Time-resolved gain dynamics in silicon nanocrystals

Time-resolved variable stripe length (VSL) experiments on a set of silicon nanocrystal waveguides obtained by plasma enhanced chemical vapor deposition (PECVD) have revealed a fast recombination dynamics (20 ns) related to population inversion under 6 ns optical pumping at 355 nm. Modal gain values about 10 cm(-1) have been measured at 760 run by VSL technique for the fast recombination component while optical losses about 15 cm(-1) are measured for the integrated signal in the slow (lifetime of about 10 mus) recombination tail. Threshold behavior in the emission intensity together with a pumping length and pumping power dependence of both the intensity and the time duration of the fast recombination component has been observed. These results are explained within an effective four level model to describe the strong competition among different Auger processes and stimulated emission.