  In an oxide apertured quantum dot (QD) micropillar cavity-QED system, we
found strong QD hysteresis effects and lineshape modifications even at very low
intensities corresponding to less than 0.001 intracavity photons. We attribute
this to the excitation of charges by the intracavity field; charges that 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 lineshape modifications. The cavity also enables us to observe the QD
dynamics in real time, and all experimental data agrees well with a power-law
charging model. This effect can serve as a novel tuning mechanism for quantum
dots.
