26th Australian Institute of Physics Congress and the Australian and New Zealand Conference on Optics and Photonics

Phase-locked dual soliton crystal microcombs

Not scheduled

20m

Belinda Hutchinson Building (The University of Sydney )

Contributed Oral ANZOS | Photonics and Optics (ANZCOP)

Description

Optical microcombs are light sources that can offer a multitude of wavelength lines for many applications ranging from optical communications to spectroscopy. Thanks to their phase coherence, they could replace individual lasers at both transmitter and receiver sides, reducing complexity and easing signal processing since the wavelength lines share the same phase noise. The coherence can be further improved when the dual combs are phase locked. This provides the finer accuracy required for dual-comb spectroscopy and enables joint-phase compensation in coherent communications systems. Although sharing- and recycling- pump generation have been demonstrated for phase-locked dual combs, the techniques face challenges in the microcomb regime due to bulk optics, a small number of comb lines from electro-optic modulation, and the fact that two devices for microcomb generation might require different pump wavelengths.

Therefore, in this work, we demonstrate dual-microcomb (soliton crystals) generation using optical injection locking. This approach regenerates a comb line from the first microcomb (leader) to pump the second microcomb (follower), which operates at a different pump wavelength from the leader. By utilising two microring resonators with similar free spectral ranges (FSRs), we heterodyne the dual microcombs and witness RF comb linewidth broadening from 100 to 500 kHz. Since the dual-microcombs are mutually locked optically, while their repetition rates are free-running, the linewidth broadening might stem from the independent repetition rate noise.

With the external locking from an RF source for pump intensity or wavelength modulation on both sides, the repetition rate noise is reduced, which could improve the heterodyne RF linewidth. This is particularly useful for spectroscopy, where sub-kHz RF linewidth enables higher precision and long-term averaging. Meanwhile, if the dual microcombs are locked to the same RF frequency, they can enhance joint-phase estimation in communications systems.