Near-infrared free-carrier absorption in silicon nanocrystals

Abstract

We report quantification of the free-carrier absorption (FCA) cross section in silicon nanocrystals embedded in a thin SiO(2) film at 1540 nm using a collinear pump-probe method. To this end, we measured the pump-intensity dependence of both the light transmission through the film and the photoexcited carrier density in the nanocrystals. From these measurements, we extracted a FCA cross section of sigma(FCA)=(3.6+/-1.4)x10(-17) cm(2), consistent with previous results in the visible range and the known lambda(2) scaling behavior of this quantity. Given the rapidly rising prevalence of silicon-based active photonic devices, our finding assumes particular significance for Si-nanocrystal-sensitized rare-earth-atom lasers and all optical switches at important telecom wavelengths.