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
Absorption spectroscopy of fundamental ro-vibrational transitions in the mid-infrared region provides a powerful tool for studying the structure and dynamics of molecules in the gas phase and for sensitive and quantit...Absorption spectroscopy of fundamental ro-vibrational transitions in the mid-infrared region provides a powerful tool for studying the structure and dynamics of molecules in the gas phase and for sensitive and quantitative gas sensing.Laser frequency combs permit novel approaches to perform broadband molecular spectroscopy.Multiplex dual-comb spectroscopy without moving parts can achieve particularly high speed,sensitivity and resolution.However,achieving Doppler-limited resolution in the mid-infrared still requires overcoming instrumental challenges.Here we demonstrate a new approach based on difference-frequency generation of frequency-agile near-infrared frequency combs that are produced using electro-optic modulators.The combs have a remarkably flat intensity distribution,and their positions and line spacings can be freely selected by simply dialing a knob.Using the proposed technique,we record,in the 3-μm region,Doppler-limited absorption spectra with resolved comb lines within milliseconds,and precise molecular line parameters are retrieved.Our technique holds promise for fast and sensitive time-resolved studies of,for example,trace gases.展开更多
The digestion of cellulose by fungus-growing termites involves a complex of different organisms, such as the termites themselves, fungi and bacteria. To further investigate the symbiotic relationships of fungus-growin...The digestion of cellulose by fungus-growing termites involves a complex of different organisms, such as the termites themselves, fungi and bacteria. To further investigate the symbiotic relationships of fungus-growing termites, the microbial communities of the termite gut and fungus combs of Odontotermes yunnanensis were examined. The major fungus species was identified as Termitomyces sp. To compare the micro-organism diversity between the digestive tract of termites and fungus combs, four polymerase chain reaction clone libraries were created （two fungus-targeted internal transcribed spacer [ITS] - ribosomal DNA [rDNA] libraries and two bacteria-targeted 16S rDNA libraries）, and one library of each type was produced for the host termite gut and the symbiotic fimgus comb. Results of the fungal clone libraries revealed that only Termitomyces sp. was detected on the fungus comb; no non-Termitomyces fungi were detected. Meanwhile, the same fungus was also found in the termite gut. The bacterial clone libraries showed higher numbers and greater diversity of bacteria in the termite gut than in the fungus comb. Both bacterial clone libraries from the insect gut included Firmicutes, Bacteroidetes, Proteobacteria, Spirochaetes, Nitrospira, Deferribacteres, and Fibrobacteres, whereas the bacterial clone libraries from the fungal comb only contained Firmicutes, Bacteroidetes, Proteobacteria, and Acidobacteris.展开更多
Dual-comb spectroscopy(DCS)is an emerging spectroscopic tool with the potential to simultaneously achieve a broad spectral coverage and ultrahigh spectral resolution with rapid data acquisition.However,the need for tw...Dual-comb spectroscopy(DCS)is an emerging spectroscopic tool with the potential to simultaneously achieve a broad spectral coverage and ultrahigh spectral resolution with rapid data acquisition.However,the need for two independently stabilized ultrafast lasers significantly hampers the potential application of DCS.We demonstrate mode-resolved DCS in the THz region based on a free-running singlecavity dual-comb fiber laser with the adaptive sampling method.While the use of a free-running single-cavity dual-comb fiber laser eliminates the need for two mode-locked lasers and their frequency control,the adaptive sampling method strongly prevents the degradation of spectroscopic performance caused by the residual timing jitter in the free-running dual-comb laser.Doppler-limit-approaching absorption features with linewidths down to 25 MHz are investigated for low-pressure acetonitrile/air mixed gas by comb-mode-resolved THz spectroscopy.The successful demonstration clearly indicates its great potential for the realization of lowcomplexity,Doppler-limited THz spectroscopy instrumentation.展开更多
This paper discusses the developement and investigation of a silica microbubble resonator(MBR) that is optimized to cancel mode dispersion with material dispersion, at a wavelength of approximately 1550 nm and maintai...This paper discusses the developement and investigation of a silica microbubble resonator(MBR) that is optimized to cancel mode dispersion with material dispersion, at a wavelength of approximately 1550 nm and maintain a quality factor of an optical mode as large as 5.4 × 10~7. Benefitting from the near-zero dispersion and high quality factor, a primary optical comb is generated in the MBR using cascaded four-wave mixing processes, which span over 300 nm with several tens of teeth. Furthermore, the frequency comb could be gradually tuned by mechanically stretching the MBR. This tunable Kerr comb has multiple potential applications in precision measurements and sensing applications, such as molecular spectroscopy and ranging.展开更多
Optical frequency combs,as powerful tools for precision spectroscopy and research into optical frequency standards,have driven continuous progress and significant breakthroughs in applications such as time-frequency t...Optical frequency combs,as powerful tools for precision spectroscopy and research into optical frequency standards,have driven continuous progress and significant breakthroughs in applications such as time-frequency transfer,measurement of fundamental physical constants,and high-precision ranging,achieving a series of milestone results in ground-based environments.With the continuous maturation and evolution of femtosecond lasers and related technologies,optical frequency combs are moving from ground-based applications to astronomical and space-based applications,playing an increasingly important role in atomic clocks,exoplanet observations,gravitational wave measurements,and other areas.This paper,focusing on astronomical and space-based applications,reviews research progress on astronomical frequency combs,optical clock time-frequency networks,gravitational waves,dark matter measurement,dual-comb large-scale absolute ranging,and high-resolution atmospheric spectroscopy.With enhanced performance and their gradual application in the field of space-based research,optical frequency combs will undoubtedly provide more powerful support for astronomical science and cosmic exploration in the future.展开更多
We demonstrate an optical frequency comb based on an erbium-doped-fiber femtosecond laser with the nonlinear polarization evolution scheme. The repetition rate of the laser is about 209 MHz. By controlling an intra-ca...We demonstrate an optical frequency comb based on an erbium-doped-fiber femtosecond laser with the nonlinear polarization evolution scheme. The repetition rate of the laser is about 209 MHz. By controlling an intra-cavity electro- optic modulator and a piezo-transducer, the repetition rate can be stabilized with a high-bandwidth servo in a frequency range of 3 kHz, enabling long-term repetition rate phase-locking. The in-loop frequency stability of repetition rate is about 1.6× 10-13 in an integration time of 1 s, limited by the measurement system; and it is inversely proportional to integration time in the short term. Furthermore, using a common path f-2f interferometer, the carrier envelope offset frequency of the comb is obtained with a signal-to-noise ratio of 40 dB in a 3-MHz resolution bandwidth. Stabilized cartier envelope offset frequency exhibits a deviation of 0.6 mHz in an integration time of 1 s.展开更多
The microresonator-based soliton microcomb has shown a promising future in many applications.In this work,we report the fabrication of high quality[Q]Si_(3)N_(4)microring resonators for soliton microcomb generation.By...The microresonator-based soliton microcomb has shown a promising future in many applications.In this work,we report the fabrication of high quality[Q]Si_(3)N_(4)microring resonators for soliton microcomb generation.By developing the fabri-cation process with crack isolation trenches and annealing,we can deposit thick stoichiometric Si3N4 film of 800 nm without cracks in the central area.The highest intrinsic Q of the Si_(3)N_(4)microring obtained in our experiments is about 6×10^(6),corresponding to a propagation loss as low as 0.058 dBm/cm.With such a high Q film,we fabricate microrings with the anomalous dispersion and demonstrate the generation of soliton microcombs with 100 mW on-chip pump power,with an optical parametric oscillation threshold of only 13.4 mW.Our Si_(3)N_(4)integrated chip provides an ideal platform for researches and applications of nonlinear photonics and integrated photonics.展开更多
High-precision time transfer plays an important role in the areas of fundamental research and applications. Accompanying w ith the remarkable improvements in the ability of generating and measuring high-accuracy time-...High-precision time transfer plays an important role in the areas of fundamental research and applications. Accompanying w ith the remarkable improvements in the ability of generating and measuring high-accuracy time-frequency signal,seeking for new time-transfer techniques betw een distant clocks w ith much further improved accuracy attracts attentions w orld-w idely. The time-transfer technique based on optical pulses has the highest precision presently,and the further improvement in the accuracy is heavily dependent on the time-domain properties of the pulse as w ell as the sensitivity of the applied measurement on the exchanged pulse. The application of optical frequency comb in time transfer for a precision up to femtosecond level are currently the focus of much interest,and has recently achieved many breakthroughs. Further investigations show that,utilizing quantum techniques,i.e. quantum measurement technique and quantum optical pulse source,can lead to a new limit on the measured timing information. Furthermore,it can be immune from atmospheric parameters,such as pressure,temperature,humidity and so on.Such quantum improvements on time-transfer have a bright prospect in the future applications requiring extremely high-accuracy timing and ranging. The potential achievements w ill form a technical basis for the future realization of sub-femtosecond time transfer system.展开更多
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European Research Council(Advanced Investigator Grant 267854)Munich Center for Advanced Photonics Max Planck Foundation+1 种基金IXCORE Fondation pour la RecherchePARI PHOTCOM Région Bourgogne,Labex ACTION program(Contract No.ANR-11-LABX-0001-01).
文摘Absorption spectroscopy of fundamental ro-vibrational transitions in the mid-infrared region provides a powerful tool for studying the structure and dynamics of molecules in the gas phase and for sensitive and quantitative gas sensing.Laser frequency combs permit novel approaches to perform broadband molecular spectroscopy.Multiplex dual-comb spectroscopy without moving parts can achieve particularly high speed,sensitivity and resolution.However,achieving Doppler-limited resolution in the mid-infrared still requires overcoming instrumental challenges.Here we demonstrate a new approach based on difference-frequency generation of frequency-agile near-infrared frequency combs that are produced using electro-optic modulators.The combs have a remarkably flat intensity distribution,and their positions and line spacings can be freely selected by simply dialing a knob.Using the proposed technique,we record,in the 3-μm region,Doppler-limited absorption spectra with resolved comb lines within milliseconds,and precise molecular line parameters are retrieved.Our technique holds promise for fast and sensitive time-resolved studies of,for example,trace gases.
文摘The digestion of cellulose by fungus-growing termites involves a complex of different organisms, such as the termites themselves, fungi and bacteria. To further investigate the symbiotic relationships of fungus-growing termites, the microbial communities of the termite gut and fungus combs of Odontotermes yunnanensis were examined. The major fungus species was identified as Termitomyces sp. To compare the micro-organism diversity between the digestive tract of termites and fungus combs, four polymerase chain reaction clone libraries were created （two fungus-targeted internal transcribed spacer [ITS] - ribosomal DNA [rDNA] libraries and two bacteria-targeted 16S rDNA libraries）, and one library of each type was produced for the host termite gut and the symbiotic fimgus comb. Results of the fungal clone libraries revealed that only Termitomyces sp. was detected on the fungus comb; no non-Termitomyces fungi were detected. Meanwhile, the same fungus was also found in the termite gut. The bacterial clone libraries showed higher numbers and greater diversity of bacteria in the termite gut than in the fungus comb. Both bacterial clone libraries from the insect gut included Firmicutes, Bacteroidetes, Proteobacteria, Spirochaetes, Nitrospira, Deferribacteres, and Fibrobacteres, whereas the bacterial clone libraries from the fungal comb only contained Firmicutes, Bacteroidetes, Proteobacteria, and Acidobacteris.
基金The work at Tokushima University was supported by grants for the Exploratory Research for Advanced Technology(ERATO)MINOSHIMA Intelligent Optical Synthesizer(IOS)Project(JPMJER1304)the Japanese Science and Technology Agency+3 种基金a Grant-in-Aid for Scientific Research(A)(19H00871/26246031)the Ministry of Education,Culture,Sports,Science,and Technology of JapanSubsidy for Regional University and Regional Industry Creation,Cabinet Office,Japan.The work at Beihang University was supported by NSFC(61435002/61521091/61675014/61675015)Fundamental Research Funds for the Central Universities.The authors declare no competing financial interests.
文摘Dual-comb spectroscopy(DCS)is an emerging spectroscopic tool with the potential to simultaneously achieve a broad spectral coverage and ultrahigh spectral resolution with rapid data acquisition.However,the need for two independently stabilized ultrafast lasers significantly hampers the potential application of DCS.We demonstrate mode-resolved DCS in the THz region based on a free-running singlecavity dual-comb fiber laser with the adaptive sampling method.While the use of a free-running single-cavity dual-comb fiber laser eliminates the need for two mode-locked lasers and their frequency control,the adaptive sampling method strongly prevents the degradation of spectroscopic performance caused by the residual timing jitter in the free-running dual-comb laser.Doppler-limit-approaching absorption features with linewidths down to 25 MHz are investigated for low-pressure acetonitrile/air mixed gas by comb-mode-resolved THz spectroscopy.The successful demonstration clearly indicates its great potential for the realization of lowcomplexity,Doppler-limited THz spectroscopy instrumentation.
基金supported by the National Key R&D Program of China(Grant No.2016YFA0301303)the Anhui Initiative in Quantum Information Technologies(Grant No.AHY130200)+2 种基金the National Natural Science Foundation of China(Grant Nos.11934012,61575184,and 11722436)the Fundamental Research Funds for the Central Universitiesthe Key Science and Technology Program of Henan Province,China(Grant No.182102410070)。
文摘This paper discusses the developement and investigation of a silica microbubble resonator(MBR) that is optimized to cancel mode dispersion with material dispersion, at a wavelength of approximately 1550 nm and maintain a quality factor of an optical mode as large as 5.4 × 10~7. Benefitting from the near-zero dispersion and high quality factor, a primary optical comb is generated in the MBR using cascaded four-wave mixing processes, which span over 300 nm with several tens of teeth. Furthermore, the frequency comb could be gradually tuned by mechanically stretching the MBR. This tunable Kerr comb has multiple potential applications in precision measurements and sensing applications, such as molecular spectroscopy and ranging.
基金support of the National Natural Sci-ence Foundation of China(NSFC)(62305373)the Strategic Priority Research Program of the Chinese Academy of Sciences(XDA1502040404,XDB2101040004).
文摘Optical frequency combs,as powerful tools for precision spectroscopy and research into optical frequency standards,have driven continuous progress and significant breakthroughs in applications such as time-frequency transfer,measurement of fundamental physical constants,and high-precision ranging,achieving a series of milestone results in ground-based environments.With the continuous maturation and evolution of femtosecond lasers and related technologies,optical frequency combs are moving from ground-based applications to astronomical and space-based applications,playing an increasingly important role in atomic clocks,exoplanet observations,gravitational wave measurements,and other areas.This paper,focusing on astronomical and space-based applications,reviews research progress on astronomical frequency combs,optical clock time-frequency networks,gravitational waves,dark matter measurement,dual-comb large-scale absolute ranging,and high-resolution atmospheric spectroscopy.With enhanced performance and their gradual application in the field of space-based research,optical frequency combs will undoubtedly provide more powerful support for astronomical science and cosmic exploration in the future.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.91336101 and 61127901)West Light Foundation of the Chinese Academy of Sciences(Grant No.2013ZD02)
文摘We demonstrate an optical frequency comb based on an erbium-doped-fiber femtosecond laser with the nonlinear polarization evolution scheme. The repetition rate of the laser is about 209 MHz. By controlling an intra-cavity electro- optic modulator and a piezo-transducer, the repetition rate can be stabilized with a high-bandwidth servo in a frequency range of 3 kHz, enabling long-term repetition rate phase-locking. The in-loop frequency stability of repetition rate is about 1.6× 10-13 in an integration time of 1 s, limited by the measurement system; and it is inversely proportional to integration time in the short term. Furthermore, using a common path f-2f interferometer, the carrier envelope offset frequency of the comb is obtained with a signal-to-noise ratio of 40 dB in a 3-MHz resolution bandwidth. Stabilized cartier envelope offset frequency exhibits a deviation of 0.6 mHz in an integration time of 1 s.
基金This work was supported by the National Key Research and Development Program of China(No.2020YFB2205801)National Natural Science Foundation of China(Nos.11934012,11874342,and 92050109)the Fundamental Research Funds for the Central Universities.C.H.Dong was also supported by the State Key Laboratory of Advanced Optical Communication Systems and Networks,Shanghai Jiao Tong University,China.This work was partially carried out at the USTC Center for Micro and Nanoscale Research and Fabrication.The authors declare no conflicts of interest.
文摘The microresonator-based soliton microcomb has shown a promising future in many applications.In this work,we report the fabrication of high quality[Q]Si_(3)N_(4)microring resonators for soliton microcomb generation.By developing the fabri-cation process with crack isolation trenches and annealing,we can deposit thick stoichiometric Si3N4 film of 800 nm without cracks in the central area.The highest intrinsic Q of the Si_(3)N_(4)microring obtained in our experiments is about 6×10^(6),corresponding to a propagation loss as low as 0.058 dBm/cm.With such a high Q film,we fabricate microrings with the anomalous dispersion and demonstrate the generation of soliton microcombs with 100 mW on-chip pump power,with an optical parametric oscillation threshold of only 13.4 mW.Our Si_(3)N_(4)integrated chip provides an ideal platform for researches and applications of nonlinear photonics and integrated photonics.
文摘High-precision time transfer plays an important role in the areas of fundamental research and applications. Accompanying w ith the remarkable improvements in the ability of generating and measuring high-accuracy time-frequency signal,seeking for new time-transfer techniques betw een distant clocks w ith much further improved accuracy attracts attentions w orld-w idely. The time-transfer technique based on optical pulses has the highest precision presently,and the further improvement in the accuracy is heavily dependent on the time-domain properties of the pulse as w ell as the sensitivity of the applied measurement on the exchanged pulse. The application of optical frequency comb in time transfer for a precision up to femtosecond level are currently the focus of much interest,and has recently achieved many breakthroughs. Further investigations show that,utilizing quantum techniques,i.e. quantum measurement technique and quantum optical pulse source,can lead to a new limit on the measured timing information. Furthermore,it can be immune from atmospheric parameters,such as pressure,temperature,humidity and so on.Such quantum improvements on time-transfer have a bright prospect in the future applications requiring extremely high-accuracy timing and ranging. The potential achievements w ill form a technical basis for the future realization of sub-femtosecond time transfer system.
