Hecht, J. et al. The bandwidth bottleneck. Nature 536, 139–142 (2016).
Betz, J. W. Engineering Satellite-based Navigation and Timing: Global Navigation Satellite Systems, Signals, and Receivers (John Wiley & Sons, 2015).
Kodheli, O. et al. Satellite communications in the new space era: a survey and future challenges. IEEE Commun. Surv. Tutor. 23, 70–109 (2020).
Schlüter, W. & Behrend, D. The international VLBI service for geodesy and astrometry (IVS): current capabilities and future prospects. J. Geod. 81, 379–387 (2007).
Doviak, R. J. et al. Doppler Radar and Weather Observations (Courier Corporation, 2006).
Huang, W., Liu, X. & Gill, E. W. Ocean wind and wave measurements using X-band marine radar: a comprehensive review. Remote Sens. 9, 1261 (2017).
Ayhan, S. et al. Impact of frequency ramp nonlinearity, phase noise, and SNR on FMCW radar accuracy. IEEE Trans. Microw. Theory Tech. 64, 3290–3301 (2016).
Maleki, L. The optoelectronic oscillator. Nat. Photon. 5, 728–730 (2011).
Tang, J. et al. Integrated optoelectronic oscillator. Opt. Express 26, 12257–12265 (2018).
Li, J., Lee, H. & Vahala, K. J. Microwave synthesizer using an on-chip Brillouin oscillator. Nat. Commun. 4, 2097 (2013).
Gundavarapu, S. et al. Sub-hertz fundamental linewidth photonic integrated Brillouin laser. Nat. Photon. 13, 60–67 (2019).
Kittlaus, E. A. et al. A low-noise photonic heterodyne synthesizer and its application to millimeter-wave radar. Nat. Commun. 12, 4397 (2021).
Diddams, S. A., Vahala, K. & Udem, T. Optical frequency combs: coherently uniting the electromagnetic spectrum. Science 369, eaay3676 (2020).
Yao, Y., Jiang, Y. & Ma, L. Optical frequency division. Natl Sci. Rev. 7, 1801–1802 (2020).
Fortier, T. M. et al. Generation of ultrastable microwaves via optical frequency division. Nat. Photon. 5, 425–429 (2011).
Li, J., Yi, X., Lee, H., Diddams, S. A. & Vahala, K. J. Electro-optical frequency division and stable microwave synthesis. Science 345, 309–313 (2014).
Xie, X. et al. Photonic microwave signals with zeptosecond-level absolute timing noise. Nat. Photon. 11, 44–47 (2017).
Nakamura, T. et al. Coherent optical clock down-conversion for microwave frequencies with 10−18 instability. Science 368, 889–892 (2020).
Li, J. & Vahala, K. Small-sized, ultra-low phase noise photonic microwave oscillators at X-Ka bands. Optica 10, 33–34 (2023).
Tetsumoto, T. et al. Optically referenced 300 GHz millimetre-wave oscillator. Nat. Photon. 15, 516–522 (2021).
Diddams, S. et al. An optical clock based on a single trapped 199Hg+ ion. Science 293, 825–828 (2001).
Kessler, T. et al. A sub-40-mHz-linewidth laser based on a silicon single-crystal optical cavity. Nat. Photon. 6, 687–692 (2012).
Kudelin, I. et al. Photonic chip-based low-noise microwave oscillator. Nature 627, 534–539 (2024).
Sun, S. et al. Integrated optical frequency division for microwave and mmwave generation. Nature 627, 540–545 (2024).
Kippenberg, T. J., Gaeta, A. L., Lipson, M. & Gorodetsky, M. L. Dissipative Kerr solitons in optical microresonators. Science 361, eaan8083 (2018).
Matsko, A. B., Savchenkov, A. A., Yu, N. & Maleki, L. Whispering-gallery-mode resonators as frequency references. I. Fundamental limitations. J. Opt. Soc. Am. B 24, 1324–1335 (2007).
Alnis, J. et al. Thermal-noise-limited crystalline whispering-gallery-mode resonator for laser stabilization. Phys. Rev. A 84, 011804 (2011).
Liu, K. et al. 36 Hz integral linewidth laser based on a photonic integrated 4.0 m coil resonator. Optica 9, 770–775 (2022).
Jin, W. et al. Hertz-linewidth semiconductor lasers using CMOS-ready ultra-high-Q microresonators. Nat. Photon. 15, 346–353 (2021).
Lee, H. et al. Chemically etched ultrahigh-Q wedge-resonator on a silicon chip. Nat. Photon. 6, 369–373 (2012).
Wang, C. Y. et al. Mid-infrared optical frequency combs at 2.5 µm based on crystalline microresonators. Nat. Commun. 4, 1345 (2013).
Liang, W. et al. High spectral purity Kerr frequency comb radio frequency photonic oscillator. Nat. Commun. 6, 7957 (2015).
Yao, L. et al. Soliton microwave oscillators using over-sized billion Q optical microresonators. Optica 9, 561–564 (2022).
Puckett, M. W. et al. 422 million intrinsic quality factor planar integrated all-waveguide resonator with sub-MHz linewidth. Nat. Commun. 12, 934 (2021).
Qu, Z. et al. Fabrication of an ultra-high quality MgF2 micro-resonator for a single soliton comb generation. Opt. Express 31, 3005–3016 (2023).
Ye, Z. et al. Foundry manufacturing of tight-confinement, dispersion-engineered, ultralow-loss silicon nitride photonic integrated circuits. Photon. Res. 11, 558–568 (2023).
Yi, X., Yang, Q.-F., Yang, K. Y. & Vahala, K. Theory and measurement of the soliton self-frequency shift and efficiency in optical microcavities. Opt. Lett. 41, 3419–3422 (2016).
Jeong, D. et al. Ultralow jitter silica microcomb. Optica 7, 1108–1111 (2020).
Lao, C. et al. Quantum decoherence of dark pulses in optical microresonators. Nat. Commun. 14, 1802 (2023).
Carr, J. J. in The Technician’s EMI Handbook 163–195 (Newnes, 2000).
Lucas, E. et al. Ultralow-noise photonic microwave synthesis using a soliton microcomb-based transfer oscillator. Nat. Commun. 11, 374 (2020).
Helgason, O’. B. et al. Surpassing the nonlinear conversion efficiency of soliton microcombs. Nat. Photon. 17, 992–999 (2023).
Yang, Q.-F., Hu, Y., Torres-Company, V. & Vahala, K. Efficient microresonator frequency combs. eLight 4, 18 (2024).
Boes, A. et al. Lithium niobate photonics: unlocking the electromagnetic spectrum. Science 379, eabj4396 (2023).
Wang, C. et al. Integrated lithium niobate electro-optic modulators operating at CMOS-compatible voltages. Nature 562, 101–104 (2018).
Shao, L. et al. Integrated microwave acousto-optic frequency shifter on thin-film lithium niobate. Opt. Express 28, 23728–23738 (2020).
Li, B. et al. Reaching fiber-laser coherence in integrated photonics. Opt. Lett. 46, 5201–5204 (2021).
Stern, B., Ji, X., Okawachi, Y., Gaeta, A. L. & Lipson, M. Battery-operated integrated frequency comb generator. Nature 562, 401–405 (2018).
Raja, A. S. et al. Electrically pumped photonic integrated soliton microcomb. Nat. Commun. 10, 680 (2019).
Shen, B. et al. Integrated turnkey soliton microcombs. Nature 582, 365–369 (2020).
Xiang, C. et al. Laser soliton microcombs heterogeneously integrated on silicon. Science 373, 99–103 (2021).
Liu, Y. et al. A photonic integrated circuit-based erbiumdoped amplifier. Science 376, 1309–1313 (2022).
Liu, G. et al. Low-loss prism-waveguide optical coupling for ultrahigh-Q low-index monolithic resonators. Optica 5, 219–226 (2018).
Anderson, M. et al. Highly efficient coupling of crystalline microresonators to integrated photonic waveguides. Opt. Lett. 43, 2106–2109 (2018).
Liang, W. et al. Ultralow noise miniature external cavity semiconductor laser. Nat. Commun. 6, 7371 (2015).
Liu, J. et al. Photonic microwave generation in the X- and K-band using integrated soliton microcombs. Nat. Photon. 14, 486–491 (2020).
Zhao, Y. et al. All-optical frequency division on-chip using a single laser. Nature 627, 546–552 (2024).
Kondratiev, N. & Gorodetsky, M. Thermorefractive noise in whispering gallery mode microresonators: analytical results and numerical simulation. Phys. Lett. A 382, 2265–2268 (2018).
Gordon, J. P. & Haus, H. A. Random walk of coherently amplified solitons in optical fiber transmission. Opt. Lett. 11, 665–667 (1986).
Sun, S. et al. Microcavity Kerr optical frequency division with integrated silicon nitride photonics. Nat. Photon. https://doi.org/10.1038/s41566-025-01668-3 (2025).
Ji, Q.-X. et al. Dispersive-wave-agile optical frequency division. Nat. Photon. https://doi.org/10.1038/s41566-025-01667-4 (2025).