The influence of series resistance on the longitudinal spatial hole burning in semiconductor optical amplifier

The longitudinal spatial hole burning (LSHB) in semiconductor optical amplifiers (SOA) is investigated using an improved wideband numerical model. The main new feature of the model is that it takes into account the current self-distribution effect, which induced by the axial variations of the separation between quise-Fermi levels in active region. The current self-distribution effect leads to the nonuniform current injection, and it tends to smoothen the carrier density distribution over the active region and reduces the strength of LSHB. It is found that the internal series resistance of SOA, which comes from mental-semiconductor Ohmic contacts, heterointerface and semiconductor bulk resist, significantly influences the strength of current self-distribution effect. The assumption of current injected uniformly gives rise to an overestimation of the strength of LSHB in SOA. The simulation results also show that the series resistance influences the gain and noise figure of SOA greatly. It is proposed that reducing the series resistance can enhance the small signal gain and reduced the noise figure of SOA efficiently.