Theoretical analysis of ultra-fast phase recovery in semiconductor optical amplifiers

We present results from theoretical analysis of the phase dynamics in semiconductor optical amplifiers (SOAs). In particular, we focus on an aspect of the ultra-fast phase recovery that currently does not have adequate in-depth theoretical analysis and clear explanation of the physical mechanism. We build up a numerical model to analyze the ultra-fast phase recovery of semiconductor optical amplifiers in details. To investigate the phase response characteristics, we analyze the different contributions to the phase shift, including intra-band effects such as carrier heating, spectral hole burning, and inter-band effects such as carrier depletion. In addition, the impact of the pulses energy on phase shift is also investigated. Based on the analysis of phase response characteristics, we further explain the reason why a delay occurs between gain response and phase response. The analysis results are in good agreement with the reported experimental results. The results presented in this paper are useful for the SOA-based ultra-fast optical signal processing, such as optical switches, optical logic gates, and optical Add/Drop multiplexer.