Novel scheme of assist-light injection through waveguide coupling in a semiconductor optical amplifier for fast gain recovery

We propose a novel scheme for injection of assist-light into the active region of a semiconductor optical amplifier (SOA) for fast gain recovery. In the proposed scheme, the assist-light is coupled into the active region of the SOA through an adjacent channel waveguide. Numerical results based on the well established model for carrier dynamics in SOA show that the gain recovery is faster in the proposed scheme as compared to the earlier reported scheme of counter-propagating assist-light injection. Our analysis shows that a desired power profile of the assist-light can be maintained in the active region of the SOA by tailoring the coupling through suitable design of the adjacent channel waveguide. The dependence of gain recovery on the input power of the assist-light in the proposed scheme has also been studied. Under typical operating conditions, it is found that 20 dBm of assist-light power injection in the proposed scheme is as effective as 27 dBm of assist-light power in the counter-propagating scheme.