Two-color femtosecond strobe lighting of coherent acoustic phonons emitted by quantum dots

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The transient acoustic pulse emitted by a single InAs quantum dots layer was measured depending on the pump wavelength. By tuning the pump wavelength through the transition energies of the GaAs barrier, the wetting layer and the quantum dots themselves, the acoustic phonon emission is shown to be strongly correlated to the electronic structure of the quantum dots layer system. The contributions of the wetting layer and the quantum dots to the acoustic signal were clearly identified and quantified by comparing different regions of the same sample containing or not quantum dots.