Soliton crystals in Kerr resonators


Self-organized solitons confined to an optical resonator would offer unique capabilities for experiments in communication, computation and sensing with light. Here, we report the observation of soliton crystals in monolithic Kerr microresonators—spontaneously and collectively ordered ensembles of co-propagating solitons whose interactions discretize their allowed temporal separations. We unambiguously identify and characterize soliton crystals through analysis of their ‘fingerprint’ optical spectra, which arise from spectral interference between the solitons. We identify a rich space of soliton crystals exhibiting crystallographic defects and we perform time-domain measurements to directly confirm our inference of their crystal structure. Soliton crystallization is explained by long-range soliton interactions mediated by resonator mode degeneracies, and we probe the qualitative difference between soliton crystals and the disorganized soliton liquid that would form in the absence of these interactions. Our work explores the physics of monolithic Kerr resonators in a regime of dense soliton occupation and offers a way to increase the efficiency of Kerr combs. Furthermore, the extreme degeneracy of the configuration space of soliton crystals suggests an implementation for an on-chip optical buffer.

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Fig. 1: Generation of a soliton crystal using the Kerr nonlinearity in a χ (3)-nonlinear medium (here silica).
Fig. 2: Investigation of a superstructured crystal.
Fig. 3: A taxonomy of soliton crystals.
Fig. 4: Intensity cross-correlation measurements of crystal j from Fig. 3.


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The authors thank D. Hickstein and K. Beloy for comments on the manuscript and K.Y. Yang and K. Vahala for providing the 16 GHz wedge resonators. This material is based on work supported by the Air Force Office of Scientific Research under award no. FA9550-16-1-0016. Additional support was provided by the NIST-on-a-Chip programme and the DARPA QuASAR and PULSE programmes. D.C.C. acknowledges support from the NSF GRFP under grant no. DGE 1144083.

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E.S.L., D.C.C., P.D.’H. and S.B.P. performed the crystal generation experiments. D.C.C. analysed the data, developed the model, and performed the numerical simulations. E.S.L. performed the cross-correlation experiments. D.C.C. wrote the manuscript. All authors discussed the experiments and the model and contributed to revision of the manuscript.

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Correspondence to Daniel C. Cole.

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Soliton crystals in Kerr resonators

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Cole, D.C., Lamb, E.S., Del’Haye, P. et al. Soliton crystals in Kerr resonators. Nature Photon 11, 671–676 (2017).

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