Gain dynamics and ultrafast spectral hole burning in In(Ga)As self-organized quantum dots

Abstract

Using a femtosecond three-pulse pump-probe technique, we investigated spectral hole-burning and gain recovery dynamics in self-organized In(Ga)As quantum dots. The spectral hole dynamics are qualitatively different from those observed in quantum wells, and allow us to distinguish unambiguously the gain recovery due to intradot relaxation and that due to carrier capture. The gain recovery due to carrier–carrier scattering-dominated intradot relaxation is very fast $\text{(∼130\hspace{0.17em}}\mathrm{fs}\mathrm{),}$ indicating that this is not the factor limiting the bandwidth of directly modulated quantum dot lasers.