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(Color online) Schematic diagram of the double SL structure and the geometry of the pump-probe experiments. The samples consist of a thick GaAs layer of 1.2 or between two identical SLs.
Time-domain data for samples and . Pump pulses generate sound waves on the front superlattice, that are later detected on the front (a) and the back side (b) of the sample. Trace (a) and the inset of (b), obtained on sample , show folded phonon oscillations superimposed on the larger, low frequency oscillations associated with stimulated Brillouin scattering.
(Color online) (a) Fourier transform of the time trace for sample A. We observe three peaks that correspond to the backscattering (BS) and forward scattering (FS) modes accessible in Raman experiments; (b) calculated spectrum for the double SL structure, where the probe is incident on the second SL and (c) calculated spectrum for a semi-infinite structure showing the BS doublet. The lower panel shows the dispersion relation for an infinite SL.
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