Nonlinear Rabi Oscillations of Excitons in Dense Quantum Dot System

Nonlinear optical response and optical coherence of excitons in semiconductor dense quantum dots in GaAs single quantum wells has been studied by using photon echo techniques. At low temperatures, the optical coherence is estimated to be 2 ns from the decay curve in the photon echo signal. Rabi oscillations are also observed. Unlike the results for a single quantum dot in the literature to date, the oscillation shows nonlinear behavior affected strongly by the pre-excited carrier density. The results can be explained by the theory of the local field correction originating from exciton-exciton interaction between the inter dots.