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

Abstract

The carrier dynamics in an electrically pumped InAs quantum-dot amplifier emitting near 1.3-μm-wavelength at room temperature is measured with femtosecond time resolution performing a pump–probe and a four-wave mixing experiment resonant to the dot ground–state transition. In contrast to the dynamics of the absorption bleaching over hundreds of picoseconds, an ultrafast gain recovery is measured, promising for high-speed applications of strongly confined InAs dots. Moreover, a dephasing time of 220 fs is measured in the 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 et al., Appl. Phys. Lett. 76, 1380 (2000)] indicating that the strong confinement can indeed lower the homogeneous broadening under electrical injection.