Highlights:
- Achieved an octave-spanning soliton microcomb with over 50% pump-to-comb conversion efficiency.
- Overcame the long-standing bandwidth-efficiency trade-off in soliton microcombs.
- Utilized spatial mode coupling within a single microresonator to maintain strong pump coupling and low power use.
- Breakthrough expected to advance optical clocks, spectroscopy, and integrated photonics.
TLDR:
A team of researchers led by Yang Liu and colleagues has demonstrated a novel method to overcome the bandwidth-efficiency trade-off in soliton microcombs by using spatial mode coupling. Their approach achieves an octave-spanning frequency comb with record-high efficiency, unlocking new possibilities for high-performance optical and photonic technologies.
In a significant advance for photonic science, a team of physicists led by Yang Liu, Andreas Jacobsen, Thibault Wildi, Yanjing Zhao, Chaochao Ye, Yi Zheng, Camiel Op de Beeck, José Carreira, Michael Geiselmann, Kresten Yvind, Tobias Herr, and Minhao Pu has reported a groundbreaking breakthrough in soliton microcomb technology. Their study, titled *’Breaking the bandwidth-efficiency trade-off in soliton microcombs via mode coupling’*, published on [arXiv:2512.05090v1](https://arxiv.org/abs/2512.05090), resolves a fundamental limitation that has long constrained the efficiency and spectral range of optical frequency combs.
Optical microcombs—tiny structures that generate precise, evenly spaced light frequencies—are essential for cutting-edge applications such as optical atomic clocks, precision spectroscopy, frequency synthesis, and astronomical spectrometer calibration. These microcombs rely on dissipative Kerr solitons formed within optical microresonators. However, until now, researchers have faced a persistent trade-off: extending the comb’s bandwidth required large pump detuning, which in turn reduced coupling efficiency and limited the overall power conversion to just a few percent. This trade-off restricted the development of broadband, energy-efficient photonic sources suitable for real-world deployment.
The new study introduces an elegant method to resolve this dichotomy by harnessing mode coupling between spatial modes within a single microresonator. The researchers found that mode hybridization creates an additional power-transfer channel that preserves strong pump-to-resonator coupling even under large detuning conditions. This breakthrough mechanism allows for broadband soliton generation at significantly lower pump power levels. The team demonstrated an octave-spanning soliton comb with over 50% pump-to-comb conversion efficiency—a record achievement that effectively breaks through the inherent bandwidth-efficiency barrier.
This development has far-reaching implications for integrated photonic systems and next-generation optical devices. With high efficiency and broad spectral coverage now achievable simultaneously, the path toward fully integrated, energy-efficient frequency combs is clearer than ever. Advances like these could revolutionize technologies that depend on accurate light sources, such as quantum communications, precision measurement, and ultra-fast computing. The work of Liu and collaborators thus marks a pivotal step toward realizing practical, broadly deployable optical frequency combs capable of supporting the next wave of scientific and industrial innovation.
Source:
Source:
Original research: Liu, Y., Jacobsen, A., Wildi, T., Zhao, Y., Ye, C., Zheng, Y., Op de Beeck, C., Carreira, J., Geiselmann, M., Yvind, K., Herr, T., & Pu, M. (2025). Breaking the bandwidth-efficiency trade-off in soliton microcombs via mode coupling. arXiv:2512.05090 [physics.optics]. https://arxiv.org/abs/2512.05090