Laser frequency microcombs provide a series of equidistant,coherent frequency markers across a broad spectrum,enabling advancements in laser spectroscopy,dense optical communications,precision distance metrology,and a...Laser frequency microcombs provide a series of equidistant,coherent frequency markers across a broad spectrum,enabling advancements in laser spectroscopy,dense optical communications,precision distance metrology,and astronomy.Here,we design and fabricate silicon nitride,dispersion-managed microresonators that effectively suppress avoided-mode crossings and achieve close-to-zero averaged dispersion.Both the stochastic noise and mode-locking dynamics of the resonator are numerically and experimentally investigated.First,we experimentally demonstrate thermally stabilized microcomb formation in the microresonator across different mode-locked states,showing negligible center frequency shifts and a broad frequency bandwidth.Next,we characterize the femtosecond timing jitter of the microcombs,supported by precise metrology of the timing phase and relative intensity noise.For the single-soliton state,we report a relative intensity noise of−153.2 dB∕Hz,close to the shot-noise limit,and a quantum-noise–limited timing jitter power spectral density of 0.4 as 2∕Hz at a 100 kHz offset frequency,measured using a self-heterodyne linear interferometer.In addition,we achieve an integrated timing jitter of 1.7 fs±0.07 fs,measured from 10 kHz to 1 MHz.Measuring and understanding these fundamental noise parameters in high clock rate frequency microcombs is critical for advancing soliton physics and enabling new applications in precision metrology.展开更多
Mode-locked microcombs with flat spectral profiles provide the high signal-to-noise ratio and are in high demand for wavelength division multiplexing(WDM)-based applications,particularly in future high-capacity commun...Mode-locked microcombs with flat spectral profiles provide the high signal-to-noise ratio and are in high demand for wavelength division multiplexing(WDM)-based applications,particularly in future high-capacity communication and parallel optical computing.Here,we present two solutions to generate local relatively flat spectral profiles.One microcavity with ultra-flat integrated dispersion is pumped to generate one relatively flat single soliton source spanning over 150 nm.Besides,one extraordinary soliton crystal with single vacancy demonstrates the local relatively flat microcomb lines when the inner soliton spacings are slightly irregular.Our work paves a new way for soliton-based applications owing to the relatively flat spectral characteristics.展开更多
Single-crystalline Ga-doped SnO2 nanowires and SnO2：Ga2O3 heterogeneous microcombs were synthesized by a simple one-step thermal evaporation and condensation method. They were characterized by means of X-ray powder d...Single-crystalline Ga-doped SnO2 nanowires and SnO2：Ga2O3 heterogeneous microcombs were synthesized by a simple one-step thermal evaporation and condensation method. They were characterized by means of X-ray powder diffraction （XRD）, field-emission scanning electron microscopy （FE-SEM）, energy-dispersive X-ray spectroscopy （EDS）, transmission electron microscopy （TEM） and selected-area electron diffraction （SAED）. FE-SEM images showed that the products consisted of nanowires and mierocombs that represent a novel morphology. XRD, SAED and EDS indicated that they were single-crystalline tetragonal SnO2. The influence of experimental conditions on the morphologies of the products is discussed. The morphology of the product showed a ribbon-like stem and nanoribbon array aligned evenly along one or both side of the nanoribbon. It was found that many Ga2O3 nanoparticles deposited on the surface of the microcombs. The major core nanoribbon grew mainly along the [110] direction and the self-organized branching nanoribbons grew epitaxially along [110] or [110] orientation from the （110） plane of the stem. A growth process was proposed for interpreting the growth of these remarkable SnO2：Ga2O3 heterogeneous microcombs. Due to the heavy doping of Ga, the emission peak in photoluminescence spectra has red-shifted as well as broadened significantly.展开更多
Optical frequency division(OFD)produces low-noise microwave and millimeter-wave(mmWave)signals by transferring the exceptional stability of optical references to electronic frequency domains.Recent developments in int...Optical frequency division(OFD)produces low-noise microwave and millimeter-wave(mmWave)signals by transferring the exceptional stability of optical references to electronic frequency domains.Recent developments in integrated optical references and soliton microcombs have paved the way for miniaturizing OFD oscillators to chip scale.Critical to this realization is a rapid tunable frequency comb that is stabilized to the optical references,thereby coherently linking optical and electronic frequencies.In this work,we advance the on-chip OFD technology using an integrated high-speed lead zirconate titanate(PZT)stress-optic actuator on the SiN soliton microcomb resonator.The integrated PZT actuator tunes the resonance frequency of the soliton-generating microresonator with a bandwidth exceeding 10s MHz and thus adjusts the soliton repetition rate.Optical frequency division and low-noise mmWave generation are demonstrated by feedback control of the soliton repetition rate through the integrated PZT-actuator,and the soliton microcomb is stabilized to a pair of reference lasers that are locked to an integrated 4 m SiN coil reference cavity.Our approach provides a fast,versatile,and integrated control mechanism for OFD oscillators and their applications in advanced communications,sensing,and precise timing.展开更多
The demand for high-throughput,low-latency data aggregation at network edges is growing rapidly.However,existing integrated wavelength-division multiplexing(WDM)parallel light sources often suffer from limited coheren...The demand for high-throughput,low-latency data aggregation at network edges is growing rapidly.However,existing integrated wavelength-division multiplexing(WDM)parallel light sources often suffer from limited coherence,low optical carrier-to-noise ratio(OCNR),insufficient output power,or large footprint,hindering the deployment of efficient and lightweight optical interconnects at network edges.展开更多
An optical frequency comb comprises a cluster of equally spaced,phase-locked spectral lines.Replacing these classical components with correlated quantum light gives rise to cluster quantum frequency combs,providing ab...An optical frequency comb comprises a cluster of equally spaced,phase-locked spectral lines.Replacing these classical components with correlated quantum light gives rise to cluster quantum frequency combs,providing abundant quantum resources for measurement-based quantum computation,and multi-user quantum networks.We propose and generate cluster quantum microcombs within an on-chip optical microresonator driven by multi-frequency lasers.Through resonantly enhanced four-wave mixing processes,continuous-variable cluster states with 60 qumodes are deterministically created.The graph structures can be programmed into one-and two-dimensional lattices by adjusting the configurations of the pump lines,which are confirmed inseparable based on the measured covariance matrices.Our work demonstrates the largest-scale cluster states with unprecedented raw squeezing levels from a photonic chip,offering a compact and scalable platform for computational and communicational tasks with quantum advantages.展开更多
The exceptional temporal and spatial photon confinement properties of whispering gallery mode (WGM) microcavities render them ideally suitable for nonlinear frequency conversion.Here,we present a reliable packaged mic...The exceptional temporal and spatial photon confinement properties of whispering gallery mode (WGM) microcavities render them ideally suitable for nonlinear frequency conversion.Here,we present a reliable packaged microcavity device with vibration isolation,air tightness,temperature adaptability,and quality factors greater than 2 billion that can serve as a compact and stable platform for soliton optical comb generation.Low-noise soliton combs can be initiated with a repetition rate of 24.98 GHz at wavelengths near 1550 nm with 4 mW threshold power.Our work provides innovative solutions for investigating and manufacturing miniature,economical,and robust microcomb devices.展开更多
Soliton microcombs offer a compact means to generate equally spaced spectral lines via a delicate balance of Kerr nonlinearity and anomalous dispersion in nonlinear microresonators. However, the simultaneous excitatio...Soliton microcombs offer a compact means to generate equally spaced spectral lines via a delicate balance of Kerr nonlinearity and anomalous dispersion in nonlinear microresonators. However, the simultaneous excitation of multiple transverse mode families can disrupt soliton formation and degrade spectral uniformity. Here, we demonstrate universal spectral purification of microresonators with ultrahigh intrinsic Q factors exceeding 10^(8). An aluminum ring is deposited onto a silica microdisk to eliminate high-order transverse modes selectively by introducing additional losses. The resulting soliton microcombs exhibit an ideal sech^(2) spectral envelope and enable continuous tuning of the soliton repetition frequency over a 300 kHz range without compromising phase noise performance. Our approach can be universally applied to integrated photonic platforms to reduce transverse modes crowding in high-Q resonators, facilitating the generation of broadband classical and quantum light with ideal performance.展开更多
In recent years,microcomb technology has emerged as a transformative tool in photonics,providing a compact and energyefficient on-chip source for optical frequency combs that have wide-ranging applications in high-pre...In recent years,microcomb technology has emerged as a transformative tool in photonics,providing a compact and energyefficient on-chip source for optical frequency combs that have wide-ranging applications in high-precision metrology,frequency synthesis,and optical communications[1–3].Generated in high-Q microresonators,microcombs have gained attention due to their ability to generate broadband optical combs in a small footprint,offering much compactness over traditional laser-based frequency combs.Most notably,microcombs can provide large-scale parallel frequency with compressible noise,making them a cornerstone technology for next-generation integrated photonic information systems[3–5].展开更多
Visible optical frequency combs are essential to optical atomic clocks, astronomical spectrograph calibration, and biological imaging. However, due to the limitations of the dispersion properties of available material...Visible optical frequency combs are essential to optical atomic clocks, astronomical spectrograph calibration, and biological imaging. However, due to the limitations of the dispersion properties of available materials and the Q-factors of the optical microresonators working at visible wavelengths, the generation of the visible soliton microcomb remains highly challenging. Here, we demonstrate a chip-based visible single-soliton microcomb spanning two-thirds of an octave(ranging from 632.5 to 950.1 nm) by precisely engineering the dispersion of a silica microdisk resonator. Two dispersion waves at the spectrum edges are created by simultaneously employing the higher order dispersion and mode interaction in a microresonator. In particular,we achieve a high Q-factor with small mode volume at the short wavelength, which facilitates the generation of the visible soliton microcombs with 1.1 mW pump power. Moreover, based on the soliton self-frequency shift,we implement a precise adjustment of the dispersive wave, which makes the highest power tooth within the dispersive wave access the transition of ^(88)Sr+for the application in optical atomic clocks.展开更多
Acoustic perception is a fairly basic but extraordinary feature in nature,relying on multidimensional signal processing for detection,localization,and recognition.Replicating this capability in compact artificial syst...Acoustic perception is a fairly basic but extraordinary feature in nature,relying on multidimensional signal processing for detection,localization,and recognition.Replicating this capability in compact artificial systems,however,remains a formidable challenge due to limitations in scalability,sensitivity,and integration.Here,imitating the auditory system of insects,we introduce an opto-acoustic perception paradigm using fully-stabilized dual-soliton microcombs.By integrating digitally stabilized on-chip dual-microcombs,silicon optoelectronics and bionic fiber-microphone arrays on a single platform,we achieve parallelized interrogation of over 100 sensors.Leveraging the low-noise,multi-channel coherence of fully-stabilized soliton microcombs,this synergy enables ultra-sensitive detection of 29.3 nPa/Hz^(1/2),sub centimeter precise localization,real-time tracking and identification for versatile acoustic targets.Bridging silicon photonics,optical fiber sensing and intelligent signal processing in a chiplet microsystem,our scheme delivers outof-lab deployable capability on autonomous robotics.This work not only deepens the understanding of frequency comb science,but also establishes a concept of dual-comb-driven sensor networks as a scalable foundation for nextgeneration opto-acoustic intelligence.展开更多
Coherent frequency microcombs,generated in nonlinear high-Q microresonators and driven by a single continuouswave laser,have enabled several scientific breakthroughs in the past decade,thanks to their high intrinsic p...Coherent frequency microcombs,generated in nonlinear high-Q microresonators and driven by a single continuouswave laser,have enabled several scientific breakthroughs in the past decade,thanks to their high intrinsic phase coherence and individual comb line powers.Here,we report terabit-per-second-scale coherent data communications over a free-space atmospheric link,using a platicon frequency microcomb,employing wavelength-and polarizationdivision multiplexing for next-generation optical wireless networks.Spanning more than 55 optical carriers with 115 GHz channel spacing,we report the first free-space coherent communication link using a frequency microcomb,achieving up to 8.21 Tbit/s aggregate data transmission at a 20 Gbaud symbol rate per carrier over 160 m,even under log-normal turbulent conditions.Utilizing 16-state quadrature amplitude modulation,we demonstrate retrieved constellation maps across the broad microcomb spectrum,achieving bit-error rates below both hardand soft-decision thresholds for forward-error correction.Next,we examine a wavelength-division multiplexing free-space passive optical network as a baseline for free-space fronthaul,achieving an aggregate data rate of up to 5.21 Tbit/s and a field-tested spectral efficiency of 1.29 bit/s/Hz in the microcomb-based atmospheric link.We also quantify experimental power penalties of≈3.8 dB at the error-correction threshold,relative to the theoretical additive white Gaussian noise limit.Furthermore,we introduce the first-ever demonstration of master–slave free-space carrier phase retrieval with frequency microcombs,and the compensation for turbulence-induced intensity scintillation and pointing error fluctuations,to improve end-to-end symbol error rates.This work provides a foundational platform for broadband vertical heterogeneous connectivity,terrestrial backbone links,and groundsatellite communication.展开更多
Chip-based soliton frequency microcombs combine compact size,broad bandwidth,and high coherence,presenting a promising solution for integrated optical telecommunications,precision sensing,and spectroscopy.Recent progr...Chip-based soliton frequency microcombs combine compact size,broad bandwidth,and high coherence,presenting a promising solution for integrated optical telecommunications,precision sensing,and spectroscopy.Recent progress in ferroelectric thin films,particularly thin-film lithium niobate(LiNbO_(3))and thin-film lithium tantalate(LiTaO_(3)),has significantly advanced electro-optic(EO)modulation and soliton microcombs generation,leveraging their strong third-order nonlinearity and high Pockels coefficients.However,achieving soliton frequency combs in X-cut ferroelectric materials remains challenging due to the competing effects of thermo-optic and photorefractive phenomena.These issues hinder the simultaneous realization of soliton generation and high-speed EO modulation.Here,following the thermal-regulated carrier behavior and auxiliary-laser-assisted approach,we propose a convenient mechanism to suppress both photorefractive and thermal dragging effects at once,and implement a facile method for soliton formation and its longterm stabilization in integrated X-cut LiTaO_(3) microresonators for the first time,to the best of our knowledge.The resulting mode-locked states exhibit robust stability against perturbations,enabling new pathways for fully integrated photonic circuits that combine Kerr nonlinearity with high-speed EO functionality.展开更多
Kerr soliton microcombs have the potential to disrupt a variety of applications such as ultra-high-speed optical communications,ultra-fast distance measurements,massively parallel light detection and ranging(LiDAR)or ...Kerr soliton microcombs have the potential to disrupt a variety of applications such as ultra-high-speed optical communications,ultra-fast distance measurements,massively parallel light detection and ranging(LiDAR)or high-resolution optical spectroscopy.Similarly,ultra-broadband photonic-electronic signal processing could also benefit from chip-scale frequency comb sources that offer wideband optical emission along with ultra-low phase noise and timing jitter.However,while photonic analogue-to-digital converters(ADC)based on femtosecond lasers have been shown to overcome the jitter-related limitations of electronic oscillators,the potential of Kerr combs in photonic-electronic signal processing remains to be explored.In this work,we demonstrate a microcomb-based photonic-electronic ADC that combines a high-speed electro-optic modulator with a Kerr comb for spectrally sliced coherent detection of the generated optical waveform.The system offers a record-high acquisition bandwidth of 320 GHz,corresponding to an effective sampling rate of at least 640GSa/s.In a proof-of-concept experiment,we demonstrate the viability of the concept by acquiring a broadband analogue data signal comprising different channels with centre frequencies between 24 GHz and 264 GHz,offering bit error ratios(BER)below widely used forward-error-correction(FEC)thresholds.To the best of our knowledge,this is the first demonstration of a microcomb-based ADC,leading to the largest acquisition bandwidth demonstrated for any ADC so far.展开更多
Optical frequency combs,a revolutionary light source characterized by discrete and equally spaced frequencies,are usually regarded as a cornerstone for advanced frequency metrology,precision spectroscopy,high-speed co...Optical frequency combs,a revolutionary light source characterized by discrete and equally spaced frequencies,are usually regarded as a cornerstone for advanced frequency metrology,precision spectroscopy,high-speed communication,distance ranging,molecule detection,and many others.Due to the rapid development of micro/nanofabrication technology,breakthroughs in the quality factor of microresonators enable ultrahigh energy buildup inside cavities,which gives birth to microcavity-based frequency combs.In particular,the full coherent spectrum of the soliton microcomb(SMC)provides a route to low-noise ultrashort pulses with a repetition rate over two orders of magnitude higher than that of traditional mode-locking approaches.This enables lower power consumption and cost for a wide range of applications.This review summarizes recent achievements in SMCs,including the basic theory and physical model,as well as experimental techniques for single-soliton generation and various extraordinary soliton states(soliton crystals,Stokes solitons,breathers,molecules,cavity solitons,and dark solitons),with a perspective on their potential applications and remaining challenges.展开更多
Dual-comb spectroscopy(DCS) is a powerful tool in molecular spectroscopy benefiting from the advantages of high resolution and short measurement time. The recently developed soliton microcomb(SMC) can potentially tran...Dual-comb spectroscopy(DCS) is a powerful tool in molecular spectroscopy benefiting from the advantages of high resolution and short measurement time. The recently developed soliton microcomb(SMC) can potentially transfer the dual-comb method to an on-chip platform. In this paper, we demonstrate DCS using two frequency scanning SMCs, termed scanning dual-microcomb spectroscopy(SDMCS). The two SMCs are generated by an auxiliary-assisted thermal balance scheme, and the pump laser frequency sweeps over one free spectral range of the microresonator(~49 GHz) using a feedback control system. The proposed SDMCS has a spectral resolution of 12.5 MHz, which is determined by the minimum sweeping step of the pump laser. Using this SDMCS system, we perform three types of gas molecule absorption spectroscopy recognition and gas concentration detection.This study paves the way for integrated DCS with a high signal-to-noise ratio, high spectral resolution, and fast acquisition rate.展开更多
The dissipative Kerr soliton microcomb provides a promising laser source for wavelength-division multiplexing(WDM)communication systems thanks to its compatibility with chip integration.However,the soliton microcomb c...The dissipative Kerr soliton microcomb provides a promising laser source for wavelength-division multiplexing(WDM)communication systems thanks to its compatibility with chip integration.However,the soliton microcomb commonly suffers from a low-power level due to the intrinsically limited energy conversion efficiency from the continuous-wave pump laser to ultra-short solitary pulses.Here,we exploit laser injection locking to amplify and equalize dissipative Kerr soliton comb lines,superior gain factor larger than 30 dB,and optical-signal-to-noise-ratio(OSNR)as high as 60 dB obtained experimentally,providing a potential pathway to constitute a high-power chip-integrated WDM laser source for optical communications.展开更多
Microcombs are revolutionizing optoelectronics by providing parallel, mutually coherent wavelengthchannels for time-frequency metrology and information processing. To implement this essential function inintegrated pho...Microcombs are revolutionizing optoelectronics by providing parallel, mutually coherent wavelengthchannels for time-frequency metrology and information processing. To implement this essential function inintegrated photonic systems, it is desirable to drive microcombs directly with an on-chip laser in a simpleand flexible way. However, two major difficulties have prevented this goal: (1) generating mode-lockedcomb states usually requires a significant amount of pump power and (2) the requirement to align laser andresonator frequency significantly complicates operation and limits the tunability of the comb lines. Here, weaddress these problems by using microresonators on an AlGaAs on-insulator platform to generate dark-pulsemicrocombs. This highly nonlinear platform dramatically relaxes fabrication requirements and leads to arecord-low pump power of <1 mW for coherent comb generation. Dark-pulse microcombs facilitated bythermally controlled avoided mode crossings are accessed by direct distributed feedback laser pumping.Without any feedback or control circuitries, the comb shows good coherence and stability. With around150 mW on-chip power, this approach also leads to an unprecedentedly wide tuning range of over one freespectral range (97.5 GHz). Our work provides a route to realize power-efficient, simple, and reconfigurablemicrocombs that can be seamlessly integrated with a wide range of photonic systems.展开更多
For the applications of the frequency comb in microresonators,it is essential to obtain a fully frequency-stabilized microcomb laser source.In this study,we present a system for generating a fully atom-referenced stab...For the applications of the frequency comb in microresonators,it is essential to obtain a fully frequency-stabilized microcomb laser source.In this study,we present a system for generating a fully atom-referenced stabilized soliton microcomb.The pump light around 1560.48 nm is locked to an ultra-low-expansion(ULE)cavity.This pump light is then frequency-doubled and referenced to the atomic transition of87Rb.The repetition rate of the soliton microcomb is injection-locked to an atomic-clockstabilized radio frequency(RF)source,leading to mHz stabilization at 1 s.As a result,all comb lines have been frequencystabilized based on the atomic reference and the ULE cavity,achieving a very high precision of approximately 18 Hz at 1 s,corresponding to the frequency stability of 9.5×10^(-14).Our approach provides a fully stabilized microcomb experiment scheme with no requirement of f-2f technique,which could be easily implemented and generalized to various photonic platforms,thus paving the way towards the ultraprecise optical sources for high precision spectroscopy.展开更多
The optical frequency comb based on microresonators(microcombs)is an integrated coherent light source and has the potential to promise a high-precision frequency standard;self-reference and a long-term stable microcom...The optical frequency comb based on microresonators(microcombs)is an integrated coherent light source and has the potential to promise a high-precision frequency standard;self-reference and a long-term stable microcomb are the keys to this realization.Here,we demonstrated a 0.7-octave spectrum Kerr comb via dispersion engineering in a thin-film lithium niobate microresonator,and the single-soliton state can be accessed passively with long-term stability over 3 h.With such a robust broadband coherent comb source using thin-film lithium niobate,a fully stabilized microcomb can be expected for massive practical applications.展开更多
基金support from the Lawrence Livermore National Laboratory(Grant No.B622827)the National Science Foundation(Grant Nos.1824568,1810506,1741707,and 1829071)the Office of Naval Research(Grant No.N00014-16-1-2094).
文摘Laser frequency microcombs provide a series of equidistant,coherent frequency markers across a broad spectrum,enabling advancements in laser spectroscopy,dense optical communications,precision distance metrology,and astronomy.Here,we design and fabricate silicon nitride,dispersion-managed microresonators that effectively suppress avoided-mode crossings and achieve close-to-zero averaged dispersion.Both the stochastic noise and mode-locking dynamics of the resonator are numerically and experimentally investigated.First,we experimentally demonstrate thermally stabilized microcomb formation in the microresonator across different mode-locked states,showing negligible center frequency shifts and a broad frequency bandwidth.Next,we characterize the femtosecond timing jitter of the microcombs,supported by precise metrology of the timing phase and relative intensity noise.For the single-soliton state,we report a relative intensity noise of−153.2 dB∕Hz,close to the shot-noise limit,and a quantum-noise–limited timing jitter power spectral density of 0.4 as 2∕Hz at a 100 kHz offset frequency,measured using a self-heterodyne linear interferometer.In addition,we achieve an integrated timing jitter of 1.7 fs±0.07 fs,measured from 10 kHz to 1 MHz.Measuring and understanding these fundamental noise parameters in high clock rate frequency microcombs is critical for advancing soliton physics and enabling new applications in precision metrology.
基金funding support from Dream X International Innovation Teamthe support from the startup grant from Nanyang Technological University (022527-00001)。
文摘Mode-locked microcombs with flat spectral profiles provide the high signal-to-noise ratio and are in high demand for wavelength division multiplexing(WDM)-based applications,particularly in future high-capacity communication and parallel optical computing.Here,we present two solutions to generate local relatively flat spectral profiles.One microcavity with ultra-flat integrated dispersion is pumped to generate one relatively flat single soliton source spanning over 150 nm.Besides,one extraordinary soliton crystal with single vacancy demonstrates the local relatively flat microcomb lines when the inner soliton spacings are slightly irregular.Our work paves a new way for soliton-based applications owing to the relatively flat spectral characteristics.
基金This work was supported by the National Natural Science Foundation of China （No.20671027）, and the Natural Science Foundation of Anhui province, China （No.050440904）.
文摘Single-crystalline Ga-doped SnO2 nanowires and SnO2：Ga2O3 heterogeneous microcombs were synthesized by a simple one-step thermal evaporation and condensation method. They were characterized by means of X-ray powder diffraction （XRD）, field-emission scanning electron microscopy （FE-SEM）, energy-dispersive X-ray spectroscopy （EDS）, transmission electron microscopy （TEM） and selected-area electron diffraction （SAED）. FE-SEM images showed that the products consisted of nanowires and mierocombs that represent a novel morphology. XRD, SAED and EDS indicated that they were single-crystalline tetragonal SnO2. The influence of experimental conditions on the morphologies of the products is discussed. The morphology of the product showed a ribbon-like stem and nanoribbon array aligned evenly along one or both side of the nanoribbon. It was found that many Ga2O3 nanoparticles deposited on the surface of the microcombs. The major core nanoribbon grew mainly along the [110] direction and the self-organized branching nanoribbons grew epitaxially along [110] or [110] orientation from the （110） plane of the stem. A growth process was proposed for interpreting the growth of these remarkable SnO2：Ga2O3 heterogeneous microcombs. Due to the heavy doping of Ga, the emission peak in photoluminescence spectra has red-shifted as well as broadened significantly.
基金Defense Advanced Research Projects Agency(HR0011-22-2-0008,N660012424000)National Science Foundation(2023775)。
文摘Optical frequency division(OFD)produces low-noise microwave and millimeter-wave(mmWave)signals by transferring the exceptional stability of optical references to electronic frequency domains.Recent developments in integrated optical references and soliton microcombs have paved the way for miniaturizing OFD oscillators to chip scale.Critical to this realization is a rapid tunable frequency comb that is stabilized to the optical references,thereby coherently linking optical and electronic frequencies.In this work,we advance the on-chip OFD technology using an integrated high-speed lead zirconate titanate(PZT)stress-optic actuator on the SiN soliton microcomb resonator.The integrated PZT actuator tunes the resonance frequency of the soliton-generating microresonator with a bandwidth exceeding 10s MHz and thus adjusts the soliton repetition rate.Optical frequency division and low-noise mmWave generation are demonstrated by feedback control of the soliton repetition rate through the integrated PZT-actuator,and the soliton microcomb is stabilized to a pair of reference lasers that are locked to an integrated 4 m SiN coil reference cavity.Our approach provides a fast,versatile,and integrated control mechanism for OFD oscillators and their applications in advanced communications,sensing,and precise timing.
文摘The demand for high-throughput,low-latency data aggregation at network edges is growing rapidly.However,existing integrated wavelength-division multiplexing(WDM)parallel light sources often suffer from limited coherence,low optical carrier-to-noise ratio(OCNR),insufficient output power,or large footprint,hindering the deployment of efficient and lightweight optical interconnects at network edges.
基金supported by the National Key R&D Plan of China(Grant No.2021ZD0301500)Beijing Natural Science Foundation(Z210004,Z240007)+2 种基金National Natural Science Foundation of China(92150108,62222515,12125402,12174438)the High-performance Computing Platform of Peking Universitysupported by the Micro/nano Fabrication Laboratory of Synergetic Extreme Condition User Facility(SECUF).
文摘An optical frequency comb comprises a cluster of equally spaced,phase-locked spectral lines.Replacing these classical components with correlated quantum light gives rise to cluster quantum frequency combs,providing abundant quantum resources for measurement-based quantum computation,and multi-user quantum networks.We propose and generate cluster quantum microcombs within an on-chip optical microresonator driven by multi-frequency lasers.Through resonantly enhanced four-wave mixing processes,continuous-variable cluster states with 60 qumodes are deterministically created.The graph structures can be programmed into one-and two-dimensional lattices by adjusting the configurations of the pump lines,which are confirmed inseparable based on the measured covariance matrices.Our work demonstrates the largest-scale cluster states with unprecedented raw squeezing levels from a photonic chip,offering a compact and scalable platform for computational and communicational tasks with quantum advantages.
基金supported by the National Natural Science Foundation of China (No. 62305006)the Natural Science FoundationofJiangsuProvince(Nos.BK20230287 and BK20230286)the Nantong Social Livelihood Science and Technology Planning Project (Nos. MS12022003 and MS2023071)。
文摘The exceptional temporal and spatial photon confinement properties of whispering gallery mode (WGM) microcavities render them ideally suitable for nonlinear frequency conversion.Here,we present a reliable packaged microcavity device with vibration isolation,air tightness,temperature adaptability,and quality factors greater than 2 billion that can serve as a compact and stable platform for soliton optical comb generation.Low-noise soliton combs can be initiated with a repetition rate of 24.98 GHz at wavelengths near 1550 nm with 4 mW threshold power.Our work provides innovative solutions for investigating and manufacturing miniature,economical,and robust microcomb devices.
基金National Natural Science Foundation of China(62222515, 12174438)Innovation Program for Quantum Science and Technology (2023ZD0301100)+2 种基金National Key Research and Development Program of China(2021YFA1400700)Basic Frontier Science Research Program of Chinese Academy of Sciences (ZDBS-LYJSC003)CAS Project for Young Scientists in Basic Research (YSBR-100)
文摘Soliton microcombs offer a compact means to generate equally spaced spectral lines via a delicate balance of Kerr nonlinearity and anomalous dispersion in nonlinear microresonators. However, the simultaneous excitation of multiple transverse mode families can disrupt soliton formation and degrade spectral uniformity. Here, we demonstrate universal spectral purification of microresonators with ultrahigh intrinsic Q factors exceeding 10^(8). An aluminum ring is deposited onto a silica microdisk to eliminate high-order transverse modes selectively by introducing additional losses. The resulting soliton microcombs exhibit an ideal sech^(2) spectral envelope and enable continuous tuning of the soliton repetition frequency over a 300 kHz range without compromising phase noise performance. Our approach can be universally applied to integrated photonic platforms to reduce transverse modes crowding in high-Q resonators, facilitating the generation of broadband classical and quantum light with ideal performance.
文摘In recent years,microcomb technology has emerged as a transformative tool in photonics,providing a compact and energyefficient on-chip source for optical frequency combs that have wide-ranging applications in high-precision metrology,frequency synthesis,and optical communications[1–3].Generated in high-Q microresonators,microcombs have gained attention due to their ability to generate broadband optical combs in a small footprint,offering much compactness over traditional laser-based frequency combs.Most notably,microcombs can provide large-scale parallel frequency with compressible noise,making them a cornerstone technology for next-generation integrated photonic information systems[3–5].
基金supported by the Guangdong Major Project of Basic and Applied Basic Research(Grant No.2020B0301030009)National Natural Science Foundation of China(NSFC)(Grant Nos.12293054,12341403,and 92463304)+1 种基金National Key R&D Program of China(Grant Nos.2021YFA1400803 and 2023YFB3906401)Fundamental Research Funds for the Central Universities(Grant Nos.021314380260 and 021314380283).
文摘Visible optical frequency combs are essential to optical atomic clocks, astronomical spectrograph calibration, and biological imaging. However, due to the limitations of the dispersion properties of available materials and the Q-factors of the optical microresonators working at visible wavelengths, the generation of the visible soliton microcomb remains highly challenging. Here, we demonstrate a chip-based visible single-soliton microcomb spanning two-thirds of an octave(ranging from 632.5 to 950.1 nm) by precisely engineering the dispersion of a silica microdisk resonator. Two dispersion waves at the spectrum edges are created by simultaneously employing the higher order dispersion and mode interaction in a microresonator. In particular,we achieve a high Q-factor with small mode volume at the short wavelength, which facilitates the generation of the visible soliton microcombs with 1.1 mW pump power. Moreover, based on the soliton self-frequency shift,we implement a precise adjustment of the dispersive wave, which makes the highest power tooth within the dispersive wave access the transition of ^(88)Sr+for the application in optical atomic clocks.
基金National Natural Science Foundation of China,U24A20311,BAICHENG YAO,62305050,Teng TanNational Key Research and Development Program of China,2023YFB2806200,BAICHENG YAO,2023YFB2805600,Teng TanNational Postdoctoral Innovation Talent Support Program of China,BX20220056,Teng Tan。
文摘Acoustic perception is a fairly basic but extraordinary feature in nature,relying on multidimensional signal processing for detection,localization,and recognition.Replicating this capability in compact artificial systems,however,remains a formidable challenge due to limitations in scalability,sensitivity,and integration.Here,imitating the auditory system of insects,we introduce an opto-acoustic perception paradigm using fully-stabilized dual-soliton microcombs.By integrating digitally stabilized on-chip dual-microcombs,silicon optoelectronics and bionic fiber-microphone arrays on a single platform,we achieve parallelized interrogation of over 100 sensors.Leveraging the low-noise,multi-channel coherence of fully-stabilized soliton microcombs,this synergy enables ultra-sensitive detection of 29.3 nPa/Hz^(1/2),sub centimeter precise localization,real-time tracking and identification for versatile acoustic targets.Bridging silicon photonics,optical fiber sensing and intelligent signal processing in a chiplet microsystem,our scheme delivers outof-lab deployable capability on autonomous robotics.This work not only deepens the understanding of frequency comb science,but also establishes a concept of dual-comb-driven sensor networks as a scalable foundation for nextgeneration opto-acoustic intelligence.
基金financial support from the Office of Naval Research(N00014-16-1-2094)the National Science Foundation(1824568,1810506,1741707,and 1919355).
文摘Coherent frequency microcombs,generated in nonlinear high-Q microresonators and driven by a single continuouswave laser,have enabled several scientific breakthroughs in the past decade,thanks to their high intrinsic phase coherence and individual comb line powers.Here,we report terabit-per-second-scale coherent data communications over a free-space atmospheric link,using a platicon frequency microcomb,employing wavelength-and polarizationdivision multiplexing for next-generation optical wireless networks.Spanning more than 55 optical carriers with 115 GHz channel spacing,we report the first free-space coherent communication link using a frequency microcomb,achieving up to 8.21 Tbit/s aggregate data transmission at a 20 Gbaud symbol rate per carrier over 160 m,even under log-normal turbulent conditions.Utilizing 16-state quadrature amplitude modulation,we demonstrate retrieved constellation maps across the broad microcomb spectrum,achieving bit-error rates below both hardand soft-decision thresholds for forward-error correction.Next,we examine a wavelength-division multiplexing free-space passive optical network as a baseline for free-space fronthaul,achieving an aggregate data rate of up to 5.21 Tbit/s and a field-tested spectral efficiency of 1.29 bit/s/Hz in the microcomb-based atmospheric link.We also quantify experimental power penalties of≈3.8 dB at the error-correction threshold,relative to the theoretical additive white Gaussian noise limit.Furthermore,we introduce the first-ever demonstration of master–slave free-space carrier phase retrieval with frequency microcombs,and the compensation for turbulence-induced intensity scintillation and pointing error fluctuations,to improve end-to-end symbol error rates.This work provides a foundational platform for broadband vertical heterogeneous connectivity,terrestrial backbone links,and groundsatellite communication.
基金National Key Research and Development Program of China(2022YFA1404601)National Natural Science Foundation of China(62293520,62293521,12074400,62205363,12104442,12404446,12293052)+4 种基金Shanghai Science and Technology Innovation Action Plan Program(20JC1416200,22JC1403300)CAS Project for Young Scientists in Basic Research(YSBR-69)Natural Science Foundation of Anhui Province(2408085QA010)China Postdoctoral Science Foundation(2024M753078)Postdoctoral Fellowship Program of CPSF(GZC20232560)。
文摘Chip-based soliton frequency microcombs combine compact size,broad bandwidth,and high coherence,presenting a promising solution for integrated optical telecommunications,precision sensing,and spectroscopy.Recent progress in ferroelectric thin films,particularly thin-film lithium niobate(LiNbO_(3))and thin-film lithium tantalate(LiTaO_(3)),has significantly advanced electro-optic(EO)modulation and soliton microcombs generation,leveraging their strong third-order nonlinearity and high Pockels coefficients.However,achieving soliton frequency combs in X-cut ferroelectric materials remains challenging due to the competing effects of thermo-optic and photorefractive phenomena.These issues hinder the simultaneous realization of soliton generation and high-speed EO modulation.Here,following the thermal-regulated carrier behavior and auxiliary-laser-assisted approach,we propose a convenient mechanism to suppress both photorefractive and thermal dragging effects at once,and implement a facile method for soliton formation and its longterm stabilization in integrated X-cut LiTaO_(3) microresonators for the first time,to the best of our knowledge.The resulting mode-locked states exhibit robust stability against perturbations,enabling new pathways for fully integrated photonic circuits that combine Kerr nonlinearity with high-speed EO functionality.
基金supported by the ERC Consolidator Grant TeraSHAPE(#773248)the H2020 project TeraSlice(#863322)+10 种基金by the EIC Transition projects MAGNIFY(#101113302),HDLN(#101113260),and CombTools(#101136978)by the H2020 Marie Skłodowska-Curie Innovative Training Network“MICROCOMB”(#812818)by the Deutsche Forschungsgemeinschaft(DFG)project PACE(#403188360)within the Priority Programme“Electronic-Photonic Integrated Systems for Ultrafast Signal Processing”(SPP 2111)by the DFG Collaborative Research Centre(CRC)WavePhenomena(SFB 1173,Project-ID 258734477)by the BMBF project Open6GHub(#16KISK010)by the Alfried Krupp von Bohlen und Halbach-Stiftungby the Max-Planck School of Photonics(MPSP)by the European Regional Development Fund(ERDF,grant EFRE/FEIH_776267)the Deutsche Forschungsgemeinschaft(DFGgrants DFG/INST 121384/166-1 and DFG/INST 121384/167-1The Si3N4 samples were fabricated in the Centre of MicroNano Technology(CMi)at EPFL.
文摘Kerr soliton microcombs have the potential to disrupt a variety of applications such as ultra-high-speed optical communications,ultra-fast distance measurements,massively parallel light detection and ranging(LiDAR)or high-resolution optical spectroscopy.Similarly,ultra-broadband photonic-electronic signal processing could also benefit from chip-scale frequency comb sources that offer wideband optical emission along with ultra-low phase noise and timing jitter.However,while photonic analogue-to-digital converters(ADC)based on femtosecond lasers have been shown to overcome the jitter-related limitations of electronic oscillators,the potential of Kerr combs in photonic-electronic signal processing remains to be explored.In this work,we demonstrate a microcomb-based photonic-electronic ADC that combines a high-speed electro-optic modulator with a Kerr comb for spectrally sliced coherent detection of the generated optical waveform.The system offers a record-high acquisition bandwidth of 320 GHz,corresponding to an effective sampling rate of at least 640GSa/s.In a proof-of-concept experiment,we demonstrate the viability of the concept by acquiring a broadband analogue data signal comprising different channels with centre frequencies between 24 GHz and 264 GHz,offering bit error ratios(BER)below widely used forward-error-correction(FEC)thresholds.To the best of our knowledge,this is the first demonstration of a microcomb-based ADC,leading to the largest acquisition bandwidth demonstrated for any ADC so far.
基金This work was supported by the National Natural Science Foundation of China(Grant Nos.61635013 and 61675231)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB24030600)the Youth Innovation Promotion Association of CAS(Grant No.2016353)。
文摘Optical frequency combs,a revolutionary light source characterized by discrete and equally spaced frequencies,are usually regarded as a cornerstone for advanced frequency metrology,precision spectroscopy,high-speed communication,distance ranging,molecule detection,and many others.Due to the rapid development of micro/nanofabrication technology,breakthroughs in the quality factor of microresonators enable ultrahigh energy buildup inside cavities,which gives birth to microcavity-based frequency combs.In particular,the full coherent spectrum of the soliton microcomb(SMC)provides a route to low-noise ultrashort pulses with a repetition rate over two orders of magnitude higher than that of traditional mode-locking approaches.This enables lower power consumption and cost for a wide range of applications.This review summarizes recent achievements in SMCs,including the basic theory and physical model,as well as experimental techniques for single-soliton generation and various extraordinary soliton states(soliton crystals,Stokes solitons,breathers,molecules,cavity solitons,and dark solitons),with a perspective on their potential applications and remaining challenges.
基金supported by the National Key R&D Program of China(Grant No. 2021YFB2800600)National Natural Science Foundation of China (Grant No. 62075238)。
文摘Dual-comb spectroscopy(DCS) is a powerful tool in molecular spectroscopy benefiting from the advantages of high resolution and short measurement time. The recently developed soliton microcomb(SMC) can potentially transfer the dual-comb method to an on-chip platform. In this paper, we demonstrate DCS using two frequency scanning SMCs, termed scanning dual-microcomb spectroscopy(SDMCS). The two SMCs are generated by an auxiliary-assisted thermal balance scheme, and the pump laser frequency sweeps over one free spectral range of the microresonator(~49 GHz) using a feedback control system. The proposed SDMCS has a spectral resolution of 12.5 MHz, which is determined by the minimum sweeping step of the pump laser. Using this SDMCS system, we perform three types of gas molecule absorption spectroscopy recognition and gas concentration detection.This study paves the way for integrated DCS with a high signal-to-noise ratio, high spectral resolution, and fast acquisition rate.
基金supported by the National Key R&D Program of China(Nos.2019YFB-2203103 and 2018YFA0307400)the National Natural Science Foundation of China(NSFC)(Nos.62001086 and 61705033)。
文摘The dissipative Kerr soliton microcomb provides a promising laser source for wavelength-division multiplexing(WDM)communication systems thanks to its compatibility with chip integration.However,the soliton microcomb commonly suffers from a low-power level due to the intrinsically limited energy conversion efficiency from the continuous-wave pump laser to ultra-short solitary pulses.Here,we exploit laser injection locking to amplify and equalize dissipative Kerr soliton comb lines,superior gain factor larger than 30 dB,and optical-signal-to-noise-ratio(OSNR)as high as 60 dB obtained experimentally,providing a potential pathway to constitute a high-power chip-integrated WDM laser source for optical communications.
文摘Microcombs are revolutionizing optoelectronics by providing parallel, mutually coherent wavelengthchannels for time-frequency metrology and information processing. To implement this essential function inintegrated photonic systems, it is desirable to drive microcombs directly with an on-chip laser in a simpleand flexible way. However, two major difficulties have prevented this goal: (1) generating mode-lockedcomb states usually requires a significant amount of pump power and (2) the requirement to align laser andresonator frequency significantly complicates operation and limits the tunability of the comb lines. Here, weaddress these problems by using microresonators on an AlGaAs on-insulator platform to generate dark-pulsemicrocombs. This highly nonlinear platform dramatically relaxes fabrication requirements and leads to arecord-low pump power of <1 mW for coherent comb generation. Dark-pulse microcombs facilitated bythermally controlled avoided mode crossings are accessed by direct distributed feedback laser pumping.Without any feedback or control circuitries, the comb shows good coherence and stability. With around150 mW on-chip power, this approach also leads to an unprecedentedly wide tuning range of over one freespectral range (97.5 GHz). Our work provides a route to realize power-efficient, simple, and reconfigurablemicrocombs that can be seamlessly integrated with a wide range of photonic systems.
基金supported by the National Key Research and Development Program of China(Grant No.2020YFB2205801)the National Natural Science Foundation of China(Grant Nos.12293052,12293050,11934012,12104442,12304435,and 92050109)+3 种基金the CAS Project for Young Scientists in Basic Research(Grant No.YSBR-069)the Fundamental Research Funds for the Central Universitiesthe China Postdoctoral Science Foundation(Grant No.2023M733414)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB24030600)。
文摘For the applications of the frequency comb in microresonators,it is essential to obtain a fully frequency-stabilized microcomb laser source.In this study,we present a system for generating a fully atom-referenced stabilized soliton microcomb.The pump light around 1560.48 nm is locked to an ultra-low-expansion(ULE)cavity.This pump light is then frequency-doubled and referenced to the atomic transition of87Rb.The repetition rate of the soliton microcomb is injection-locked to an atomic-clockstabilized radio frequency(RF)source,leading to mHz stabilization at 1 s.As a result,all comb lines have been frequencystabilized based on the atomic reference and the ULE cavity,achieving a very high precision of approximately 18 Hz at 1 s,corresponding to the frequency stability of 9.5×10^(-14).Our approach provides a fully stabilized microcomb experiment scheme with no requirement of f-2f technique,which could be easily implemented and generalized to various photonic platforms,thus paving the way towards the ultraprecise optical sources for high precision spectroscopy.
基金This work was supported by the National Key R&D Program of China(Nos.2022YFA1205100,2023YFB2805700,and 2019YFA0705000)the National Natural Science Foundation of China(Nos.62293523 and 12304421)+4 种基金the Leading-edge Technology Program of Jiangsu Natural Science Foundation(No.BK20192001)the Zhangjiang Laboratory(No.ZJSP21A001)the Guangdong Major Project of Basic and Applied Basic Research(No.2020B0301030009)the Jiangsu Natural Science Foundation(No.BK20230770)the Jiangsu Funding Program for Excellent Postdoctoral Talent.
文摘The optical frequency comb based on microresonators(microcombs)is an integrated coherent light source and has the potential to promise a high-precision frequency standard;self-reference and a long-term stable microcomb are the keys to this realization.Here,we demonstrated a 0.7-octave spectrum Kerr comb via dispersion engineering in a thin-film lithium niobate microresonator,and the single-soliton state can be accessed passively with long-term stability over 3 h.With such a robust broadband coherent comb source using thin-film lithium niobate,a fully stabilized microcomb can be expected for massive practical applications.
