Ultrafast gain and index dynamics of quantum dash structures emitting at 1.55μm

The authors systematically characterize the ultrafast gain and index recovery of a quantum dash semiconductor optical amplifier after it has amplified a strong femtosecond pulse. The results show a recovery dominated by a fast time constant of 1.4ps with an ultimate recovery taking place on a 150ps time scale. The results are distinctly different from the recovery of quantum dot amplifiers and reflect the special density of states of the quantum-wire-like dashes.