Observation of laser oscillation in aggregates of ultrasmall silicon nanoparticles

We report laser oscillation at ∼610 nm in aggregates of ultrasmall elemental Si nanoparticles. The particles are ultrabright red emitting, dispersed from bulk Si by electrochemistry. The aggregates are excited by radiation at 550–570 nm from a mercury lamp. Intense directed Gaussian beams, with a threshold, manifest the emission. We observe line narrowing, and speckle patterns, indicating spatial coherence. This microlasing constitutes an important step towards the realization of a laser on a chip, hence optoelectronics integration and optical interconnects.