Quantum dot nonlinearity through cavity-enhanced feedback with a charge memory

In an oxide apertured quantum dot (QD) micropillar cavity-QED system, we observe strong QD hysteresis effects and line-shape modifications even at very low intensities corresponding to <10(-3) intracavity photons. We attribute this to the excitation of charges by the intracavity field; they get trapped at the oxide aperture, where they screen the internal electric field and blueshift the QD transition. This in turn strongly modulates light absorption by cavity-QED effects, eventually leading to the observed hysteresis and line-shape modifications. The cavity also enables us to observe the QD dynamics in real time, and all experimental data agree well with a power-law charging model. The observed charging effect can serve as a tuning mechanism for quantum dots.