Dresden 2003 – wissenschaftliches Programm
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HL: Halbleiterphysik
HL 39: Ultrakurzzeitph
änomene I
HL 39.9: Vortrag
Donnerstag, 27. März 2003, 13:00–13:15, BEY/81
Rabi flopping of intersubband transitions in GaAs/AlGaAs MQWs — •C. W. Luo1, K. Reimann1, M. Woerner1, T. Elsaesser1, R. Hey2, and K. H. Ploog2 — 1Max-Born-Institut, Berlin, Germany — 2Paul-Drude-Institut, Berlin, Germany
We report the first Rabi flopping of intersubband (IS) transitions in n-type modulation-doped GaAs/AlGaAs multiple quantum wells which is directly observed by electro-optic sampling of ultrashort THz transients with large electric-field amplitudes transmitted through the sample. For this, we developed a new scheme for the generation and full characterization of THz transients with MV/cm amplitude at a repetition rate of 1 kHz [1]. The sample consists of 50 10-nm wide GaAs wells separated by 20-nm wide AlGaAs barriers with an electron sheet density of 5×1010 cm−2. We performed measurements for various electric field amplitudes of 200-fs-long THz transients resonant to the IS transition between the two lowest electron subbands at a temperature of 80 K. After transmission through the sample, the electric field of the transient is time-resolved by electro-optic sampling. The difference between the transients with and without sample is the electric field emitted by the coherent nonlinear IS polarization, which has in the linear case a phase opposite to the input field. A THz transient of large amplitude [≈ 30 kV/cm], however, results in (i) a strong saturation of the coherent IS polarization and (ii) a phase shift of π of the emitted radiation after the complete inversion of the IS transition giving direct evidence for a Rabi flop of the Bloch vector.
[1] K. Reimann et al., Opt. Lett. (in print).