Mid-infrared wavelength conversion in silicon waveguides using ultracompact telecom-band-derived pump source

Mid-infrared light sources are essential for applications that include free-space communication, chemical and biomolecular sensing and infrared spectroscopy(1-3), but no devices comparable to those in the near-infrared regime have emerged to date. Indeed, sources operating above 1.8 mu m, including optical parametric oscillators and thulium-doped fibre lasers, do not combine a large tunable range and narrow linewidth, and generally cannot be modulated to support advanced applications(4,5). Widely tunable mid-infrared quantum cascade lasers are available; however, room-temperature operation in the 3-4 mu m range still presents a challenge because of material limitations(6,7). Wavelength conversion in silicon offers promise for the development of an ultracompact mid-infrared source that combines wide wavelength tuning, narrow linewidth and arbitrarily complex modulation rivalling those in the telecom window. Here, we report four-wave mixing in silicon waveguides in the spectral region beyond 2 mm, using probe and pump waves derived from ultracompact telecom fibre-optic sources, achieving generation of 2,388 nm light.