Gain Dynamics in Quantum-Dot Semiconductor Optical Amplifiers at 1550 nm

We report an experimental study of the gain recovery of an InAs-InGaAsP-InP columnar-quantum-dot semiconductor optical amplifier around 1550 nm. We find a three-step recovery process that gives around 85% gain recovery in only 10 ps and 100% in around 30 ps in case of a quite complete gain saturation. We also give a possible physical explanation for the peculiar gain dynamics.