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 ${\text{SiO}}_2$ 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 ${\sigma }_{\text{FCA}}=\left(3.6\pm 1.4\right)\times {10}^{-17}{\text{cm}}^2$, 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.

© 2009 Optical Society of America

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