[1] C. H. Townes, A. L. Schawlow. Microwave Spectroscopy(2013).

[2] M. A. Richards, J. Scheer, W. A. Holm. Principles of Modern Radar(2010).

[3] K. Siddiq, M. K. Hobden, S. R. Pennock. Phase noise in FMCW radar systems. IEEE Trans. Aerosp. Electron. Syst., 55, 70-81(2018).

[4] P. Ghelfi, F. Laghezza, F. Scotti. A fully photonics-based coherent radar system. Nature, 507, 341-345(2014).

[5] S. Koenig, D. Lopez-Diaz, J. Antes. Wireless sub-THz communication system with high data rate. Nat. Photonics, 7, 977-981(2013).

[6] M. R. Khanzadi, D. Kuylenstierna, A. Panahi. Calculation of the performance of communication systems from measured oscillator phase noise. IEEE Trans. Circuits Syst. I Regul. Pap., 61, 1553-1565(2014).

[7] B. Razavi, R. Behzad. RF Microelectronics, 2(2012).

[8] J. Clarke, F. K. Wilhelm. Superconducting quantum bits. Nature, 453, 1031-1042(2008).

[9] J. C. Bardin, D. H. Slichter, D. J. Reilly. Microwaves in quantum computing. IEEE J. Microw., 1, 403-427(2021).

[10] S. A. Diddams, K. Vahala, T. Udem. Optical frequency combs: coherently uniting the electromagnetic spectrum. Science, 369, eaay3676(2020).

[11] T. M. Fortier, M. S. Kirchner, F. Quinlan. Generation of ultrastable microwaves via optical frequency division. Nat. Photonics, 5, 425-429(2011).

[12] X. Xie, R. Bouchand, D. Nicolodi. Photonic microwave signals with zeptosecond-level absolute timing noise. Nat. Photonics, 11, 44-47(2017).

[13] J. Li, K. Vahala. Small-sized, ultra-low phase noise photonic microwave oscillators at X-Ka bands. Optica, 10, 33-34(2023).

[14] J. Li, X. Yi, H. Lee. Electro-optical frequency division and stable microwave synthesis. Science, 345, 309-313(2014).

[15] S. Sun, B. Wang, K. Liu. Integrated optical frequency division for microwave and mm-wave generation. Nature, 627, 540-545(2024).

[16] I. Kudelin, W. Groman, Q.-X. Ji. Photonic chip-based low-noise microwave oscillator. Nature, 627, 534-539(2024).

[17] Y. Zhao, J. K. Jang, G. J. Beals. All-optical frequency division on-chip using a single laser. Nature, 627, 546-552(2024).

[18] Y. He, L. Cheng, H. Wang. Chip-scale high-performance photonic microwave oscillator. Sci. Adv., 10, eado9570(2024).

[19] K. Liu, N. Chauhan, J. Wang. 36 Hz integral linewidth laser based on a photonic integrated 4.0 m coil resonator. Optica, 9, 770-775(2022).

[20] S. Sun, M. W. Harrington, F. Tabatabaei. Kerr optical frequency division with integrated photonics for stable microwave and mmwave generation. arXiv(2024).

[21] Q.-X. Ji, W. Zhang, P. Liu. Dispersive-wave-agile optical frequency division. arXiv(2024).

[22] X. Jin, Z. Xie, X. Zhang. Microresonator-referenced soliton microcombs with zeptosecond-level timing noise. arXiv(2024).

[23] R. W. Drever, J. L. Hall, F. V. Kowalski. Laser phase and frequency stabilization using an optical resonator. Appl. Phys. B, 31, 97-105(1983).

[24] W. Jin, Q.-F. Yang, L. Chang. Hertz-linewidth semiconductor lasers using CMOS-ready ultra-high-Q microresonators. Nat. Photonics, 15, 346-353(2021).

[25] B. Li, W. Jin, L. Wu. Reaching fiber-laser coherence in integrated photonics. Opt. Lett., 46, 5201-5204(2021).

[26] M. Yu, D. Barton, R. Cheng. Integrated femtosecond pulse generator on thin-film lithium niobate. Nature, 612, 252-258(2022).

[27] C. Wang, M. Zhang, X. Chen. Integrated lithium niobate electro-optic modulators operating at CMOS-compatible voltages. Nature, 562, 101-104(2018).

[28] P. Kharel, C. Reimer, K. Luke. Breaking voltage–bandwidth limits in integrated lithium niobate modulators using micro-structured electrodes. Optica, 8, 357-363(2021).

[29] W. Groman, I. Kudelin, A. Lind. Photonic millimeter-wave generation beyond the cavity thermal limit. Optica, 11, 1583-1587(2024).

[30] Y. Liu, D. Lee, T. Nakamura. Low-noise microwave generation with an air-gap optical reference cavity. APL Photonics, 9(2024).

[31] J. Li, H. Lee, K. J. Vahala. Microwave synthesizer using an on-chip brillouin oscillator. Nat. Commun., 4, 2097(2013).

[32] S. Gundavarapu, G. M. Brodnik, M. Puckett. Sub-hertz fundamental linewidth photonic integrated Brillouin laser. Nat. Photonics, 13, 60-67(2019).

[33] C. Xiang, W. Jin, O. Terra. 3D integration enables ultralow-noise isolator-free lasers in silicon photonics. Nature, 620, 78-85(2023).

[34] M. Zhang, B. Buscaino, C. Wang. Broadband electro-optic frequency comb generation in a lithium niobate microring resonator. Nature, 568, 373-377(2019).

[35] Y. Hu, M. Yu, B. Buscaino. High-efficiency and broadband on-chip electro-optic frequency comb generators. Nat. Photonics, 16, 679-685(2022).

[36] M. L. Gorodetsky, I. S. Grudinin. Fundamental thermal fluctuations in microspheres. J. Opt. Soc. Am. B, 21, 697-705(2004).

[37] G. Huang, E. Lucas, J. Liu. Thermorefractive noise in silicon-nitride microresonators. Phys. Rev. A, 99, 061801(2019).

[38] Z. Yuan, H. Wang, P. Liu. Correlated self-heterodyne method for ultra-low-noise laser linewidth measurements. Opt. Express, 30, 25147-25161(2022).