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We investigate the dynamic and static gain characteristics of quantum-dot semiconductor optical amplifiers (QD-SOAs) operating at 1.55 μ m based upon the experimental measurements performed on an InAs/InGaAsP/InP QD-SOA and simple modeling tools. A two-level rate equation model proved to be sufficient to explain the experimental gain dynamics as a function of current. The simple model allowed the derivation of the saturation power of QD-SOAs in the static regime. We show that the saturation power of QD-SOAs, in contrast to bulk and quantum well amplifiers, is enhanced by a factor of roughly two that depends on the material and device parameters. Our modeling tools are based on the experimentally obtained quantities and facilitates the analysis of different devices' designs and the identification of the parameters that play a key role in the fast QD-SOA gain recovery and its high saturation output power, namely, a fast capture time of carriers into the dot and a large energy difference between wetting layer and quantum dot states.

Time-resolved gain and phase dynamics of an InAs/InGaAsP/InP quantum-dot semiconductor optical amplifier are investigated. The recovery is dominated by an ultrafast component (~1 ps), indicating strongly that the gain medium is genuinely dot-like in character.

We propose a quasi-three-dimensional frequency-domain model to investigate the lasing modes of an InGaAsP/InP quantum-dot microdisk laser. The model requires a complex susceptibility to solve the electromagnetic fields of the microdisk laser. We use the model to investigate the size limitations of the quantum-dot laser by evaluating its performance through the cavity quality-factor ( Q -factor), from which the linewidth can be inferred. We find that higher order modes with high Q -factors (∼ 2.4 × 10 4 ) and consequently narrow linewidths (∼ 65 pm) propagating in the 1.5 μm wavelength region can be sustained in a microdisk laser with a radius as small as 1.6 μm and a thickness of 200 nm. Our model can be used to study other types of microdisks provided that the susceptibility of the medium is known.