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Nonuniform DFB-SOAs: dynamic Characteristics of bistability and a novel configuration based on linearly variable current injection

Starting from the coupled-mode equation and carrier rate equation, this paper has analyzed numerically the bistable dynamic characteristics of phased-shifted and chirped distributed-feedback semiconductor optical amplifiers (DFB-SOAs). The results show that phase shift first worsens the shape distortion of the falling edge of the output pulse and then alleviates it with the decreased initial detuning. This tendency can be suppressed by introducing chirp. We also proposed a novel configuration based on linearly variable current injection, which not only enhances the on-off switching ratio, but also has a similar transmission spectrum with phase-shift effects and similar bistable features, such as the wide frequency band and the flat upper branch of the hysteresis, with chirp effects.