Energy dependence of the linear and dynamical photo-induced dichroisms of InAs/GaAs quantum dots
Résumé
We present pump-probe measurements of the photo-induced dynamics of the lowest electron-hole (e-h) transitions in ensembles of InAs/GaAs quantum dots, as a function of interband emission energy 1.30-1.40 eV. We used two different beam-polarization configurations to obtain information on the electronic structure of both e-h states, and on their relaxation and decoherence. In linear dichroism experiments, we address the population evolution of the e-h states: we measured two different e-h radiative times, with almost constant mean value 1 ns and ratio 0.8-0.9. In dynamical dichroism experiments, we observe the evolution of the coherence between the e-h states: we deduced an inhomogeneous decoherence time 10-25 ps, and an energy splitting monotonically decreasing with emission energy, from 80 to 20 mu eV.