Coherent Optical-to-Microwave Link Using an Integrated Microcomb

Microcombs are advancing optical frequency comb technology towards a chip-integrable form. Here, we characterize a microwave signal source based upon the two-point optical frequency division (2P-OFD) technique. The system uses a frequency microcomb to transfer relative frequency stability of two low-noise optical oscillators to the microcomb repetition rate tone. The two optical oscillators are based on semiconductor lasers jointly stabilized to an ultra-stable Fabry–Pérot cavity. The coherence of the comb spectrum is confirmed through multiple stability comparisons between its repetition rate and comb line spectrum. The results underscore the excellent performance of microcombs as coherent links between optical and microwave frequencies, and how they enable simplified, miniaturized architectures for optical frequency division.