Single quantum dot states measured by optical modulation spectroscopy

Using optical modulation spectroscopy, we report the direct observation of absorption lines from excitons localized in GaAs single quantum dot potenti als. The data provide a measurement of the linewidth, resonance energy, and oscillator strength of the transitions, and show that states which decay p rimarily by nonradiative processes can be directly probed using this techni que. The experiments establish this technique for the characterization of s ingle quantum dot transitions, thereby complementing luminescence studies. (C) 1999 American Institute of Physics. [S0003-6951(99)00939-0].