Effect of Nonuniform Current Injection On a Tapered-Waveguide Quantum Dot Semiconductor Optical Amplifier

Quantum-dot semiconductor optical amplifiers (QD-SOAs) possess many advantages compared to conventional SOAs like high gain, wide-bandwidth of operation, and ultrafast gain recovery. However, a major shortcoming in QDSOAs is a reduction in the carrier density that occurs along the active-region, as light passes along it (the active-region). Tapered-waveguide QDSOAs (TW-QDSOAs) can compensate for this. In this paper, a tapered-waveguide quantum-dot semiconductor optical amplifier (TW-QDSOA) is modeled using the rate-equation model. These rate-equations are solved in turn by using the finite difference method (FDM). The influence of a nonuniform injection current profile on the output photon density of the TW-QDSOA is investigated. It is found that the positive impact of waveguide tapering on the output photon density is improved by using a nonuniform profile for the injection current.