Ultrafast gain dynamics in 1.3 μm InAs/GaAs quantum-dot optical amplifiers:: The effect of p doping

Ultrafast gain dynamics of the ground-state transition are measured in electrically pumped InAs/GaAs quantum-dot amplifiers emitting near 1.3 mu m at room temperature. Gain recovery on a subpicosecond time scale occurs at high electrical injection. However, when comparing p-doped and undoped devices fabricated under identical conditions and operating at the same gain, faster absorption recovery but slower gain dynamics are observed in p-doped amplifiers. The slower gain dynamics is attributed to a reduced reservoir of excited-state electrons in p-doped quantum-dot devices, which limits the recovery of the electron ground-state occupation mediated by intradot carrier-carrier scattering. (C) 2007 American Institute of Physics.