Theoretical investigation on gain recovery dynamics in step quantum well semiconductor optical amplifiers

In this paper, gain recovery dynamic characteristics in the step quantum well (QW) semiconductor optical amplifier (SOA) are theoretically investigated via a detailed model. We numerically solve the coupled rate equations including microscopically calculated carrier-phonon scattering rates between the carrier reservoir and the ground state on the basis of Fermi’s golden rule. The carrier-phonon scattering rates are given as functions of the width and height of the step in the QW of the SOA. It is demonstrated that the electron scattering rate in the step QW SOA depends on the potential parameters of the carrier reservoir region. Finally, it is shown that the SOA with a larger transition rate has a shorter carrier recovery time than the other SOAs via analyzing and comparing the gain and phase recovery dynamics in different types of SOA samples.