Non-linear THz spectroscopy in semiconductor quantum structures

• Main Author: Teich, Martin
• Other Authors: Technische Universität Dresden, Fakultät Mathematik und Naturwissenschaften
• Format: Doctoral Thesis
• Language: English
• Published: Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden 2014
• Subjects: Halbleiter; Spektroskopie; THz; FEL; semiconductor; spectroscopy; QW; QD; ddc:530; rvk:UP 2800
• Online Access: http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-154595; http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-154595; http://www.qucosa.de/fileadmin/data/qucosa/documents/15459/Diss_Teich_2014_.pdf

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.