Time-resolved measurements of optical gain and photoluminescence in silicon nanocrystals

In this paper, we present time-resolved optical gain spectroscopy using a combination of the variable stripe length and the shifting excitation spot techniques under pulsed nanosecond excitation at 355 nm. Optical gain measurements in the temporal detection window of 10 ns width, coincident with the excitation pulse, revealed induced absorption losses, whereas measurements with a different detection gate width and delay in two main photoluminescence components (a fast band at ~430 nm decaying in nanoseconds and a slow band at ~620 nm decaying in microseconds) show a positive optical gain of the order of tens of cm-1.