1 Intraduction .................................................
2 Theoretical background ....................................... 5
2.1 Semiconductor quantum structures ....................... 5
2.2 Selection rules for optical excitation .................. 8
2.3 Linewidth of an optical transition ..................... 10
2.4 Excitons in a quantum well ............................. 10
2.4.1 Excitonic linewidth ............................. 13
2.4.2 The concept of exciton-polariton and exeiton
formation ....................................... 15
2.5 Electron-phonon interaction in a quantum dot ........... 18
2.5.1 Phonons in GaAs ................................. 18
2.5.2 Interaction of electrons with phonons ........... 20
2.5.3 The phonon bottleneck ........................... 22
2.5.4 Anharmonicity and LO phonon disintegration ...... 23
2.6 Light-matter interaction ............................... 27
2.6.1 The two-level system ............................ 27
2.6.2 Autler-Townes splitting ......................... 30
2.6.3 Optical Bloch Equations ......................... 33
2.6.4 Bloch sphere and photon echo .................... 36
3 Experimental Methods ........................................ 41
3.1 The Dresden free-electron laser FELBE .................. 41
3.2 THz pump - NIR probe setup ............................. 43
3.3 QW samples ............................................. 47
3.4 THz pump-probe and four-wave mixing setup .............. 50
3.5 Thermally annealed QD samples .......................... 50
4 Intra-excitonic Autler-Townes effect in quantum wells ....... 55
4.1 Experimental data ...................................... 56
4.1.1 Resonant and detuned intra-excitonic
excitation ...................................... 56
4.1.2 Anti-crossing behavior .......................... 59
4.1.3 Temperature dependence .......................... 60
4.2 Comparison of experimental data with microscopic
theory ................................................. 63
4.2.1 Exciton linewidth ............................... 64
4.2.2 Anti-crossing from microscopic theory ........... 69
4.2.3 Rabi oscillations and polarization
redistribution .................................. 69
4.3 Summary ................................................ 72
5 Inter-sublevel coherence in InAs/GaAs quantum dots .......... 73
5.1 Strong electron-phonon coupling ........................ 74
5.2 Dephasing above the Restrahlen band .................... 77
5.3 Pump-probe and transient four-wave-mixing
measurements below the Reststrahlenband ................ 80
5.4 Temperature dependence ................................. 80
5.5 Summary ................................................ 84
6 Appendix .................................................... 85
6.1 Appendix A - Autler-Townes splitting calculated in
a three-level config-uration ........................... 85
6.2 Appendix В - Microscopic theory ........................ 88
6.3 Appendix С - Coherent oscillations in the THz pump-
probe signal ........................................... 92
Bibliography ................................................... 94
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