Chinese Science Bulletin, Volume 65 , Issue 27 : 3028-3042(2020) https://doi.org/10.1360/TB-2020-0333

Research advances of ultrahigh-Q on-chip microcavity photonics

More info
  • ReceivedMar 28, 2020
  • AcceptedMay 21, 2020
  • PublishedMay 22, 2020




Author information

肖云峰, 北京大学博雅特聘教授、长江特聘教授、美国光学学会会士, 主要从事超高品质因子光学微腔研究. 近年来, 成果两次入选“中国高校十大科技进展”, 四次入选“中国光学十大进展”.


[1] Vahala K J. Optical microcavities. Nature, 2003, 424: 839−846. Google Scholar

[2] Ward J, Benson O. WGM microresonators: Sensing, lasing and fundamental optics with microspheres. Laser Photon Rev, 2011, 5553-570 CrossRef Google Scholar

[3] Cao H, Wiersig J. Dielectric microcavities: Model systems for wave chaos and non-Hermitian physics. Rev Mod Phys, 2015, 8761-111 CrossRef Google Scholar

[4] McCall S L, Levi A F J, Slusher R E, et al. Whispering-gallery mode microdisk lasers. Appl Phys Lett, 1992, 60289-291 CrossRef Google Scholar

[5] Garrett C G B, Kaiser W, Bond W L. Stimulated emission into optical whispering modes of spheres. Phys Rev, 1961, 1241807-1809 CrossRef Google Scholar

[6] Tzeng H M, Wall K F, Long M B, et al. Laser emission from individual droplets at wavelengths corresponding to morphology-dependent resonances. Opt Lett, 1984, 9499-501 CrossRef Google Scholar

[7] Yang L, Armani D K, Vahala K J. Fiber-coupled erbium microlasers on a chip. Appl Phys Lett, 2003, 83825-826 CrossRef Google Scholar

[8] Min B, Kim S, Okamoto K, et al. Ultralow threshold on-chip microcavity nanocrystal quantum dot lasers. Appl Phys Lett, 2006, 89191124 CrossRef Google Scholar

[9] Zhou T, Tang M, Xiang G, et al. Ultra-low threshold InAs/GaAs quantum dot microdisk lasers on planar on-axis Si (001) substrates. Optica, 2019, 6430-435 CrossRef Google Scholar

[10] Jiang X F, Zou C L, Wang L, et al. Whispering-gallery microcavities with unidirectional laser emission. Laser Photon Rev, 2016, 1040-61 CrossRef Google Scholar

[11] Miao P, Zhang Z, Sun J, et al. Orbital angular momentum microlaser. Science, 2016, 353464-467 CrossRef Google Scholar

[12] He L, Özdemir Ş K, Yang L. Whispering gallery microcavity lasers. Laser Photon Rev, 2013, 760-82 CrossRef Google Scholar

[13] Zhang J, Peng B, Özdemir Ş K, et al. A phonon laser operating at an exceptional point. Nat Photonics, 2018, 12479-484 CrossRef Google Scholar

[14] Ye Y, Wong Z J, Lu X, et al. Monolayer excitonic laser. Nat Photonics, 2015, 9733-737 CrossRef Google Scholar

[15] Yang L, Carmon T, Min B, et al. Erbium-doped and Raman microlasers on a silicon chip fabricated by the sol-gel process. Appl Phys Lett, 2005, 86: 091114. Google Scholar

[16] Wu J, Jiang S, Qua T, et al. 2 μm lasing from highly thulium doped tellurite glass microsphere. Appl Phys Lett, 2005, 87211118 CrossRef Google Scholar

[17] Ostby E P, Yang L, Vahala K J. Ultralow-threshold Yb3+:SiO2 glass laser fabricated by the solgel process. Opt Lett, 2007, 322650-2652 CrossRef Google Scholar

[18] Tulek A, Vardeny Z V. Unidirectional laser emission from π-conjugated polymer microcavities with broken symmetry. Appl Phys Lett, 2007, 90161106 CrossRef Google Scholar

[19] Slusher R E, Levi A F J, Mohideen U, et al. Threshold characteristics of semiconductor microdisk lasers. Appl Phys Lett, 1993, 631310-1312 CrossRef Google Scholar

[20] Van Campenhout J, Rojo Romeo P, Regreny P, et al. Electrically pumped InP-based microdisk lasers integrated with a nanophotonic silicon-on-insulator waveguide circuit. Opt Express, 2007, 156744-6749 CrossRef Google Scholar

[21] Wan Y, Li Q, Liu A Y, et al. Temperature characteristics of epitaxially grown InAs quantum dot micro-disk lasers on silicon for on-chip light sources. Appl Phys Lett, 2016, 109011104 CrossRef Google Scholar

[22] Wang K, Wang S, Xiao S, et al. Recent advances in perovskite micro- and nanolasers. Adv Opt Mater, 2018, 61800278 CrossRef Google Scholar

[23] Zhang Q, Su R, Du W, et al. Advances in small perovskite-based lasers. Small Methods, 2017, 11700163 CrossRef Google Scholar

[24] Zhang Q, Ha S T, Liu X, et al. Room-temperature near-infrared high-Q perovskite whispering-gallery planar nanolasers. Nano Lett, 2014, 145995-6001 CrossRef Google Scholar

[25] Zhang N, Sun W, Rodrigues S P, et al. Highly reproducible organometallic halide perovskite microdevices based on top-down lithography. Adv Mater, 2017, 291606205 CrossRef Google Scholar

[26] Nöckel J U, Stone A D. Ray and wave chaos in asymmetric resonant optical cavities. Nature, 1997, 38545-47 CrossRef Google Scholar

[27] Gmachl C. High-power directional emission from microlasers with chaotic resonators. Science, 1998, 2801556-1564 CrossRef Google Scholar

[28] Sui S S, Huang Y Z, Tang M Y, et al. Locally deformed-ring hybrid microlasers exhibiting stable unidirectional emission from a Si waveguide. Opt Lett, 2016, 413928 CrossRef Google Scholar

[29] Wang Q J, Yan C, Yu N, et al. Whispering-gallery mode resonators for highly unidirectional laser action. Proc Natl Acad Sci USA, 2010, 10722407-22412 CrossRef Google Scholar

[30] Redding B, Cerjan A, Huang X, et al. Low spatial coherence electrically pumped semiconductor laser for speckle-free full-field imaging. Proc Natl Acad Sci USA, 2015, 1121304-1309 CrossRef Google Scholar

[31] Bittner S, Guazzotti S, Zeng Y, et al. Suppressing spatiotemporal lasing instabilities with wave-chaotic microcavities. Science, 2018, 3611225-1231 CrossRef Google Scholar

[32] Hodaei H, Miri M A, Heinrich M, et al. Parity-time-symmetric microring lasers. Science, 2014, 346975-978 CrossRef Google Scholar

[33] Feng L, Wong Z J, Ma R M, et al. Single-mode laser by parity-time symmetry breaking. Science, 2014, 346972-975 CrossRef Google Scholar

[34] Boyd R W. Nonlinear Optics. 3rd ed. Amsterdam, Boston: Academic Press, 2008. Google Scholar

[35] Acker W P, Leach D H, Chang R K. Third-order optical sum-frequency generation in micrometer-sized liquid droplets. Opt Lett, 1989, 14402-404 CrossRef Google Scholar

[36] Snow J B, Qian S X, Chang R K. Stimulated Raman scattering from individual water and ethanol droplets at morphology-dependent resonances. Opt Lett, 1985, 1037-39 CrossRef Google Scholar

[37] Braginsky V B, Gorodetsky M L, Ilchenko V S. Quality-factor and nonlinear properties of optical whispering-gallery modes. Phys Lett A, 1989, 137393-397 CrossRef Google Scholar

[38] Li Y, Jiang X, Zhao G, et al. Whispering gallery mode microresonator for nonlinear optics. 2018, arxiv: 1809.04878. arXiv Google Scholar

[39] Kippenberg T J, Spillane S M, Armani D K, et al. Ultralow-threshold microcavity Raman laser on a microelectronic chip. Opt Lett, 2004, 291224-1226 CrossRef Google Scholar

[40] Li J, Lee H, Vahala K J. Microwave synthesizer using an on-chip Brillouin oscillator. Nat Commun, 2013, 42097 CrossRef Google Scholar

[41] Carmon T, Vahala K J. Visible continuous emission from a silica microphotonic device by third-harmonic generation. Nat Phys, 2007, 3430-435 CrossRef Google Scholar

[42] Levy J S, Foster M A, Gaeta A L, et al. Harmonic generation in silicon nitride ring resonators. Opt Express, 2011, 1911415-11421 CrossRef Google Scholar

[43] Del’Haye P, Schliesser A, Arcizet O, et al. Optical frequency comb generation from a monolithic microresonator. Nature, 2007, 450: 1214−1217. Google Scholar

[44] Kippenberg T J, Holzwarth R, Diddams S A. Microresonator-based optical frequency combs. Science, 2011, 332555-559 CrossRef Google Scholar

[45] Chen H J, Ji Q X, Wang H, et al. Chaos-assisted two-octave-spanning microcombs. Nat Commun, 2020, 112336 CrossRef Google Scholar

[46] Lee H, Chen T, Li J, et al. Chemically etched ultrahigh-Q wedge-resonator on a silicon chip. Nat Photonics, 2012, 6369-373 CrossRef Google Scholar

[47] Yang K Y, Oh D Y, Lee S H, et al. Bridging ultrahigh-Q devices and photonic circuits. Nat Photonics, 2018, 12297-302 CrossRef Google Scholar

[48] Ji X, Barbosa F A S, Roberts S P, et al. Ultra-low-loss on-chip resonators with sub-milliwatt parametric oscillation threshold. Optica, 2017, 4619-624 CrossRef Google Scholar

[49] Chang L, Xie W, Shu H, et al. Ultra-efficient frequency comb generation in AlGaAs-on-insulator microresonators. Nat Commun, 2020, 111331 CrossRef Google Scholar

[50] Lin J, Yao N, Hao Z, et al. Broadband quasi-phase-matched harmonic generation in an on-chip monocrystalline lithium niobate microdisk resonator. Phys Rev Lett, 2019, 122173903 CrossRef Google Scholar

[51] Liu X, Sun C, Xiong B, et al. Aluminum nitride-on-sapphire platform for integrated high-Q microresonators. Opt Express, 2017, 25587-594 CrossRef Google Scholar

[52] Merklein M, Stiller B, Kabakova I V, et al. Widely tunable, low phase noise microwave source based on a photonic chip. Opt Lett, 2016, 414633-4636 CrossRef Google Scholar

[53] Özdemir Ş K, Zhu J, Yang X, et al. Highly sensitive detection of nanoparticles with a self-referenced and self-heterodyned whispering-gallery Raman microlaser. Proc Natl Acad Sci USA, 2014, 111E3836-E3844 CrossRef Google Scholar

[54] Li B B, Clements W R, Yu X C, et al. Single nanoparticle detection using split-mode microcavity Raman lasers. Proc Natl Acad Sci USA, 2014, 11114657-14662 CrossRef Google Scholar

[55] Lai Y H, Suh M G, Lu Y K, et al. Earth rotation measured by a chip-scale ring laser gyroscope. Nat Photonics, 2020, 14345-349 CrossRef Google Scholar

[56] Wang C, Zhang M, Stern B, et al. Nanophotonic lithium niobate electro-optic modulators. Opt Express, 2018, 261547-1555 CrossRef Google Scholar

[57] Hua S, Wen J, Jiang X, et al. Demonstration of a chip-based optical isolator with parametric amplification. Nat Commun, 2016, 713657 CrossRef Google Scholar

[58] Guo X, Zou C L, Jung H, et al. On-chip strong coupling and efficient frequency conversion between telecom and visible optical modes. Phys Rev Lett, 2016, 117123902 CrossRef Google Scholar

[59] Fan L, Wang J, Varghese L T, et al. An all-silicon passive optical diode. Science, 2012, 335447-450 CrossRef Google Scholar

[60] Fortsch M, Furst J U, Wittmann C, et al. A versatile source of single photons for quantum information processing. Nat Commun, 2013, 4: 1−5. Google Scholar

[61] Huang R, Miranowicz A, Liao J Q, et al. Nonreciprocal photon blockade. Phys Rev Lett, 2018, 121153601 CrossRef Google Scholar

[62] Kues M, Reimer C, Roztocki P, et al. On-chip generation of high-dimensional entangled quantum states and their coherent control. Nature, 2017, 546622-626 CrossRef Google Scholar

[63] Fürst J U, Strekalov D V, Elser D, et al. Quantum light from a whispering-gallery-mode disk resonator. Phys Rev Lett, 2011, 106113901 CrossRef Google Scholar

[64] Strekalov D V, Marquardt C, Matsko A B, et al. Nonlinear and quantum optics with whispering gallery resonators. J Opt, 2016, 18123002 CrossRef Google Scholar

[65] Cao Q T, Wang H, Dong C H, et al. Experimental demonstration of spontaneous chirality in a nonlinear microresonator. Phys Rev Lett, 2017, 118033901 CrossRef Google Scholar

[66] Zhang F, Feng Y, Chen X, et al. Synthetic anti-PT symmetry in a single microcavity. Phys Rev Lett, 2020, 124053901 CrossRef Google Scholar

[67] Zheng Y, Yang J, Shen Z, et al. Optically induced transparency in a micro-cavity. Light Sci Appl, 2016, 5e16072 CrossRef Google Scholar

[68] Jang J K, Klenner A, Ji X, et al. Synchronization of coupled optical microresonators. Nat Photonics, 2018, 12688-693 CrossRef Google Scholar

[69] Xu D, Han Z, Lu Y, et al. Synchronization and temporal nonreciprocity of optical microresonators via spontaneous symmetry breaking. Adv Photon, 2019, 1: 046002. Google Scholar

[70] Zhang X, Cao Q T, Wang Z, et al. Symmetry-breaking-induced nonlinear optics at a microcavity surface. Nat Photonics, 2019, 1321-24 CrossRef Google Scholar

[71] Diddams S A. The evolving optical frequency comb. J Opt Soc Am B, 2010, 27B51 CrossRef Google Scholar

[72] Kovach A, Chen D, He J, et al. Emerging material systems for integrated optical Kerr frequency combs. Adv Opt Photonics, 2020, 12135 CrossRef Google Scholar

[73] Herr T, Brasch V, Jost J D, et al. Temporal solitons in optical microresonators. Nat Photonics, 2014, 8145-152 CrossRef Google Scholar

[74] Yang Q F, Yi X, Yang K Y, et al. Stokes solitons in optical microcavities. Nat Phys, 2017, 1353-57 CrossRef Google Scholar

[75] Brasch V, Geiselmann M, Herr T, et al. Photonic chip-based optical frequency comb using soliton Cherenkov radiation. Science, 2016, 351357-360 CrossRef Google Scholar

[76] Karpov M, Pfeiffer M H P, Guo H, et al. Dynamics of soliton crystals in optical microresonators. Nat Phys, 2019, 151071-1077 CrossRef Google Scholar

[77] Lucas E, Karpov M, Guo H, et al. Breathing dissipative solitons in optical microresonators. Nat Commun, 2017, 8736 CrossRef Google Scholar

[78] Kippenberg T J, Gaeta A L, Lipson M, et al. Dissipative Kerr solitons in optical microresonators. Science, 2018, 361: 129−162. Google Scholar

[79] Stern B, Ji X, Okawachi Y, et al. Battery-operated integrated frequency comb generator. Nature, 2018, 562401-405 CrossRef Google Scholar

[80] Shen B, Chang L, Liu J, et al. Integrated turnkey soliton microcombs operated at CMOS frequencies. 2019, arxiv: 1911.02636. arXiv Google Scholar

[81] Kues M, Reimer C, Lukens J M, et al. Quantum optical microcombs. Nat Photonics, 2019, 13170-179 CrossRef Google Scholar

[82] Wang F, Wang W, Niu R, et al. Quantum key distribution with on-chip dissipative Kerr soliton. Laser Photon Rev, 2020, 141900190 CrossRef Google Scholar

[83] Wang C, Zhang M, Yu M, et al. Monolithic lithium niobate photonic circuits for Kerr frequency comb generation and modulation. Nat Commun, 2019, 10978 CrossRef Google Scholar

[84] Rokhsari H, Vahala K J. Ultralow loss, high Q, Four port resonant couplers for quantum optics and photonics. Phys Rev Lett, 2004, 92253905 CrossRef Google Scholar

[85] Jiang X, Shao L, Zhang S X, et al. Chaos-assisted broadband momentum transformation in optical microresonators. Science, 2017, 358344-347 CrossRef Google Scholar

[86] Zhang M, Wang C, Hu Y, et al. Electronically programmable photonic molecule. Nat Photonics, 2019, 1336-40 CrossRef Google Scholar

[87] Dong C H, Shen Z, Zou C L, et al. Brillouin-scattering-induced transparency and non-reciprocal light storage. Nat Commun, 2015, 66193 CrossRef Google Scholar

[88] Little B E, Chu S T, Haus H A, et al. Microring resonator channel dropping filters. J Lightwave Technol, 1997, 15998-1005 CrossRef Google Scholar

[89] Jalas D, Petrov A, Eich M, et al. What is — and what is not — an optical isolator. Nat Photonics, 2013, 7579-582 CrossRef Google Scholar

[90] Shen Z, Zhang Y L, Chen Y, et al. Experimental realization of optomechanically induced non-reciprocity. Nat Photonics, 2016, 10657-661 CrossRef Google Scholar

[91] Kim J H, Kuzyk M C, Han K, et al. Non-reciprocal Brillouin scattering induced transparency. Nat Phys, 2015, 11275-280 CrossRef Google Scholar

[92] Sohn D B, Kim S, Bahl G. Time-reversal symmetry breaking with acoustic pumping of nanophotonic circuits. Nat Photonics, 2018, 1291-97 CrossRef Google Scholar

[93] Del Bino L, Silver J M, Stebbings S L, et al. Symmetry breaking of counter-propagating light in a nonlinear resonator. Sci Rep, 2017, 743142 CrossRef Google Scholar

[94] Del Bino L, Silver J M, Woodley M T M, et al. Microresonator isolators and circulators based on the intrinsic nonreciprocity of the Kerr effect. Optica, 2018, 5279-282 CrossRef Google Scholar

[95] Chang L, Jiang X, Hua S, et al. Parity-time symmetry and variable optical isolation in active-passive-coupled microresonators. Nat Photonics, 2014, 8524-529 CrossRef Google Scholar

[96] Peng B, Özdemir Ş K, Lei F, et al. Parity-time-symmetric whispering-gallery microcavities. Nat Phys, 2014, 10394-398 CrossRef Google Scholar

[97] Maayani S, Dahan R, Kligerman Y, et al. Flying couplers above spinning resonators generate irreversible refraction. Nature, 2018, 558569-572 CrossRef Google Scholar

[98] Lodahl P, Mahmoodian S, Stobbe S, et al. Chiral quantum optics. Nature, 2017, 541473-480 CrossRef Google Scholar

[99] Xu Q, Schmidt B, Pradhan S, et al. Micrometre-scale silicon electro-optic modulator. Nature, 2005, 435325-327 CrossRef Google Scholar

[100] Xiong C, Pernice W H P, Sun X, et al. Aluminum nitride as a new material for chip-scale optomechanics and nonlinear optics. New J Phys, 2012, 14095014 CrossRef Google Scholar

[101] Phare C T, Daniel Lee Y H, Cardenas J, et al. Graphene electro-optic modulator with 30 GHz bandwidth. Nat Photonics, 2015, 9511-514 CrossRef Google Scholar

[102] Knight J C, Cheung G, Jacques F, et al. Phase-matched excitation of whispering-gallery-mode resonances by a fiber taper. Opt Lett, 1997, 221129-1131 CrossRef Google Scholar

[103] Vollmer F, Yang L. Review Label-free detection with high-Q microcavities: A review of biosensing mechanisms for integrated devices. Nanophotonics, 2012, 1267-291 CrossRef Google Scholar

[104] Zhi Y, Yu X C, Gong Q, et al. Single nanoparticle detection using optical microcavities. Adv Mater, 2017, 291604920 CrossRef Google Scholar

[105] Tang S J, Li B B, Xiao Y F. Optical sensing with whispering-gallery microcavities. Physics, 2019, 48: 137−147. Google Scholar

[106] Vollmer F, Braun D, Libchaber A, et al. Protein detection by optical shift of a resonant microcavity. Appl Phys Lett, 2002, 804057-4059 CrossRef Google Scholar

[107] Vollmer F, Arnold S, Keng D. Single virus detection from the reactive shift of a whispering-gallery mode. Proc Natl Acad Sci USA, 2008, 10520701-20704 CrossRef Google Scholar

[108] Zhu J, Ozdemir S K, Xiao Y F, et al. On-chip single nanoparticle detection and sizing by mode splitting in an ultrahigh-Q microresonator. Nat Photonics, 2010, 446-49 CrossRef Google Scholar

[109] Shao L, Jiang X F, Yu X C, et al. Detection of single nanoparticles and lentiviruses using microcavity resonance broadening. Adv Mater, 2013, 255616-5620 CrossRef Google Scholar

[110] Shen B Q, Yu X C, Zhi Y, et al. Detection of single nanoparticles using the dissipative interaction in a high-Q microcavity. Phys Rev Appl, 2016, 5024011 CrossRef Google Scholar

[111] Dantham V R, Holler S, Barbre C, et al. Label-free detection of single protein using a nanoplasmonic-photonic hybrid microcavity. Nano Lett, 2013, 133347-3351 CrossRef Google Scholar

[112] Baaske M D, Foreman M R, Vollmer F. Single-molecule nucleic acid interactions monitored on a label-free microcavity biosensor platform. Nat Nanotechnol, 2014, 9933-939 CrossRef Google Scholar

[113] Su J, Goldberg A F, Stoltz B M. Label-free detection of single nanoparticles and biological molecules using microtoroid optical resonators. Light Sci Appl, 2016, 5e16001 CrossRef Google Scholar

[114] Forstner S, Prams S, Knittel J, et al. Cavity optomechanical magnetometer. Phys Rev Lett, 2012, 108120801 CrossRef Google Scholar

[115] Forstner S, Sheridan E, Knittel J, et al. Ultrasensitive optomechanical magnetometry. Adv Mater, 2014, 266348-6353 CrossRef Google Scholar

[116] Li B B, Bílek J, Hoff U B, et al. Quantum enhanced optomechanical magnetometry. Optica, 2018, 5850-856 CrossRef Google Scholar

[117] Li J, Suh M G, Vahala K. Microresonator Brillouin gyroscope. Optica, 2017, 4346-348 CrossRef Google Scholar

[118] Sunada S, Harayama T. Sagnac effect in resonant microcavities. Phys Rev A, 2006, 74021801 CrossRef Google Scholar

[119] Ge L, Sarma R, Cao H. Rotation-induced evolution of far-field emission patterns of deformed microdisk cavities. Optica, 2015, 2323-328 CrossRef Google Scholar

[120] Sarma R, Ge L, Wiersig J, et al. Rotating optical microcavities with broken chiral symmetry. Phys Rev Lett, 2015, 114053903 CrossRef Google Scholar

[121] Sunada S. Large Sagnac frequency splitting in a ring resonator operating at an exceptional point. Phys Rev A, 2017, 96033842 CrossRef Google Scholar

[122] Ren J, Hodaei H, Harari G, et al. Ultrasensitive micro-scale parity-time-symmetric ring laser gyroscope. Opt Lett, 2017, 421556-1559 CrossRef Google Scholar

[123] Lai Y H, Lu Y K, Suh M G, et al. Observation of the exceptional-point-enhanced Sagnac effect. Nature, 2019, 57665-69 CrossRef Google Scholar

  • Figure 1

    Schemitic illustration of whispering gallery mode (WGM). (a) Light ray propagates along the surface inside the cavity by total internal reflectioin. (b) Echo wall at Temple of Heaven in Beijing (image from internet). (c) Typical electric field distribution of optical WGM (clockwise)

  • Figure 2

    On-chip WGM microlasers. (a) Erbium-doped microtoroid laser[7]. (b) CdSe/ZnS quantum-dots (QDs)-coated toriod microlaser[8]. The left panel is the scanning electron micrograph (SEM) of the microlaser, and the right panel is the optical micrograph of the microlaser with light emission under the pump. (c) InAs/GaAs semiconductor QD microdisk laser with ultra-low threshold under the continuous-wave pump at room temperature[9]. (d) Unidirectional emission of WGM microlaser[10]. (e) Orbital angular momentum WGM microlaser[11]

  • Figure 3

    Typical nonlinear optical effects in on-chip WGM microcavities. (a) Raman laser spectrum in a silica microtoroid[39]. Inset: The sideview of the microcavity used in the experiment. (b) Back-spectrum of stimulated Brillouin scattering in a silica microdisk[40]. (c) Optical spectra of third harmonic generation in a silicon nitride microring[42]. Inset: Topview image of the microring with third harmonic light. (d) Ultra-broadband microcomb generation in a silica asymmetric microtoroid by combining multiple nonlinear effects including four-wave mixing, third-order sum frequency generation, symetry-breaking induced second-order sum frequency generation[45]. Inset: Multi-color light emission image observed by an optical microscope

  • Figure 4

    Application areas of microcombs[78]. From top, clockwise: Ultrafast distance measurements (LIDAR), optical atomic clocks, photonic radar, dual-comb spectroscopy, optical coherence tomography, low-noise microwaves, optical frequency synthesizer, astronomical spectrometer calibration, and coherent communications

  • Figure 5

    Applications of on-chip microcavities in photonic integrated circuits. (a) Monolithic lithium niobate photonic circuits[83], where lithium niobite microring cavities are used for multifunctional devices, including the generation of microcombs light source, optical filtering, electrooptical modulation. (b) Silica microtoroid with add-drop coupling structure for optical filter[84]. Port 1 is input, and port 4 is output. (c) Optical isolator by using optothermal effect and asymmetric coupling in silicon microrings (the coupling gaps at G2 and G3 are different)[59]. (d) Nonlinear strong couling and nonreciprocal light propagation by second-order sum frequency generation effect in an aluminium nitride microring[58]. (e) On-chip electro-optic modulators by Pockel effect in lithium niobite race-track and microring cavities[56]. (f) Ultra-broadband coupling in the asymmetric microcavity-nanowaguide system[85]

  • Figure 6

    Single nanoparticle detection with the WGM sensor. When a nanoparticle approaches to the WGM cavity, the mode variation can represent as mode shift (a)[107], mode splitting (b)[108], or mode broadening (c)[109]


Contact and support