Soliton pulse pairs at multiple colors in normal dispersion microresonators
Soliton microcombs are helping to advance the miniaturization of a range of comb systems. These combs mode lock through the formation of short temporal pulses in anomalous dispersion resonators. Here, a new microcomb is demonstrated that mode locks through the formation of pulse pairs in normal-dispersion coupled-ring resonators. Unlike conventional microcombs, pulses in this system cannot exist alone, and instead must phase lock in pairs to form a bright soliton comb. Also, the pulses can form at recurring spectral windows and the pulses in each pair feature different optical spectra. This pairwise mode-locking modality extends to higher dimensions and we demonstrate 3-ring systems in which 3 pulses mode lock through alternating pairwise pulse coupling. The results are demonstrated using the new CMOS-foundry platform that has not previously produced bright solitons on account of its inherent normal dispersion. The ability to generate multi-color pulse pairs over multiple rings is an important new feature for microcombs. It can extend the concept of all-optical soliton buffers and memories to multiple storage rings that multiplex pulses with respect to soliton color and that are spatially addressable. The results also suggest a new platform for the study of quantum combs and topological photonics.
Additional InformationAttribution 4.0 International (CC BY 4.0). The authors thank Chao Xiang for providing the optical images of the resonators. This work is supported by the Defense Advanced Research Projects Agency (HR0011-22-2-0009), the Defense Threat Reduction Agency-Joint Science and Technology Office for Chemical and Biological Defense (grant No. HDTRA11810047), the Air Force Office of Scientific Research (FA9550-18-1-0353) and the Kavli Nanoscience Institute at Caltech. The content of the information does not necessarily reflect the position or the policy of the federal government, and no official endorsement should be inferred. Author Contributions: Concepts were developed by Z.Y., M.G., Y.Y., H.W., W.J., J.B. and K.V. Measurements and modeling were performed by Z.Y., M.G., Y.Y., H.W., W.J., Q.-X.J. Structures were designed by W.J. and H.W. Sample preparation and logistical support provided by A.F. and M.P. All authors contributed to the writing of the manuscript. The project was supervised by J.B. and K.V. Data Availability. The data that supports the plots within this paper and other findings of this study are available from the corresponding author upon reasonable request. Code Availability. The codes that support findings of this study are available from the corresponding author upon reasonable request. The authors declare no competing interests.
Submitted - 2301.10976.pdf