Graded index silicon germanium photonics circuits in the mid-infrared (Invited Paper)

A photonics platform based on graded SiGe waveguides has been developed for operating in the mid-IR range, with experimental demonstrations up to 11 μm wavelength. Applications are related with absorption spectroscopy and sensing in the fingerprint region, and with free space communications. After an overview of the platform, the presentation will focus on: (i) integrated high speed modulators operating in a wide spectral range, based on free carrier plasma dispersion effect, (ii) integrated resonators operating around 8 μm wavelength with quality factors beyond 10⁵ . We will also show that mid-IR graded SiGe photonics circuits can be fabricated on industrial-scale 200 mm wafers, and that low propagation losses can be obtained in a wide spectral range of the mid-IR. These results thus pave the way for a scalable silicon compatible mid-infrared platform.