Due to their unique physical properties,nonlinear materials are gradually demonstrating significant potential in the field of optics.Gold nanoparticles supported on carbon black(Au/CB),possessing low loss and high non...Due to their unique physical properties,nonlinear materials are gradually demonstrating significant potential in the field of optics.Gold nanoparticles supported on carbon black(Au/CB),possessing low loss and high nonlinear characteristics,serve as an excellent material for saturable absorber(SA) in ultrafast fiber lasers.In this study,we investigated the performance of Au/CB material and designed an ultrafast fiber laser based on Au/CB SA,successfully observing stable fundamental mode-locking and pulse bunch phenomena.Specifically,when the fiber laser operates in fundamental mode-locking state,the center wavelength of optical spectrum is 1 558.82 nm,with a 3 dB bandwidth of 2.26 nm.Additionally,to investigate the evolution of real-time spectra,the dispersive Fourier transform(DFT) technology is employed.On the other hand,the pulse bunch emitted by the laser is actually composed of numerous random sub-pulses,exhibiting high-energy characteristics.The number of sub-pulses increases with the increase of pump power.These findings contribute to further exploring the properties of Au/CB material and reveal its potential applications in ultrafast optics.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
Transition metal disulfides are widely applied as nonlinear optical materials for laser pulse generation.In this paper,TaS_(2)is successfully used for the first time to achieve a high-energy passively Q-switched erbiu...Transition metal disulfides are widely applied as nonlinear optical materials for laser pulse generation.In this paper,TaS_(2)is successfully used for the first time to achieve a high-energy passively Q-switched erbium-doped fiber(EDF)laser.TaS_(2)nanosheets are prepared by the liquid phase exfoliation method,and then the TaS_(2)solution is mixed with polyvinyl alcohol(PVA).TaS_(2)/PVA film is prepared,which is cut into 1 mm×1 mm flakes.TaS_(2)/PVA saturable absorber(SA)is obtained by sandwiching a small flake between two fiber optic patch cable connectors.With the TaS_(2)/PVA SA added to an EDF laser,a Q-switched fiber laser with a center wavelength of 1560 nm and a repetition rate ranging from 51.33 k Hz to 83.04 k Hz is realized.At the pump power of 231 m W,the maximum output power is 1094μW,and the shortest pulse duration is 3.48μs.The results confirm that the TaS_(2)material has excellent potential for application in nonlinear optics.展开更多
A multi-wavelength and transversely mode-switchable fiber laser based on a ring-core fiber Bragg grating(RCFBG) is proposed. Two RCFBGs with high and low reflectivity are inscribed using a femtosecond laser and the ph...A multi-wavelength and transversely mode-switchable fiber laser based on a ring-core fiber Bragg grating(RCFBG) is proposed. Two RCFBGs with high and low reflectivity are inscribed using a femtosecond laser and the phase mask scanning technique, serving as the mirrors in an all-fiber laser linear resonator. Leveraging the polarization dependence of the RCFBG through side exposure, we can readily achieve switchable single-wavelength, dual-wavelength, or triple-wavelength laser outputs by adjusting the polarization controller(PC) inside the resonator. Additionally, three distinct modes, namely, cylindrical vector beam(CVB), fundamental and mixed modes, are successfully obtained in single-wavelength laser operation.Azimuthally or radially polarized lasers can be realized by tuning two PCs inside and outside the resonator while operating in CVB mode. This innovative multi-wavelength and transversely mode-switchable fiber laser based on RCFBGs holds significant potential for applications in wavelength division multiplexing and mode division multiplexing systems.展开更多
Compact and robust wavelength-tunable mid-infrared fiber lasers are urgently needed in the fields of spectroscopic sensing,polymer processing,and free-space communications.In this work,we experimentally reported a hig...Compact and robust wavelength-tunable mid-infrared fiber lasers are urgently needed in the fields of spectroscopic sensing,polymer processing,and free-space communications.In this work,we experimentally reported a high-power wavelength-tunable Er^(3+)/Dy^(3+)codoped fluoride fiber laser by diode clad pumping at 974 nm.Adopting a ruled diffraction grating,the laser wavelength could be continuously tuned in the region of 2854 nm-3510 nm(656 nm)based on the ^(6)H_(13/2)→^(6)H_(15/2)transition of Dy^(3+),where 3510 nm represented the longest wavelength achieved from a Dy^(3+)-doped fluoride fiber laser.Within the wide range of 3018 nm-3331 nm(312 nm),the output power was always kept at>1 W,with the maximum power of 1.75 W obtained at 3181 nm.To the best of our knowledge,this is the first watt-level wavelength-tunable fiber laser in the region of>3μm.Further scaling the power and expanding the tuning range are expected by increasing the pump power while protecting the pumped fiber end.展开更多
Recently, Bi_(4)Br_(4) is proved to be a member of topological insulators and is expected to be a promising candidate for ultrafast photonic device. However, experimental studies on the nonlinear optical properties of...Recently, Bi_(4)Br_(4) is proved to be a member of topological insulators and is expected to be a promising candidate for ultrafast photonic device. However, experimental studies on the nonlinear optical properties of Bi_(4)Br_(4) are limited, and its broadband absorption capabilities have not been validated. This study presents the first preparation of Bi_(4)Br_(4) samples using the chemical vapor transport method, resulting in a saturable absorber(SA) with a high modulation depth(46.23%) and low non-saturable loss(6.5%). The optical nonlinearity ranks among the best in similar studies. Additionally, this work applies Bi_(4)Br_(4)-SA for the first time in 1-μm fiber laser, developing a ring-cavity mode-locked fiber laser with a central wavelength of 1029.79 nm, a pulse duration of 442 fs, and a maximum output power of 90.83 m W. And a linear-cavity mode-locked fiber laser with a central wavelength of 1031.24 nm, a pulse duration of 511 fs, and a maximum output power of 92.81 m W is constructed. It is worth noting that the optical-to-optical conversion efficiency has reached about 11.54% and 33.58%.This study verifies Bi_(4)Br_(4)-SA's modulation effectiveness for 1-μm pulse lasers and provides a powerful reference for the design of high-efficiency fiber lasers.展开更多
Based on the nonlinear saturable absorption properties(NSAPs)of a two-dimensional(2D)material of antimony selenide(Sb_(2)Se_(3)),a Q-switched erbium-doped fiber(EDF)laser is systematically demonstrated.The Sb_(2)Se_(3...Based on the nonlinear saturable absorption properties(NSAPs)of a two-dimensional(2D)material of antimony selenide(Sb_(2)Se_(3)),a Q-switched erbium-doped fiber(EDF)laser is systematically demonstrated.The Sb_(2)Se_(3)nano sheets are prepared by liquid-phase exfoliation(LPE)method.After the sandwich-structured Sb_(2)Se_(3)saturable absorber(SA)is fabricated,the NSAPs are characterized and the modulation depth,the saturation intensity and the unsaturated loss are determined to be 25.2%,2.02 MW/cm^(2),and 3.29%,respectively.When the as-prepared Sb_(2)Se_(3)-SA is integrated into the ring cavity,the laser operates at a stable Q-switching regime in the pump power range of 100—400 mW.The laser oscillates at the central wavelength of 1558.48 nm with a 3 dB bandwidth of 2.32 nm.Take the advantages of the Sb_(2)Se_(3)-SA,the pulse duration can be compressed from 40.49 kHz to 128.12 kHz.At the pump power of 400 mW,the Q-switching laser gives the narrowest pulse duration the highest average output power,the largest pulse energy,and the signal-to-noise ratio(SNR)of 0.93μs,2.16 mW,16.89 nJ,and 53 dB,respectively.Our new attempt on Sb_(2)Se_(3)-based Q-switched EDF laser,combining the existing mode-locking achievements,proves that Sb_(2)Se_(3)is a powerful candidate for pulse compression due to the characteristics of high modulation depth and high stability.展开更多
Soliton molecules(SMs),bounded and self-assembled of particle-like dissipative solitons,exist with versatile mutual interactions and manifest substantial potential in soliton communication and optical data storage.How...Soliton molecules(SMs),bounded and self-assembled of particle-like dissipative solitons,exist with versatile mutual interactions and manifest substantial potential in soliton communication and optical data storage.However,controllable manipulation of the bounded molecular patterns remains challenging,as reaching a specific operation regime in lasers generally involves adjusting multiple control parameters in connection with a wide range of accessible pulse dynamics.An evolutionary algorithm is implemented for intelligent control of SMs in a 2μm ultrafast fiber laser mode locked through nonlinear polarization rotation.Depending on the specifications of the merit function used for the optimization procedure,various SM operations are obtained,including spectra shape programming and controllable deterministic switching of doublet and triplet SMs operating in stationary or pulsation states with reconfigurable temporal separations,frequency locking of pulsation SMs,doublet and SM complexes with controllable pulsation ratio,etc.Digital encoding is further demonstrated in this platform by employing the self-assembled characteristics of SMs.Our work opens up an avenue for active SM control beyond conventional telecom bands and brings useful insights into nonlinear science and applications.展开更多
A wavelength-interval switchable Brillouin–Raman random fiber laser(BRRFL) based on Brillouin pump(BP) manipulation is proposed in this paper. The proposed wavelength-interval switchable BRRFL has a full-open cavity ...A wavelength-interval switchable Brillouin–Raman random fiber laser(BRRFL) based on Brillouin pump(BP) manipulation is proposed in this paper. The proposed wavelength-interval switchable BRRFL has a full-open cavity configuration, featuring multiwavelength output with wavelength interval of double Brillouin frequency shifts. Through simultaneously injecting the BP light and its first-order stimulated Brillouin-scattered light into the cavity, the laser output exhibits a wavelength interval of single Brillouin frequency shift. The wavelength-interval switching effect can be manipulated by controlling the power of the first-order stimulated Brillouin scattering light. The experimental results show the multiwavelength output can be switched between double Brillouin frequency shift multiwavelength emission with a broad bandwidth of approximately 60 nm and single Brillouin frequency shift multiwavelength emission of 44 nm. The flexible optically controlled random fiber laser with switchable wavelength interval makes it useful for a wide range of applications and holds significant potential in the field of wavelength-division multiplexing optical communication.展开更多
In this paper,a conventional soliton(CS)mode-locked erbium-doped fiber(EDF)laser was de-veloped using MAX phase material(MAX-PM)Nb_(4)AlC_(3)as a saturable absorber(SA).First,the liquid phase exfoliation(LPE)method wa...In this paper,a conventional soliton(CS)mode-locked erbium-doped fiber(EDF)laser was de-veloped using MAX phase material(MAX-PM)Nb_(4)AlC_(3)as a saturable absorber(SA).First,the liquid phase exfoliation(LPE)method was utilized to prepare Nb_(4)AlC_(3)nanosheets,and then a piece of tapered fiber was adopted to fabricate Nb_(4)AlC_(3)-SA.It was found that the saturation intensity and modulation depth of the Nb_(4)AlC_(3)-SA are 2.02 MW/cm^(2)and 1.88%.Based on the Nb_(4)AlC_(3)-SA,a conventional soliton(CS)mode-locked EDF laser was achieved.The central wavelength,pulse duration,and pulse repetition rate were found to be 1565.65 nm,615.37 fs,and 24.63 MHz,respectively.The performance is competitive and particularly superior in terms of pulse duration.This study fully confirms that Nb_(4)AlC_(3)possesses marvellous nonlinear saturable absorption properties and opens new possibilities for further research on air-stable ultrafast photon-ic devices.展开更多
In this work,we theoretically unlock the potential of Ho^(3+)-doped InF3 fiber for efficient~3.2μm laser generation(from the ^(5)F_(4),^(5)S_(2)→^(5)F_(5) transition),by employing a novel dual-wavelength pumping sch...In this work,we theoretically unlock the potential of Ho^(3+)-doped InF3 fiber for efficient~3.2μm laser generation(from the ^(5)F_(4),^(5)S_(2)→^(5)F_(5) transition),by employing a novel dual-wavelength pumping scheme at 1150 nm and 980 nm,for the first time.Under clad-coupled 1150 nm pumping of 5 W,~3.2μm power of 3.6 W has been predicted with the optical-to-optical efficiency of 14.4%.Further efficient power scaling,however,is blocked by the output saturation with 980 nm pumping.To alleviate this behavior,the cascaded ^(5)I_(5)→^(5)I_(6) transition,targeting~3.9μm,has been activated simultaneously,therefore accelerating the population circulation between the laser upper level ^(5)F_(4),^(5)S_(2) and long-lived ^(5)I_(6) level under 980 nm pumping.As a result,enhanced~3.2μm power of 4.68 W has been obtained with optical-to-optical efficiency of 15.6%.Meanwhile the~3.9μm laser,yielding power of 2.76 W with optical-to-optical efficiency of 9.2%,is theoretically achievable as well with a moderate heat load,of which the performance is even better than the prior experimentally and theoretically reported Ho^(3+)-doped InF3 fiber lasers emitting at~3.9μm alone.This work demonstrates a versatile platform for laser generation at~3.2μm and~3.9μm,thus providing the new opportunities for many potential applications,e.g.,polymer processing,infrared countermeasures,and free-space communications.展开更多
A widely-wavelength-tunable Brillouin fiber laser(BFL)with improved optical signal-to-noise ratio(OSNR)based on parity-time(PT)symmetric and saturable absorption(SA)effect is present.This novel BFL realizes PT symmetr...A widely-wavelength-tunable Brillouin fiber laser(BFL)with improved optical signal-to-noise ratio(OSNR)based on parity-time(PT)symmetric and saturable absorption(SA)effect is present.This novel BFL realizes PT symmetry and SA effect through polarization-maintaining erbium-doped fiber(PM-EDF)Sagnac loop,which is composed of a PM-EDF,a coupler and two polarization controllers(PCs).By using the inherent birefringence characteristic of PM-EDF,two feedback loops in orthogonal polarization state are formed when the Strokes signal in injected.One of these loops provides gain in the clockwise direction with in the Sagnac loop,while the other loop generates loss in the counterclockwise direction.By adjusting the PCs to control the polarization state of the PM-EDF,a single-longitudinal-mode(SLM)BFL can be achieved,as the PT symmetry is broken when the SA participating stimulated Brillouin scattering(SBS)gain and loss are well-matched and the gain surpasses the coupling coefficient.Compared to previous BFLs,the proposed BFL has a more streamlined structure and a wider wavelength tunable range,at the same time,it is not being limited by the bandwidth of the erbium-doped fiber amplifier while still maintaining narrow linewidth SLM output.Additionally,thanks to SA effect of the PM-EDF,the PT symmetric SBS gain contract is enhanced,resulting in a higher optical signal-to-noise(OSNR).The experimental results show that the laser has a wide tunable range of 1526.088 nm to 1565.498 nm,an improved OSNR of 77 dB,and a fine linewidth as small as 140.5 Hz.展开更多
Coherent beam combining(CBC) of fiber laser array is a promising technique to realize high output power while maintaining near diffraction-limited beam quality. To implement CBC, an appropriate phase control feedback ...Coherent beam combining(CBC) of fiber laser array is a promising technique to realize high output power while maintaining near diffraction-limited beam quality. To implement CBC, an appropriate phase control feedback structure should be established to realize phase-locking. In this paper, an innovative internal active phase control CBC fiber laser array based on photodetector array is proposed. The dynamic phase noises of the laser amplifiers are compensated before being emitted into free space. And the static phase difference compensation of emitting laser array is realized by interference measurement based on photodetector array. The principle of the technique is illustrated and corresponding simulations are carried out, and a CBC system with four laser channels is built to verify the technique. When the phase controllers are turned on, the phase deviation of the laser array is less than λ/20, and ~ 95% fringe contrast of the irradiation distribution is obtained. The technique proposed in this paper could provide a reference for the system design of a massive high-power CBC system.展开更多
We present a Brillouin–Raman random fiber laser(BRRFL)with full-open linear cavity structure to generate broadband Brillouin frequency comb(BFC)with double Brillouin-frequency-shift spacing.The incorporation of a reg...We present a Brillouin–Raman random fiber laser(BRRFL)with full-open linear cavity structure to generate broadband Brillouin frequency comb(BFC)with double Brillouin-frequency-shift spacing.The incorporation of a regeneration portion consisting of an erbium-doped fiber and a single-mode fiber enables the generation of broadband BFC.The dynamics of broadband BFC generation changing with the pump power(EDF and Raman)and Brillouin pump(BP)wavelength are investigated in detail,respectively.Under suitable conditions,the bidirectional BRRFL proposed can produce a flatamplitude BFC with 40.7-nm bandwidth ranging from 1531 nm to 1571.7 nm,and built-in 242-order Brillouin Stokes lines(BSLs)with double Brillouin-frequency-shift spacing.Moreover,the linewidth of single BSL is experimentally measured to be about 2.5 kHz.The broadband bidirectional narrow-linewidth BRRFL has great potential applications in optical communication,optical sensing,spectral measurement,and so on.展开更多
This study reports a passive mode-locked Thulium-Holmium co-doped fiber laser featuring a figure-9 shaped resonator structure.The laser utilizes a nonlinear amplifying loop mirror(NALM)as the mode-locking device.By in...This study reports a passive mode-locked Thulium-Holmium co-doped fiber laser featuring a figure-9 shaped resonator structure.The laser utilizes a nonlinear amplifying loop mirror(NALM)as the mode-locking device.By increasing pump power,the laser’s output evolution was experimentally observed,showing that bright-dark pulse pairs first split into double pulses and then into a second harmonic state.Additionally,the time intervals between bright and dark pulses and between double pulses increased with higher pump power.The RF spectrum of the bright-dark pulse pairs exhibited envelope modulation,with a modulation frequency approximately equal to the reciprocal of the time interval between bright and dark pulses.When the pump power increased from 0.46 W to 0.72 W,the reciprocal of the modulation frequency showed a linear growth trend.These findings contribute to understanding the evolution patterns of bright-dark pulse pairs in passive mode-locked fiber lasers.展开更多
Although visible femtosecond lasers based on nonlinear frequency conversion of Ti:sapphire femtosecond oscillators or near-infrared ultrafast lasers have been well developed,limitations in terms of footprint,cost,and ...Although visible femtosecond lasers based on nonlinear frequency conversion of Ti:sapphire femtosecond oscillators or near-infrared ultrafast lasers have been well developed,limitations in terms of footprint,cost,and efficiency have called for alternative laser solutions.The fiber femtosecond mode-locked oscillator as an ideal solution has achieved great success in the 0.9 to 3.5μm infrared wavelengths,but remains an outstanding challenge in the visible spectrum(390 to 780 nm).Here,we tackle this challenge by introducing a visible-wavelength mode-locked femtosecond fiber oscillator along with an amplifier.This fiber femtosecond oscillator emits red light at 635 nm,employs a figure-nine cavity configuration,applies a double-clad Pr3þ-doped fluoride fiber as the visible gain medium,incorporates a visible-wavelength phase-biased nonlinear amplifying loop mirror(PB-NALM)for mode locking,and utilizes a pair of customized high-efficiency and high-groove-density diffraction gratings for dispersion management.Visible self-starting mode locking established by the PB-NALM directly yields red laser pulses with a minimum pulse duration of 196 fs and a repetition rate of 53.957 MHz from the oscillator.Precise control of the grating pair spacing can switch the pulse state from a dissipative soliton or a stretched-pulse soliton to a conventional soliton.In addition,a chirped-pulse amplification system built alongside the oscillator immensely boosts the laser performance,resulting in an average output power over 1W,a pulse energy of 19.55 nJ,and a dechirped pulse duration of 230 fs.Our result represents a concrete step toward high-power femtosecond fiber lasers covering the visible spectral region and could have important applications in industrial processing,biomedicine,and scientific research.展开更多
The optical rogue wave(RW),known as a short-lived extraordinarily high amplitude dynamics phenomenon with small appearing probabilities,plays an important role in revealing and understanding the fundamental physics of...The optical rogue wave(RW),known as a short-lived extraordinarily high amplitude dynamics phenomenon with small appearing probabilities,plays an important role in revealing and understanding the fundamental physics of nonlinear wave propagations in optical systems.The random fiber laser(RFL),featured with cavity-free and“modeless”structure,has opened up new avenues for fundamental physics research and potential practical applications combining nonlinear optics and laser physics.Here,the extreme event of optical RW induced by noise-driven modulation instability that interacts with the cascaded stimulated Brillouin scattering,the quasi-phase-matched four-wave mixing as well as the random mode resonance process is observed in a Brillouin random fiber laser comb(BRFLC).Temporal and statistical characteristics of the RWs concerning their emergence and evolution are experimentally explored and analyzed.Specifically,temporally localized structures with high intensities including chair-like pulses with a sharp leading edge followed by a trailing plateau appear frequently in the BRFLC output,which can evolve to chair-like RW pulses with adjustable pulse duration and amplitude under controlled conditions.This investigation provides a deep insight into the extreme event of RWs and paves the way for RW manipulation for its generation and elimination in RFLs through adapted laser configuration.展开更多
Random fiber lasers(RFLs)have attracted extensive attention due to their rich physical properties and wide applications.Here,a RFL using a cascaded fiber loop mirror(CFLM)is proposed and presented.A CFLM with 10 fiber...Random fiber lasers(RFLs)have attracted extensive attention due to their rich physical properties and wide applications.Here,a RFL using a cascaded fiber loop mirror(CFLM)is proposed and presented.A CFLM with 10 fiber loop mirrors(FLMs)is simulated by the transfer matrix method and used to provide random feedback.Multiple spikes are observed in both the simulated and measured reflection spectra.The RFL operates in a single longitudinal mode near the threshold and a time-varying multilongitudinal mode at higher pump powers.The RFL exhibits a time-varying radio-frequency spectrum.The Lévy–Gaussian distribution transition is observed,as in many RFLs.The operation mechanism of the lasing longitudinal modes and the impact of complex mode competition and mode hopping on the output characteristics are discussed through experimental and theoretical results.In this study,we unveil an artificial random feedback structure and pave another way for the realization of RFLs,which should be a platform for multidisciplinary studies in complex systems.展开更多
After a half century of development, fiber laser has evolved from a concept to a great family penetrating into various fields of applications. This paper reviews the history and current development of fiber lasers, wi...After a half century of development, fiber laser has evolved from a concept to a great family penetrating into various fields of applications. This paper reviews the history and current development of fiber lasers, with topics covering both continuous wave and short pulse fiber lasers. Important issues such as the major rare earth dopants, fiber laser brightness, polarization effects, clad pumping technology, beam combination, mode locking and pulse shaping are discussed in this paper.展开更多
In order to decrease the metallurgical porosity and keyhole-induced porosity during deep penetration laser welding of Al and its alloys, and increase the mechanical properties of work-piece, the effects of welding par...In order to decrease the metallurgical porosity and keyhole-induced porosity during deep penetration laser welding of Al and its alloys, and increase the mechanical properties of work-piece, the effects of welding parameters such as laser power, welding speed and defocusing value on both kinds of porosities were systemically analyzed respectively, and the shape and fluctuation of plume of the keyhole were observed to reflect the stability of the keyhole. The results show that increasing laser power or decreasing laser spot size can lead to the rising of both number and occupied area of pores in the weld; meanwhile, the plume fluctuates violently over the keyhole, which is always companied with the intense metallic vapor, liquid metal spatter and collapsing in the keyhole, thus more pores are generated in the weld. The porosity in the weld reaches the minimum at welding velocity of 2.0 m/min when laser power is 5 kW and defocusing value is 0.展开更多
基金supported by the Natural Science Foundation of Guangdong Province (No.2023A1515010093)the Shenzhen Fundamental Research Program (Nos.JCYJ20220809170611004, JCYJ20231121110828001 and JCYJ20231121113641002)。
文摘Due to their unique physical properties,nonlinear materials are gradually demonstrating significant potential in the field of optics.Gold nanoparticles supported on carbon black(Au/CB),possessing low loss and high nonlinear characteristics,serve as an excellent material for saturable absorber(SA) in ultrafast fiber lasers.In this study,we investigated the performance of Au/CB material and designed an ultrafast fiber laser based on Au/CB SA,successfully observing stable fundamental mode-locking and pulse bunch phenomena.Specifically,when the fiber laser operates in fundamental mode-locking state,the center wavelength of optical spectrum is 1 558.82 nm,with a 3 dB bandwidth of 2.26 nm.Additionally,to investigate the evolution of real-time spectra,the dispersive Fourier transform(DFT) technology is employed.On the other hand,the pulse bunch emitted by the laser is actually composed of numerous random sub-pulses,exhibiting high-energy characteristics.The number of sub-pulses increases with the increase of pump power.These findings contribute to further exploring the properties of Au/CB material and reveal its potential applications in ultrafast optics.
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Project supported by the National Natural Science Foundation of China(Grant No.12075190)the Shaanxi Fundamental Science Research Project for Mathematics and Physics(Grant No.23JSY019)。
文摘Transition metal disulfides are widely applied as nonlinear optical materials for laser pulse generation.In this paper,TaS_(2)is successfully used for the first time to achieve a high-energy passively Q-switched erbium-doped fiber(EDF)laser.TaS_(2)nanosheets are prepared by the liquid phase exfoliation method,and then the TaS_(2)solution is mixed with polyvinyl alcohol(PVA).TaS_(2)/PVA film is prepared,which is cut into 1 mm×1 mm flakes.TaS_(2)/PVA saturable absorber(SA)is obtained by sandwiching a small flake between two fiber optic patch cable connectors.With the TaS_(2)/PVA SA added to an EDF laser,a Q-switched fiber laser with a center wavelength of 1560 nm and a repetition rate ranging from 51.33 k Hz to 83.04 k Hz is realized.At the pump power of 231 m W,the maximum output power is 1094μW,and the shortest pulse duration is 3.48μs.The results confirm that the TaS_(2)material has excellent potential for application in nonlinear optics.
基金Project supported by the National Natural Science Foundation of China (Grant No. 62075182)the National Key Research and Development Program of China (Grant No. 2022YFB3207502)。
文摘A multi-wavelength and transversely mode-switchable fiber laser based on a ring-core fiber Bragg grating(RCFBG) is proposed. Two RCFBGs with high and low reflectivity are inscribed using a femtosecond laser and the phase mask scanning technique, serving as the mirrors in an all-fiber laser linear resonator. Leveraging the polarization dependence of the RCFBG through side exposure, we can readily achieve switchable single-wavelength, dual-wavelength, or triple-wavelength laser outputs by adjusting the polarization controller(PC) inside the resonator. Additionally, three distinct modes, namely, cylindrical vector beam(CVB), fundamental and mixed modes, are successfully obtained in single-wavelength laser operation.Azimuthally or radially polarized lasers can be realized by tuning two PCs inside and outside the resonator while operating in CVB mode. This innovative multi-wavelength and transversely mode-switchable fiber laser based on RCFBGs holds significant potential for applications in wavelength division multiplexing and mode division multiplexing systems.
基金supported in parts by the National Natural Science Foundation of China under Grant No.62475035.
文摘Compact and robust wavelength-tunable mid-infrared fiber lasers are urgently needed in the fields of spectroscopic sensing,polymer processing,and free-space communications.In this work,we experimentally reported a high-power wavelength-tunable Er^(3+)/Dy^(3+)codoped fluoride fiber laser by diode clad pumping at 974 nm.Adopting a ruled diffraction grating,the laser wavelength could be continuously tuned in the region of 2854 nm-3510 nm(656 nm)based on the ^(6)H_(13/2)→^(6)H_(15/2)transition of Dy^(3+),where 3510 nm represented the longest wavelength achieved from a Dy^(3+)-doped fluoride fiber laser.Within the wide range of 3018 nm-3331 nm(312 nm),the output power was always kept at>1 W,with the maximum power of 1.75 W obtained at 3181 nm.To the best of our knowledge,this is the first watt-level wavelength-tunable fiber laser in the region of>3μm.Further scaling the power and expanding the tuning range are expected by increasing the pump power while protecting the pumped fiber end.
基金Project supported by the Beijing Natural Science Foundation (Grant No. JQ21019)the National Key Research and Development Program of China (Grant Nos. 2022YFA1604200 and 2022YFA1204100)the Fund from Beijing Municipal Commission of Science and Technology (Grant No. Z231100006623006)。
文摘Recently, Bi_(4)Br_(4) is proved to be a member of topological insulators and is expected to be a promising candidate for ultrafast photonic device. However, experimental studies on the nonlinear optical properties of Bi_(4)Br_(4) are limited, and its broadband absorption capabilities have not been validated. This study presents the first preparation of Bi_(4)Br_(4) samples using the chemical vapor transport method, resulting in a saturable absorber(SA) with a high modulation depth(46.23%) and low non-saturable loss(6.5%). The optical nonlinearity ranks among the best in similar studies. Additionally, this work applies Bi_(4)Br_(4)-SA for the first time in 1-μm fiber laser, developing a ring-cavity mode-locked fiber laser with a central wavelength of 1029.79 nm, a pulse duration of 442 fs, and a maximum output power of 90.83 m W. And a linear-cavity mode-locked fiber laser with a central wavelength of 1031.24 nm, a pulse duration of 511 fs, and a maximum output power of 92.81 m W is constructed. It is worth noting that the optical-to-optical conversion efficiency has reached about 11.54% and 33.58%.This study verifies Bi_(4)Br_(4)-SA's modulation effectiveness for 1-μm pulse lasers and provides a powerful reference for the design of high-efficiency fiber lasers.
基金supported by the National Natural Science Foundation of China(No.11304184)the Shandong University of Technology and Zibo City Integration Development Project(No.2019ZBXC120)。
文摘Based on the nonlinear saturable absorption properties(NSAPs)of a two-dimensional(2D)material of antimony selenide(Sb_(2)Se_(3)),a Q-switched erbium-doped fiber(EDF)laser is systematically demonstrated.The Sb_(2)Se_(3)nano sheets are prepared by liquid-phase exfoliation(LPE)method.After the sandwich-structured Sb_(2)Se_(3)saturable absorber(SA)is fabricated,the NSAPs are characterized and the modulation depth,the saturation intensity and the unsaturated loss are determined to be 25.2%,2.02 MW/cm^(2),and 3.29%,respectively.When the as-prepared Sb_(2)Se_(3)-SA is integrated into the ring cavity,the laser operates at a stable Q-switching regime in the pump power range of 100—400 mW.The laser oscillates at the central wavelength of 1558.48 nm with a 3 dB bandwidth of 2.32 nm.Take the advantages of the Sb_(2)Se_(3)-SA,the pulse duration can be compressed from 40.49 kHz to 128.12 kHz.At the pump power of 400 mW,the Q-switching laser gives the narrowest pulse duration the highest average output power,the largest pulse energy,and the signal-to-noise ratio(SNR)of 0.93μs,2.16 mW,16.89 nJ,and 53 dB,respectively.Our new attempt on Sb_(2)Se_(3)-based Q-switched EDF laser,combining the existing mode-locking achievements,proves that Sb_(2)Se_(3)is a powerful candidate for pulse compression due to the characteristics of high modulation depth and high stability.
基金supported by the Research Grants Council of the Hong Kong Special Administrative Region of China(Grant Nos.HKU 17212824,HKU 17210522,HKU C7074-21G,HKU R7003-21,and HKU 17205321)the Innovation and Technology Commission of the Hong Kong SAR Government(Grant Nos.MHP/073/20 and MHP/057/21),and the Health@InnoHK program.
文摘Soliton molecules(SMs),bounded and self-assembled of particle-like dissipative solitons,exist with versatile mutual interactions and manifest substantial potential in soliton communication and optical data storage.However,controllable manipulation of the bounded molecular patterns remains challenging,as reaching a specific operation regime in lasers generally involves adjusting multiple control parameters in connection with a wide range of accessible pulse dynamics.An evolutionary algorithm is implemented for intelligent control of SMs in a 2μm ultrafast fiber laser mode locked through nonlinear polarization rotation.Depending on the specifications of the merit function used for the optimization procedure,various SM operations are obtained,including spectra shape programming and controllable deterministic switching of doublet and triplet SMs operating in stationary or pulsation states with reconfigurable temporal separations,frequency locking of pulsation SMs,doublet and SM complexes with controllable pulsation ratio,etc.Digital encoding is further demonstrated in this platform by employing the self-assembled characteristics of SMs.Our work opens up an avenue for active SM control beyond conventional telecom bands and brings useful insights into nonlinear science and applications.
基金Poject supported by the National Natural Science Foundation of China(Grant Nos.62175116 and 62311530343)the Postgraduate Research Innovation Program of Jiangsu Province,China(Grant No.KYCX22_0913)。
文摘A wavelength-interval switchable Brillouin–Raman random fiber laser(BRRFL) based on Brillouin pump(BP) manipulation is proposed in this paper. The proposed wavelength-interval switchable BRRFL has a full-open cavity configuration, featuring multiwavelength output with wavelength interval of double Brillouin frequency shifts. Through simultaneously injecting the BP light and its first-order stimulated Brillouin-scattered light into the cavity, the laser output exhibits a wavelength interval of single Brillouin frequency shift. The wavelength-interval switching effect can be manipulated by controlling the power of the first-order stimulated Brillouin scattering light. The experimental results show the multiwavelength output can be switched between double Brillouin frequency shift multiwavelength emission with a broad bandwidth of approximately 60 nm and single Brillouin frequency shift multiwavelength emission of 44 nm. The flexible optically controlled random fiber laser with switchable wavelength interval makes it useful for a wide range of applications and holds significant potential in the field of wavelength-division multiplexing optical communication.
文摘In this paper,a conventional soliton(CS)mode-locked erbium-doped fiber(EDF)laser was de-veloped using MAX phase material(MAX-PM)Nb_(4)AlC_(3)as a saturable absorber(SA).First,the liquid phase exfoliation(LPE)method was utilized to prepare Nb_(4)AlC_(3)nanosheets,and then a piece of tapered fiber was adopted to fabricate Nb_(4)AlC_(3)-SA.It was found that the saturation intensity and modulation depth of the Nb_(4)AlC_(3)-SA are 2.02 MW/cm^(2)and 1.88%.Based on the Nb_(4)AlC_(3)-SA,a conventional soliton(CS)mode-locked EDF laser was achieved.The central wavelength,pulse duration,and pulse repetition rate were found to be 1565.65 nm,615.37 fs,and 24.63 MHz,respectively.The performance is competitive and particularly superior in terms of pulse duration.This study fully confirms that Nb_(4)AlC_(3)possesses marvellous nonlinear saturable absorption properties and opens new possibilities for further research on air-stable ultrafast photon-ic devices.
基金supported in parts by the National Natural Science Foundation of China under Grants No.62005040 and No.U20A20210.
文摘In this work,we theoretically unlock the potential of Ho^(3+)-doped InF3 fiber for efficient~3.2μm laser generation(from the ^(5)F_(4),^(5)S_(2)→^(5)F_(5) transition),by employing a novel dual-wavelength pumping scheme at 1150 nm and 980 nm,for the first time.Under clad-coupled 1150 nm pumping of 5 W,~3.2μm power of 3.6 W has been predicted with the optical-to-optical efficiency of 14.4%.Further efficient power scaling,however,is blocked by the output saturation with 980 nm pumping.To alleviate this behavior,the cascaded ^(5)I_(5)→^(5)I_(6) transition,targeting~3.9μm,has been activated simultaneously,therefore accelerating the population circulation between the laser upper level ^(5)F_(4),^(5)S_(2) and long-lived ^(5)I_(6) level under 980 nm pumping.As a result,enhanced~3.2μm power of 4.68 W has been obtained with optical-to-optical efficiency of 15.6%.Meanwhile the~3.9μm laser,yielding power of 2.76 W with optical-to-optical efficiency of 9.2%,is theoretically achievable as well with a moderate heat load,of which the performance is even better than the prior experimentally and theoretically reported Ho^(3+)-doped InF3 fiber lasers emitting at~3.9μm alone.This work demonstrates a versatile platform for laser generation at~3.2μm and~3.9μm,thus providing the new opportunities for many potential applications,e.g.,polymer processing,infrared countermeasures,and free-space communications.
文摘A widely-wavelength-tunable Brillouin fiber laser(BFL)with improved optical signal-to-noise ratio(OSNR)based on parity-time(PT)symmetric and saturable absorption(SA)effect is present.This novel BFL realizes PT symmetry and SA effect through polarization-maintaining erbium-doped fiber(PM-EDF)Sagnac loop,which is composed of a PM-EDF,a coupler and two polarization controllers(PCs).By using the inherent birefringence characteristic of PM-EDF,two feedback loops in orthogonal polarization state are formed when the Strokes signal in injected.One of these loops provides gain in the clockwise direction with in the Sagnac loop,while the other loop generates loss in the counterclockwise direction.By adjusting the PCs to control the polarization state of the PM-EDF,a single-longitudinal-mode(SLM)BFL can be achieved,as the PT symmetry is broken when the SA participating stimulated Brillouin scattering(SBS)gain and loss are well-matched and the gain surpasses the coupling coefficient.Compared to previous BFLs,the proposed BFL has a more streamlined structure and a wider wavelength tunable range,at the same time,it is not being limited by the bandwidth of the erbium-doped fiber amplifier while still maintaining narrow linewidth SLM output.Additionally,thanks to SA effect of the PM-EDF,the PT symmetric SBS gain contract is enhanced,resulting in a higher optical signal-to-noise(OSNR).The experimental results show that the laser has a wide tunable range of 1526.088 nm to 1565.498 nm,an improved OSNR of 77 dB,and a fine linewidth as small as 140.5 Hz.
基金Project supported by the National Natural Science Foundation of China(Grant No.62275272)the Training Program for Excellent Young Innovators of Changsha(Grant No.KQ2305025)。
文摘Coherent beam combining(CBC) of fiber laser array is a promising technique to realize high output power while maintaining near diffraction-limited beam quality. To implement CBC, an appropriate phase control feedback structure should be established to realize phase-locking. In this paper, an innovative internal active phase control CBC fiber laser array based on photodetector array is proposed. The dynamic phase noises of the laser amplifiers are compensated before being emitted into free space. And the static phase difference compensation of emitting laser array is realized by interference measurement based on photodetector array. The principle of the technique is illustrated and corresponding simulations are carried out, and a CBC system with four laser channels is built to verify the technique. When the phase controllers are turned on, the phase deviation of the laser array is less than λ/20, and ~ 95% fringe contrast of the irradiation distribution is obtained. The technique proposed in this paper could provide a reference for the system design of a massive high-power CBC system.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 62175116 and 91950105)the 1311 Talent Plan of Nanjing University of Posts and Telecommunications, Chinathe Postgraduate Research & Practice Innovation Program, Jiangsu Province, China (Grant No. SJCX21_0276)
文摘We present a Brillouin–Raman random fiber laser(BRRFL)with full-open linear cavity structure to generate broadband Brillouin frequency comb(BFC)with double Brillouin-frequency-shift spacing.The incorporation of a regeneration portion consisting of an erbium-doped fiber and a single-mode fiber enables the generation of broadband BFC.The dynamics of broadband BFC generation changing with the pump power(EDF and Raman)and Brillouin pump(BP)wavelength are investigated in detail,respectively.Under suitable conditions,the bidirectional BRRFL proposed can produce a flatamplitude BFC with 40.7-nm bandwidth ranging from 1531 nm to 1571.7 nm,and built-in 242-order Brillouin Stokes lines(BSLs)with double Brillouin-frequency-shift spacing.Moreover,the linewidth of single BSL is experimentally measured to be about 2.5 kHz.The broadband bidirectional narrow-linewidth BRRFL has great potential applications in optical communication,optical sensing,spectral measurement,and so on.
文摘This study reports a passive mode-locked Thulium-Holmium co-doped fiber laser featuring a figure-9 shaped resonator structure.The laser utilizes a nonlinear amplifying loop mirror(NALM)as the mode-locking device.By increasing pump power,the laser’s output evolution was experimentally observed,showing that bright-dark pulse pairs first split into double pulses and then into a second harmonic state.Additionally,the time intervals between bright and dark pulses and between double pulses increased with higher pump power.The RF spectrum of the bright-dark pulse pairs exhibited envelope modulation,with a modulation frequency approximately equal to the reciprocal of the time interval between bright and dark pulses.When the pump power increased from 0.46 W to 0.72 W,the reciprocal of the modulation frequency showed a linear growth trend.These findings contribute to understanding the evolution patterns of bright-dark pulse pairs in passive mode-locked fiber lasers.
基金supported by the National Natural Science Foundation of China (Grant Nos.62022069,62235014,and 62305275)the Shenzhen Science and Technology Projects (Grant No.JCYJ20210324115813037)the China National Postdoctoral Program for Innovative Talents (Grant No.BX20230199).
文摘Although visible femtosecond lasers based on nonlinear frequency conversion of Ti:sapphire femtosecond oscillators or near-infrared ultrafast lasers have been well developed,limitations in terms of footprint,cost,and efficiency have called for alternative laser solutions.The fiber femtosecond mode-locked oscillator as an ideal solution has achieved great success in the 0.9 to 3.5μm infrared wavelengths,but remains an outstanding challenge in the visible spectrum(390 to 780 nm).Here,we tackle this challenge by introducing a visible-wavelength mode-locked femtosecond fiber oscillator along with an amplifier.This fiber femtosecond oscillator emits red light at 635 nm,employs a figure-nine cavity configuration,applies a double-clad Pr3þ-doped fluoride fiber as the visible gain medium,incorporates a visible-wavelength phase-biased nonlinear amplifying loop mirror(PB-NALM)for mode locking,and utilizes a pair of customized high-efficiency and high-groove-density diffraction gratings for dispersion management.Visible self-starting mode locking established by the PB-NALM directly yields red laser pulses with a minimum pulse duration of 196 fs and a repetition rate of 53.957 MHz from the oscillator.Precise control of the grating pair spacing can switch the pulse state from a dissipative soliton or a stretched-pulse soliton to a conventional soliton.In addition,a chirped-pulse amplification system built alongside the oscillator immensely boosts the laser performance,resulting in an average output power over 1W,a pulse energy of 19.55 nJ,and a dechirped pulse duration of 230 fs.Our result represents a concrete step toward high-power femtosecond fiber lasers covering the visible spectral region and could have important applications in industrial processing,biomedicine,and scientific research.
基金supported by the National Natural Science Foundation of China (Grant No.62105180)the Natural Science Foundation of Shandong Province (Grant Nos.ZR2020MF110 and ZR2020MF118)+2 种基金the Taishan Scholar Foundation of Shandong Province (Grant No.tsqn202211027)the Qilu Young Scholar Program of Shandong Universitythe National Grant Program for High-level Returning Oversea Talents (2023).
文摘The optical rogue wave(RW),known as a short-lived extraordinarily high amplitude dynamics phenomenon with small appearing probabilities,plays an important role in revealing and understanding the fundamental physics of nonlinear wave propagations in optical systems.The random fiber laser(RFL),featured with cavity-free and“modeless”structure,has opened up new avenues for fundamental physics research and potential practical applications combining nonlinear optics and laser physics.Here,the extreme event of optical RW induced by noise-driven modulation instability that interacts with the cascaded stimulated Brillouin scattering,the quasi-phase-matched four-wave mixing as well as the random mode resonance process is observed in a Brillouin random fiber laser comb(BRFLC).Temporal and statistical characteristics of the RWs concerning their emergence and evolution are experimentally explored and analyzed.Specifically,temporally localized structures with high intensities including chair-like pulses with a sharp leading edge followed by a trailing plateau appear frequently in the BRFLC output,which can evolve to chair-like RW pulses with adjustable pulse duration and amplitude under controlled conditions.This investigation provides a deep insight into the extreme event of RWs and paves the way for RW manipulation for its generation and elimination in RFLs through adapted laser configuration.
基金supported by the National Key R&D Program of China(Grant No.2023YFE0105800)the National Natural Science Foundation of China(Grant Nos.62275093 and 61775074)the Key R&D Program of Hubei Province(Grant No.2021BAA036).
文摘Random fiber lasers(RFLs)have attracted extensive attention due to their rich physical properties and wide applications.Here,a RFL using a cascaded fiber loop mirror(CFLM)is proposed and presented.A CFLM with 10 fiber loop mirrors(FLMs)is simulated by the transfer matrix method and used to provide random feedback.Multiple spikes are observed in both the simulated and measured reflection spectra.The RFL operates in a single longitudinal mode near the threshold and a time-varying multilongitudinal mode at higher pump powers.The RFL exhibits a time-varying radio-frequency spectrum.The Lévy–Gaussian distribution transition is observed,as in many RFLs.The operation mechanism of the lasing longitudinal modes and the impact of complex mode competition and mode hopping on the output characteristics are discussed through experimental and theoretical results.In this study,we unveil an artificial random feedback structure and pave another way for the realization of RFLs,which should be a platform for multidisciplinary studies in complex systems.
文摘After a half century of development, fiber laser has evolved from a concept to a great family penetrating into various fields of applications. This paper reviews the history and current development of fiber lasers, with topics covering both continuous wave and short pulse fiber lasers. Important issues such as the major rare earth dopants, fiber laser brightness, polarization effects, clad pumping technology, beam combination, mode locking and pulse shaping are discussed in this paper.
基金Project(51204109)supported by the National Natural Science Foundation of China
文摘In order to decrease the metallurgical porosity and keyhole-induced porosity during deep penetration laser welding of Al and its alloys, and increase the mechanical properties of work-piece, the effects of welding parameters such as laser power, welding speed and defocusing value on both kinds of porosities were systemically analyzed respectively, and the shape and fluctuation of plume of the keyhole were observed to reflect the stability of the keyhole. The results show that increasing laser power or decreasing laser spot size can lead to the rising of both number and occupied area of pores in the weld; meanwhile, the plume fluctuates violently over the keyhole, which is always companied with the intense metallic vapor, liquid metal spatter and collapsing in the keyhole, thus more pores are generated in the weld. The porosity in the weld reaches the minimum at welding velocity of 2.0 m/min when laser power is 5 kW and defocusing value is 0.
