Low-Phase-Noise Microwave Generated by an Optical Frequency Comb Locked to an On-Chip Interferometer

We generated a low-phase-noise microwave by stabilizing an optical frequency comb with a 56.5-cm long photonic-integrated Mach-Zehnder interferometer that was fabricated in a commercial foundry. The phase noise of the 9.987-GHz tone was −105 dBc/Hz at a 1-kHz offset frequency, corresponding to a reduction of the free-running phase noise by 15 dB. Our results point towards a fully integrated low-phase-noise microwave source.