Compact optical frequency comb source based on a DFB butt-coupled to a silicon nitride microring

We demonstrate an integrated Kerr frequency comb source based on the butt coupling between a III-V DFB laser and a silicon nitride (Si3 N4) microresonator. The 30-dB bandwidth of the optical comb is measured to be 148.7 nm (18 THz), centered at 1576 nm, which is, to the best of our knowledge, the largest ever measured on an ultra-compact source. This hybrid compact source can also be used for soliton investigations.