We achieved an ultra-flat broad spectrum output with a 20-dB bandwidth of 77.85 nm in a double-clad Yb-doped fiber laser.The intensity difference between the highest and lowest points of the spectrum indicates a flatn...We achieved an ultra-flat broad spectrum output with a 20-dB bandwidth of 77.85 nm in a double-clad Yb-doped fiber laser.The intensity difference between the highest and lowest points of the spectrum indicates a flatness better than4 dB.More notably,this ultra-flat broad spectrum maintains a stable single-pulse mode-locking state.With the increase of pump power,an ultra-wide spectrum with a 20-dB bandwidth approaching 100 nm was formed at a pump power of 2.25 W.Additionally,we obtained a 9-pulse mode-locked state at another PC station with the same pump,which is the highest number of stable mode-locked pulse bursts observed so far with a first-order Raman frequency shift.This fiber laser shows its benefits of ultra-flat broad spectrum,high stability,and ease of fabrication,which provides a new method of obtaining the broadband light source for multiple practical applications.展开更多
A self-starting mode-locked femtosecond laser is accomplished with an oxoborate self-frequency doubling crystal Yb：YCa4O（BO3）3 （Yb：YCOB） as the gain medium and a semiconductor mirror as the saturable absorber. P...A self-starting mode-locked femtosecond laser is accomplished with an oxoborate self-frequency doubling crystal Yb：YCa4O（BO3）3 （Yb：YCOB） as the gain medium and a semiconductor mirror as the saturable absorber. Pumped by a 976-nm fiber-coupled diode laser with 50-ktm core diameter, stable mode-locked laser pulses up to 430 mW were obtained at a repetition rate of 83.61 MHz under 5-W pump power. The autocorrelation measurement shows that the pulse duration is as short as 150 fs by assuming the sech2 pulse shape at a central wavelength of 1048 nm. This work has demonstrated a compact and reliable femtosecond laser source for prospective low-cost applications.展开更多
In the last few years,research on advanced ultrafast photonic devices has attracted great interest from laser physicists.As a semiconductor material with excellent nonlinear saturation absorption characteristics,Ga As...In the last few years,research on advanced ultrafast photonic devices has attracted great interest from laser physicists.As a semiconductor material with excellent nonlinear saturation absorption characteristics,Ga As has been used in solidstate and fiber lasers as a mode-locker.However,the pulse widths that have been reported in the searchable published literature are all long and the shortest is tens of picoseconds.Femtosecond pulse widths,desired for a variety of applications,have not yet been reported in Ga As-based pulsed lasers.In this work,we further explore the nonlinear characteristics of Ga As that has been magnetron sputtered onto the surface of a tapered fiber and its application in the generation of femtosecond lasing via effective dispersion optimization and nonlinearity management.With the enhanced interaction between evanescent waves and Ga As nanosheets,mode-locked soliton pulses as short as 830 fs are generated at repetition rates of 4.64 MHz.As far as we know,this is the first time that femtosecond-level pulses have been generated with a Ga As-based saturable absorber.In addition,soliton molecules,including in the dual-pulse state,are also realized under stronger pumping.This work demonstrates that Ga As-based photonic devices have good application prospects in effective polymorphous ultrashort pulsed laser generation.展开更多
A stable continuous wave mode-locked picosecond Ti：sapphire laser by using a fast semiconductor saturable absorber mirror （SESAM） is demonstrated. The laser delivers pulse width of 20 ps at a central wavelength of ...A stable continuous wave mode-locked picosecond Ti：sapphire laser by using a fast semiconductor saturable absorber mirror （SESAM） is demonstrated. The laser delivers pulse width of 20 ps at a central wavelength of 813 nm and a repetition rate of 100 MHz. The maximum output power is 1.34 W with pump power of 7 W which corresponds to an optical^optical conversion efficiency of 19.1%.展开更多
Groundwater lowering is one of the most important countermeasures to avoid the risk of rainfall-triggered landslides.However,the long-term reliability of many drainage methods is often a matter of concern since the dr...Groundwater lowering is one of the most important countermeasures to avoid the risk of rainfall-triggered landslides.However,the long-term reliability of many drainage methods is often a matter of concern since the drains may easily get clogged.A new hydraulic-driven self-starting drainage method is presented in this paper.In the proposed Random Forest(RF)based robust design approach for the selfstarting drains,the datasets are generated using an automatically controlled numerical modeling technology.The deterministic analysis is carried out based on uncertain soil parameters and the specific designs selected using Uniform Design(UD).The ensemble of RF models is applied in the design process to improve computing efficiency.Safety requirements,design robustness,and cost efficiency are simultaneously considered utilizing multiobjective optimization.A straightforward and efficient framework that focuses on difficulties caused by an enormous design space is established for the robust design of the self-starting drains,and improved computation efficiency is achieved.The effectiveness of the proposed approach is illustrated with a case study,the Qili landslide in Zhejiang Province,China.展开更多
The present work deals with an investigation of the self-starting aerodynamic characteristics of VAWT under fluctuating wind. In contrast to the previous studies, the rotational speed of the turbine is not fixed, the ...The present work deals with an investigation of the self-starting aerodynamic characteristics of VAWT under fluctuating wind. In contrast to the previous studies, the rotational speed of the turbine is not fixed, the rotation of the turbine is determined by the dynamic interaction between the fluctuating wind and turbine. A weak coupling method is developed to simulate the dynamic interaction between the fluctuating wind and passive rotation turbine, and the results show that if the fluctuating wind with appropriate fluctuation amplitude and frequency, the self-starting aerodynamic characteristics of VAWT will be enhanced. It is also found that compared with the fluctuation amplitude, the fluctuation frequency of the variation in wind velocity is shown to have a minor effect on the performance of the turbine. The analysis will provide straightforward physical insight into the self-starting aerodynamic characteristics of VAWT under fluctuating wind.展开更多
CsPbBr3 nanocrystal is used as the saturable absorber(SA) for mode-locking Tm-doped fiber laser in a ring fiber cavity.The modulation depth, saturable intensity, and non-saturable loss of the fabricated SA are 14.1%, ...CsPbBr3 nanocrystal is used as the saturable absorber(SA) for mode-locking Tm-doped fiber laser in a ring fiber cavity.The modulation depth, saturable intensity, and non-saturable loss of the fabricated SA are 14.1%, 2.5 MW/cm^2,and 5.9%, respectively.In the mode-locking operation, the mode-locked pulse train has a repetition rate of 16.6 MHz with pulse width of 24.2 ps.The laser wavelength is centered at 1992.9 nm with 3-dB spectrum width of 2.5 nm.The maximum output power is 110 mW with slope efficiency of 7.1%.Our experiment shows that CsPbBr3 nanocrystal can be used as an efficient SA in the 2-μm wavelength region.展开更多
In this study,wind tunnel experiment was carried out to investigate the self-staring capability for straight-bladed vertical axis wind turbine.The flow visualization also was been performed at the rest of the rotor.Th...In this study,wind tunnel experiment was carried out to investigate the self-staring capability for straight-bladed vertical axis wind turbine.The flow visualization also was been performed at the rest of the rotor.The effect of the azimuthal angle of blade position relative to wind direction on the self-starting capability was discussed based on the results of flow visualization.The torque and centripetal force of the rotor when the self-starting behavior starts were roughly calculated with the flow visualization results of the rotor.It is suggested that there exists the condition of wind speed and configuration of the blade position of the rotor at the rest of rotor to the reach to situational rotation number.展开更多
Using Langevin simulations, we study numerically the directional mode-locking of the dynamics of two- dimensional superpararnagnetic colloidal system in a periodic pinning array. When the colloidal particles are initi...Using Langevin simulations, we study numerically the directional mode-locking of the dynamics of two- dimensional superpararnagnetic colloidal system in a periodic pinning array. When the colloidal particles are initially commensurate with the pinning sites, there appear mode-locking steps in the average velocity of colloidal particles along certain directions of the external driving force. With an increase in the pinning strength, the width of the step increases linearly but the velocity at the step decreases parabolically.展开更多
Passive harmonic mode locking of an erbium-doped fiber laser based on few-layer molybdenum disulfide(MoS2)saturable absorber(SA) is demonstrated. The few-layer MoS2 is prepared by the chemical vapor deposition(CVD) me...Passive harmonic mode locking of an erbium-doped fiber laser based on few-layer molybdenum disulfide(MoS2)saturable absorber(SA) is demonstrated. The few-layer MoS2 is prepared by the chemical vapor deposition(CVD) method and then transferred onto the end face of a fiber connector to form a fiber-compatible Mo S2SA. The 20 th harmonic modelocked pulses at 216-MHz repetition rate are stably generated with a pulse duration of 1.42 ps and side-mode suppression ratio(SMSR) of 36.1dB. The results confirm that few-layer MoS2 can serve as an effective SA for mode-locked fiber lasers.展开更多
Self-starting Q-switching,Q-switched mode-locking and mode-locking operation modes are achieved sequentially in an all-fiber erbium-doped fiber laser with thulium-doped fiber saturable absorber for the first time.The ...Self-starting Q-switching,Q-switched mode-locking and mode-locking operation modes are achieved sequentially in an all-fiber erbium-doped fiber laser with thulium-doped fiber saturable absorber for the first time.The central wavelengths of Q-switching,Q-switched mode-locking and mode-locking operation modes are 1569.7 nm,1570.9 nm,and 1572 nm,respectively.The mode-locking operation of the proposed fiber laser generates stable dark soliton with a repetition rate of 0.99 MHz and signal-to-noise ratio of 65 dB.The results validate the capability of generating soliton pulse by doped fiber saturable absorber.Furthermore,the proposed fiber laser is beneficial to the applications of optical communication and signal processing system.展开更多
The pulse generation from active mode-locking terahertz quantum cascade laser is studied by Maxwell-Bloch equations.It is shown that longer dephasing time will lead to multiple pulses generation from the laser.The dep...The pulse generation from active mode-locking terahertz quantum cascade laser is studied by Maxwell-Bloch equations.It is shown that longer dephasing time will lead to multiple pulses generation from the laser.The dependence of output field on modulation length and radio-frequency parameters is obtained.In order to achieve short pulse generation,the DC bias should close to threshold value and modulation length should be shorter than 0.256 mm.The output pulse is unstable and the envelope shows many oscillations in the presence of spatial hole burning,resulting destabilization of mode-locking.展开更多
As a representative transition metal dichalcogenides(TMD),NiTe_(2)has an ultra-fast optical response,high carrier mobility,and excellent environmental stability.It has a broad application prospect in the fields of ene...As a representative transition metal dichalcogenides(TMD),NiTe_(2)has an ultra-fast optical response,high carrier mobility,and excellent environmental stability.It has a broad application prospect in the fields of ener-gy,biomedicine,optoelectronic devices,and so on.At present,there have been scant reports on the application of NiTe_(2)in the field of ultrafast photonics.In this work,NiTe_(2)was synthesized by chemical vapor deposition(CVD)and integrated with a tapered optical fiber to achieve mode-locking in an erbium-doped fiber laser(EDFL)and a thu-lium-doped fiber laser(TDFL).The mode-locked EDFL exhibited a pulse width of 678 fs and an output power of 3.92 mW.The pulse width of mode-locked TDFL was estimated to have a pulse width of 694 fs with an output power of 21.64 mW.These results demonstrate that NiTe_(2)is an effective saturable absorber material with potential applica-tions in the field of ultrafast optics.展开更多
Ytterbium(Yb)-based mode-locked fiber lasers have undergone significant development and found widespread applications owing to their high efficiency,compact size,and low cost.However,these lasers typically operate wit...Ytterbium(Yb)-based mode-locked fiber lasers have undergone significant development and found widespread applications owing to their high efficiency,compact size,and low cost.However,these lasers typically operate within the 1030 to 1080 nm range,and expanding their operational wavelength is crucial for applications across various fields.We present the direct generation of a mode-locked laser at 1120.06 nm using an all-polarization-maintaining structure,establishing the longest wavelength reported to date for Yb-doped fiber-based mode-locked lasers.A stable picosecond pulse laser at 1120 nm was realized by combining high-concentration Yb-doping and phase-biasing technology within a figure-9 cavity configuration.The laser delivers a pulse duration of 6.20 ps,a spectral width of 0.19 nm centered at 1120.06 nm,and a repetition rate of 21.52 MHz and reaches a maximum output power of 1.39 W via a double-cladding Yb fiber power amplifier in a master oscillator power amplifier configuration.Furthermore,we present a theoretical investigation of the laser performance,with simulation results aligning well with experimental findings.In addition,a 560.06-nm ultrafast yellow-green laser was generated through frequency doubling in a lithium triborate crystal.We present an approach for long-wavelength Yb-doped mode-locked lasers,with the potential to advance the development and application of Yb-based fiber lasers.展开更多
Ultra-narrow bandwidth mode-locked lasers with tunable pulse duration can be versatile light sources for diverse applications.However,the spectral-temporal control of a narrow bandwidth mode-locked laser is challengin...Ultra-narrow bandwidth mode-locked lasers with tunable pulse duration can be versatile light sources for diverse applications.However,the spectral-temporal control of a narrow bandwidth mode-locked laser is challenging due to limited gain and nonlinearity,hindering practical applications of such lasers.We demonstrate a pulse duration widely tunable mode-locked ultra-narrow bandwidth laser using a composite filtering mechanism and a single-wall carbon nanotube.The laser pulse duration can be adjusted from 481 ps to 1.38 ns,which is the widest tuning range achieved in narrow-bandwidth passively mode-locked lasers.When the pulse duration is 1.38 ns,the corresponding spectral width reaches 4 pm(502 MHz).Numerical simulations support the experimental results and show that the evolution of long pulses in the laser cavity behaves similarly to a quasi-continuous wave with a low breathing ratio.We have not only designed a simple and flexible tunable scheme for the dilemma of spectral-temporal control in narrow-bandwidth mode-locked fiber lasers but also provided a unique and idealized light source for various applications that takes into account robust output.展开更多
We report on a Kerr-lens mode-locked(KLM)femtosecond Yb:CaYAlO_(4)(Yb:CYA)laser operating at a repetition rate of 1.04 GHz,pumped by a single-mode fiber laser.The laser delivers an average output power of 1.37 W with ...We report on a Kerr-lens mode-locked(KLM)femtosecond Yb:CaYAlO_(4)(Yb:CYA)laser operating at a repetition rate of 1.04 GHz,pumped by a single-mode fiber laser.The laser delivers an average output power of 1.37 W with a pulse duration of 109 fs.Potential improvements,including scaling the pump power,increasing the repetition rate,and further reducing the pulse duration,are discussed.This study contributes to the advancement of Watt-level GHz femtosecond laser generation and its applications.展开更多
Passively mode-locked fiber lasers emit femtosecond pulse trains with excellent short-term stability. The quantum-limited timing jitter of a free running femtosecond erbium-doped fiber laser working at room temperatur...Passively mode-locked fiber lasers emit femtosecond pulse trains with excellent short-term stability. The quantum-limited timing jitter of a free running femtosecond erbium-doped fiber laser working at room temperature is considerably below one femtosecond at high Fourier frequency. The ultrashort pulse train with ultralow timing jitter enables absolute time-of-flight measurements based on a dual-comb implementation, which is typically composed of a pair of optical frequency combs generated by femtosecond lasers. Dead-zone-free absolute distance measurement with sub-micrometer precision and kHz update rate has been routinely achieved with a dual-comb configuration, which is promising for a number of precision manufacturing applications, from large step-structure measurements prevalent in microelectronic profilometry to three coordinate measurements in large-scale aerospace manufacturing and shipbuilding. In this paper, we first review the sub-femtosecond precision timing jitter characterization methods and approaches for ultralow timing jitter mode-locked fiber laser design. Then, we provide an overview of the state-of-the-art dual-comb absolute ranging technology in terms of working principles, experimental implementations, and measurement precisions. Finally, we discuss the impact of quantum-limited timing jitter on the dual-comb ranging precision at a high update rate. The route to highprecision dual-comb range finder design based on ultralow jitter femtosecond fiber lasers is proposed.展开更多
Using graphene-covered-microfiber （GCM） as a saturable absorber, the generation and evolution of multiple operation states are proposed and demonstrated in passively mode-locked thulium-doped fiber laser. The microf...Using graphene-covered-microfiber （GCM） as a saturable absorber, the generation and evolution of multiple operation states are proposed and demonstrated in passively mode-locked thulium-doped fiber laser. The microfiber was fabricated using the flame brushing method to an interaction length of - 1.2 cm with a waist diameter of -10 μm. Graphene layers were grown on copper foils by chemical vapor deposition and transferred onto the polydimethylsiloxane （PDMS） to form a PDMS/graphene film, which allowed light-graphene interaction via evanescent field. With the increase of the pump power from 1.25 W to 2.15 W, five different lasing regimes, including continuous-wave, conventional soliton mode-locking, multi- soliton mode-locking, a period of transition, and noise-like mode-locking, were achieved in a fiber ring cavity. To the best of our knowledge, it is the first report of the generation and evolution of multiple operation states by covering graphene on the microfiber in the 2-μ.m region. The results demonstrate that GCM can be a promising method for fabricating all fiber SA, and the switchable operation states can provide more portability in complex application domain.展开更多
We report on a diode-pumped passively continuous wave （cw） mode-locked Tm：YAP laser with a double-wall carbon nanotube （DWCNT） absorber operating at a wavelength of 2023 nm for the first time, to the best our kno...We report on a diode-pumped passively continuous wave （cw） mode-locked Tm：YAP laser with a double-wall carbon nanotube （DWCNT） absorber operating at a wavelength of 2023 nm for the first time, to the best our knowledge. The DWCNT absorber is fabricated on a hydrophilic quartz substrate by using the vertical evaporation technique. The output power is as high as 375 mW. A stable pulse train with a repetition rate of 72.26 MHz is generated with a highest single pulse energy of 5.2 μJ.展开更多
A 980-nm semiconductor saturable absorber mirror（SESAM） mode-locked Yb-doped phosphate fiber laser is demonstrated by using an all-fiber linear cavity configuration. Two different kinds of cavity lengths are introdu...A 980-nm semiconductor saturable absorber mirror（SESAM） mode-locked Yb-doped phosphate fiber laser is demonstrated by using an all-fiber linear cavity configuration. Two different kinds of cavity lengths are introduced into the oscillator to obtain a robust and stable mode-locked seed source. When the cavity length is chosen to be 6 m, the oscillator generates an average output power of 3.5 m W and a pulse width of 76.27 ps with a repetition rate of 17.08 MHz. As the cavity length is optimized to short, 4.4-m W maximum output power and 61.15-ps pulse width are produced at a repetition rate of 20.96 MHz. The output spectrum is centered at 980 nm with a narrow spectral bandwidth of 0.13 nm. In the experiment, no undesired amplified spontaneous emission（ASE） nor harmful oscillation around 1030 nm is observed. Moreover,through a two-stage all-fiber-integrated amplifier, an output power of 740 m W is generated with a pulse width of 200 ps.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant No.12204132)the Natural Science Foundation of Shandong Province,China(Grant No.ZR2021MF122)+1 种基金Shandong Province TechnologyBased SME Innovation Enhancement Project(Grant No.2024TSGC0715)the Postgraduate Education Reform Project of Shandong Province,China(Grant No.SDYJSJGC2024107)。
文摘We achieved an ultra-flat broad spectrum output with a 20-dB bandwidth of 77.85 nm in a double-clad Yb-doped fiber laser.The intensity difference between the highest and lowest points of the spectrum indicates a flatness better than4 dB.More notably,this ultra-flat broad spectrum maintains a stable single-pulse mode-locking state.With the increase of pump power,an ultra-wide spectrum with a 20-dB bandwidth approaching 100 nm was formed at a pump power of 2.25 W.Additionally,we obtained a 9-pulse mode-locked state at another PC station with the same pump,which is the highest number of stable mode-locked pulse bursts observed so far with a first-order Raman frequency shift.This fiber laser shows its benefits of ultra-flat broad spectrum,high stability,and ease of fabrication,which provides a new method of obtaining the broadband light source for multiple practical applications.
基金Project supported by the National Natural Science Foundation of China(Grant No.61205130)the National Key Scientific Instruments Development Program of China(Grant No.2012YQ120047)the Fundamental Research Funds for the Central Universities of Ministry of Education of China(Grant No.K5051305008)
文摘A self-starting mode-locked femtosecond laser is accomplished with an oxoborate self-frequency doubling crystal Yb：YCa4O（BO3）3 （Yb：YCOB） as the gain medium and a semiconductor mirror as the saturable absorber. Pumped by a 976-nm fiber-coupled diode laser with 50-ktm core diameter, stable mode-locked laser pulses up to 430 mW were obtained at a repetition rate of 83.61 MHz under 5-W pump power. The autocorrelation measurement shows that the pulse duration is as short as 150 fs by assuming the sech2 pulse shape at a central wavelength of 1048 nm. This work has demonstrated a compact and reliable femtosecond laser source for prospective low-cost applications.
基金Project supported by the National Natural Science Foundation of China(Grant No.12164030)Young Science and Technology Talents of Inner Mongolia,China(Grant No.NJYT22101)+1 种基金the Central Government Guides Local Science,the Technology Development Fund Projects(Grant No.2023ZY0005)the Science and Technology Plan Projects of Inner Mongolia Autonomous Region of China(Grant No.2023KYPT0012)。
文摘In the last few years,research on advanced ultrafast photonic devices has attracted great interest from laser physicists.As a semiconductor material with excellent nonlinear saturation absorption characteristics,Ga As has been used in solidstate and fiber lasers as a mode-locker.However,the pulse widths that have been reported in the searchable published literature are all long and the shortest is tens of picoseconds.Femtosecond pulse widths,desired for a variety of applications,have not yet been reported in Ga As-based pulsed lasers.In this work,we further explore the nonlinear characteristics of Ga As that has been magnetron sputtered onto the surface of a tapered fiber and its application in the generation of femtosecond lasing via effective dispersion optimization and nonlinearity management.With the enhanced interaction between evanescent waves and Ga As nanosheets,mode-locked soliton pulses as short as 830 fs are generated at repetition rates of 4.64 MHz.As far as we know,this is the first time that femtosecond-level pulses have been generated with a Ga As-based saturable absorber.In addition,soliton molecules,including in the dual-pulse state,are also realized under stronger pumping.This work demonstrates that Ga As-based photonic devices have good application prospects in effective polymorphous ultrashort pulsed laser generation.
基金Project supported by the National Natural Science Foundation of China （Grant Nos 60225005 and 60308001）.
文摘A stable continuous wave mode-locked picosecond Ti：sapphire laser by using a fast semiconductor saturable absorber mirror （SESAM） is demonstrated. The laser delivers pulse width of 20 ps at a central wavelength of 813 nm and a repetition rate of 100 MHz. The maximum output power is 1.34 W with pump power of 7 W which corresponds to an optical^optical conversion efficiency of 19.1%.
基金supported by the National Natural Science Foundation of China(Grant No.41772276)the Key R&D project of Zhejiang Province(Grant No.2017C03006)the Zhejiang University and the Norwegian Geotechnical Institute for funding his research stay at NGI。
文摘Groundwater lowering is one of the most important countermeasures to avoid the risk of rainfall-triggered landslides.However,the long-term reliability of many drainage methods is often a matter of concern since the drains may easily get clogged.A new hydraulic-driven self-starting drainage method is presented in this paper.In the proposed Random Forest(RF)based robust design approach for the selfstarting drains,the datasets are generated using an automatically controlled numerical modeling technology.The deterministic analysis is carried out based on uncertain soil parameters and the specific designs selected using Uniform Design(UD).The ensemble of RF models is applied in the design process to improve computing efficiency.Safety requirements,design robustness,and cost efficiency are simultaneously considered utilizing multiobjective optimization.A straightforward and efficient framework that focuses on difficulties caused by an enormous design space is established for the robust design of the self-starting drains,and improved computation efficiency is achieved.The effectiveness of the proposed approach is illustrated with a case study,the Qili landslide in Zhejiang Province,China.
基金Projects(61105086,51505347)supported by the National Natural Science Foundation of China
文摘The present work deals with an investigation of the self-starting aerodynamic characteristics of VAWT under fluctuating wind. In contrast to the previous studies, the rotational speed of the turbine is not fixed, the rotation of the turbine is determined by the dynamic interaction between the fluctuating wind and turbine. A weak coupling method is developed to simulate the dynamic interaction between the fluctuating wind and passive rotation turbine, and the results show that if the fluctuating wind with appropriate fluctuation amplitude and frequency, the self-starting aerodynamic characteristics of VAWT will be enhanced. It is also found that compared with the fluctuation amplitude, the fluctuation frequency of the variation in wind velocity is shown to have a minor effect on the performance of the turbine. The analysis will provide straightforward physical insight into the self-starting aerodynamic characteristics of VAWT under fluctuating wind.
基金Project supported by the National Key R&D Program of China(Grant No.2018YFB0504500)the National Natural Science Foundation of China(Grant Nos.51472162,51672177,and 61475171)the Talent Introduction Research Project of Shanghai Institute of Technology,China(Grant No.YJ 2018-8)
文摘CsPbBr3 nanocrystal is used as the saturable absorber(SA) for mode-locking Tm-doped fiber laser in a ring fiber cavity.The modulation depth, saturable intensity, and non-saturable loss of the fabricated SA are 14.1%, 2.5 MW/cm^2,and 5.9%, respectively.In the mode-locking operation, the mode-locked pulse train has a repetition rate of 16.6 MHz with pulse width of 24.2 ps.The laser wavelength is centered at 1992.9 nm with 3-dB spectrum width of 2.5 nm.The maximum output power is 110 mW with slope efficiency of 7.1%.Our experiment shows that CsPbBr3 nanocrystal can be used as an efficient SA in the 2-μm wavelength region.
基金supported in part by International Platform for Dryland Research and Education (IPDRE),Tottori University
文摘In this study,wind tunnel experiment was carried out to investigate the self-staring capability for straight-bladed vertical axis wind turbine.The flow visualization also was been performed at the rest of the rotor.The effect of the azimuthal angle of blade position relative to wind direction on the self-starting capability was discussed based on the results of flow visualization.The torque and centripetal force of the rotor when the self-starting behavior starts were roughly calculated with the flow visualization results of the rotor.It is suggested that there exists the condition of wind speed and configuration of the blade position of the rotor at the rest of rotor to the reach to situational rotation number.
基金Supported by the Scientific Research Foundation of Graduate School of Zhengzhou Universitythe Natural Science Research Foundation of Henan Provincial Department of Science and Technology under Grant No. 112300410151
文摘Using Langevin simulations, we study numerically the directional mode-locking of the dynamics of two- dimensional superpararnagnetic colloidal system in a periodic pinning array. When the colloidal particles are initially commensurate with the pinning sites, there appear mode-locking steps in the average velocity of colloidal particles along certain directions of the external driving force. With an increase in the pinning strength, the width of the step increases linearly but the velocity at the step decreases parabolically.
基金supported by the National Natural Science Foundation of China(Grant Nos.61378028,61421002,61475030,and 61377042)the National Basic Research Program of China(Grant No.2012CB315701)the New Century Excellent Talents Program in University,China(Grant No.NCET-13-0092)
文摘Passive harmonic mode locking of an erbium-doped fiber laser based on few-layer molybdenum disulfide(MoS2)saturable absorber(SA) is demonstrated. The few-layer MoS2 is prepared by the chemical vapor deposition(CVD) method and then transferred onto the end face of a fiber connector to form a fiber-compatible Mo S2SA. The 20 th harmonic modelocked pulses at 216-MHz repetition rate are stably generated with a pulse duration of 1.42 ps and side-mode suppression ratio(SMSR) of 36.1dB. The results confirm that few-layer MoS2 can serve as an effective SA for mode-locked fiber lasers.
基金supported by the Science and Technology Innovation Program of Hunan Province,China(Grant No.2021RC5012).
文摘Self-starting Q-switching,Q-switched mode-locking and mode-locking operation modes are achieved sequentially in an all-fiber erbium-doped fiber laser with thulium-doped fiber saturable absorber for the first time.The central wavelengths of Q-switching,Q-switched mode-locking and mode-locking operation modes are 1569.7 nm,1570.9 nm,and 1572 nm,respectively.The mode-locking operation of the proposed fiber laser generates stable dark soliton with a repetition rate of 0.99 MHz and signal-to-noise ratio of 65 dB.The results validate the capability of generating soliton pulse by doped fiber saturable absorber.Furthermore,the proposed fiber laser is beneficial to the applications of optical communication and signal processing system.
基金Project supported by the National Key Research and Development Program of China(Grant No.2017YFF0106302)the National Natural Science Foundation of China(Grant Nos.61975225 and 61927813)Shanghai International Cooperation Project,China(Grant No.18590780100).
文摘The pulse generation from active mode-locking terahertz quantum cascade laser is studied by Maxwell-Bloch equations.It is shown that longer dephasing time will lead to multiple pulses generation from the laser.The dependence of output field on modulation length and radio-frequency parameters is obtained.In order to achieve short pulse generation,the DC bias should close to threshold value and modulation length should be shorter than 0.256 mm.The output pulse is unstable and the envelope shows many oscillations in the presence of spatial hole burning,resulting destabilization of mode-locking.
基金Supported by Guangdong Basic and Applied Basic Research Fund,China(2024A1515012429)。
文摘As a representative transition metal dichalcogenides(TMD),NiTe_(2)has an ultra-fast optical response,high carrier mobility,and excellent environmental stability.It has a broad application prospect in the fields of ener-gy,biomedicine,optoelectronic devices,and so on.At present,there have been scant reports on the application of NiTe_(2)in the field of ultrafast photonics.In this work,NiTe_(2)was synthesized by chemical vapor deposition(CVD)and integrated with a tapered optical fiber to achieve mode-locking in an erbium-doped fiber laser(EDFL)and a thu-lium-doped fiber laser(TDFL).The mode-locked EDFL exhibited a pulse width of 678 fs and an output power of 3.92 mW.The pulse width of mode-locked TDFL was estimated to have a pulse width of 694 fs with an output power of 21.64 mW.These results demonstrate that NiTe_(2)is an effective saturable absorber material with potential applica-tions in the field of ultrafast optics.
基金supported by the National Natural Science Foundation of China(Grant No.92477133)the Guangdong Basic and Applied Basic Research Foundation(Grant No.2025A1515011662)+1 种基金the National Natural Science Foundation of Fujian Province(Grant No.2025J01060)the National Natural Science Foundation of Xiamen(Grant No.3502Z202571016).
文摘Ytterbium(Yb)-based mode-locked fiber lasers have undergone significant development and found widespread applications owing to their high efficiency,compact size,and low cost.However,these lasers typically operate within the 1030 to 1080 nm range,and expanding their operational wavelength is crucial for applications across various fields.We present the direct generation of a mode-locked laser at 1120.06 nm using an all-polarization-maintaining structure,establishing the longest wavelength reported to date for Yb-doped fiber-based mode-locked lasers.A stable picosecond pulse laser at 1120 nm was realized by combining high-concentration Yb-doping and phase-biasing technology within a figure-9 cavity configuration.The laser delivers a pulse duration of 6.20 ps,a spectral width of 0.19 nm centered at 1120.06 nm,and a repetition rate of 21.52 MHz and reaches a maximum output power of 1.39 W via a double-cladding Yb fiber power amplifier in a master oscillator power amplifier configuration.Furthermore,we present a theoretical investigation of the laser performance,with simulation results aligning well with experimental findings.In addition,a 560.06-nm ultrafast yellow-green laser was generated through frequency doubling in a lithium triborate crystal.We present an approach for long-wavelength Yb-doped mode-locked lasers,with the potential to advance the development and application of Yb-based fiber lasers.
基金supported by the National Natural Science Foundation of China(Grant No.61975107)the Natural Science Foundation of Shanghai(Grant Nos.24ZR1422000 and 20ZR1471500),and the“111”Project(Grant No.D20031).
文摘Ultra-narrow bandwidth mode-locked lasers with tunable pulse duration can be versatile light sources for diverse applications.However,the spectral-temporal control of a narrow bandwidth mode-locked laser is challenging due to limited gain and nonlinearity,hindering practical applications of such lasers.We demonstrate a pulse duration widely tunable mode-locked ultra-narrow bandwidth laser using a composite filtering mechanism and a single-wall carbon nanotube.The laser pulse duration can be adjusted from 481 ps to 1.38 ns,which is the widest tuning range achieved in narrow-bandwidth passively mode-locked lasers.When the pulse duration is 1.38 ns,the corresponding spectral width reaches 4 pm(502 MHz).Numerical simulations support the experimental results and show that the evolution of long pulses in the laser cavity behaves similarly to a quasi-continuous wave with a low breathing ratio.We have not only designed a simple and flexible tunable scheme for the dilemma of spectral-temporal control in narrow-bandwidth mode-locked fiber lasers but also provided a unique and idealized light source for various applications that takes into account robust output.
基金supported by the National Key Research and Development Program of China(Grant No.2022YFB4600158)。
文摘We report on a Kerr-lens mode-locked(KLM)femtosecond Yb:CaYAlO_(4)(Yb:CYA)laser operating at a repetition rate of 1.04 GHz,pumped by a single-mode fiber laser.The laser delivers an average output power of 1.37 W with a pulse duration of 109 fs.Potential improvements,including scaling the pump power,increasing the repetition rate,and further reducing the pulse duration,are discussed.This study contributes to the advancement of Watt-level GHz femtosecond laser generation and its applications.
基金supported by National Natural Science Foundation of China (Grant Nos.61475162,61675150,and 61535009)Tianjin Natural Science Foundation (Grant No.18JCYBJC16900)Tianjin Research Program of Application Foundation and Advanced Technology (Grant No.17JCJQJC43500)
文摘Passively mode-locked fiber lasers emit femtosecond pulse trains with excellent short-term stability. The quantum-limited timing jitter of a free running femtosecond erbium-doped fiber laser working at room temperature is considerably below one femtosecond at high Fourier frequency. The ultrashort pulse train with ultralow timing jitter enables absolute time-of-flight measurements based on a dual-comb implementation, which is typically composed of a pair of optical frequency combs generated by femtosecond lasers. Dead-zone-free absolute distance measurement with sub-micrometer precision and kHz update rate has been routinely achieved with a dual-comb configuration, which is promising for a number of precision manufacturing applications, from large step-structure measurements prevalent in microelectronic profilometry to three coordinate measurements in large-scale aerospace manufacturing and shipbuilding. In this paper, we first review the sub-femtosecond precision timing jitter characterization methods and approaches for ultralow timing jitter mode-locked fiber laser design. Then, we provide an overview of the state-of-the-art dual-comb absolute ranging technology in terms of working principles, experimental implementations, and measurement precisions. Finally, we discuss the impact of quantum-limited timing jitter on the dual-comb ranging precision at a high update rate. The route to highprecision dual-comb range finder design based on ultralow jitter femtosecond fiber lasers is proposed.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11304409 and 61705028)the Natural Science Foundation of Chongqing City,China(Grant Nos.csct2013jcyjA4004 and cstc2017jcyjA0893)+1 种基金the Scientific and Technological Research Program of Chongqing Municipal Education Commission,China(Grant No.KJ1500422)the Postgraduate Research Innovation Foundation of Chongqing City,China(Grant No.CYS17240)
文摘Using graphene-covered-microfiber （GCM） as a saturable absorber, the generation and evolution of multiple operation states are proposed and demonstrated in passively mode-locked thulium-doped fiber laser. The microfiber was fabricated using the flame brushing method to an interaction length of - 1.2 cm with a waist diameter of -10 μm. Graphene layers were grown on copper foils by chemical vapor deposition and transferred onto the polydimethylsiloxane （PDMS） to form a PDMS/graphene film, which allowed light-graphene interaction via evanescent field. With the increase of the pump power from 1.25 W to 2.15 W, five different lasing regimes, including continuous-wave, conventional soliton mode-locking, multi- soliton mode-locking, a period of transition, and noise-like mode-locking, were achieved in a fiber ring cavity. To the best of our knowledge, it is the first report of the generation and evolution of multiple operation states by covering graphene on the microfiber in the 2-μ.m region. The results demonstrate that GCM can be a promising method for fabricating all fiber SA, and the switchable operation states can provide more portability in complex application domain.
基金Project supported by the National Natural Science Foundation of China (Grant No. 61078032)the Science and Technology Funds on Solide-State Laser Laboratory of China (Grant No. 9140C0403011106)
文摘We report on a diode-pumped passively continuous wave （cw） mode-locked Tm：YAP laser with a double-wall carbon nanotube （DWCNT） absorber operating at a wavelength of 2023 nm for the first time, to the best our knowledge. The DWCNT absorber is fabricated on a hydrophilic quartz substrate by using the vertical evaporation technique. The output power is as high as 375 mW. A stable pulse train with a repetition rate of 72.26 MHz is generated with a highest single pulse energy of 5.2 μJ.
基金supported by the National Natural Science Foundation of China(Grant No.61205047)
文摘A 980-nm semiconductor saturable absorber mirror（SESAM） mode-locked Yb-doped phosphate fiber laser is demonstrated by using an all-fiber linear cavity configuration. Two different kinds of cavity lengths are introduced into the oscillator to obtain a robust and stable mode-locked seed source. When the cavity length is chosen to be 6 m, the oscillator generates an average output power of 3.5 m W and a pulse width of 76.27 ps with a repetition rate of 17.08 MHz. As the cavity length is optimized to short, 4.4-m W maximum output power and 61.15-ps pulse width are produced at a repetition rate of 20.96 MHz. The output spectrum is centered at 980 nm with a narrow spectral bandwidth of 0.13 nm. In the experiment, no undesired amplified spontaneous emission（ASE） nor harmful oscillation around 1030 nm is observed. Moreover,through a two-stage all-fiber-integrated amplifier, an output power of 740 m W is generated with a pulse width of 200 ps.
