Time-resolved emission from self-assembled single quantum dots using scanning near-field optical microscope

We study time-resolved emission from self-assembled single InGaAs/GaAs quan tum dots by the time-correlated single photon counting method using near-fi eld optical microscopy. The decay time of the emission fi um discrete level s of a single quantum dot increases with the decrease in the emission energ y and with the increase in the excitation intensity. We develop a rate equa tion model which accounts for the initial filling of the states, cascade re laxation, state filling and carrier feeding from a wetting layer. High coll ection efficiency of a double-tapered-type fiber probe enables us to study the emission even at very weak excitation intensities. The direct excitatio n into a single dot is dominant at this excitation level, State filling, ca scade relaxation and extra carrier feeding from the wetting layer become pr onounced when the excitation intensity increases.