Microwave frequency synthesis via multifrequency self-injection locking

In this work we propose using the multifrequency self-injection locking effect for microwave frequency synthesis. This regime is obtained by locking several modes of a free-spectral-range-tunable Fabry–Pérot laser to adjacent modes of an integrated Si3N4 microring resonator with a free spectral range of 15 GHz. A microwave signal is generated via beating of the locked laser frequencies on a fast photodetector. The single-sideband phase noise is found to be -50 dBc/Hz at 10^4 Hz and -90 dBc/Hz at 5*10^5 Hz. Found regimes demonstrate significant potential for generating low-phase-noise microwave signals and have substantial implications for telecommunications, microwave photonics, sensing, and radio-over-fiber systems.