Linearity and nonlinearity of quantum-dot semiconductor optical amplifiers

Linearity and nonlinearity of quantum-dot semiconductor optical amplifiers (QD-SOAs) are analyzed in this paper using numerical and analytical solutions. The basic formulas are derived from rate equations of multiple-states QD-SOAs. The solutions reveal that linearity and nonlinearity of QD-SOAs, which is quantificationally characterized by the maximal linear output power and the nonlinear factor, are strongly dependent on injected current, modal gain and spontaneous radiative lifetime. Additionally, the solutions also provide some useful suggestions in designing and using of QD-SOAs, either be used in linear or nonlinear operational region.