Photoluminescence up-conversion of single InAs/GaAs quantum dots

We report the observation of an efficient photoluminescence up-conversion in single InAs/GaAs quantum dots by micro-photoluminescence measurements under cw-excitation. Power dependent measurements show a nearly quadratic dependence of the up-converted photoluminescence signal from the quantum dots (QDs). The intermediate states that allow the efficient photoluminescence up-conversion are deep electronic states located at the vicinity of the QDs. This observation of photoluminescence up-conversion demonstrates the influence on the quantum dot properties of its environment.