Twofold gain enhancement by elongation of QDs in polarization preserving QD-SOAs

The impact of quantum dot (QD) elongation on key parameters of QD-based semiconductor optical amplifiers (SOAs) is investigated using a combination of 8-band $k\cdot p$-theory including strain and piezoelectricity up to second order and a rate equation model describing the population of QD ground, excited and wetting layer states. By considering columnar QDs of selected aspect ratios, we show that chip gain and saturation gain can be enhanced by up to +3.6 dB via an increased elongation of the individual QDs while retaining polarization preserving amplification and gain recovery times below 700 fs. Our results enable the optimization of polarization preserving QD-SOA devices which combine ultrafast gain recovery with high gain and low power consumption. (paper)