One Octave Supercontinuum Generation in Silicon Germanium on Silicon-Nitride Platforms for Mid-Infrared Applications

The development of on-chip supercontinuum generation (SCG) emitting over a wide wavelength range in the mid-infrared opens up new possibilities for applications such as molecular spectroscopy [1] and high-resolution imaging [2]. Mid-IR supercontinuum generation have been demonstrated using silicon-germanium waveguides on silicon substrate, but these typically require a relatively high input power, more than 3kW coupled power are used to achieve broad supercontinuum [3]. This is partly due to the relatively low index contrast provided by the SiGe/Si platform <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(\Delta \mathrm{n}\sim 0.1143\ \text{at}\ \lambda=4\mu \mathrm{m})$</tex>. Other materials, like silicon nitride are also compatible with the mid-IR range, while affording a larger index contrast with silicon germanium <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(\Delta \mathrm{n}\sim 1.1461\ \text{at}\ \lambda=4\mu \mathrm{m})$</tex>, which can further boost the nonlinear <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\gamma$</tex> parameter that drives SCG. In addition, SiGe/ SiN platforms yield more opportunities for dispersion engineering, which is key to SCG. This new material platform thus appears to be very promising for the generation of mid-IR supercontinuum with reduced input pump power [4].