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Degeneracy-locked optical parametric oscillator

Nature Photonics (2026)Cite this article

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Abstract

Optical parametric oscillators (OPOs) are widely utilized in photonics as classical and quantum light sources. Conventional OPOs produce co-propagating signal and idler waves that can be either degenerately or non-degenerately phase matched. This configuration, however, renders their frequencies highly sensitive to external disturbances. Here we demonstrate a degeneracy-locked OPO achieved through backward phase matching in a submicrometre periodically poled thin-film lithium niobate microresonator. Although backward phase matching establishes frequency degeneracy of the signal and idler, the backscattering in the waveguide further ensures phase locking between them. Their interplay permits the locking of the OPO’s degeneracy over a broad parameter space, resulting in deterministic degenerate OPO initiation and robust operation against both pump detuning and temperature fluctuations. This work, thus, provides a new approach for synchronized operations in nonlinear photonics and extends the functionality of optical parametric oscillators. With its potential for large-scale integration, it provides a chip-based platform for advanced applications, such as squeezed light generation, coherent optical computing and investigations of complex nonlinear phenomena.

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Fig. 1: Comparison between forward and backward phase-matched OPO.
Fig. 2: Simulated phase diagram and representative behaviours of the DL-OPO system.
Fig. 3: Device design, characterization and experimental setup.
Fig. 4: Measurement results of DL-OPO.
Fig. 5: Influence of initial resonance mismatch.

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Data availability

The data that support the findings of this study are available via Zenodo at https://doi.org/10.5281/zenodo.18489947 (ref. 44).

Code availability

All relevant computer codes supporting this study are available from the corresponding author upon reasonable request.

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Acknowledgements

This work is supported by DARPA through its INSPIRED program under cooperative agreement number D24AC00180. The part of the research that involves LN thin-film preparation is supported by the US Department of Energy Co-design Center for Quantum Advantage (C2QA) under contract number DE-SC0012704. We thank M. Li, J. Lu and H. Zhao for fruitful discussions. We thank our cleanroom staff Y. Sun, L. McCabe, Y. Shin, K. Woods and M. Rooks for assistance with device fabrication.

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Authors and Affiliations

  1. Department of Electrical Engineering, Yale University, New Haven, CT, USA

    Fengyan Yang, Jiacheng Xie, Yiyu Zhou, Yubo Wang, Chengxing He, Yu Guo & Hong X. Tang

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Contributions

H.X.T. and F.Y. conceived the experiment. F.Y. fabricated the device, performed the experiment and analysed the data. J.X., Y.Z., Y.W., C.H. and Y.G. helped with the project. F.Y., J.X. and Y.Z. wrote the manuscript, and all authors contributed to the manuscript. H.X.T. supervised the work.

Corresponding author

Correspondence to Hong X. Tang.

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Nature Photonics thanks Alfredo de Rossi and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Supplementary Sections I–III.

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Yang, F., Xie, J., Zhou, Y. et al. Degeneracy-locked optical parametric oscillator. Nat. Photon. (2026). https://doi.org/10.1038/s41566-026-01874-7

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