Dresden 2006 – wissenschaftliches Programm
Bereiche | Tage | Auswahl | Suche | Downloads | Hilfe
HL: Halbleiterphysik
HL 24: Ultra fast phenomena
HL 24.5: Vortrag
Dienstag, 28. März 2006, 16:15–16:30, POT 151
Observation of coherent acoustic phonons in semiconductors via asynchronous optical sampling — •Florian Hudert1, Albrecht Bartels1, Christof Janke1, Thomas Dekorsy1, and Klaus Köhler2 — 1Department of Physics and Center for Applied Photonics, University of Konstanz, D-78457 Konstanz — 2Fraunhofer-Institut für Angewandte Festkörperphysik, D-79108 Freiburg
We report on the observation of coherent acoustic phonons in bulk semiconductors (GaAs, GaSb) as well as in semiconductor superlattices (GaAs/AlGaAs) via a recently developed femtosecond time resolved pump-probe technique without a mechanical delay line. The experimental setup constitutes of two modelocked femtosecond lasers with a repetition rate of 1 GHz that are coupled at a fixed difference of 11 kHz with one laser providing the pump and the other one providing the probe pulse. This setup allows scanning a measuring window of one nanosecond with 11 kHz and a resolution of about 200 femtoseconds. The measurement of the transient reflectivity reveals coherent longitudinal acoustic phonons over more than a few hundred picoseconds. The frequencies observed agree very well with Brillouin scattering theory. The decay of the coherent amplitude is dominated by propagation of the acoustic modes.