Nonlinear carrier dynamics in silicon nano-waveguides

Abstract

Carrier recombination dynamics in strip silicon nano-waveguides is analyzed through time-resolved pump-and-probe experiments, revealing a complex recombination dynamics at densities ranging from $10^{14}$ to $10^{17}$cm${}^{-3}$. Our results show that the carrier lifetime varies as recombination evolves, with faster decay rates at the initial stages (with lifetime of $\sim 800$ps), and much slower lifetimes at later stages (up to $\sim 300$ns). We also observe experimentally the effect of trapping, manifesting as a decay curve highly dependent on the initial carrier density. We further demonstrate that operating at high carrier density can lead to faster recombination rates. Finally, we present a theoretical discussion based on trap-assisted recombination statistics applied to nano-waveguides. Our results can impact the dynamics of several nonlinear nanophotonic devices in which free-carriers play a critical role, and open further opportunities to enhance the performance of all-optical silicon-based devices based on carrier recombination engineering.