Impact of Coulomb scattering on the ultrafast gain recovery in InGaAs quantum dots.

Institut fu¨r Theoretische Physik, Technische Universita¨t Berlin, 10623 Berlin, Germany(Received 6 June 2008; published 16 December 2008)The application of quantum dot (QD) semiconductor optical amplifiers (SOAs) in above 100-GbitEthernet networks demands an ultrafast gain recovery on time scales similar to that of the input pulse 100 GHz repetition frequency. Microscopic scattering processes have to act at shortest possible timescales and mechanisms speeding up the Coulomb scattering have to be explored, controlled, andexploited. We present a microscopic description of the gain recovery by coupled polarization- andpopulation dynamics in a thermal nonequilibrium situation going beyond rate-equation models anddiscuss the limitations of Coulomb scattering between 0D and 2D-confined quantum states. An experi-ment is designed which demonstrates the control of gain recovery for THz pulse trains in InGaAs QD-based SOAs under powerful electrical injection.