- Titel
- Non-linear THz spectroscopy in semiconductor quantum structures
- Zitierfähige Url:
- https://nbn-resolving.org/urn:nbn:de:bsz:14-qucosa-154595
- Datum der Einreichung
- 24.04.2014
- Datum der Verteidigung
- 26.09.2014
- Abstract (EN)
- In this thesis the strong coupling of excitons with intense THz radiation in GaAs/AlGaAs and InGaAs/GaAs multi-quantum wells (MQW) and the strong coupling of electrons to phonons in InAs/GaAs quantum dots (QD) are investigated. Experimental studies in the field of non-linear terahertz (THz) spectroscopy were carried out using the narrowband THz emission of a free-electron laser (FEL). In the first part intra-excitonic transitions are pumped with intense THz radiation. The THz-pump–near-infrared(NIR)-probe experiments are analysed focusing on the behaviour of the Autler-Townes (AT) splittings with increasing THz field strength. Furthermore measurements of the temperature dependence up to room temperature are discussed. With the help of a microscopic theory the contribution of higher lying intra-excitonic states to the lineshape and splitting of the heavy-hole absorption line is analysed at low temperatures. The second part is about the lifetime and dephasing time of polarons in InAs/GaAs QDs that was measured for inter-sublevel excitation in the THz spectral region (below the Reststrahlen band). Single electrons inside QDs strongly interact with phonons and form quasi-particles called polarons. The temperature dependence of the dephasing behavior and the contribution of pure dephasing is discussed.
- Freie Schlagwörter (DE)
- Halbleiter, Spektroskopie, THz, FEL
- Freie Schlagwörter (EN)
- semiconductor, spectroscopy, THz, QW, QD, FEL
- Klassifikation (DDC)
- 530
- Klassifikation (RVK)
- UP 2800
- GutachterIn
- Prof. Dr. Manfred Helm
- Prof. Dr. Thomas Dekorsy
- BetreuerIn
- Prof. Dr. Manfred Helm
- Den akademischen Grad verleihende / prüfende Institution
- Technische Universität Dresden, Dresden
- URN Qucosa
- urn:nbn:de:bsz:14-qucosa-154595
- Veröffentlichungsdatum Qucosa
- 05.11.2014
- Dokumenttyp
- Dissertation
- Sprache des Dokumentes
- Englisch
- Lizenz / Rechtehinweis
- Inhaltsverzeichnis
1 Introduction 1 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 exciton 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 configuration 85 6.2 Appendix B - Microscopic theory 88 6.3 Appendix C - Coherent oscillations in the THz pump-probe signal 92 Bibliography 94