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HL: Halbleiterphysik
HL 41: Ultrakurzzeitph
änomene II
HL 41.6: Talk
Friday, March 30, 2001, 12:45–13:00, S9/10
Ultrafast gain dynamics and dephasing in quantum dot amplifier emitting at 1.3 µm — •Wolfgang Langbein1, Stephan Schneider1, Paola Borri1, Ulrike Woggon1, Nikolai N. Ledentsov2, and Dieter Bimberg2 — 1Experimentelle Physik IIb, Universität Dortmund, Otto-Hahn-Str. 4, 44221 Dortmund — 2Institut für Festkörperphysik, TU Berlin, D-10623 Berlin, Germany
The ultrafast gain dynamics and the dephasing of the ground state transition are measured in electrically pumped quantum dot active waveguides emitting at 1.3 µm at room temperature. Differential transmission spectroscopy is used to investigate gain, absorption, and refractive index dynamics in an heterodyne detection scheme with pump and probe pulses co-linearly propagating in the single-mode ridge waveguide [1]. Gain, transparency, and absorption operation regimes of the device are accessed using different bias currents. While the absorption bleaching recovery is a multi-exponential decay over several hundert picoseconds, the gain compression is dominated by an ultrafast recovery on a sub picosecond timescale. The dephasing was measured using four-wave mixing in the same heterodyne scheme. A dephasing time of only few hundert femtoseconds is measured in the absorption regime, that fastens further with increasing bias current. The large difference between the population and polarization dynamics indicates the elastic nature of the dephasing processes also in these strongly confined quantum dots.
[1] P. Borri et. al., IEEE J. Sel. Topics in Q. El. 6, 544 (2000)