Observation of interband Kelly sidebands in coupled-ring soliton microcombs

Creators: Gao, Maodong; Yuan, Zhiquan; Yu, Yan; Jin, Warren; Ji, Qing-Xin; Ge, Jinhao; Feshali, Avi; Paniccia, Mario; Bowers, John E.; Vahala, Kerry J.¹

1. California Institute of Technology

Abstract

Kelly sidebands are a special type of dispersive wave that appear in mode-locked systems and they have recently been observed by pulsed excitation in integrated microcombs. Here, Kelly sidebands are generated by continuous-wave excitation in a partially coupled racetrack-resonator microcomb. The coupled-racetrack system supports two optical bands so that, in contrast to earlier studies, the soliton and Kelly sideband reside in distinct bands. The resulting interband excitation of the Kelly sidebands relaxes power requirements and continuous-wave sideband excitation is demonstrated. Tuning of sideband spectral position under pulsed excitation is also studied. Numerical simulation and the experiment show that the sidebands rely upon symmetry breaking caused by partial coupling of the two-ring system. More generally, multiband systems provide a new way to engineer Kelly sidebands for spectral broadening of microcombs.

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Acknowledgement

The authors thank Peng Liu, Dr. Hao-Jing Chen, and Joel Guo for helpful discussions. 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.

Contributions

Concepts were developed by M.G., Z.Y., Y.Y., J.B., and K.V. Measurements and modeling were performed by M.G., Z.Y., Y.Y., Q.-X.J., and J.G. Sample preparation and logistical support provided by W.J., A.F., and M.P. All authors contributed to the writing of the manuscript. The project was supervised by J.B. and K.V.

Funding

Air Force Office of Scientific Research (FA9550-23-1-0587); Defense Advanced Research Projects Agency (HR0011-22-2-0009, W911NF2310178); Kavli Nanoscience Institute, California Institute of Technology.

Data Availability

Data underlying the results presented in this paper are not publicly available at this time but may be obtained from the corresponding author, K. V., upon reasonable request.

Conflict of Interest

The authors declare no conflicts of interest.

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