Spiral resonator referenced low noise microwave generation via integrated optical frequency division

A low noise oscillator is a crucial component in determining system performance in modern communication, microwave spectroscopy, microwave-based sensing (including radar and remote sensing), and metrology systems. In recent years, ultra-low phase noise photonic microwave oscillators based on optical frequency division have become a paradigm shift for the generation of high performance microwave signals. In this work, we report on-chip low phase noise photonic microwave generation based on spiral resonator referenced lasers and an integrated electro-optical frequency comb. Dual lasers are co-locked to an ultra-high- Q silicon nitride spiral resonator and their relative phase noise is measured below the cavity thermal noise limit, resulting in record low on-chip optical phase noise. A broadband integrated electro-optic frequency comb is utilized to divide down the relative phase noise of the spiral resonator referenced lasers to the microwave domain, resulting in record-low phase noise for chip-based oscillators (−69 dBc /Hz at 10 Hz offset, and −144 dBc /Hz at 10 kHz offset for a 10 GHz carrier scaled from 37.3 GHz output). The exceptional phase noise performance, planar chip design, high technology readiness level, and foundry-ready processing of the current work represent a major advance of integrated photonic microwave oscillators.