Excited State Contribution To Gain Integral In Quantum Dot Semiconductor Optical Amplifiers

Earlier, the gain integral in the quantum dot (QD) semiconductor optical amplifiers (SOAs) was calculated from an SOA bulk-like relation, and QD layers' characteristics were not considered. This work predicts the gain integral in the QD SOAs, considering a three-level (3-L) QD system (wetting layer WL, excited state ES, and ground state GS). In this new model, the QD capture time is redefined by an effective value covering occupation probability and relaxations instead of the capture time defining the transition to the GS from the WL that was used earlier. The GS in the 3-L model exhibits the fastest time recovery (0.49ps). This property (in addition to the two contributions from WL and ES) makes the GS in the 3-L model have the highest occupation.