Coherent mid-infrared frequency combs in silicon-microresonators in the presence of Raman effects.

We demonstrate the first low-noise mid-IR frequency comb source using a silicon microresonator. Our observation of strong Raman scattering lines in the generated comb suggests that interplay between Raman and four-wave mixing plays a role in the generated low-noise state. In addition, we characterize, the intracavity comb generation dynamics using an integrated PIN diode, which takes advantage of the inherent three-photon absorption process in silicon.