Radiatively limited dephasing in InAs quantum dots

We measure the dephasing time of the exciton ground-state transition in In1-xGaxAs quantum dots using a sensitive four-wave mixing technique. We find experimental evidence that the dephasing time is given only by the radiative lifetime at low temperatures. We demonstrate the tunability of the radiatively limited dephasing time from 400 ps up to 2 ns in a series of annealed In1-xGaxAs quantum dots with increasing quantum-confinement energy from 69 meV to 330 meV.