Based on a semiconductor laser （SL） with incoherent optical feedback, a novel all-optical scheme for generating tunable and broadband microwave frequency combs （MFCs） is proposed and investigated numerically. The ...Based on a semiconductor laser （SL） with incoherent optical feedback, a novel all-optical scheme for generating tunable and broadband microwave frequency combs （MFCs） is proposed and investigated numerically. The results show that, under suitable operation parameters, the SL with incoherent optical feedback can be driven to operate at a regular pulsing state, and the generated MFCs have bandwidths broader than 40 GHz within a 10 dB amplitude variation. For a fixed bias current, the line spacing （or repetition frequency） of the MFCs can be easily tuned by varying the feedback delay time and the feedback strength, and the tuning range of the line spacing increases with the increase in the bias current. The linewidth of the MFCs is sensitive to the variation of the feedback delay time and the feedback strength, and a linewidth of tens of KHz can be achieved through finely adjusting the feedback delay time and the feedback strength. In addition, mappings of amplitude variation, repetition frequency, and linewidth of MFCs in the parameter space of the feedback delay time and the feedback strength are presented.展开更多
The optical injection locking of semiconductor lasers to dual-frequency lasers is studied by numerical simulations.The beat-note signals can be effectively transformed to optical frequency combs due to the effective f...The optical injection locking of semiconductor lasers to dual-frequency lasers is studied by numerical simulations.The beat-note signals can be effectively transformed to optical frequency combs due to the effective four wave-mixing in the active semiconductor gain medium. The low-noise Gaussian-like pulse can be obtained by locking the relaxation oscillation and compensating the gain asymmetry. The simulations suggest that pulse trains of width below 30 ps and repetition rate in GHz frequency can be generated simply by the optical injection locking of semiconductor lasers. Since the optical injection locking can broaden the spectrum and amplify the optical power simultaneously, it can be a good initial stage for generating optical frequency combs from dual-frequency lasers by multi-stage of spectral broadening in nonlinear waveguides.展开更多
A novel dispersion-compensation scheme based on double-chirped Bragg mirrors is implemented in a mid-infrared quantum cascade laser.As a result,stable and broadband frequency combs are generated,which are indispensabl...A novel dispersion-compensation scheme based on double-chirped Bragg mirrors is implemented in a mid-infrared quantum cascade laser.As a result,stable and broadband frequency combs are generated,which are indispensable for high-precision applications in spectroscopy and metrology.展开更多
Dispersion engineering is critical for the creation of integrated broadband laser frequency combs.In the long wavelength infrared range(LWIR,8-13µm),frequency combs based on quantum cascade lasers are attractive ...Dispersion engineering is critical for the creation of integrated broadband laser frequency combs.In the long wavelength infrared range(LWIR,8-13µm),frequency combs based on quantum cascade lasers are attractive since they are monolithic,fundamental oscillators with high power levels and efficiencies.One effective approach for expanding quantum cascade laser gain bandwidth is by stacking multiple gain media with different center lasing frequencies,as this leads to flatter broadband gain spectra.However,as the gain bandwidth is increased,dispersion becomes the main limiting factor for comb bandwidth.Therefore,achieving broadband combs requires schemes that can flexibly engineer the dispersion over broad bandwidths.Here,we demonstrate the ultimate nanophotonic dispersion compensation scheme:an air-dielectric slab double-chirped mirror,which we fully integrate with the quantum cascade laser gain section.This scheme relies on the highest possible index contrast and therefore provides the maximum correction per unit length over a very broad bandwidth.With this approach,we report the successful demonstration of a broadband room-temperature LWIR laser frequency comb on a gain medium that normally does not form combs without deliberate dispersion compensations.Our air-dielectric mirrors are versatile and can be extended to other integrated laser frequency combs in different material platforms and frequency bands.展开更多
Frequency combs show various applications in molecular fingerprinting,imaging,communications,and so on.In the terahertz frequency range,semiconductor-based quantum cascade lasers(QCLs)are ideal platforms for realizing...Frequency combs show various applications in molecular fingerprinting,imaging,communications,and so on.In the terahertz frequency range,semiconductor-based quantum cascade lasers(QCLs)are ideal platforms for realizing the frequency comb operation.Although self-started frequency comb operation can be obtained in free-running terahertz QCLs due to the four-wave mixing locking effects,resonant/off-resonant microwave injection,phase locking,and femtosecond laser based locking techniques have been widely used to broaden and stabilize terahertz QCL combs.These active locking methods indeed show significant effects on the frequency stabilization of terahertz QCL combs,but they simultaneously have drawbacks,such as introducing large phase noise and requiring complex optical coupling and/or electrical circuits.Here,we demonstrate Farey tree locking of terahertz QCL frequency combs under microwave injection.The frequency competition between the Farey fraction frequency and the cavity round-trip frequency results in the frequency locking of terahertz QCL combs,and the Farey fraction frequencies can be accurately anticipated based on the downward trend of the Farey tree hierarchy.Furthermore,dual-comb experimental results show that the phase noise of the dual-comb spectral lines is significantly reduced by employing the Farey tree locking method.These results pave the way to deploying compact and low phase noise terahertz frequency comb sources.展开更多
Optical frequency combs are indispensable links between the optical and microwave domains.Chip-scale integration promises compact,scalable,and power-efficient frequency comb sources,enabled by the resonantly-enhanced ...Optical frequency combs are indispensable links between the optical and microwave domains.Chip-scale integration promises compact,scalable,and power-efficient frequency comb sources,enabled by the resonantly-enhanced Kerr effect or the electro-optic effect.While combs utilizing the former can reach octave-spanning bandwidths,and combs based on the latter can feature microwave-rate spacings,achieving both features at the same time has been challenging.Here,we simultaneously leverage the strong Kerr and electro-optic effects on thin-film lithium niobate,where dissipative Kerr soliton generation is followed by electro-optic phase modulation,to realize an integrated frequency comb reference with 2,589 lines spaced by 29.308 GHz and spanning 75.9THz(588 nm).Further,we demonstrate electronic stabilization and control of the comb spacing,naturally facilitated by this approach.The broadband,microwave-rate frequency comb in our work overcomes the spacing-span tradeoff that exists in nonlinear integrated frequency comb sources,paving the way towards chip-scale solutions for next-generation laser spectroscopy,microwave and millimeter wave synthesis,as well as optical communications.展开更多
This paper presents a novel technique for low-power generation of frequency combs(FC)over a wide frequency range.It leverages modal interactions between electrical and mechanical resonators in electrostatic NEMS opera...This paper presents a novel technique for low-power generation of frequency combs(FC)over a wide frequency range.It leverages modal interactions between electrical and mechanical resonators in electrostatic NEMS operating in air to provide a simple architecture for FC generators.A biased voltage signal drives the electrical resonator at resonance which is set to match an integer submultiple of twice the mechanical resonator’s resonance.Experimental results demonstrate that the NEMS displacement exhibit more than 150 equidistant peaks in the case of a 2:1 modal interaction and more than 60 equidistant peaks in the case of a 1:1 modal interaction.In both cases,the Free Spectral Range(FSR)was equal to the mechanical resonance frequency.Comparison between the FCs generated by the 2:1 and 1:1 modal interactions demonstrate the superiority of the former in terms of bandwidth and stability.The superior phase coherence of the FC generated via the 2:1 modal interaction was demonstrated via time-domain analysis.Our technique has the flexibility to generate multiple frequency combs and to fine-tune their FSR depending on the number of mechanical modes accessible to and the order of the activated modal interaction.It can be integrated into portable devices and is well aligned with modern miniaturization technology.展开更多
We propose a novel automatic phase-matching method for generating optical frequency combs using cascaded electrooptic modulators.By analyzing the power changes of different spectral lines,our method enables real-time ...We propose a novel automatic phase-matching method for generating optical frequency combs using cascaded electrooptic modulators.By analyzing the power changes of different spectral lines,our method enables real-time monitoring and dynamic adjustment to achieve precise phase matching.Experiments have confirmed the fast phase matching and the adjustable spacing of a flat electro-optic frequency comb and its long-term stability.This method provides flexible and efficient light source solutions for optical communications,spectral analysis,and optical measurements.展开更多
Optical frequency combs(OFCs)with precise line spacing play a crucial role in modern optical communication systems.We propose and fabricate a dumbbell-shaped-taper(DST)quantum-well laser diode that generates a frequen...Optical frequency combs(OFCs)with precise line spacing play a crucial role in modern optical communication systems.We propose and fabricate a dumbbell-shaped-taper(DST)quantum-well laser diode that generates a frequency-modulated(FM)optical frequency comb.Effective control of the optical field distribution can be achieved by adjusting the ridge width.In the ridge design,the wide section delivers high optical gain and a broadband spectral output,while the narrow section simultaneously serves as a high-order lateral-mode filter and provides strong optical nonlinearity.Compared with a conventional Fabry-Pérot structure,the device achieves an output power of 48 mW at a drive current of 420 m A and expands the 3 dB spectral bandwidth to 0.90 THz,along with a notable reduction in radio frequency linewidth.Relying on a quantum-well active region,this design avoids complex epitaxial engineering and furnishes a low-cost,high-power,and broadband OFC source.展开更多
Optical frequency combs(OFCs)are highly promising candidates as multichannel light sources for photonic integrated circuits(PICs).We present a tunable on-chip OFC source based on quantum dot collidingpulse mode-locked...Optical frequency combs(OFCs)are highly promising candidates as multichannel light sources for photonic integrated circuits(PICs).We present a tunable on-chip OFC source based on quantum dot collidingpulse mode-locked lasers(QD-CPMLs),capable of generating both amplitude-modulated(AM)and frequencymodulated(FM)combs through external-cavity locking.A free-running fourth-order QD-CPML with a 100 GHz repetition rate is demonstrated to produce FM and AM combs under different bias conditions,achieving an ultra-wide comb with a 3-dB bandwidth of 1.8 THz and a 10-dB bandwidth of 2.5 THz.By leveraging externalcavity locking,the modulation dynamics of the comb are finely tuned,significantly expanding the AM comb range while reducing pulse width and chirp.The shortest pulse width achieved is 0.6 ps,with a minimum time-bandwidth product of 0.33,approaching the transform limit for hyperbolic secant pulses.The near-zero linewidth enhancement factor of the QD-CPML effectively suppresses coherence collapse under optical feedback,whereas its low group velocity dispersion facilitates the generation of narrow pulses and broad bandwidths.The ability to dynamically control AM and FM comb regions through external-cavity locking represents an innovative strategy for tunable OFC generation,offering potential for applications in sensing,spectroscopy,and optical communications within PICs.展开更多
Dual-pumped microring-resonator-based optical frequency combs(OFCs) and their temporal characteristics are numerically investigated and experimentally explored. The calculation results obtained by solving the driven a...Dual-pumped microring-resonator-based optical frequency combs(OFCs) and their temporal characteristics are numerically investigated and experimentally explored. The calculation results obtained by solving the driven and damped nonlinear Schr?dinger equation indicate that an ultralow coupled pump power is required to excite the primary comb modes through a non-degenerate four-wave-mixing(FWM) process and, when the pump power is boosted, both the comb mode intensities and spectral bandwidths increase. At low pump powers, the field intensity profile exhibits a cosine variation manner with frequency equal to the separation of the two pumps, while a roll Turing pattern is formed resulting from the increased comb mode intensities and spectral bandwidths at high pump powers. Meanwhile, we found that the power difference between the two pump fields can be transferred to the newly generated comb modes, which are located on both sides of the pump modes, through a cascaded FWM process. Experimentally, the dual-pumped OFCs were realized by coupling two self-oscillating pump fields into a microring resonator. The numerically calculated comb spectrum is verified by generating an OFC with 2.0 THz mode spacing over 160 nm bandwidth. In addition, the formation of a roll Turing pattern at high pump powers is inferred from the measured autocorrelation trace of a 10 free spectral range(FSR) OFC. The experimental observations accord well with the numerical predictions. Due to their large and tunable mode spacing, robustness,and flexibility, the proposed dual-pumped OFCs could find potential applications in a wide range of fields,including arbitrary optical waveform generation, high-capacity optical communications, and signal-processing systems.展开更多
A magnonic counterpart to optical frequency combs is vital for high-precision magnonic frequency metrology and spectroscopy.Here,we present an efficient mechanism for the generation of robust magnonic frequency combs ...A magnonic counterpart to optical frequency combs is vital for high-precision magnonic frequency metrology and spectroscopy.Here,we present an efficient mechanism for the generation of robust magnonic frequency combs in a yttrium iron garnet(YIG)sphere via magnetostrictive effects.We show that magnonic and vibrational dynamics in the ferrimagnetic sphere can be substantively modified in the presence of magnetostrictive effects,which results in degenerate and non-degenerate magnonic four-wave mixing and frequency conversion.Particularly,resonantly enhanced magnetostrictive effects can induce phonon laser action above a threshold,which leads to significant magnonic nonlinearity and enables a potentially practical scheme for the generation of robust magnonic frequency combs.Numerical calculations of both magnonic and phononic dynamics show excellent agreement with this theory.These results deepen our understanding of magnetostrictive interaction,open a novel and efficient pathway to realize magnonic frequency conversion and mixing in a magnonic device,and provide a sensitive tool for precision measurement.展开更多
By overcoming fabrication limitations, we have successfully fabricated silica toroid microcavities with both large diameter(of 1.88 mm) and ultra-high-Q factor(of 3.3 × 10~8) for the first time, to the best of ou...By overcoming fabrication limitations, we have successfully fabricated silica toroid microcavities with both large diameter(of 1.88 mm) and ultra-high-Q factor(of 3.3 × 10~8) for the first time, to the best of our knowledge. By employing these resonators, we have further demonstrated low-threshold Kerr frequency combs on a silicon chip,which allow us to obtain a repetition rate as low as 36 GHz. Such a low repetition rate frequency comb can now bedirectly measured through a commercialized optical-electronic detector.展开更多
The results of an optoelectronic system—frequency-shifted feedback(FSF)laser experimental examination are presented.The considered FSF laser is seeded only with optical amplifer spontaneous emission(ASE)and operates ...The results of an optoelectronic system—frequency-shifted feedback(FSF)laser experimental examination are presented.The considered FSF laser is seeded only with optical amplifer spontaneous emission(ASE)and operates in the mode-locked regime,whereby the output radiation is sequence of short pulses with a repetition rate determined by the delay time in its optical feedback circuit.In the frequency domain,the spectrum of such a pulse sequence is an optical frequency comb(OFC).These OFCs we call initial.We consider the possibility of tunable acousto-optic(AO)dual and quad-comb frequency spacing downconversion in the FSF laser seeded with ASE and operating in the mode-locked regime.The examined system applies a single frequency shifting loop with single AO tunable flter as the frequency shifter that is fed with several radio frequency signals simultaneously.The initial OFCs with frequency spacing of about 6.5 MHz may be obtained in the wide spectral range and their width,envelope shape and position in the optical spectrum may be tuned.The dual-combs are obtained with a pair of initial OFCs aroused by two various ultrasound waves in the acousto-optic tunable flter(AOTF).The dual-combs frequency spacing is determined by the frequency diference of the signals applied to the AOTF piezoelectric transducer and can be tuned simply.The quad-combs are obtained with three initial OFCs,forming a pair of dual-combs,appearing when three ultrasound frequencies feed the AOTF transducer.The quad-combs frequency spacing is defned by the diference between the frequency spacing of dual-combs.Quad-combs with more than 5000 spectral lines and tunable frequency spacing are observed.The successive frequency downconversion gives the possibility to reduce the OFC frequency spacing form several MHz for initial OFC to tens of kHz for quad-combs.展开更多
Octave-spanning frequency comb generation in microresonators is promising, but strong spectral losses caused by material absorption and mode coupling between two polarizations or mode families can be detrimental. We e...Octave-spanning frequency comb generation in microresonators is promising, but strong spectral losses caused by material absorption and mode coupling between two polarizations or mode families can be detrimental. We examine the impact of the spectral loss and propose robust comb generation with a loss of even 300 dB/cm.Cavity nonlinear dynamics show that a phase change associated with spectral losses can facilitate phase matching and Kerr comb generation. Given this unique capability, we propose a novel architecture of on-chip spectroscopy systems.展开更多
Kerr frequency combs have been attracting significant interest due to their rich physics and broad applications in metrology,microwave photonics,and telecommunications.In this review,we first introduce the fundamental...Kerr frequency combs have been attracting significant interest due to their rich physics and broad applications in metrology,microwave photonics,and telecommunications.In this review,we first introduce the fundamental physics,master equations,simulation methods,and dynamic process of Kerr frequency combs.We then analyze the most promising material platform for realizing Kerr frequency combs—silicon nitride on insulator(SNOI)in comparison with other material platforms.Moreover,we discuss the fabrication methods,process optimization as well as tuning and measurement schemes of SNOI-based Kerr frequency combs.Furthermore,we highlight several emerging applications of Kerr frequency combs in metrology,including spectroscopy,ranging,and timing.Finally,we summarize this review and envision the future development of chip-scale Kerr frequency combs from the viewpoint of theory,material platforms,and tuning methods.展开更多
We demonstrate the stabilization of an optical frequency comb(OFC) using a segment of fiber delay line as a reference. A mode-locked Er-doped fiber laser is phase locked to a kilometer-long fiber delay line using thre...We demonstrate the stabilization of an optical frequency comb(OFC) using a segment of fiber delay line as a reference. A mode-locked Er-doped fiber laser is phase locked to a kilometer-long fiber delay line using three different schemes. The short-term stability of the comb modes in the OFC stabilized by these schemes is obviously enhanced, down to the 10;level at millisecond average time. Among these three schemes, phase locking two bunches of comb modes in the OFC to the same fiber delay line exhibits the lowest residual phase noise. Fiber-delay-line-referenced OFCs can provide reliable laser sources in precise metrology owing to the advances of low cost, compactness, and high integration.展开更多
Photonic microwave harmonic down-converters (PMHDCs) based on self-oscillation optical frequency combs (OFCs) are interesting because of their broad bandwidth compared with plain optoelectronic oscillators. In this pa...Photonic microwave harmonic down-converters (PMHDCs) based on self-oscillation optical frequency combs (OFCs) are interesting because of their broad bandwidth compared with plain optoelectronic oscillators. In this paper, a high-efficiency and flexible PMHDC is proposed and demonstrated. The properties of the OFC, such as the carrier-to-noise ratio (CNR),bandwidth and free spectral range (FSR), and the influence of optical injection, are investigated. The broadband OFC provides a frequency tunable and high-quality local oscillation (LO), which guarantees flexible down-conversion for the radio frequency (RF) signal. The sideband selective amplification (SSA) effect not only improves the conversion efficiency but also promotes single-sideband modulation. The conversion range can reach 100 GHz. The 12–40 GHz RF signal can be downconverted to intermediate frequency (IF) signals with a high conversion efficiency of 14.9 dB. The fixed 40-GHz RF signal is flexibly down-converted to an IF signal with the frequency from 55.4 to 2129.4 MHz. The phase noise of an IF signal at a frequency offset of 10 kHz is the same as that of the input RF signal. The PMHDC shows great performance and will find applications in radio-over-fiber (RoF) networks, electronic warfare receivers, avionics, and wireless communication systems.展开更多
We review recent work on broadband RF channelizers based on integrated optical frequency Kerr micro-combs combined with passive micro-ring resonator filters,with microcombs having channel spacings of 200 and 49 GHz.Th...We review recent work on broadband RF channelizers based on integrated optical frequency Kerr micro-combs combined with passive micro-ring resonator filters,with microcombs having channel spacings of 200 and 49 GHz.This approach to realizing RF channelizers offers reduced complexity,size,and potential cost for a wide range of applications to microwave signal detection.展开更多
Dispersion engineering of optical waveguides is among the most important steps in enabling the realization of Kerr optical frequency combs.A recurring problem is the limited bandwidth in which the nonlinear phase matc...Dispersion engineering of optical waveguides is among the most important steps in enabling the realization of Kerr optical frequency combs.A recurring problem is the limited bandwidth in which the nonlinear phase matching condition is satisfied,due to the dispersion of the waveguide.This limitation is particularly stringent in high-index-contrast technologies such as silicon-on-insulator.We propose a general approach to stretch the bandwidth of Kerr frequency combs based on subwavelength engineering of single-mode waveguides with self-adaptive boundaries.The wideband flattened dispersion operation comes from the particular property of the waveguide optical mode that automatically self-adapts its spatial profile at different wavelengths to slightly different effective spatial spans determined by its effective index values.This flattened dispersion relies on the squeezing of small normal-dispersion regions between two anomalous spectral zones,which enables it to achieve two Cherenkov radiation points and substantially broaden the comb,achieving a bandwidth between 2.2 and 3.4μm wavelength.This strategy opens up a design space for trimming the spectra of Kerr frequency combs using high-index-contrast platforms and can provide benefits to various nonlinear applications in which the manipulation of energy spacing and phase matching are pivotal.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.61178011,11204248,61475127,and 61275116)the Natural Science Foundation of Chongqing City,China(Grant Nos.2012jj B40011 and 2012jj A40012)the Open Fund of the State Key Lab of Millimeter Waves of China(Grant No.K201418)
文摘Based on a semiconductor laser （SL） with incoherent optical feedback, a novel all-optical scheme for generating tunable and broadband microwave frequency combs （MFCs） is proposed and investigated numerically. The results show that, under suitable operation parameters, the SL with incoherent optical feedback can be driven to operate at a regular pulsing state, and the generated MFCs have bandwidths broader than 40 GHz within a 10 dB amplitude variation. For a fixed bias current, the line spacing （or repetition frequency） of the MFCs can be easily tuned by varying the feedback delay time and the feedback strength, and the tuning range of the line spacing increases with the increase in the bias current. The linewidth of the MFCs is sensitive to the variation of the feedback delay time and the feedback strength, and a linewidth of tens of KHz can be achieved through finely adjusting the feedback delay time and the feedback strength. In addition, mappings of amplitude variation, repetition frequency, and linewidth of MFCs in the parameter space of the feedback delay time and the feedback strength are presented.
基金Project supported by the National Natural Science Foundation of China(Grant No.62005215)。
文摘The optical injection locking of semiconductor lasers to dual-frequency lasers is studied by numerical simulations.The beat-note signals can be effectively transformed to optical frequency combs due to the effective four wave-mixing in the active semiconductor gain medium. The low-noise Gaussian-like pulse can be obtained by locking the relaxation oscillation and compensating the gain asymmetry. The simulations suggest that pulse trains of width below 30 ps and repetition rate in GHz frequency can be generated simply by the optical injection locking of semiconductor lasers. Since the optical injection locking can broaden the spectrum and amplify the optical power simultaneously, it can be a good initial stage for generating optical frequency combs from dual-frequency lasers by multi-stage of spectral broadening in nonlinear waveguides.
文摘A novel dispersion-compensation scheme based on double-chirped Bragg mirrors is implemented in a mid-infrared quantum cascade laser.As a result,stable and broadband frequency combs are generated,which are indispensable for high-precision applications in spectroscopy and metrology.
基金supported in part by the Spectral Combs from UV to THz(SCOUT)and SIGMA+programs from the Defense Advanced Research Project Agency(DARPA)support from the Gordon and Betty Moore Foundation through Grant GBMF11446 to the University of Texas at Austin.
文摘Dispersion engineering is critical for the creation of integrated broadband laser frequency combs.In the long wavelength infrared range(LWIR,8-13µm),frequency combs based on quantum cascade lasers are attractive since they are monolithic,fundamental oscillators with high power levels and efficiencies.One effective approach for expanding quantum cascade laser gain bandwidth is by stacking multiple gain media with different center lasing frequencies,as this leads to flatter broadband gain spectra.However,as the gain bandwidth is increased,dispersion becomes the main limiting factor for comb bandwidth.Therefore,achieving broadband combs requires schemes that can flexibly engineer the dispersion over broad bandwidths.Here,we demonstrate the ultimate nanophotonic dispersion compensation scheme:an air-dielectric slab double-chirped mirror,which we fully integrate with the quantum cascade laser gain section.This scheme relies on the highest possible index contrast and therefore provides the maximum correction per unit length over a very broad bandwidth.With this approach,we report the successful demonstration of a broadband room-temperature LWIR laser frequency comb on a gain medium that normally does not form combs without deliberate dispersion compensations.Our air-dielectric mirrors are versatile and can be extended to other integrated laser frequency combs in different material platforms and frequency bands.
基金supported by the Innovation Program for Quantum Science and Technology(2023ZD0301000)the National Science Fund for Distinguished Young Scholars(62325509)+2 种基金the National Natural Science Foundation of China(62235019,61875220,61927813,61991430,62035005,62105351,and 62305364)the“From 0 to 1”Innovation Program of the Chinese Academy of Sciences(ZDBS-LY-JSC009)the CAS Project for Young Scientists in Basic Research(YSBR-069).
文摘Frequency combs show various applications in molecular fingerprinting,imaging,communications,and so on.In the terahertz frequency range,semiconductor-based quantum cascade lasers(QCLs)are ideal platforms for realizing the frequency comb operation.Although self-started frequency comb operation can be obtained in free-running terahertz QCLs due to the four-wave mixing locking effects,resonant/off-resonant microwave injection,phase locking,and femtosecond laser based locking techniques have been widely used to broaden and stabilize terahertz QCL combs.These active locking methods indeed show significant effects on the frequency stabilization of terahertz QCL combs,but they simultaneously have drawbacks,such as introducing large phase noise and requiring complex optical coupling and/or electrical circuits.Here,we demonstrate Farey tree locking of terahertz QCL frequency combs under microwave injection.The frequency competition between the Farey fraction frequency and the cavity round-trip frequency results in the frequency locking of terahertz QCL combs,and the Farey fraction frequencies can be accurately anticipated based on the downward trend of the Farey tree hierarchy.Furthermore,dual-comb experimental results show that the phase noise of the dual-comb spectral lines is significantly reduced by employing the Farey tree locking method.These results pave the way to deploying compact and low phase noise terahertz frequency comb sources.
基金support by the Defense Advanced Research Projects Agency(D23AP00251-00)Y.S.,Y.H.,and M.L.acknowledge support by the Defense Advanced Research Projects Agency(HR001120C0137)+4 种基金Office of Naval Research(N00014-22-C-1041)National Science Foundation(OMA-2137723,OMA-2138068)Korea Advanced Institute of Science and Technology(NRF-2022M3K4A1094782)support by the AWS Generation Q Fund at the Harvard Quantum Initiativesupported by the National Science Foundation under NSF award no.ECCS-2025158.
文摘Optical frequency combs are indispensable links between the optical and microwave domains.Chip-scale integration promises compact,scalable,and power-efficient frequency comb sources,enabled by the resonantly-enhanced Kerr effect or the electro-optic effect.While combs utilizing the former can reach octave-spanning bandwidths,and combs based on the latter can feature microwave-rate spacings,achieving both features at the same time has been challenging.Here,we simultaneously leverage the strong Kerr and electro-optic effects on thin-film lithium niobate,where dissipative Kerr soliton generation is followed by electro-optic phase modulation,to realize an integrated frequency comb reference with 2,589 lines spaced by 29.308 GHz and spanning 75.9THz(588 nm).Further,we demonstrate electronic stabilization and control of the comb spacing,naturally facilitated by this approach.The broadband,microwave-rate frequency comb in our work overcomes the spacing-span tradeoff that exists in nonlinear integrated frequency comb sources,paving the way towards chip-scale solutions for next-generation laser spectroscopy,microwave and millimeter wave synthesis,as well as optical communications.
基金K.M.acknowledges funding from the Canada Foundation for Innovation John R.Evans Leaders Fund(Project 35552)Ontario Research Fund—Research Infrastructure(Project 35552),the Waterloo Institute for Nanotechnology(WIN-NRC seed grant),and a Mitacs Globalink Research Award.
文摘This paper presents a novel technique for low-power generation of frequency combs(FC)over a wide frequency range.It leverages modal interactions between electrical and mechanical resonators in electrostatic NEMS operating in air to provide a simple architecture for FC generators.A biased voltage signal drives the electrical resonator at resonance which is set to match an integer submultiple of twice the mechanical resonator’s resonance.Experimental results demonstrate that the NEMS displacement exhibit more than 150 equidistant peaks in the case of a 2:1 modal interaction and more than 60 equidistant peaks in the case of a 1:1 modal interaction.In both cases,the Free Spectral Range(FSR)was equal to the mechanical resonance frequency.Comparison between the FCs generated by the 2:1 and 1:1 modal interactions demonstrate the superiority of the former in terms of bandwidth and stability.The superior phase coherence of the FC generated via the 2:1 modal interaction was demonstrated via time-domain analysis.Our technique has the flexibility to generate multiple frequency combs and to fine-tune their FSR depending on the number of mechanical modes accessible to and the order of the activated modal interaction.It can be integrated into portable devices and is well aligned with modern miniaturization technology.
基金supported by the National Key Research and Development Program of China(No.2021YFB2800800)。
文摘We propose a novel automatic phase-matching method for generating optical frequency combs using cascaded electrooptic modulators.By analyzing the power changes of different spectral lines,our method enables real-time monitoring and dynamic adjustment to achieve precise phase matching.Experiments have confirmed the fast phase matching and the adjustable spacing of a flat electro-optic frequency comb and its long-term stability.This method provides flexible and efficient light source solutions for optical communications,spectral analysis,and optical measurements.
基金supported by the National Key Research and Development Program of China(No.2022YFB2803104)the Taishan Scholars Program。
文摘Optical frequency combs(OFCs)with precise line spacing play a crucial role in modern optical communication systems.We propose and fabricate a dumbbell-shaped-taper(DST)quantum-well laser diode that generates a frequency-modulated(FM)optical frequency comb.Effective control of the optical field distribution can be achieved by adjusting the ridge width.In the ridge design,the wide section delivers high optical gain and a broadband spectral output,while the narrow section simultaneously serves as a high-order lateral-mode filter and provides strong optical nonlinearity.Compared with a conventional Fabry-Pérot structure,the device achieves an output power of 48 mW at a drive current of 420 m A and expands the 3 dB spectral bandwidth to 0.90 THz,along with a notable reduction in radio frequency linewidth.Relying on a quantum-well active region,this design avoids complex epitaxial engineering and furnishes a low-cost,high-power,and broadband OFC source.
基金supported by the National Key Research and Development Program of China (Grant No.2022YFB2803600)the National Natural Science Foundation of China (Grant Nos.62204072, 62334013, and U22A2093)+4 种基金the Basic and Applied Basic Research Foundation of Guangdong Province(Grant Nos.2021A1515110076 and 2023A1515012304)the Shenzhen Science and Technology Innovation Program (Grant Nos.GXWD20220811163623002, RCBS20210609103824050,JCYJ20240813104819027, and KJZD20240903101100002)the Research Fund of the National Key Laboratory of Laser Spatial Information (Grant No.LSI2025WDZC03)the Open Research Program of the State Key Laboratory of Radio Frequency Heterogeneous Integration (Grant No.KF2025010)support from the Institut Mines Telecom
文摘Optical frequency combs(OFCs)are highly promising candidates as multichannel light sources for photonic integrated circuits(PICs).We present a tunable on-chip OFC source based on quantum dot collidingpulse mode-locked lasers(QD-CPMLs),capable of generating both amplitude-modulated(AM)and frequencymodulated(FM)combs through external-cavity locking.A free-running fourth-order QD-CPML with a 100 GHz repetition rate is demonstrated to produce FM and AM combs under different bias conditions,achieving an ultra-wide comb with a 3-dB bandwidth of 1.8 THz and a 10-dB bandwidth of 2.5 THz.By leveraging externalcavity locking,the modulation dynamics of the comb are finely tuned,significantly expanding the AM comb range while reducing pulse width and chirp.The shortest pulse width achieved is 0.6 ps,with a minimum time-bandwidth product of 0.33,approaching the transform limit for hyperbolic secant pulses.The near-zero linewidth enhancement factor of the QD-CPML effectively suppresses coherence collapse under optical feedback,whereas its low group velocity dispersion facilitates the generation of narrow pulses and broad bandwidths.The ability to dynamically control AM and FM comb regions through external-cavity locking represents an innovative strategy for tunable OFC generation,offering potential for applications in sensing,spectroscopy,and optical communications within PICs.
基金Strategic Priority Research Program of the Chinese Academy of Sciences(CAS)(XDB 24030600)National Key Research and Development Program of China(2016YFF0200702)+1 种基金National Natural Science Foundation of China(NSFC)(61690222,61308037,61635013)CASSAFEA International Partnership Program for Creative Research Teams
文摘Dual-pumped microring-resonator-based optical frequency combs(OFCs) and their temporal characteristics are numerically investigated and experimentally explored. The calculation results obtained by solving the driven and damped nonlinear Schr?dinger equation indicate that an ultralow coupled pump power is required to excite the primary comb modes through a non-degenerate four-wave-mixing(FWM) process and, when the pump power is boosted, both the comb mode intensities and spectral bandwidths increase. At low pump powers, the field intensity profile exhibits a cosine variation manner with frequency equal to the separation of the two pumps, while a roll Turing pattern is formed resulting from the increased comb mode intensities and spectral bandwidths at high pump powers. Meanwhile, we found that the power difference between the two pump fields can be transferred to the newly generated comb modes, which are located on both sides of the pump modes, through a cascaded FWM process. Experimentally, the dual-pumped OFCs were realized by coupling two self-oscillating pump fields into a microring resonator. The numerically calculated comb spectrum is verified by generating an OFC with 2.0 THz mode spacing over 160 nm bandwidth. In addition, the formation of a roll Turing pattern at high pump powers is inferred from the measured autocorrelation trace of a 10 free spectral range(FSR) OFC. The experimental observations accord well with the numerical predictions. Due to their large and tunable mode spacing, robustness,and flexibility, the proposed dual-pumped OFCs could find potential applications in a wide range of fields,including arbitrary optical waveform generation, high-capacity optical communications, and signal-processing systems.
文摘A magnonic counterpart to optical frequency combs is vital for high-precision magnonic frequency metrology and spectroscopy.Here,we present an efficient mechanism for the generation of robust magnonic frequency combs in a yttrium iron garnet(YIG)sphere via magnetostrictive effects.We show that magnonic and vibrational dynamics in the ferrimagnetic sphere can be substantively modified in the presence of magnetostrictive effects,which results in degenerate and non-degenerate magnonic four-wave mixing and frequency conversion.Particularly,resonantly enhanced magnetostrictive effects can induce phonon laser action above a threshold,which leads to significant magnonic nonlinearity and enables a potentially practical scheme for the generation of robust magnonic frequency combs.Numerical calculations of both magnonic and phononic dynamics show excellent agreement with this theory.These results deepen our understanding of magnetostrictive interaction,open a novel and efficient pathway to realize magnonic frequency conversion and mixing in a magnonic device,and provide a sensitive tool for precision measurement.
基金National Key R&D Program of China(2017YFA0303703,2016YFA0302500)National Natural Science Foundation of China(NSFC)(61435007,11574144,61475099)+1 种基金Natural Science Foundation of Jiangsu Province,China(BK20150015)Fundamental Research Funds for the Central Universities(021314380086)
文摘By overcoming fabrication limitations, we have successfully fabricated silica toroid microcavities with both large diameter(of 1.88 mm) and ultra-high-Q factor(of 3.3 × 10~8) for the first time, to the best of our knowledge. By employing these resonators, we have further demonstrated low-threshold Kerr frequency combs on a silicon chip,which allow us to obtain a repetition rate as low as 36 GHz. Such a low repetition rate frequency comb can now bedirectly measured through a commercialized optical-electronic detector.
基金Russian Science Foundation.Sections 1,2,and 3.3 were supported by Grant 23-12-00057,Sects.3.1 and 3.2 were supported by Grant 20-12-00344.
文摘The results of an optoelectronic system—frequency-shifted feedback(FSF)laser experimental examination are presented.The considered FSF laser is seeded only with optical amplifer spontaneous emission(ASE)and operates in the mode-locked regime,whereby the output radiation is sequence of short pulses with a repetition rate determined by the delay time in its optical feedback circuit.In the frequency domain,the spectrum of such a pulse sequence is an optical frequency comb(OFC).These OFCs we call initial.We consider the possibility of tunable acousto-optic(AO)dual and quad-comb frequency spacing downconversion in the FSF laser seeded with ASE and operating in the mode-locked regime.The examined system applies a single frequency shifting loop with single AO tunable flter as the frequency shifter that is fed with several radio frequency signals simultaneously.The initial OFCs with frequency spacing of about 6.5 MHz may be obtained in the wide spectral range and their width,envelope shape and position in the optical spectrum may be tuned.The dual-combs are obtained with a pair of initial OFCs aroused by two various ultrasound waves in the acousto-optic tunable flter(AOTF).The dual-combs frequency spacing is determined by the frequency diference of the signals applied to the AOTF piezoelectric transducer and can be tuned simply.The quad-combs are obtained with three initial OFCs,forming a pair of dual-combs,appearing when three ultrasound frequencies feed the AOTF transducer.The quad-combs frequency spacing is defned by the diference between the frequency spacing of dual-combs.Quad-combs with more than 5000 spectral lines and tunable frequency spacing are observed.The successive frequency downconversion gives the possibility to reduce the OFC frequency spacing form several MHz for initial OFC to tens of kHz for quad-combs.
基金National Basic Research Program of China(973)(2014CB340104/3,61775164,61335005,61377076,61575142,61431009)Advanced Integrated Optoelectronics Facility at the Tianjin University
文摘Octave-spanning frequency comb generation in microresonators is promising, but strong spectral losses caused by material absorption and mode coupling between two polarizations or mode families can be detrimental. We examine the impact of the spectral loss and propose robust comb generation with a loss of even 300 dB/cm.Cavity nonlinear dynamics show that a phase change associated with spectral losses can facilitate phase matching and Kerr comb generation. Given this unique capability, we propose a novel architecture of on-chip spectroscopy systems.
基金the National Key Research and Development Program of China(2021YFA1401000,2021YFB2801600,and 2017YFF0206104)National Natural Science Foundation of China(62075114 and 62175121)the Beijing Natural Science Foundation(4212050)。
文摘Kerr frequency combs have been attracting significant interest due to their rich physics and broad applications in metrology,microwave photonics,and telecommunications.In this review,we first introduce the fundamental physics,master equations,simulation methods,and dynamic process of Kerr frequency combs.We then analyze the most promising material platform for realizing Kerr frequency combs—silicon nitride on insulator(SNOI)in comparison with other material platforms.Moreover,we discuss the fabrication methods,process optimization as well as tuning and measurement schemes of SNOI-based Kerr frequency combs.Furthermore,we highlight several emerging applications of Kerr frequency combs in metrology,including spectroscopy,ranging,and timing.Finally,we summarize this review and envision the future development of chip-scale Kerr frequency combs from the viewpoint of theory,material platforms,and tuning methods.
基金This work was supported by the National Natural Science Foundation of China(Nos.61975144 and 61827821)the Tianjin Research Program of Application Foundation and Advanced Technology of China(No.17JCJQJC43500)。
文摘We demonstrate the stabilization of an optical frequency comb(OFC) using a segment of fiber delay line as a reference. A mode-locked Er-doped fiber laser is phase locked to a kilometer-long fiber delay line using three different schemes. The short-term stability of the comb modes in the OFC stabilized by these schemes is obviously enhanced, down to the 10;level at millisecond average time. Among these three schemes, phase locking two bunches of comb modes in the OFC to the same fiber delay line exhibits the lowest residual phase noise. Fiber-delay-line-referenced OFCs can provide reliable laser sources in precise metrology owing to the advances of low cost, compactness, and high integration.
基金supported in part by the National Natural Science Foundation of China (Nos.62071487,62201615,62301569,and 62371470)。
文摘Photonic microwave harmonic down-converters (PMHDCs) based on self-oscillation optical frequency combs (OFCs) are interesting because of their broad bandwidth compared with plain optoelectronic oscillators. In this paper, a high-efficiency and flexible PMHDC is proposed and demonstrated. The properties of the OFC, such as the carrier-to-noise ratio (CNR),bandwidth and free spectral range (FSR), and the influence of optical injection, are investigated. The broadband OFC provides a frequency tunable and high-quality local oscillation (LO), which guarantees flexible down-conversion for the radio frequency (RF) signal. The sideband selective amplification (SSA) effect not only improves the conversion efficiency but also promotes single-sideband modulation. The conversion range can reach 100 GHz. The 12–40 GHz RF signal can be downconverted to intermediate frequency (IF) signals with a high conversion efficiency of 14.9 dB. The fixed 40-GHz RF signal is flexibly down-converted to an IF signal with the frequency from 55.4 to 2129.4 MHz. The phase noise of an IF signal at a frequency offset of 10 kHz is the same as that of the input RF signal. The PMHDC shows great performance and will find applications in radio-over-fiber (RoF) networks, electronic warfare receivers, avionics, and wireless communication systems.
文摘We review recent work on broadband RF channelizers based on integrated optical frequency Kerr micro-combs combined with passive micro-ring resonator filters,with microcombs having channel spacings of 200 and 49 GHz.This approach to realizing RF channelizers offers reduced complexity,size,and potential cost for a wide range of applications to microwave signal detection.
基金the French national research agency(BRIGHT ANR project)
文摘Dispersion engineering of optical waveguides is among the most important steps in enabling the realization of Kerr optical frequency combs.A recurring problem is the limited bandwidth in which the nonlinear phase matching condition is satisfied,due to the dispersion of the waveguide.This limitation is particularly stringent in high-index-contrast technologies such as silicon-on-insulator.We propose a general approach to stretch the bandwidth of Kerr frequency combs based on subwavelength engineering of single-mode waveguides with self-adaptive boundaries.The wideband flattened dispersion operation comes from the particular property of the waveguide optical mode that automatically self-adapts its spatial profile at different wavelengths to slightly different effective spatial spans determined by its effective index values.This flattened dispersion relies on the squeezing of small normal-dispersion regions between two anomalous spectral zones,which enables it to achieve two Cherenkov radiation points and substantially broaden the comb,achieving a bandwidth between 2.2 and 3.4μm wavelength.This strategy opens up a design space for trimming the spectra of Kerr frequency combs using high-index-contrast platforms and can provide benefits to various nonlinear applications in which the manipulation of energy spacing and phase matching are pivotal.
