Large-Scale Photonic Chip Based Pulse Interleaver for Low-Noise Microwave Generation

We demonstrate a 64-times multiplication of a mode-locked laser’s 217 MHz pulse repetition rate to 14 GHz using an integrated Si3N4 interleaver. Six cascaded stages of Mach-Zehnder interferometers with up to 33 cm long optical delay lines are fully integrated into a very compact footprint of 8.5 mm × 1.7 mm. By overcoming photodetector saturation during the high power peak, the generated microwave power was improved by 36 dB, which reduces the phase noise floor by more than 10-fold to −160 dBc/Hz on the 14 GHz carrier.