[1] L. Maleki. The optoelectronic oscillator. Nat. Photonics, 2011, 5: 728-730.

[2] X. S. Yao, L. Maleki. Optoelectronic oscillator for photonic systems. IEEE J. Quantum Electron., 1996, 32(7): 1141-1149.

[3] X. S. Yao, L. Maleki. Optoelectronic microwave oscillator. J. Opt. Soc. Am. B, 1996, 13(8): 1725-1735.

[4] D.Eliyahu, D.Seidel and L.Maleki, “Phase noise of a high performance OEO and an ultra low noise floor cross-correlation microwave photonic homodyne system,” in IEEE Int. Freq. Control Symp., Honolulu, Hawaii (2008).

[5] A. Matsko, et al.. Whispering gallery mode based optoelectronic microwave oscillator. J. Mod. Opt., 2003, 50(15–17): 2523-2542.

[6] K. Volyanskiy, et al.. Compact optoelectronic microwave oscillators using ultra-high Q whispering gallery mode disk-resonators and phase modulation. Opt. Express, 2010, 18(21): 22358-22363.

[7] X. S. Yao, L. Maleki. Dual microwave and optical oscillator. Opt. Lett., 1997, 22(24): 1867-1869.

[8] X. S.Yaoet al., “Dual-loop optoelectronic oscillator,” in Proc. IEEE Int. Freq. Control Symp. FCS ’98, pp. 545–549 (1998).

[9] D.Eliyahu and L.Maleki, “Tunable, ultralow phase noise YIG based optoelectronic oscillator,” in Proc. IEEE MTT-S Int. Microwave Symp. Digest, Vol. 3, pp. 2185–2187 (2003).

[10] L. Huo, et al.. Clock extraction using an optoelectronic oscillator from high-speed NRZ signal and NRZ-to-RZ format transformation. IEEE Photonics Technol. Lett., 2003, 15(7): 981-983.

[11] W. Zhou, G. Blasche. Injection-locked dual opto-electronic oscillator with ultra-low phase noise and ultra-low spurious level. IEEE Trans. Microwave Theory Tech., 2005, 53(3): 929-933.

[12] T.Sakamoto, T.Kawanishi and M.Izutsu, “Optoelectronic oscillator using push-pull Mach–Zehnder modulator biased at null point for optical two-tone signal generation,” in Proc. Conf. Lasers Electro-Opt., Baltimore, Maryland, pp. 877–879 (2005).

[13] T. Sakamoto, T. Kawanishi, M. Izutsu. Optoelectronic oscillator using a LiNbO3 phase modulator for self-oscillating frequency comb generation. Opt. Lett., 2006, 31(6): 811-813.

[14] Y. K. Chembo, et al.. Dynamic instabilities of microwaves generated with optoelectronic oscillators. Opt. Lett., 2007, 32(17): 2571-2573.

[15] V. J. Urick, et al.. Channelisation of radio-frequency signals using optoelectronic oscillator. Electron. Lett., 2009, 45(24): 1242-1244.

[16] L. D. Nguyen, K. Nakatani, B. Journet. Refractive index measurement by using an optoelectronic oscillator. IEEE Photonics Technol. Lett., 2010, 22(12): 857-859.

[17] D. Zhu, S. Pan, D. Ben. Tunable frequency-quadrupling dual-loop optoelectronic oscillator. IEEE Photonics Technol. Lett., 2012, 24(3): 194-196.

[18] M.Liet al., “Femtometer-resolution wavelength interrogation using an optoelectronic oscillator,” in Proc. IEEE Photonics Conf., Burlingame, California, pp. 298–299 (2012).

[19] W. Li, F. Kong, J. Yao. Arbitrary microwave waveform generation based on a tunable optoelectronic oscillator. J. Lightwave Technol., 2013, 31(23): 3780-3786.

[20] T. Hao, et al.. Breaking the limitation of mode building time in an optoelectronic oscillator. Nat. Commun., 2018, 9: 1839.

[21] Y. Liu, et al. Observation of parity-time symmetry in microwave photonics. Light Sci. Appl., 2018, 7(1): 38.

[22] J. Zhang, J. P. Yao. Parity-time symmetric optoelectronic oscillator. Sci. Adv., 2018, 4(6): eaar6782.

[23] J.Tanget al., “An integrated optoelectronic oscillator,” in Int. Top. Meeting Microwave Photonics (MWP), Beijing, pp. 1–4 (2017).

[24] W.Zhang and J. P.Yao, “A silicon photonic integrated frequency-tunable optoelectronic oscillator,” in Int. Top. Meeting Microwave Photonics (MWP), Beijing, pp. 1–4 (2017).

[25] X. S. Yao, L. Davis, L. Maleki. Coupled optoelectronic oscillators for generating both RF signal and optical pulses. J. Lightwave Technol., 2000, 18(1): 73-78.

[26] J. Lasri, et al.. Self-starting optoelectronic oscillator for generating ultra-low-jitter high-rate (100 GHz or higher) optical pulses. Opt. Exp., 2003, 11(12): 1430-1435.

[27] D. Dahan, E. Shumakher, G. Eisenstein. Self-starting ultralow-jitter pulse source based on coupled optoelectronic oscillators with all intracavity fiber parametric amplifier. Opt. Lett., 2005, 30(13): 1623-1625.

[28] C. Williams, et al.. Noise characterization of an injection-locked COEO with long-term stabilization. J. Lightwave Technol., 2011, 29(19): 2906-2912.

[29] X. S. Yao, L. Maleki. Multiloop optoelectronic oscillator. IEEE J. Quantum Electron., 2000, 36(1): 79-84.

[30] T. Bánky, B. Horváth, T. Berceli. Optimum configuration of multiloop optoelectronic oscillators. J. Opt. Soc. Am. B, 2006, 23(7): 1371-1380.

[31] T. Berceli, T. Bánky, B. Horváth. Opto-electronic generation of stable and low noise microwave signals. IEE Proc. Optoelectron., 2006, 153(3): 119-127.

[32] J. Yang, et al.. An optical domain combined dual-loop optoelectronic oscillator. IEEE Photonics Technol. Lett., 2007, 19(11): 807-809.

[33] E. Shumakher, G. Eisenstein. A novel multiloop optoelectronic oscillator. IEEE Photonics Technol. Lett., 2008, 20(22): 1881-1883.

[34] X. Liu, et al.. A reconfigurable optoelectronic oscillator based on cascaded coherence-controllable recirculating delay lines. Opt. Express, 2012, 20(12): 13296-13301.

[35] S. Jia, et al.. A novel optoelectronic oscillator based on wavelength multiplexing. IEEE Photonics Technol. Lett., 2014, 27(2): 213-216.

[36] K. H. Lee, J. Y. Kim, W. Y. Choi. Injection-locked hybrid optoelectronic oscillators for single-mode oscillation. IEEE Photonics Technol. Lett., 2008, 20(19): 1645-1647.

[37] Z. Q. Fan, et al.. Tunable low-drift spurious-free optoelectronic oscillator based on injection locking and time delay compensation. Opt. Lett., 2019, 44(3): 534-537.

[38] E. Shumakher, S. Ó Dúill, G. Eisenstein. Optoelectronic oscillator tunable by an SOA based slow light element. J. Lightwave Technol., 2009, 27(18): 4063-4068.

[39] S. Pan, J. P. Yao. Wideband and frequency-tunable microwave generation using an optoelectronic oscillator incorporating a Fabry–Perot laser diode with external optical injection. Opt. Lett., 2010, 35(11): 1911-1913.

[40] W. Li, J. P. Yao. An optically tunable optoelectronic oscillator. J. Lightwave Technol., 2010, 28(18): 2640-2645.

[41] M. Li, W. Li, J. P. Yao. Tunable optoelectronic oscillator incorporating a high-Q spectrum-sliced photonic microwave transversal filter. IEEE Photonics Technol. Lett., 2012, 24(14): 1251-1253.

[42] Z. Tang, et al.. Tunable optoelectronic oscillator based on a polarization modulator and a chirped FBG. IEEE Photonics Technol. Lett., 2012, 24(17): 1487-1489.

[43] W. Li, J. P. Yao. Wideband frequency-tunable optoelectronic oscillator incorporating a tunable microwave-photonic filter based on phase-modulation to intensity modulation conversion using a phase-shifted fiber-Bragg grating. IEEE Trans. Microwave Theory Tech., 2012, 60(6): 1735-1742.

[44] B. Yang, et al.. A wideband frequency-tunable optoelectronic oscillator based on a narrowband phase-shifted FBG and wavelength tuning of laser. IEEE Photonics Technol. Lett., 2012, 24(1): 73-75.

[45] F. Jiang, et al.. An optically tunable wideband optoelectronic oscillator based on a bandpass microwave photonic filter. Opt. Express, 2013, 21(14): 16381-16389.

[46] X. Xie, et al.. Wideband tunable optoelectronic oscillator based on a phase modulator and a tunable optical filter. Opt. Lett., 2013, 38(5): 655-657.

[47] H. Peng, et al.. Tunable DC-60 GHz RF generation utilizing a dual-loop optoelectronic oscillator based on stimulated Brillouin scattering. J. Lightwave Technol., 2015, 33(13): 2707-2715.

[48] H. Peng, et al.. Wideband tunable optoelectronic oscillator based on the deamplification of stimulated Brillouin scattering. Opt. Express, 2017, 25(9): 10287-10305.

[49] H. T. Tang, et al.. Wideband tunable optoelectronic oscillator based on a microwave photonic filter with an ultranarrow passband. Opt. Lett., 2018, 43(10): 2328-2331.

[50] M. Y. Shi, et al.. Generation and phase noise analysis of a wide optoelectronic oscillator with ultra-high resolution based on stimulated Brillouin scattering. Opt. Express, 2018, 26(13): 16113-16124.

[51] Z. Zeng, et al.. Stable and finely tunable optoelectronic oscillator based on stimulated Brillouin scattering and an electro-optic frequency shift. Appl. Opt., 2020, 59(3): 589-594.

[52] M. Shin, V. S. Grigoryan, P. Kumar. Frequency-doubling optoelectronic oscillator for generating high-frequency microwave signals with low phase noise. Electron. Lett., 2007, 43(4): 242-244.

[53] S. L. Pan, J. P. Yao. A frequency-doubling optoelectronic oscillator using a polarization modulator. IEEE Photonics Technol. Lett., 2009, 21(13): 929-931.

[54] L. X. Wang, et al.. A frequency-doubling optoelectronic oscillator based on a dual-parallel Mach–Zehnder modulator and a chirped fiber Bragg grating. IEEE Photonics Technol. Lett., 2011, 23(22): 1688-1690.

[55] W. Li, J. P. Yao. An optically tunable frequency-multiplying optoelectronic oscillator. IEEE Photonics Technol. Lett., 2012, 24(10): 812-814.

[56] X. Liu, et al.. Frequency-doubling optoelectronic oscillator using DSB-SC modulation and carrier recovery based on stimulated Brillouin scattering. IEEE Photonics J., 2013, 5(2): 6600606.

[57] W. Li, J. G. Liu, N. H. Zhu. A widely and continuously tunable frequency doubling optoelectronic oscillator. IEEE Photonics Technol. Lett., 2015, 27(13): 1461-1464.

[58] C. Li, et al.. Frequency-sextupling optoelectronic oscillator using a Mach–Zehnder interferometer and a FBG. IEEE Photonics Technol. Lett., 2016, 28(12): 1356-1359.

[59] Y. K. Chembo, L. Larger, P. Colet. Nonlinear dynamics and spectral stability of optoelectronic microwave oscillators. IEEE J. Quantum Electron., 2008, 44(9): 858-866.

[60] M. Peil, et al.. Routes to chaos and multiple time scale dynamics in broadband bandpass nonlinear delay electro-optic oscillators. Phys. Rev. E, 2009, 79: 026208.

[61] K. Callan, et al.. Broadband chaos generated by an opto-electronic oscillator. Phys. Rev. Lett., 2010, 104(11): 113901.

[62] B. Romeira, et al.. Broadband chaotic signals and breather oscillations in an optoelectronic oscillator incorporating a microwave photonic filter. J. Lightwave Technol., 2014, 32(20): 3933-3942.

[63] Y. K. Chembo, et al.. Optoelectronic oscillators with time-delayed feedback. Rev. Mod. Phys., 2019, 91: 035006.

[64] J. Lasri, et al.. A self-starting hybrid optoelectronic oscillator generating ultra low jitter 10-GHz optical pulses and low phase noise electrical signals. IEEE Photonics Technol. Lett., 2002, 14(7): 1004-1006.

[65] P. Devgan, et al.. An optoelectronic oscillator using an 850-nm VCSEL for generating low jitter optical pulses. IEEE Photonics Technol. Lett., 2006, 18(5): 685-687.

[66] Y. K. Chembo, et al.. Generation of ultralow jitter optical pulses using optoelectronic oscillators with time-lens soliton-assisted compression. J. Lightwave Technol., 2009, 27(22): 5160-5167.

[67] N. Huang, et al.. Optical pulse generation based on an optoelectronic oscillator with cascaded nonlinear semiconductor optical amplifiers. IEEE Photonics J., 2014, 6(1): 5500208.

[68] P. Zhou, et al.. Optical pulse generation by an optoelectronic oscillator with optically injected semiconductor laser. IEEE Photonics. Technol. Lett., 2016, 28(17): 1827-1830.

[69] W. Li, et al.. Generation of flat optical frequency comb using a single polarization modulator and a Brillouin-assisted power equalizer. IEEE Photonics J., 2014, 6(2): 7900908.

[70] X. Xie, et al.. Low-noise and broadband optical frequency comb generation based on an optoelectronic oscillator. Opt. Lett., 2014, 39(4): 785-788.

[71] Z. Xie, et al.. Tunable ultraflat optical frequency comb generator based on optoelectronic oscillator using dual-parallel Mach–Zehnder modulator. Opt. Eng., 2017, 56(6): 066115.

[72] W. Li, J. Yao. Generation of linearly chirped microwave waveform with an increased time-bandwidth product based on a tunable optoelectronic oscillator and a recirculating phase modulation loop. J. Lightwave Technol., 2014, 32(20): 3573-3579.

[73] W. Y. Wang, et al.. Triangular microwave waveforms generation based on an optoelectronic oscillator. IEEE Photonics Technol. Lett., 2015, 27(5): 522-525.

[74] F. Zhang, et al.. Triangular pulse generation by polarization multiplexed optoelectronic oscillator. IEEE Photonics Technol. Lett., 2016, 28(15): 1645-1648.

[75] X. S. Yao, G. Lutes. A high-speed photonic clock and carrier recovery device. IEEE Photonics Technol. Lett., 1996, 8(5): 688-690.

[76] J. Lasri, et al.. Multiwavelength NRZ-to-RZ conversion with significant timing-jitter suppression and SNR improvement. Optics Commun., 2004, 240(4–6): 293-298.

[77] S. L. Pan, J. P. Yao. Multichannel optical signal processing in NRZ systems based on a frequency-doubling optoelectronic oscillator. IEEE J. Sel. Top. Quantum Electron., 2010, 16(5): 1460-1468.

[78] F. Kong, W. Li, J. P. Yao. Transverse load sensing based on a dual-frequency optoelectronic oscillator. Opt. Lett., 2013, 38(14): 2611-2613.

[79] O.Okusagaet al., “The OEO as an acoustic sensor,” in Proc. Joint Eur. Freq. Time Forum Int. Freq. Control Symp., Prague, pp. 66–68 (2013).

[80] T. Zhang, et al.. Improving accuracy of distance measurements based on an optoelectronic oscillator by measuring variation of fiber delay. Appl. Opt., 2013, 52(15): 3495-3499.

[81] C. H. Lee, S. H. Yim. Optoelectronic oscillator for a measurement of acoustic velocity in acousto-optic device. Opt. Express, 2014, 22(11): 13634-13640.

[82] F. Kong, et al.. A dual-wavelength fiber ring laser incorporating an injection-coupled optoelectronic oscillator and its application to transverse load sensing. J. Lightwave Technol., 2014, 32(9): 1784-1793.

[83] Y. Zhu, et al.. High-sensitivity temperature sensor based on an optoelectronic oscillator. Appl. Opt., 2014, 53(22): 5084-5087.

[84] S.Zhang, H.Chen and H.Fu, “Fiber-optic temperature sensor using an optoelectronic oscillator,” in Proc. 14th Int. Conf., Opt. Commun. Netwoking, pp. 1–3 (2015).

[85] Y. Wang, J. Zhang, J. Yao. An optoelectronic oscillator for high sensitivity temperature sensing. IEEE Photonics Technol. Lett., 2016, 28(13): 1458-1461.

[86] S. Chew, et al.. Optoelectronic oscillator based sensor using an on-chip sensing probe. IEEE Photonics J., 2017, 9(2): 5500809.

[87] P. S. Devgan, et al.. Detecting low-power RF signals using a multimode optoelectronic oscillator and integrated optical filter. IEEE Photonics Technol. Lett., 2010, 22(3): 152-154.

[88] Y. Shao, et al.. RF signal detection by a tunable optoelectronic oscillator based on a PS-FBG. Opt. Lett., 2018, 43(6): 1199-1202.

[89] G. Wang, et al.. Detection of wideband low-power RF signals using a stimulated Brillouin scattering-based optoelectronic oscillator. Opt. Commun., 2019, 439: 133-136.

[90] Z. Zhu, et al.. Highly sensitive broadband microwave frequency identification using a chip-based Brillouin optoelectronic oscillator. Opt. Express, 2019, 27(9): 12855-12868.

[91] Y. Shao, et al.. Low-power RF signal detection using a high-gain tunable OEO based on equivalent phase modulation. J. Lightwave Technol., 2019, 37(21): 5370-5379.

[92] L.Maleki, “Optoelectronic oscillators for microwave and mm-wave generation,” in 18th Int. Radar Symp., pp. 1–5 (2017).

[93] T. Hao, et al.. Toward monolithic integration of OEOs: from systems to chips. J. Lightwave Technol., 2018, 36(19): 4565-4582.

[94] X. Zou, et al.. Optoelectronic oscillators (OEOs) to sensing, measurement, and detection. IEEE J. Quantum Electron., 2016, 52(1): 0601116.

[95] J. Yao. Optoelectronic oscillators for high speed and high resolution optical sensing. J. Lightwave Technol., 2017, 35(16): 3489-3497.

[96] P. Devgan. A review of optoelectronic oscillators for high speed signal processing applications. ISRN Electron., 2013, 2013: 401969.

[97] Q. Cen, et al.. Rapidly and continuously frequency-scanning opto-electronic oscillator. Opt. Express, 2017, 25(2): 635-643.

[98] T. Hao, et al.. Tunable Fourier domain mode locked optoelectronic oscillator using stimulated Brillouin scattering. IEEE Photonics Technol. Lett., 2018, 30(21): 1842-1845.

[99] T. Hao, et al.. Fourier domain mode locked optoelectronic oscillator based on the deamplification of stimulated Brillouin scattering. OSA Continuum, 2018, 1(2): 408-415.

[100] T. Hao, et al.. Harmonically Fourier domain mode-locked optoelectronic oscillator. IEEE Photonics Technol. Lett., 2019, 31(6): 427-430.

[101] R.Liuet al., “Generating ultra-wideband LFM waveforms with large time duration based on frequency-sweeping optoelectronic oscillation,” in 18th Int. Conf. Opt. Commun. and Networks (ICOCN), Huangshan, pp. 1–3 (2019).

[102] T. Hao, et al.. Dual-chirp Fourier domain mode-locked optoelectronic oscillator. Opt. Lett., 2019, 44(8): 1912-1915.

[103] R. Liu, et al.. Simultaneous generation of ultra-wideband LFM and phase-coded LFM microwave waveforms based on an improved frequency-sweeping OEO. Opt. Commun., 2020, 459: 124938.

[104] S. Zhu, et al.. Polarization manipulated Fourier domain mode-locked optoelectronic oscillator. J. Lightwave Technol., 2020.

[105] Z. Zeng, et al.. Frequency-definable linearly chirped microwave waveform generation by a Fourier domain mode locking optoelectronic oscillator based on stimulated Brillouin scattering. Opt. Express, 2020, 28(9): 13861-13870.

[106] L. Zhang, et al.. Frequency-sweep-range-reconfigurable complementary linearly chirped microwave waveform pair generation by using a Fourier domain mode locking optoelectronic oscillator based on stimulated Brillouin scattering. IEEE Photonics J., 2020, 12(3): 5501010.

[107] X. Zhang, et al.. Novel RF-source-free reconfigurable microwave photonic radar. Opt. Express, 2020, 28(9): 13650-13661.

[108] T. Hao, et al.. Microwave photonics frequency-to-time mapping based on a Fourier domain mode locked optoelectronic oscillator. Opt. Express, 2018, 26(26): 33582-33591.

[109] T. Hao, et al.. Multiple-frequency measurement based on a Fourier domain mode-locked optoelectronic oscillator operating around oscillation threshold. Opt. Lett., 2019, 44(12): 3062-3065.

[110] L.Liet al., “A parity-time-symmetric optoelectronic oscillator based on dual-wavelength carriers in a single spatial optoelectronic loop,” in Int. Top. Meeting Microwave Photonics (MWP), Ottawa, Ontario, pp. 1–4 (2019).

[111] Z. Fan, et al.. Hybrid frequency-tunable parity-time-symmetric optoelectronic oscillator. J. Lightwave Technol., 2020, 38(8): 2127-2133.

[112] Z.Daiet al., “Frequency-tunable parity-time-symmetric optoelectronic oscillator using a polarization-dependent Sagnac loop,” in Opt. Fiber Commun. Conf. (OFC) 2020, OSA Tech. Digest, p. Th1C.3 (2020).

[113] C.Tenget al., “Widely tunable parity-time symmetric optoelectronic oscillator based on a polarization modulator,” in Int. Top. Meeting Microwave Photonics (MWP), Ottawa, Ontario, pp. 1–4 (2019).

[114] C. Teng, et al.. Fine tunable PT-symmetric optoelectronic oscillator based on laser wavelength tuning. IEEE Photonics Technol. Lett., 2020, 32(1): 47-50.

[115] J. Tang, et al.. Integrated optoelectronic oscillator. Opt. Express, 2018, 26(9): 12257-12265.

[116] W. Zhang, J. P. Yao. Silicon photonic integrated optoelectronic oscillator for frequency-tunable microwave generation. J. Lightwave Technol., 2018, 36(19): 4655-4663.

[117] Z. Xuan, L. Du, F. Aflatouni. Frequency locking of semiconductor lasers to RF oscillators using hybrid-integrated opto-electronic oscillators with dispersive delay lines. Opt. Express, 2019, 27(8): 10729-10737.

[118] M. Merklein, et al.. Widely tunable, low phase noise microwave source based on a photonic chip. Opt. Lett., 2016, 41(20): 4633-4636.

[119] L. Nielsen, M. Heck. A computationally efficient integrated coupled opto-electronic oscillator model. J. Lightwave Technol., 2020.

[120] P.T. Do, et al.. Wideband tunable microwave signal generation in a silicon-micro-ring-based optoelectronic oscillator. Sci. Rep., 2020, 10: 6982.

[121] N. Zhu, et al.. Directly modulated semiconductor laser. IEEE J. Sel. Top. Quantum Electron., 2018, 24(1): 1-19.

[122] X. S. Yao. Phase to amplitude modulation conversion using Brillouin selective sideband amplification. IEEE Photonics Technol. Lett., 1998, 10(2): 264-266.

[123] W. Li, M. Li, J. Yao. A narrow-passband and frequency-tunable microwave photonic filter based on phase-modulation to intensity-modulation conversion using a phase-shifted fiber Bragg grating. IEEE Trans. Microwave Theory Tech., 2012, 60(5): 1287-1296.

[124] N. Shi, et al.. A reconfigurable microwave photonic filter with flexible tunability using a multi-wavelength laser and a multi-channel phase-shifted fiber Bragg grating. Opt. Commun., 2018, 407: 27-32.

[125] X. Zou, et al.. Photonics for microwave measurements. Laser Photonics Rev., 2016, 10(5): 711-734.

[126] S. Pan, J. Yao. Photonics-based broadband microwave measurement. J. Lightwave Technol., 2017, 35(16): 3498-3513.

[127] C. M. Bender, S. Boettcher. Real spectra in non-Hermitian Hamiltonians having PT symmetry. Phys. Rev. Lett., 1998, 80: 5243-5246.

[128] N. Hatano, D. R. Nelson. Localization transitions in non-Hermitian quantum mechanics. Phys. Rev. Lett., 1996, 77: 570-573.

[129] C. Zheng, L. Hao, G. L. Long. Observation of a fast evolution in a parity-time-symmetric system. Philos. Trans. R. Soc. A Math. Phys. Eng. Sci., 2013, 371: 20120053.

[130] L. Feng, R. El-Ganainy, L. Ge. Non-Hermitian photonics based on parity–time symmetry. Nat. Photonics, 2017, 11: 752-762.

[131] H. Hodaei, et al.. Parity-time–symmetric microring lasers. Science, 2014, 346(6212): 975-978.

[132] L. Feng, et al.. Single-mode laser by parity-time symmetry breaking. Science, 2014, 346(6212): 972-975.

[133] W. Liu, et al.. An integrated parity-time symmetric wavelength-tunable single-mode microring laser. Nat. Commun., 2017, 8: 15389.

[134] L. Chang, et al.. Parity–time symmetry and variable optical isolation in active–passive-coupled microresonators. Nat. Photonics, 2014, 8: 524-529.

[135] B. Peng, et al.. Parity–time-symmetric whispering-gallery microcavities. Nat. Phys., 2014, 10: 394-398.

[136] J. Schindler, et al.. Experimental study of active LRC circuits with PT symmetries. Phys. Rev. A, 2011, 84: 040101.

[137] D. Marpaung, J. Yao, J. Capmany. Integrated microwave photonics. Nat. Photonics, 2019, 13: 80-90.

[138] G. de Valincourt, et al.. Photonic integrated circuit based on hybrid III-V/silicon integration. J. Lightwave Technol., 2018, 36(2): 265-273.

[139] M. Smit, et al.. An introduction to InP-based generic integration technology. Semicond. Sci. Technol., 2014, 29: 083001.

[140] D. Thomson, et al.. Roadmap on silicon photonics. J. Opt., 2016, 18: 073003.

[141] W. Zhang, J. Yao. Silicon-based integrated microwave photonics. IEEE J. Quantum Electron., 2016, 52: 0600412.

[142] , C. Koos, W. Freude. Nonlinear silicon photonics. Nat. Photonics, 2010, 4: 535-544.

[143] D. J. Moss, et al.. New CMOS compatible platforms based on silicon nitride and Hydex for nonlinear optics. Nat. Photonics, 2013, 7: 597-607.

[144] H. Park, et al.. Heterogeneous silicon nitride photonics. Optica, 2020, 7(4): 336-337.

[145] Q.Yuet al., “Heterogeneous photodiodes on silicon nitride waveguides with 20 GHz bandwidth,” in OFC 2020, San Diego, California, p. W4G.1 (2020).

[146] C. H. G. Roeloffzen, et al.. Silicon nitride microwave photonic circuits. Opt. Express, 2013, 21(19): 22937-22961.

[147] D. Liu, et al.. Large-capacity and low-loss integrated optical buffer. Opt. Express, 2019, 27(8): 11585-11593.

[148] W. Liu, et al.. A fully reconfigurable photonic integrated signal processor. Nat. Photonics, 2016, 10(3): 190-195.

[149] M. Li, et al.. Photonic integration circuits in China. IEEE J. Quantum Electron., 2016, 52(1): 0601017.

[150] M. Li, et al.. Recent progresses on optical arbitrary waveform generation. Front. Optoelectron., 2014, 7(3): 359-375.

[151] N. Shi, et al.. Dual-functional transmitter for simultaneous RF/LFM signal using a monolithic integrated DFB array. IEEE Photonics Technol. Lett., 2020, 32(5): 239-242.

[152] Q. Song, et al.. Monolithic integrated 4×25  Gb/s transmitter optical subassembly at 1.55  <. Opt. Commun., 2019, 441: 160-164.

[153] M. Burla, et al.. Integrated waveguide Bragg gratings for microwave photonics signal processing. Opt. Express, 2013, 21(21): 25120-25147.

[154] T. Hao, et al.. Optoelectronic parametric oscillator. Light Sci. Appl., 2020, 9(1): 102.

[155] J. F. Bauters, et al.. Planar waveguides with less than 0.1  dB/m propagation loss fabricated with wafer bonding. Opt. Express, 2011, 19(24): 24090-24101.

[156] J. F. Bauters, et al.. Ultra-low-loss high-aspect-ratio Si3N4 waveguides. Opt. Express, 2011, 19(4): 3163-3174.

[157] C. Xiang, et al.. Low-loss continuously tunable optical true time delay based on Si3N4 ring resonators. IEEE J. Sel. Top. Quantum Electron., 2018, 24(4): 5500109.

[158] J. J. G. M. van der Tol, et al.. InP membrane on silicon (IMOS) photonics. IEEE J. Quantum Electron., 2020, 56(1): 6300107.

[159] F. Kish, et al.. System-on-chip photonic integrated circuits. IEEE J. Sel. Top. Quantum Electron., 2018, 24(1): 6100120.

[160] Z. Zhou, B. Yin, J. Michel. On-chip light sources for silicon photonics. Light Sci. Appl., 2015, 4: e358.

[161] E. M. T. Fadaly, et al.. Direct-bandgap emission from hexagonal Ge and SiGe alloys. Nature, 2020, 580: 205-209.