  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 Raman and four-wave mixing interactions play a
role in assisting the transition to the 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.
