Effects of Shockley-Read-Hall recombination on the reflection sensitivity of quantum dot lasers directly grown on silicon

Abstract

Photonics integrated circuits on silicon are considered as a key technology for data centers and high-performance computers. Owing to the ultimate carrier confinement and reduced sensitivity to crystalline defects, semiconductor quantum dot lasers directly grown on silicon exhibit remarkable properties such as low threshold current, high temperature stability and robust tolerance to external reflections. This latter property is particularly important for achieving large-scale integrated circuits whereby unintentional back-reflections produced by the various passive/active optoelectronic components can hinder the stability of the lasers. In this context, it is known that quantum dot lasers are more resistant to optical feedback than quantum well ones thanks to the low linewidth enhancement factor, the large damping, and the possible absence of upper lasing states. In this work, we theoretically investigate the reflection sensitivity of quantum dot lasers directly grown on silicon by studying the peculiar role of the epitaxial defects, which induce nonradiative recombination through the Shockley-Read-Hall process. By using the Lang and Kobayashi model, we analyze the nonlinear properties of such quantum dot lasers through the bifurcation diagrams and with respect to the nonradiative lifetime. In particular, we show that the increase of the Shockley-Read-Hall recombination shrinks the chaotic region and shifts the first Hopf bifurcation to higher feedback values. We believe that these results can be useful for designing novel feedback resistant lasers for future photonics integrated circuits operating without optical isolator.