Accelerating gain and phase recovery in Quantum-Dot reflective Semiconductor optical Amplifier: Unraveling the influence of inhomogeneous broadening and pumping power for enhanced performance

This investigation examines the complex interaction between inhomogeneous broadening (IHB) and pumping power concerning the gain and phase recovery dynamics of Quantum-Dot (QD) Reflective Semiconductor Optical Amplifiers (RSOAs). An improved QD-RSOA model, employing coupled rate equations and incorporating IHB effects and amplified spontaneous emission is used to model and compare ultrafast gain and phase recovery responses in QD-SOAs and QD-RSOAs for an electrical and two single-color optical pumping schemes. Analysis of the contributions from QD states and Quantum Well (QW) carrier reservoirs to phase changes provides valuable insights. A reduction in IHB leads to an accelerated phase response by diminishing the slow phase recovery components for the QD ground and excited states, and so reducing the contributions from slow phase recovery in carrier reservoirs. Across all pumping schemes, the QD-RSOA exhibits more pronounced phase recovery acceleration. Despite achieving ultrafast gain and phase recovery responses observed in QD-RSOAs when subjected to electrical pumping, a significant overshoot in the phase recovery response is observed. This overshoot leads to a potentially significant chirping and distortion in amplified optical pulses. The study suggests that in long QD-SOAs and QD-RSOAs with higher gain, optical pumping schemes offer a promising strategy for achieving phase recovery acceleration without introducing distortion, which is important for applications of QD-SOAs.