Power-Dependent Spin Amplification In (In, Ga) As/Gaas Quantum Well Via Pauli Blocking By Tunnel-Coupled Quantum Dot Ensembles

Power-dependent time-resolved optical spin orientation measurements were performed on In0.1Ga0.9As quantum well (QW) and In0.5Ga0.5As quantum dot (QD) tunnel-coupled structures with an 8-nm-thick GaAs barrier. A fast transient increase of electron spin polarization was observed at the QW ground state after circular-polarized pulse excitation. The temporal maximum of polarization increased with increasing pumping fluence owing to enhanced spin blocking in the QDs, yielding a highest amplification of 174% with respect to the initial spin polarization. Further elevation of the laser power gradually quenched the polarization dynamics, which was induced by saturated spin filling of both the QDs and the QW phase spaces. (C) 2016 AIP Publishing LLC.