A chip-integrated comb-based microwave oscillator

TL;DR

This paper presents the first fully integrated chip that generates low-noise microwaves using a microcomb, combining multiple photonic and electronic components for high-performance microwave signals.

Contribution

It introduces a novel, fully integrated microcomb-based microwave oscillator chip with hybrid integration of laser, microresonator, and photodetector in CMOS-compatible manufacturing.

Findings

Achieved 6.3 mHz linewidth microwave output.

Generated 10.7 GHz microcomb with high stability.

Demonstrated low phase noise suitable for advanced applications.

Abstract

Low-noise microwave oscillators are cornerstones for wireless communication, radar and clocks. Optical frequency combs have enabled photonic microwaves with unrivalled noise performance and bandwidth. Emerging interest is to generate microwaves using chip-based frequency combs, namely microcombs. Here, we demonstrate the first, fully integrated, microcomb-based, microwave oscillator chip. The chip, powered by a microelectronic circuit, leverages hybrid integration of a DFB laser, a nonlinear microresonator, and a high-speed photodetector. Each component represents the best of its own class, yet allows large-volume manufacturing with low cost in CMOS foundries. The hybrid chip outputs an ultralow-noise laser of 6.9 Hz linewidth, a microcomb of 10.7 GHz repetition rate, and a 10.7 GHz microwave of 6.3 mHz linewidth -- all three in one entity of 76 mm$^2$ size.The microwave phase noise reaches -75/-105/-130 dBc/Hz at 1/10/100 kHz Fourier offset frequency. Our results can reinvigorate our information society for communication, sensing, timing and precision measurement.