[1] Spencer D T, Drake T, Briles T C, et al. An optical-frequency synthesizer using integrated photonics [J]. Nature, 2018, 557(7703): 81-85. doi:  10.1038/s41586-018-0065-7
[2] Suh M-G, Vahala K J. Soliton microcomb range measurement [J]. Science, 2018, 359(6378): 884-887. doi:  10.1126/science.aao1968
[3] Trocha P, Karpov M, Ganin D, et al. Ultrafast optical ranging using microresonator soliton frequency combs [J]. Science, 2018, 359(6378): 887-891. doi:  10.1126/science.aao3924
[4] Suh M-G, Yang Q F, Yang K Y, et al. Microresonator soliton dual-comb spectroscopy [J]. Science, 2016, 354(6312): 600-603. doi:  10.1126/science.aah6516
[5] Dutt A, Joshi C, Ji X, et al. On-chip dual-comb source for spectroscopy [J]. Science Advances, 2018, 4(3): e1701858. doi:  10.1126/sciadv.1701858
[6] Liu J, Lucas E, Raja A S, et al. Photonic microwave generation in the X- and K-band using integrated soliton microcombs [J]. Nature Photonics, 2020, 14: 486-491.
[7] Brasch V, Lucas E, Jost J D, et al. Self-referenced photonic chip soliton Kerr frequency comb [J]. Light: Science & Applications, 2017, 6(1): e16202.
[8] Obrzud E, Rainer M, Harutyunyan A, et al. A microphotonic astrocomb [J]. Nature Photonics, 2019, 13(1): 31-35.
[9] Suh M-G, Yi X, Lai Y H, et al. Searching for exoplanets using a microresonator astrocomb [J]. Nature Photonics, 2019, 13(1): 25-30. doi:  10.1038/s41566-018-0312-3
[10] Moille G, Chang L, Xie W, et al. Dissipative Kerr solitons in a III-V microresonator [J]. Laser & Photonics Reviews, 2020, 14(8): 2000022.
[11] Chang L, Xie W, Shu H, et al. Ultra-efficient frequency comb generation in AlGaAs-on-insulator microresonators [J]. Nature Communications, 2020, 11(1): 1331.
[12] Ji X, Barbosa F A S, Roberts S P, et al. Ultra-low-loss on-chip resonators with sub-milliwatt parametric oscillation threshold [J]. Optica, 2017, 4(6): 619. doi:  10.1364/OPTICA.4.000619
[13] Gong Z, Bruch A, Shen M, et al. High-fidelity cavity soliton generation in crystalline AlN microring resonators [J]. Optics Letters, 2018, 43(18): 4366. doi:  10.1364/OL.43.004366
[14] Liu X, Sun C, Xiong B, et al. Integrated high- Q crystalline AlN microresonators for broadband Kerr and Raman frequency combs [J]. ACS Photonics, 2018, 5(5): 1943-1950. doi:  10.1021/acsphotonics.7b01254
[15] Hausmann B J M, Bulu I, Lončar M, et al. Diamond nonlinear photonics [J]. Nature Photonics, 2014, 8(5): 369. doi:  10.1038/nphoton.2014.72
[16] He Y, Yang Q-F, Ling J, et al. Self-starting bi-chromatic LiNbO3 soliton microcomb [J]. Optica, 2019, 6(9): 1138. doi:  10.1364/OPTICA.6.001138
[17] Zheng Y, Sun C, Xiong B, et al. Integrated gallium nitride nonlinear photonics [J]. Laser & Photonics Reviews, 2022, 16(1): 2100071.
[18] Jung H, Xiong C, Fong K Y, et al. Optical frequency comb generation from aluminum nitride microring resonator [J]. Optics Letters, 2013, 38(15): 2810-2813. doi:  10.1364/OL.38.002810
[19] Jung H, Stoll R, Guo X, et al. Green, red, and IR frequency comb line generation from single IR pump in AlN microring resonator [J]. Optica, 2014, 1(6): 396. doi:  10.1364/OPTICA.1.000396
[20] Liu X, Sun C, Xiong B, et al. Integrated continuous-wave aluminum nitride Raman laser [J]. Optica, 2017, 4(8): 893. doi:  10.1364/OPTICA.4.000893
[21] Liu X, Sun C, Xiong B, et al. Generation of multiple near-visible comb lines in an AlN microring via χ(2) and χ(3) optical nonlinearities [J]. Applied Physics Letters, 2018, 113(17): 171106. doi:  10.1063/1.5046324
[22] Liu X, Gong Z, Bruch A W, et al. Aluminum nitride nanophotonics for beyond-octave soliton microcomb generation and self-referencing [J]. Nature Communications, 2021, 12(1): 5428. doi:  10.1038/s41467-021-25751-9
[23] Weng H, Liu J, Afridi A A, et al. Directly accessing octave-spanning dissipative Kerr soliton frequency combs in an AlN microresonator [J]. Photonics Research, 2021, 9(7): 1351. doi:  10.1364/PRJ.427567
[24] Tang C L, Bosenberg W R, Ukachi T, et al. Optical parametric oscillators [J]. Proceedings of the IEEE, 1992, 80(3): 365-374. doi:  10.1109/5.135353
[25] Godard A. Infrared (2–12 μm) solid-state laser sources: A review [J]. Comptes Rendus Physique, 2007, 8(10): 1100-1128. doi:  10.1016/j.crhy.2007.09.010
[26] Breunig I, Haertle D, Buse K. Continuous-wave optical parametric oscillators: recent developments and prospects [J]. Applied Physics B, 2011, 105(1): 99. doi:  10.1007/s00340-011-4702-1
[27] Bruch A W, Liu X, Surya J B, et al. On-chip χ (2) microring optical parametric oscillator [J]. Optica, 2019, 6(10): 1361. doi:  10.1364/OPTICA.6.001361
[28] Bruch A W, Liu X, Gong Z, et al. Pockels soliton microcomb [J]. Nature Photonics, 2021, 15: 21-27.
[29] Bruch A W, Liu X, Guo X, et al. 17 000%/W second-harmonic conversion efficiency in single-crystalline aluminum nitride microresonators [J]. Applied Physics Letters, 2018, 113(13): 131102. doi:  10.1063/1.5042506
[30] Bruch A W, Xiong C, Leung B, et al. Broadband nanophotonic waveguides and resonators based on epitaxial GaN thin films [J]. Applied Physics Letters, 2015, 107(14): 141113. doi:  10.1063/1.4933093
[31] Stassen E, Pu M, Semenova E, et al. High-confinement gallium nitride-on-sapphire waveguides for integrated nonlinear photonics [J]. Optics Letters, 2019, 44(5): 1064. doi:  10.1364/OL.44.001064