The mid-infrared optical frequency comb is a powerful tool for gas sensing.In this study,we demonstrate a simple midinfrared dual-comb spectrometer covering 3±4μm in Li Nb O_(3)waveguides.Based on a low-power fi...The mid-infrared optical frequency comb is a powerful tool for gas sensing.In this study,we demonstrate a simple midinfrared dual-comb spectrometer covering 3±4μm in Li Nb O_(3)waveguides.Based on a low-power fiber laser system,the mid-infrared comb is achieved via intra-pulse difference frequency generation in the Li Nb O_(3)waveguide.We construct pre-chirp management before supercontinuum generation to control spatiotemporal alignment for pump and signal pulses.The supercontinuum is directly coupled into a chirped periodically poled Li Nb O_(3)waveguide for the 3±4μm idler generation.A mid-infrared dual-comb spectrometer based on this approach provides a 100 MHz resolution over25 THz coverage.To evaluate the applicability for spectroscopy,we measure the methane spectrum using the dualcomb spectrometer.The measured results are consistent with the HITRAN database,in which the root mean square of the residual is 3.2%.This proposed method is expected to develop integrated and robust mid-infrared dual-comb spectrometers on chip for sensing.展开更多
We demonstrate an all-polarization-maintaining(APM)fiber mode-locked laser based on nonlinear polarization evolution(NPE).A well-designed Sagnac fiber loop is employed to establish the nonlinear polarization evolution...We demonstrate an all-polarization-maintaining(APM)fiber mode-locked laser based on nonlinear polarization evolution(NPE).A well-designed Sagnac fiber loop is employed to establish the nonlinear polarization evolution process in a polarization beam splitter(PBS)figure-8 fiber laser.Nonlinear loss curves are calculated to verify the saturable absorption characteristic of this NPE-based APM oscillator.Then,we simulate the pulse propagation process in the cavity to demonstrate the pulse mode-locked formation.Finally,we also design a realizable compact scheme to further reduce noise disturbances,achieving a 101-fs mode-locked pulse train with a 0.3-mrad integrated phase noise and a 0.006%integrated relative intensity noise(RIN).This figure-8 fiber laser provides a new scheme for compacting low-noise compact APM fiber lasers based on the NPE mode-locked mechanism.展开更多
Dual-comb spectroscopy(DCS)has revolutionized numerous spectroscopic applications due to its high spectral resolution and fast measurement speed.Substantial efforts have been made to obtain a coherent dual-comb source...Dual-comb spectroscopy(DCS)has revolutionized numerous spectroscopic applications due to its high spectral resolution and fast measurement speed.Substantial efforts have been made to obtain a coherent dual-comb source at various spectral regions through nonlinear frequency conversion,where the preservation of coherence has become a problem of great importance.In this study,we report the generation of coherent dual-comb sources covering from the ultraviolet to mid-infrared region based on high-order harmonic generation.Driven by high-repetition-rate femtosecond mid-infrared dual-comb pump pulses,up to ninth-order harmonic was generated from the ultraviolet to mid-infrared region using an aperiodically poled lithium niobate waveguide.To investigate the coherence property of the high-order harmonic generation,DCS was performed at every generated spectral region from 450 to 3600 nm.The measured dual-comb spectra with distinctive tooth-resolved structures show the well-preserved coherence without apparent degradation after the cascaded quadratic nonlinear processes.The subsequent methane absorption spectroscopy at multiple spectral regions of different harmonics was carried out to characterize the spectroscopic capability of the system.These results demonstrate the potential of our scheme to generate compact and coherent broadband optical frequency combs for simultaneous multi-target detections.展开更多
We report a compact,tunable,self-starting,all-fiber laser-based asynchronous optical sampling(ASOPS)system.Two Er-doped fiber oscillators were used as the pulsed-laser source,whose repetition rate could be set at 100 ...We report a compact,tunable,self-starting,all-fiber laser-based asynchronous optical sampling(ASOPS)system.Two Er-doped fiber oscillators were used as the pulsed-laser source,whose repetition rate could be set at 100 MHz with a tuning range of 1.25 MHz through a fiber delay line.By employing phase-locked and temperature control loops,the repetition rate offset of the two lasers was stabilized with 7.13×10^(−11)fractional instability at an average time of 1 s.Its capabilities in the terahertz regime were demonstrated by terahertz time-domain spectroscopy,achieving a spectral bandwidth of 3 THz with a dynamic range of 30 dB.The large range of repetition rate adjustment in our ASOPS system has the potential to be a powerful tool in the terahertz regime.展开更多
We report on a compact and robust self-referenced optical frequency comb with a tunable repetition rate,generated by an all-polarization-maintaining(PM)mode-locked Er-doped fiber laser.The spacing between comb teeth c...We report on a compact and robust self-referenced optical frequency comb with a tunable repetition rate,generated by an all-polarization-maintaining(PM)mode-locked Er-doped fiber laser.The spacing between comb teeth can be tuned above 300 kHz at a repetition rate of 101 MHz.The repetition rate and the carrier-envelope offset of the laser are stabilized separately,and the relative residual phase noises are determined to be 336µrad and 713 mrad(1 Hz-1 MHz).The accurate frequency characteristics and the stable structure show great potential for the use of such a comb in applications of precision measurements.展开更多
Mid-infrared dual-comb spectroscopy is of great interest owing to the strong spectroscopic features of trace gases,biological molecules,and solid matter with higher resolution,accuracy,and acquisition speed. However,t...Mid-infrared dual-comb spectroscopy is of great interest owing to the strong spectroscopic features of trace gases,biological molecules,and solid matter with higher resolution,accuracy,and acquisition speed. However,the prerequisite of achieving high coherence of optical sources with the use of bulk sophisticated control systems prevents their widespread use in field applications. Here we generate a highly mutually coherent dual midinfrared comb spectrometer based on the optical–optical modulation of a continuous-wave (CW) interband or quantum cascade laser. Mutual coherence was passively achieved without post-data processes or active carrier envelope phase-locking processes. The center wavelength of the generated mid-infrared frequency combs can be flexibly tuned by adjusting the wavelength of the CW seeds. The parallel detection of multiple molecular species,including C_(2)H_(2),CH_(4),H_(2)CO,H_(2)S,COS,and H_(2)O,was achieved. This technique provides a stable and robust dual-comb spectrometer that will find nonlaboratory applications including open-path atmospheric gas sensing,industrial process monitoring,and combustion.展开更多
The determination of airflow parameters is essential to the research of critical information on environment monitoring,chemical kinetics,and aerodynamic and propulsion applications.During the past few decades,tunable ...The determination of airflow parameters is essential to the research of critical information on environment monitoring,chemical kinetics,and aerodynamic and propulsion applications.During the past few decades,tunable diode laser absorption spectroscopy has become a common and efficient tool for the flow velocity measurement based on the Doppler shift of the absorption line.Dual-comb absorption spectroscopy(DCAS),as a state-of-theart Fourier-transform broadband spectroscopic technique,not only can detect multiple trace molecules in parallel but also can extract Doppler shifts to derive the flow velocity through the analysis of dozens of molecular absorption lines simultaneously with high precision.Here,we report a proof-of-principle demonstration of the velocity measurements of acetylene at various flow velocities by means of a high-resolution and broadband DCAS.Mode-resolved Doppler-shifted rotational-vibrational lines in the P branch of acetylene molecules are obtained.A model for multiline Doppler frequency determination is investigated and experimentally verified.The flow velocity measurements with a measuring uncertainty down to the submeter per second over the range from 8.7 m/s to 44.8 m/s at an effective time resolution of 1 s and a measuring uncertainty of 1.97 m/s at 0.1 s are demonstrated.With broadband mid-infrared frequency combs covering atmospheric transmission windows,the open-path measurement for monitoring diffusion of the weak pollutant source would be realized.展开更多
We report on the generation of a mid-infrared(mid-IR)frequency comb with a maximum average output power of250 mW and tunability in the 2.7-4.0μm region.The approach is based on a single-stage difference frequency gen...We report on the generation of a mid-infrared(mid-IR)frequency comb with a maximum average output power of250 mW and tunability in the 2.7-4.0μm region.The approach is based on a single-stage difference frequency generation(DFG)starting from a compact Yb-doped fiber laser system.The repetition rate of the near-infrared(NIR)comb is locked at 75 MHz.The phase noise of the repetition rate in the offset-free mid-IR comb system is measured and analyzed.Except for the intrinsic of NIR comb,environmental noise at low frequency and quantum noise at high frequency from the amplifier chain and nonlinear spectral broadening are the main noise sources of broadening the linewidth of comb teeth,which limits the precision of mid-IR dual-comb spectroscopy.展开更多
Gain-parameter-dependent transfer functions and phase-noise performances in a mode-locked Yb-doped fiber laser are measured in this study.It is discovered that the corner frequency in the amplitude and phase domains i...Gain-parameter-dependent transfer functions and phase-noise performances in a mode-locked Yb-doped fiber laser are measured in this study.It is discovered that the corner frequency in the amplitude and phase domains is determined by the absorption coefficient of the gain fiber,when the total absorption and other cavity parameters are fixed.This shows that an oscillator using gain fiber with higher dopant concentration accumulates more phase noise.Furthermore,we present net cavity dispersion-dependent transfer functions to verify the effect of dispersion management on the frequency response.We derive a guideline for optimizing mode-locked fiber laser design to achieve low phase noise and timing jitter.展开更多
Optical frequency combs(OFCs)have enabled significant opportunities for high-precision frequency metrology and high-resolution broadband spectroscopy.Although nonlinear photonics chips have the capacity of frequency e...Optical frequency combs(OFCs)have enabled significant opportunities for high-precision frequency metrology and high-resolution broadband spectroscopy.Although nonlinear photonics chips have the capacity of frequency expansion for OFCs,most of them can only access the limited bandwidths in the partial infrared region,and it is still hard to satisfy many measurement applications in the ultraviolet-to-visible region.Here,we demonstrate a compact broadband OFC scheme via the combination of three χ(2) nonlinearities in a three-stage periodically poled lithium niobate(PPLN)chain.With a supercontinuum spectrum OFC delivered into the PPLN chain,the intra-pulse diffidence frequency generation,optical parametric amplification,and high-order harmonic generation were carried out in sequence.It is crucial that the harmonics of the 1st–10th orders are simultaneously obtained with an offset-free OFC spectrum from 0.35 to 4.0μm.In view of the great potential for integration and spectral expansion,this wideband frequency comb source will open a new insight for the valuable applications of two-dimensional material analysis,biofluorescence microscopy,and nonlinear amplitude-phase metrology.展开更多
基金supported in part by the National Natural Science Foundation of China(Nos.12204178,12104162,12134004 and 12274141)。
文摘The mid-infrared optical frequency comb is a powerful tool for gas sensing.In this study,we demonstrate a simple midinfrared dual-comb spectrometer covering 3±4μm in Li Nb O_(3)waveguides.Based on a low-power fiber laser system,the mid-infrared comb is achieved via intra-pulse difference frequency generation in the Li Nb O_(3)waveguide.We construct pre-chirp management before supercontinuum generation to control spatiotemporal alignment for pump and signal pulses.The supercontinuum is directly coupled into a chirped periodically poled Li Nb O_(3)waveguide for the 3±4μm idler generation.A mid-infrared dual-comb spectrometer based on this approach provides a 100 MHz resolution over25 THz coverage.To evaluate the applicability for spectroscopy,we measure the methane spectrum using the dualcomb spectrometer.The measured results are consistent with the HITRAN database,in which the root mean square of the residual is 3.2%.This proposed method is expected to develop integrated and robust mid-infrared dual-comb spectrometers on chip for sensing.
基金supported by the National Natural Science Foundation of China(Nos.12204178,12134004,12104162,and 12274141).
文摘We demonstrate an all-polarization-maintaining(APM)fiber mode-locked laser based on nonlinear polarization evolution(NPE).A well-designed Sagnac fiber loop is employed to establish the nonlinear polarization evolution process in a polarization beam splitter(PBS)figure-8 fiber laser.Nonlinear loss curves are calculated to verify the saturable absorption characteristic of this NPE-based APM oscillator.Then,we simulate the pulse propagation process in the cavity to demonstrate the pulse mode-locked formation.Finally,we also design a realizable compact scheme to further reduce noise disturbances,achieving a 101-fs mode-locked pulse train with a 0.3-mrad integrated phase noise and a 0.006%integrated relative intensity noise(RIN).This figure-8 fiber laser provides a new scheme for compacting low-noise compact APM fiber lasers based on the NPE mode-locked mechanism.
基金National Natural Science Foundation of China(12104162,12134004,12274141)National Key Research and Development Program of China(2018YFA0306301)+2 种基金Shanghai Municipal Science and Technology Major ProjectChina Postdoctoral Science Foundation(2022M711175)Research Funds of Happiness Flower ECNU。
文摘Dual-comb spectroscopy(DCS)has revolutionized numerous spectroscopic applications due to its high spectral resolution and fast measurement speed.Substantial efforts have been made to obtain a coherent dual-comb source at various spectral regions through nonlinear frequency conversion,where the preservation of coherence has become a problem of great importance.In this study,we report the generation of coherent dual-comb sources covering from the ultraviolet to mid-infrared region based on high-order harmonic generation.Driven by high-repetition-rate femtosecond mid-infrared dual-comb pump pulses,up to ninth-order harmonic was generated from the ultraviolet to mid-infrared region using an aperiodically poled lithium niobate waveguide.To investigate the coherence property of the high-order harmonic generation,DCS was performed at every generated spectral region from 450 to 3600 nm.The measured dual-comb spectra with distinctive tooth-resolved structures show the well-preserved coherence without apparent degradation after the cascaded quadratic nonlinear processes.The subsequent methane absorption spectroscopy at multiple spectral regions of different harmonics was carried out to characterize the spectroscopic capability of the system.These results demonstrate the potential of our scheme to generate compact and coherent broadband optical frequency combs for simultaneous multi-target detections.
基金This study was supported by the National Natural Science Foundation of China(Nos.12134004,12104162,and 62127804)National Key R&D Program of China(No.2018YFA0306301)+1 种基金Shanghai Municipal Science and Technology Major ProjectChina Postdoctoral Science Foundation(No.2022M711175).
文摘We report a compact,tunable,self-starting,all-fiber laser-based asynchronous optical sampling(ASOPS)system.Two Er-doped fiber oscillators were used as the pulsed-laser source,whose repetition rate could be set at 100 MHz with a tuning range of 1.25 MHz through a fiber delay line.By employing phase-locked and temperature control loops,the repetition rate offset of the two lasers was stabilized with 7.13×10^(−11)fractional instability at an average time of 1 s.Its capabilities in the terahertz regime were demonstrated by terahertz time-domain spectroscopy,achieving a spectral bandwidth of 3 THz with a dynamic range of 30 dB.The large range of repetition rate adjustment in our ASOPS system has the potential to be a powerful tool in the terahertz regime.
基金This work was partly supported by the National Natural Science Foundation of China(Nos.11804096,11874153 and 11904105)the National Key R&D Program of China(Nos.2018YFA0306301 and 2017YFF0206000)the Shanghai Sailing Program(No.18YF1407300).
文摘We report on a compact and robust self-referenced optical frequency comb with a tunable repetition rate,generated by an all-polarization-maintaining(PM)mode-locked Er-doped fiber laser.The spacing between comb teeth can be tuned above 300 kHz at a repetition rate of 101 MHz.The repetition rate and the carrier-envelope offset of the laser are stabilized separately,and the relative residual phase noises are determined to be 336µrad and 713 mrad(1 Hz-1 MHz).The accurate frequency characteristics and the stable structure show great potential for the use of such a comb in applications of precision measurements.
基金National Natural Science Foundation of China(11904105,11874153,11621404)National Key Research and Development Program of China (2018YFA0306301)China Postdoctoral Science Foundation funded project(2020M681223)。
文摘Mid-infrared dual-comb spectroscopy is of great interest owing to the strong spectroscopic features of trace gases,biological molecules,and solid matter with higher resolution,accuracy,and acquisition speed. However,the prerequisite of achieving high coherence of optical sources with the use of bulk sophisticated control systems prevents their widespread use in field applications. Here we generate a highly mutually coherent dual midinfrared comb spectrometer based on the optical–optical modulation of a continuous-wave (CW) interband or quantum cascade laser. Mutual coherence was passively achieved without post-data processes or active carrier envelope phase-locking processes. The center wavelength of the generated mid-infrared frequency combs can be flexibly tuned by adjusting the wavelength of the CW seeds. The parallel detection of multiple molecular species,including C_(2)H_(2),CH_(4),H_(2)CO,H_(2)S,COS,and H_(2)O,was achieved. This technique provides a stable and robust dual-comb spectrometer that will find nonlaboratory applications including open-path atmospheric gas sensing,industrial process monitoring,and combustion.
基金National Natural Science Foundation of China(11874153,11904105)National Key Research and Development Program of China(2018YFA0306301).
文摘The determination of airflow parameters is essential to the research of critical information on environment monitoring,chemical kinetics,and aerodynamic and propulsion applications.During the past few decades,tunable diode laser absorption spectroscopy has become a common and efficient tool for the flow velocity measurement based on the Doppler shift of the absorption line.Dual-comb absorption spectroscopy(DCAS),as a state-of-theart Fourier-transform broadband spectroscopic technique,not only can detect multiple trace molecules in parallel but also can extract Doppler shifts to derive the flow velocity through the analysis of dozens of molecular absorption lines simultaneously with high precision.Here,we report a proof-of-principle demonstration of the velocity measurements of acetylene at various flow velocities by means of a high-resolution and broadband DCAS.Mode-resolved Doppler-shifted rotational-vibrational lines in the P branch of acetylene molecules are obtained.A model for multiline Doppler frequency determination is investigated and experimentally verified.The flow velocity measurements with a measuring uncertainty down to the submeter per second over the range from 8.7 m/s to 44.8 m/s at an effective time resolution of 1 s and a measuring uncertainty of 1.97 m/s at 0.1 s are demonstrated.With broadband mid-infrared frequency combs covering atmospheric transmission windows,the open-path measurement for monitoring diffusion of the weak pollutant source would be realized.
基金supported by the National Natural Science Foundation of China(Nos.11804096,11874153,and 11904105)the National Key R&D Program of China(Nos.2018YFA0306301 and 2017YFF0206000)the Shanghai Sailing Program(No.18YF1407300)。
文摘We report on the generation of a mid-infrared(mid-IR)frequency comb with a maximum average output power of250 mW and tunability in the 2.7-4.0μm region.The approach is based on a single-stage difference frequency generation(DFG)starting from a compact Yb-doped fiber laser system.The repetition rate of the near-infrared(NIR)comb is locked at 75 MHz.The phase noise of the repetition rate in the offset-free mid-IR comb system is measured and analyzed.Except for the intrinsic of NIR comb,environmental noise at low frequency and quantum noise at high frequency from the amplifier chain and nonlinear spectral broadening are the main noise sources of broadening the linewidth of comb teeth,which limits the precision of mid-IR dual-comb spectroscopy.
基金supported by the National Natural Science Foundation of China(Nos.11904105,11874153,and 11621404)National Key R&D Program of China(No.2018YFA0306301)China Postdoctoral Science Foundation(No.2020M681223)。
文摘Gain-parameter-dependent transfer functions and phase-noise performances in a mode-locked Yb-doped fiber laser are measured in this study.It is discovered that the corner frequency in the amplitude and phase domains is determined by the absorption coefficient of the gain fiber,when the total absorption and other cavity parameters are fixed.This shows that an oscillator using gain fiber with higher dopant concentration accumulates more phase noise.Furthermore,we present net cavity dispersion-dependent transfer functions to verify the effect of dispersion management on the frequency response.We derive a guideline for optimizing mode-locked fiber laser design to achieve low phase noise and timing jitter.
基金National Natural Science Foundation of China(12204178,12104162,12134004,12274141).
文摘Optical frequency combs(OFCs)have enabled significant opportunities for high-precision frequency metrology and high-resolution broadband spectroscopy.Although nonlinear photonics chips have the capacity of frequency expansion for OFCs,most of them can only access the limited bandwidths in the partial infrared region,and it is still hard to satisfy many measurement applications in the ultraviolet-to-visible region.Here,we demonstrate a compact broadband OFC scheme via the combination of three χ(2) nonlinearities in a three-stage periodically poled lithium niobate(PPLN)chain.With a supercontinuum spectrum OFC delivered into the PPLN chain,the intra-pulse diffidence frequency generation,optical parametric amplification,and high-order harmonic generation were carried out in sequence.It is crucial that the harmonics of the 1st–10th orders are simultaneously obtained with an offset-free OFC spectrum from 0.35 to 4.0μm.In view of the great potential for integration and spectral expansion,this wideband frequency comb source will open a new insight for the valuable applications of two-dimensional material analysis,biofluorescence microscopy,and nonlinear amplitude-phase metrology.
