Linear and dynamical photoinduced dichroisms ofInAs∕GaAsself-assembled quantum dots: Population relaxation and decoherence measurements

Abstract

We present and model our pump-probe experiments measuring the photoinduced dynamics of an ensemble of self-assembled $\mathrm{In}\mathrm{As}∕\mathrm{Ga}\mathrm{As}$ quantum dots. A pulsed pump beam, linearly polarized along an in-plane symmetry axis of the quantum dots, photoinduces a linear dichroism. We show that the dynamics of this linear dichroism is consistent with a long spin relaxation time and allows us to measure different radiative lifetimes for both nondegenerate, low-lying, electron-hole pair states. In another experimental configuration, when the pump beam creates a coherent superposition of these electron-hole pair states, it photoinduces a dynamical dichroism, which gives information about quantum decoherence and provides the electron-hole anisotropic exchange interaction energy splitting, $41\ifmmode\pm\else\textpm\fi{}8\phantom{\rule{0.3em}{0ex}}\ensuremath{\mu}\mathrm{eV}$ at $1.343\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$. A model is developed, which accounts for the dynamical dichroism and predicts the experimental observations with good accuracy.