling limit, a definitive and correct description of the QW polariton dispersion, for both confined and radiative modes, is obtained when the exciton- photon coupling is treated non perturbatively. A self-consistent perturbation theory which qualitatively agrees with the obtained results is also formulated. With increasing the incoherent damping, the orthogonality between radiative and confined polariton states is not affected, but a phase transition from the strong coupling regime to a weak coupling one occurs for both modes. The crossover between the two regimes is attributed to a topological change of the polariton dispersion curves when the damping rate reaches a critical value. A microscopic approach dealing with scattering of excitons by random impurities is formulated in terms of a quadratic Hamiltonian for QW excitons, bulk photons and localised impurities. By analyzing the preliminary results based on the calculation of the relevant eigenstates, the mixing between radiative and confined modes is observed.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:584018 |
| Date | January 2007 |
| Creators | Creatore, Celestino |
| Publisher | Cardiff University |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://orca.cf.ac.uk/54569/ |
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