Spora i uskladištena svetlost u sfernim kvantnim tačkama u lestvičastoj konfiguraciji

Abstract

This thesis investigates the weak probe laser pulse propagation through the medium consisting of semiconductor spherical quantum dots with an on-center hydrogen impurity. Under the presence of one or two strong continuous-wave control fields, the three- or four-level laddertype light–matter coupling scheme forms, leading to the coherent effect of electromagnetically induced transparency. Several cases are considered: the three-level system with non-degenerate and three-fold degenerate middle level, and the four-level system, where the additional field can behave as the probe or control field. The light– matter interaction is described by Maxwell-Bloch equations, which are solved both numerically and analytically with approximations, while quantum dot energies and wavefunctions are calculated using the Lagrange mesh method. It is shown that, in the presence of the control field, the reduced absorption is related to the increase of the dispersion curve slope, generating slow light. The light storage and retrieval are demonstrated by adiabatically switching the control field off and back on. Quantitative parameters: the group index, relative width, efficiency, and fidelity of the output pulse with respect to the laser strengths, input pulse spectral width and storage time are also calculated. The output pulse dependence on the decay rates and the external static magnetic field strength is also studied. Furthermore, the output pulse efficiency is shown to increase by using the phase-modulated control laser. Special attention is given to the comparison of numerical and analytical solutions, as well as the implementation of the obtained results in quantum information processing, optical telecommunications and magnetometry.