Poel, Mike van der2; Gehrig, Edeltraud5; Hess, Ortwin5; Birkedal, Dan4; Hvam, Jørn Märcher2
1 Nanophotonics, Department of Photonics Engineering, Technical University of Denmark2 Department of Photonics Engineering, Technical University of Denmark3 University of Surrey4 Department of Micro- and Nanotechnology, Technical University of Denmark5 University of Surrey
Ultrafast gain dynamics in an optical amplifier with an active layer of self-organized quantum dots (QDs) emitting near 1.3$muhbox m$is characterized experimentally in a pump-probe experiment and modeled theoretically on the basis of QD Maxwell–Bloch equations. Experiment and theory are in good agreement and show ultrafast subpicoseconds gain recovery followed by a slower 5 ps recovery. This behavior is found to be mainly caused by longitudinal optical phonon scattering and strongly dependents on electronic structure and confinement energy of the dots. A low amplitude-phase coupling ($alpha$factor) is theoretically predicted and demonstrated in the experiments. The fundamental analysis reveals the underlying physical processes and indicates limitations to QD-based devices.
I E E E Journal of Quantum Electronics, 2005, Vol 41, Issue 9, p. 1115-1123