Aachen PK 2003 – wissenschaftliches Programm

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PV: Plenarvorträge

PV II

PV II: Plenarvortrag

Montag, 17. März 2003, 14:45–15:30, FO1

Ultrafast dynamics of electron plasmas in semiconductor quantum wells and quantum cascade structures — •Thomas Elsaesser — Max-Born-Institut für Nichtlineare Optik und Kurzzeitspektroskopie, Max-Born-Str. 2 A, 12489 Berlin

Quasi-two-dimensional semiconductor nanostructures represent interesting model systems for studying electron plasmas under the conditions of quantum confinement. Electron dynamics after optical intersubband excitation, i.e., a transition between different conduction subbands, are characterized by a sequence of ultrafast relaxation processes which provide insight into the basic physics of such many-body systems and play an important role in semiconductor devices. Femtosecond nonlinear spectroscopy in the mid-infrared spectral range allows for monitoring such phenomena in real-time and - thus - gives direct information on the nonequilibrium dynamics of the plasma. In this talk, femtosecond infrared studies of electron dynamics in quantum wells and quantum cascade structures made from III-V semiconductors are presented. After introducing the experimental techniques, the generation and manipulation of coherent intersubband excitations will be discussed, including the first demonstration of intersubband Rabi flopping. Direct measurements of transient electron distributions reveal the mechanisms underlying electron thermalization, i.e., the formation of a hot quasi-equilibrium distribution. The relevance of such phenomena for quantum cascade lasers, a novel type of infrared emitter, will be demonstrated.