Ultrafast carrier dynamics and dephasing in InAs quantum-dot amplifiers emitting near 1.3-mu m-wavelength at room temperature

The carrier dynamics in an electrically pumped InAs quantum-dot amplifier e mitting near 1.3-mum-wavelength at room temperature is measured with femtos econd time resolution performing a pump-probe and a four-wave mixing experi ment resonant to the dot ground-state transition. In contrast to the dynami cs of the absorption bleaching over hundreds of picoseconds, an ultrafast g ain recovery is measured, promising for high-speed applications of strongly confined InAs dots. Moreover, a dephasing time of 220 fs is measured in th e absorption and of 150 fs in the gain case. This latter value is more than three times longer than our previous finding on less-confined quantum dots [P. Borri , Appl. Phys. Lett. 76, 1380 (2000)] indicating that the strong confinement can indeed lower the homogeneous broadening under electrical in jection. (C) 2001 American Institute of Physics.