Efficient, broadband third-harmonic generation in silicon nanophotonic waveguides spectrally shaped by nonlinear propagation

Optical emission from silicon is most practically accessible through nonlinear optical wave mixing, due to the indirect bandgap of the material. Although silicon is a material that absorbs visible light, third-harmonic generation driven by infrared signals can be used to generate visible light in silicon structures. In this work, we present a comprehensive investigation into thirdharmonic generation in silicon-on-insulator waveguides. We demonstrate that few-micrometer length waveguides can be used to up-convert ultrafast 1550nm laser pulses to their third-harmonic with efficiencies up to eta(TH)(G) = 2.8 x 10(-5), the highest third-harmonic generation conversion efficiency reported to date in a silicon-based structure. Nonlinear propagation through 200 mu m long waveguides produces self-compressing temporal solitons, which dramatically broaden and blue shift the observed third-harmonic spectrum. Such devices are envisioned to provide a method for generating coherent visible signals within an integrated, CMOS compatible platform. (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement