Materials exhibiting broadband nonlinear optical responses are critically important for ultrafast photonics applications,particularly as saturable absorbers(SAs)that facilitate broadband optical pulse generation.In th...Materials exhibiting broadband nonlinear optical responses are critically important for ultrafast photonics applications,particularly as saturable absorbers(SAs)that facilitate broadband optical pulse generation.In this study,tea polyphenolpolyvinyl alcohol(TP-PVA)composite films are synthesized via a polymer embedding method and employed as SAs to initiate ultrafast pulse operation in fiber lasers.The TP-PVA SA film exhibits excellent broadband saturable absorption performance at wavelengths of 1.0μm,1.5μm,and 2.0μm,with modulation depths of 54.21%,41.41%,and 51.16%,respectively.Stable passively mode-locked pulses with pulse widths of 588 fs,419 fs,and 743 fs are generated in Yb-,Er-,and Tm-doped fiber lasers,respectively.This work confirms the effective performance of TP-PVA as a broadband SA,and establishes a foundation for the integration of novel and sustainable materials within ultrafast photonic systems.The approach paves the way for developing compact broadband ultrafast laser systems operating in the near-infrared spectral region.展开更多
With the advances of our society,the application scope of energy storage technologies has expanded dramatically,spanning diverse scenarios.These include electric air vehicles(EAVs)that require instantaneous high-power...With the advances of our society,the application scope of energy storage technologies has expanded dramatically,spanning diverse scenarios.These include electric air vehicles(EAVs)that require instantaneous high-power bursts for takeoff and maneuvering,portable medical devices demanding rapid rechargeability,and grid-connected energy storage systems that must swiftly respond to load fluctuations[1].展开更多
The precise control of wrinkles and strain gradients in nanofilm is of significant interest due to their profound influence on electronic band structures and spin states.Here,we employ ultrafast electron diffraction(U...The precise control of wrinkles and strain gradients in nanofilm is of significant interest due to their profound influence on electronic band structures and spin states.Here,we employ ultrafast electron diffraction(UED)to study the picosecond-scale dynamics of laser-induced bending in 2H-MoTe2 thin films.展开更多
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
Currently,the performance,cost,and environmental sustainability of saturable absorbers(SAs)represent major bottlenecks in the development of ultrafast fiber lasers.However,the development of high-performance SAs remai...Currently,the performance,cost,and environmental sustainability of saturable absorbers(SAs)represent major bottlenecks in the development of ultrafast fiber lasers.However,the development of high-performance SAs remains challenging due to intricate fabrication processes and inadequate nonlinear performance.In this context,this work presents the natural alkaloid berberine as a promising alternative for mode-locked erbium-doped fiber lasers.The berberine-based SA exhibits excellent nonlinear optical properties,including a modulation depth of 24.40%and a saturation intensity of 1.281MW/cm^(2),and successfully enables stable femtosecond pulse generation.By employing time-stretched dispersive Fourier transform technology,the transient dynamics results indicate that the berberine-based SA significantly shortens the relaxation oscillation time and effectively suppresses pulse intensity fluctuations,thereby accelerating the self-starting process of mode-locking.This work provides a new strategy for developing high-performance,low-cost,and environmentally friendly ultrafast photonic devices,significantly advancing the practical application of green SAs.展开更多
Besides equilibrium behavior,exploring the spin–phonon coupling in multiferroic materials under non-equilibrium conditions is crucial for a deep understanding of the mechanisms as well as their high-frequency applica...Besides equilibrium behavior,exploring the spin–phonon coupling in multiferroic materials under non-equilibrium conditions is crucial for a deep understanding of the mechanisms as well as their high-frequency applications.Here,by utilizing time-resolved refectance spectroscopy,we demonstrate ultrafast spin–phonon coupling dynamics in multiferroic 0.58BiFeO_(3)-0.42Bi_(0.5)K_(0.5)TiO_(3)(BF-BKT)single crystals.With ultrafast laser pumping,coherent acoustic phonons with low damping are created in BF-BKT.Temperature-dependent results indicate that both the frequency and amplitude of laser-induced coherent phonons are sensitive to the emergence of antiferromagnetic order.Moreover,the spin state change driven by external magnetic felds can enhance the oscillation amplitude of the coherent acoustic phonons even above the magnetic Néel temperature.These fndings experimentally confrm that spin–phonon coupling in multiferroic materials exists not only in the spin-ordered state but also in the spin-disordered state,and not only in the equilibrium state but also in the non-equilibrium state excited by ultrafast lasers,suggesting their promising applications in high-frequency devices.展开更多
The ultrafast laser-matter interaction is explored to induce new pioneering principles and technologies into the realms of fundamental science and industrial production.The local thermal melting and connection propert...The ultrafast laser-matter interaction is explored to induce new pioneering principles and technologies into the realms of fundamental science and industrial production.The local thermal melting and connection properties of the ultrafast laser welding technology offer a novel method for welding of diverse transparent materials,thus having wide range of potential applications in aerospace,opto-mechanical systems,sensors,microfluidic,optics,etc.In this comprehensive review,tuning the transient electron activation processes,high-rate laser energy deposition,and dynamic evolution of plasma morphology by the temporal/spatial shaping methods have been demonstrated to facilitate the transition from conventional homogeneous transparent material welding to the more intricate realm of transparent/metal heterogeneous material welding.The welding strength and stability are also improvable through the implementation of real-time,in-situ monitoring techniques and the prompt diagnosis of welding defects.The principles of ultrafast laser welding,bottleneck problems in the welding,novel welding methods,advances in welding performance,in-situ monitoring and diagnosis,and various applications are reviewed.Finally,we offer a forward-looking perspective on the fundamental challenges within the field of ultrafast laser welding and identify key areas for future research,underscoring the imperative need for ongoing innovation and exploration.展开更多
In this paper, we have demonstrated an Er-doped ultrafast laser with a single mode fiber-gradient index multimode fiber-single mode fiber(SMF-GIMF-SMF, SMS) structure as saturable absorber(SA), which can generate not ...In this paper, we have demonstrated an Er-doped ultrafast laser with a single mode fiber-gradient index multimode fiber-single mode fiber(SMF-GIMF-SMF, SMS) structure as saturable absorber(SA), which can generate not only stable single-pulse state, but also special mode-locked pulses with the characteristics of high energy and noisy behaviors at proper pump power and cavity polarization state. In addition, we have deeply investigated the real-time spectral evolutions of the mode-locked pulses through the dispersive Fourier transformation(DFT) technique. It can be found that the pulse regime can actually consist of a lot of small noise pulses with randomly varying intensities. We believe that these results will further enrich the nonlinear dynamical processes in the ultrafast lasers.展开更多
Sodium-ion batteries have emerged as competitive substitutes for low-temperature applications due to severe capacity loss and safety concerns of lithium-ion batteries at−20°C or lower.However,the key capability o...Sodium-ion batteries have emerged as competitive substitutes for low-temperature applications due to severe capacity loss and safety concerns of lithium-ion batteries at−20°C or lower.However,the key capability of ultrafast charging at ultralow temperature for SIBs is rarely reported.Herein,a hybrid of Bi nanoparticles embedded in carbon nanorods is demonstrated as an ideal material to address this issue,which is synthesized via a high temperature shock method.Such a hybrid shows an unprecedented rate performance(237.9 mAh g^(−1) at 2 A g^(−1))at−60℃,outperforming all reported SIB anode materials.Coupled with a Na_(3)V_(2)(PO_(4))_(3)cathode,the energy density of the full cell can reach to 181.9 Wh kg^(−1) at−40°C.Based on this work,a novel strategy of high-rate activation is proposed to enhance performances of Bi-based materials in cryogenic conditions by creating new active sites for interfacial reaction under large current.展开更多
Nickel-rich cathode materials have received widespread attention due to their high energy density.However,the poor rate capability and inferior cycle stability seriously hinder their large-scale application.The tradit...Nickel-rich cathode materials have received widespread attention due to their high energy density.However,the poor rate capability and inferior cycle stability seriously hinder their large-scale application.The traditional co-precipitation method for preparing them has a long process and easily arises agglomeration leading to inhomogeneous element distribution.Here,a novel precursor containing Li element was prepared by ultrafast spray pyrolysis(SP)in 3–5 s.Then the precursor was used to synthesize pristine LiNi_(0.9)Co_(0.05)Mn_(0.05)O_(2)(NCM90)and 1%Mg modified LiNi_(0.9)Co_(0.05)Mn_(0.05)O_(2)(NCM90-Mg1).This method gets rid of mixing Li/Mg source and the precursor prepared by common co-precipitation,thus could achieve homogeneous lithiation and Mg2+doping.The cell parameter c is expanded,and the cation disorder is reduced after Mg2+doping.Furthermore,the harmful H2-H3 phase transition in NCM90-Mg1 is also well suppressed.As a result,the obtained NCM90-Mg1 shows better electrochemical performance than NCM90.Within 2.8–4.3 V(25℃),the specific discharge capacity of NCM90-Mg1 at 5 C is as high as 169.1m Ah/g,and an outstanding capacity retention of 70.0%(10.0%higher than NCM90)can be obtained after400 cycles at 0.5 C.At 45℃,a capacity retention of 81.9%after 100 cycles at 1 C is recorded for NCM90-Mg1.Moreover,the NCM90-Mg1 also exhibits superior cycle stability when cycled at high cut-off voltage(4.5 V,25℃),possessing the capacity retention of 79.2%after 200 cycles at 1 C.Therefore,SP can be proposed as a powerful method for the preparation of multi-element materials for next-generation high energy density LIBs.展开更多
Filter capacitors play an important role in altern-ating current(AC)-line filtering for stabilizing voltage,sup-pressing harmonics,and improving power quality.However,traditional aluminum electrolytic capacitors(AECs)...Filter capacitors play an important role in altern-ating current(AC)-line filtering for stabilizing voltage,sup-pressing harmonics,and improving power quality.However,traditional aluminum electrolytic capacitors(AECs)suffer from a large size,short lifespan,low power density,and poor reliability,which limits their use.In contrast,ultrafast supercapacitors(SCs)are ideal for replacing commercial AECs because of their extremely high power densities,fast charging and discharging,and excellent high-frequency re-sponse.We review the design principles and key parameters for ultrafast supercapacitors and summarize research pro-gress in recent years from the aspects of electrode materials,electrolytes,and device configurations.The preparation,structures,and frequency response performance of electrode materials mainly consisting of carbon materials such as graphene and carbon nanotubes,conductive polymers,and transition metal compounds,are focused on.Finally,future research directions for ultrafast SCs are suggested.展开更多
The heavy-atom effect of halogen(Br and I)has been widely employed for boosting spin-crossover in organic molecules,while recent investigation indicated halogen-substitution can also enhance fluorescence and even lead...The heavy-atom effect of halogen(Br and I)has been widely employed for boosting spin-crossover in organic molecules,while recent investigation indicated halogen-substitution can also enhance fluorescence and even lead to aggregation-induced emission(AIE).In this work,we investigated ultrafast excited state dynamics of a halogen-substituted model system,i.e.squaryliums NSQ-R(R=H,Cl,Br,I),by using femtosecond spectroscopy and theoretical approach.Fast external reorganization(Ex-re,~3 ps)and slow internal reorganization(In-re,5-20 ps)were observed,while quantitative fitting indicated halogen-substitution leads to a slower non-radiative S1→S0 decay(k_(NR)^(s))and subsequently enhanced fluorescence emitting.By analyzing the extracted k_(NR)^(s)within theoretical framework of non-radiative transition in the strong coupling regime,a plausible AIE mechanism of NSQs was revealed.Our work provides a clear picture on non-radiative dynamics of halogen-substituted squaryliums,which might be useful for future development of organic dyes.展开更多
Nanomaterials with promising optical,mechanical and electrical properties have garnered significant in-terest in photonics and electronics.However,the integration of nanomaterials with diverse characteristics for pote...Nanomaterials with promising optical,mechanical and electrical properties have garnered significant in-terest in photonics and electronics.However,the integration of nanomaterials with diverse characteristics for potential ultrafast photonics applications has emerged as a focal point.In this study,two-dimensional MXene(Ti_(3)C_(2)T_(x))and CuO nanoparticles were synthesized to create heterostructure materials.The surface morphology,chemical composition and nonlinear absorption properties of the heterostructure materials were investigated.First-principle-based theoretical calculations were performed to explore the electronic and optical properties of the Ti_(3)C_(2)T_(x)/CuO heterojunction,offering insights into its essential properties and supporting the potential optoelectronic applications.Importantly,the Ti_(3)C_(2)T_(x)/CuO heterojunction ef-fectively functioned as saturable absorbers in ultrafast lasers.Incorporating the Ti_(3)C_(2)T_(x)/CuO-based sat-urable absorber into a net-anomalous dispersion fiber cavity generated stable conventional-soliton pulses with duration of 495 fs.Additionally,adjusting cavity dispersion to net-normal allowed the Ti_(3)C_(2)T_(x)/CuO-based saturable absorber to generate dissipative soliton with a pulse width of 22 ps.The performance of Ti_(3)C_(2)T_(x)/CuO-based fiber lasers demonstrates enhancements over previous works.This study confirms that the Ti_(3)C_(2)T_(x)/CuO heterojunction is a promising nonlinear optical material for ultrafast applications and advanced MXene-based photonic devices.展开更多
Ultrafast reaction kinetics is essential for rapid detection,synthesis,and process monitoring,but the intrinsic energy barrier as a basic material property is challenging to tailor.With the involvement of nanointerfac...Ultrafast reaction kinetics is essential for rapid detection,synthesis,and process monitoring,but the intrinsic energy barrier as a basic material property is challenging to tailor.With the involvement of nanointerfacial chemistry,we propose a carbonization-based strategy for achieving ultrafast chemical reaction.In a case study,ultrafast Griess reaction within 1 min through the carbonization of N-(1-naphthalene)ethylenediamine(NETH)was realized.The carbonization-mediated ultrafast reaction is attributed to the synergic action of reduced electrostatic repulsion,enriched reactant concentration,and boosted NETH nucleophilicity.The enhanced reaction kinetics in o-phenylenediamine-Cu^(2)+and ophenylenediamine-ascorbic acid systems validate the universality of carbonization-engineered ultrafast chemical reaction strategy.The finding of this work offers a novel and simple tactic for the fabrication of multifunctional nanoparticles as ultrafast and effective nanoreactants and/or reporters in analytical,biological,and material aspects.展开更多
In China,electric vehicle(EV)fast-charging power has quadrupled in the past five years,progressing toward 10-minute ultrafast charging.This rapid increase raises concerns about the impact on the power grid including i...In China,electric vehicle(EV)fast-charging power has quadrupled in the past five years,progressing toward 10-minute ultrafast charging.This rapid increase raises concerns about the impact on the power grid including increased peak power demand and the need for substantial upgrades to power infrastruc-ture.Here,we introduce an integrated model to assess fast and ultrafast charging impacts for represen-tative charging stations in China,combining real-world charging patterns and detailed station optimization models.We find that larger stations with 12 or more chargers experience modest peak power increases of less than 30%when fast-charging power is doubled,primarily because shorter charg-ing sessions are less likely to overlap.For more typical stations(e.g.,8-9 chargers and 120 kW·charger^(−1)),upgrading chargers to 350-550 kW while allowing managed dynamic waiting strategies(of∼1 minute)can reduce overall charging times to∼9 minutes.At stations,deploying battery storage and/or expanding transformers can help manage future increases in station loads,yet the primary device cost of the former is∼4 times higher than that of the latter.Our results offer insights for charging infrastructure planning,EV-grid interactions,and associated policymaking.展开更多
Ultrafast phenomena induced by femtosecond laser irradiation encompass a range of highly dynamic physical processes,including but not limited to electron excitation,material ablation,plasma generation,and shock wave p...Ultrafast phenomena induced by femtosecond laser irradiation encompass a range of highly dynamic physical processes,including but not limited to electron excitation,material ablation,plasma generation,and shock wave propagation.Unveiling the dynamics of these ultrafast processes is crucial for effectively controlling laser processing.However,many of these phenomena occur on timescales ranging from femtoseconds(fs) to nanoseconds(ns),which presents significant challenges in monitoring and interpretation;thus,ultrafast optical imaging techniques are often required.This paper comprehensively reviews the ultrafast optical imaging methods employed in recent years to monitor various ultrafast processes such as electron excitation,ultrafast ablation,plasma ejection,and shock wave propagation during femtosecond laser processing of metallic,composite,and ceramic materials.These methods can be categorized into two primary types:pump-probe ultrafast optical imaging and single-shot ultrafast optical imaging techniques.The working principles and key findings associated with each type of ultrafast optical imaging technique are described in detail.Finally,the imaging principles,advantages and disadvantages,and application scenarios of various ultrafast imaging technologies are summarized,along with a discussion of future challenges and development directions in this field.展开更多
Photonic computing has emerged as a promising technology for the ever-increasing computational demands of machine learning and artificial intelligence.Due to the advantages in computing speed,integrated photonic chips...Photonic computing has emerged as a promising technology for the ever-increasing computational demands of machine learning and artificial intelligence.Due to the advantages in computing speed,integrated photonic chips have attracted wide research attention on performing convolutional neural network algorithm.Programmable photonic chips are vital for achieving practical applications of photonic computing.Herein,a programmable photonic chip based on ultrafast laser-induced phase change is fabricated for photonic computing.Through designing the ultrafast laser pulses,the Sb film integrated into photonic waveguides can be reversibly switched between crystalline and amorphous phase,resulting in a large contrast in refractive index and extinction coefficient.As a consequence,the light transmission of waveguides can be switched between write and erase states.To determine the phase change time,the transient laser-induced phase change dynamics of Sb film are revealed at atomic scale,and the time-resolved transient reflectivity is measured.Based on the integrated photonic chip,photonic convolutional neural networks are built to implement machine learning algorithm,and images recognition task is achieved.This work paves a route for fabricating programmable photonic chips by designed ultrafast laser,which will facilitate the application of photonic computing in artificial intelligence.展开更多
Understanding the dynamics of photoexcited carriers is essential for advancing photoelectronic device design.Photon absorption generates electron–hole pairs,and subsequent scatterings can induce ultrafast thermalizat...Understanding the dynamics of photoexcited carriers is essential for advancing photoelectronic device design.Photon absorption generates electron–hole pairs,and subsequent scatterings can induce ultrafast thermalization within a picosecond,forming a quasi-equilibrium distribution with overheated electrons.The high-energy tail of this distribution enables carriers to overcome energy barriers,thereby enhancing quantum efficiency—a phenomenon known as photothermionic emission(PTE).Despite its importance,the onset and mechanisms of PTE remain under debate.Using real-time timedependent density functional theory(rt-TDDFT),we investigate ultrafast carrier thermalization in two-dimensional(2D)materials graphene and PtTe2,and the results reveal distinct differences.In graphene,both electrons and holes thermalize into Fermi–Dirac distributions with good agreement to experiment,while PtTe2exhibits anomalous high-energy tails for both electrons and holes,deviating significantly from Fermi–Dirac behavior.We attribute this anomaly to differences in orbital coupling between the two materials,from which we derive design principles for identifying optimal PTE candidates and,ultimately,improving photodetector performance.展开更多
1.Introduction.In recent decades,the pursuit of miniaturization has been crucial in nanofabrication,fostering innovation,and enabling novel applications in chip manufacturing,nanophotonics,and quantum devices[1,2].Adv...1.Introduction.In recent decades,the pursuit of miniaturization has been crucial in nanofabrication,fostering innovation,and enabling novel applications in chip manufacturing,nanophotonics,and quantum devices[1,2].Advancements in nanofabrication technology are driven by the demand for higher component density and performance,necessitating precise material processing in atmospheric environments.展开更多
Single-shot ultrafast compressed imaging(UCI)is an effective tool for studying ultrafast dynamics in physics,chemistry,or material science because of its excellent high frame rate and large frame number.However,the ra...Single-shot ultrafast compressed imaging(UCI)is an effective tool for studying ultrafast dynamics in physics,chemistry,or material science because of its excellent high frame rate and large frame number.However,the random code(Rcode)used in traditional UCI will lead to low-frequency noise covering high-frequency information due to its uneven sampling interval,which is a great challenge in the fidelity of large-frame reconstruction.Here,a high-frequency enhanced compressed active photography(H-CAP)is proposed.By uniformizing the sampling interval of R-code,H-CAP capture the ultrafast process with a random uniform sampling mode.This sampling mode makes the high-frequency sampling energy dominant,which greatly suppresses the low-frequency noise blurring caused by R-code and achieves high-frequency information of image enhanced.The superior dynamic performance and large-frame reconstruction ability of H-CAP are verified by imaging optical self-focusing effect and static object,respectively.We applied H-CAP to the spatial-temporal characterization of double-pulse induced silicon surface ablation dynamics,which is performed within 220 frames in a single-shot of 300 ps.H-CAP provides a high-fidelity imaging method for observing ultrafast unrepeatable dynamic processes with large frames.展开更多
基金supported by the Opening Foundation of Hubei Key Laboratory for New Textile Materials and Applications Research(Grant No.FZXCL202410)the Key Project of Science and Technology Research Program of Hubei Provincial Department of Education,China(Grant No.D20231704)+1 种基金Wuhan Textile University(Grant No.523058)the Foundation of Wuhan Textile University(Grant No.K24058)。
文摘Materials exhibiting broadband nonlinear optical responses are critically important for ultrafast photonics applications,particularly as saturable absorbers(SAs)that facilitate broadband optical pulse generation.In this study,tea polyphenolpolyvinyl alcohol(TP-PVA)composite films are synthesized via a polymer embedding method and employed as SAs to initiate ultrafast pulse operation in fiber lasers.The TP-PVA SA film exhibits excellent broadband saturable absorption performance at wavelengths of 1.0μm,1.5μm,and 2.0μm,with modulation depths of 54.21%,41.41%,and 51.16%,respectively.Stable passively mode-locked pulses with pulse widths of 588 fs,419 fs,and 743 fs are generated in Yb-,Er-,and Tm-doped fiber lasers,respectively.This work confirms the effective performance of TP-PVA as a broadband SA,and establishes a foundation for the integration of novel and sustainable materials within ultrafast photonic systems.The approach paves the way for developing compact broadband ultrafast laser systems operating in the near-infrared spectral region.
文摘With the advances of our society,the application scope of energy storage technologies has expanded dramatically,spanning diverse scenarios.These include electric air vehicles(EAVs)that require instantaneous high-power bursts for takeoff and maneuvering,portable medical devices demanding rapid rechargeability,and grid-connected energy storage systems that must swiftly respond to load fluctuations[1].
基金supported by the High-level Talent Research Start-up Project Funding of Henan Academy of Sciences(Project No.241827012)the National Natural Science Foundation of China(Grant Nos.U22A6005 and 62271450)+1 种基金the National Key Research and Development Program of China(Grant Nos.2021YFA1301502,2024YFA1408701,and 2024YFA1408403)the Synergetic Extreme Condition User Facility(SECUF,https://cstr.cn/31123.02.SECUF)。
文摘The precise control of wrinkles and strain gradients in nanofilm is of significant interest due to their profound influence on electronic band structures and spin states.Here,we employ ultrafast electron diffraction(UED)to study the picosecond-scale dynamics of laser-induced bending in 2H-MoTe2 thin films.
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 the Key Project of Science and Technology Research Program of Hubei Provincial Department of Education,China(D20231704)the Opening Foundation of Hubei Key Laboratory for New Textile Materials and Applications Research(FZXCL202410)the Wuhan Textile University Special Fund Project。
文摘Currently,the performance,cost,and environmental sustainability of saturable absorbers(SAs)represent major bottlenecks in the development of ultrafast fiber lasers.However,the development of high-performance SAs remains challenging due to intricate fabrication processes and inadequate nonlinear performance.In this context,this work presents the natural alkaloid berberine as a promising alternative for mode-locked erbium-doped fiber lasers.The berberine-based SA exhibits excellent nonlinear optical properties,including a modulation depth of 24.40%and a saturation intensity of 1.281MW/cm^(2),and successfully enables stable femtosecond pulse generation.By employing time-stretched dispersive Fourier transform technology,the transient dynamics results indicate that the berberine-based SA significantly shortens the relaxation oscillation time and effectively suppresses pulse intensity fluctuations,thereby accelerating the self-starting process of mode-locking.This work provides a new strategy for developing high-performance,low-cost,and environmentally friendly ultrafast photonic devices,significantly advancing the practical application of green SAs.
基金supported by the National Key R&D Program of China(Grant No.2021YFA1600200)the National Natural Science Foundation of China(Grant Nos.U2032218 and 12111530283)。
文摘Besides equilibrium behavior,exploring the spin–phonon coupling in multiferroic materials under non-equilibrium conditions is crucial for a deep understanding of the mechanisms as well as their high-frequency applications.Here,by utilizing time-resolved refectance spectroscopy,we demonstrate ultrafast spin–phonon coupling dynamics in multiferroic 0.58BiFeO_(3)-0.42Bi_(0.5)K_(0.5)TiO_(3)(BF-BKT)single crystals.With ultrafast laser pumping,coherent acoustic phonons with low damping are created in BF-BKT.Temperature-dependent results indicate that both the frequency and amplitude of laser-induced coherent phonons are sensitive to the emergence of antiferromagnetic order.Moreover,the spin state change driven by external magnetic felds can enhance the oscillation amplitude of the coherent acoustic phonons even above the magnetic Néel temperature.These fndings experimentally confrm that spin–phonon coupling in multiferroic materials exists not only in the spin-ordered state but also in the spin-disordered state,and not only in the equilibrium state but also in the non-equilibrium state excited by ultrafast lasers,suggesting their promising applications in high-frequency devices.
基金supports from National Key R&D Program of China(Grant No.2023YFB4605500)National Natural Science Foundation of China(Grant No.52105498)+3 种基金Natural Science Foundation of Hunan Province(Grant No.2022JJ40597)the Science and Technology Innovation Program of Hunan Province(Grant No.2022RC1132)State Key Laboratory of Precision Manufacturing for Extreme Service Performance(Grant No.ZZYJKT2023-08)support in analyzing the status of ultrafast laser welding applications,as well as the corresponding project support(Grant No.HKF202400595).
文摘The ultrafast laser-matter interaction is explored to induce new pioneering principles and technologies into the realms of fundamental science and industrial production.The local thermal melting and connection properties of the ultrafast laser welding technology offer a novel method for welding of diverse transparent materials,thus having wide range of potential applications in aerospace,opto-mechanical systems,sensors,microfluidic,optics,etc.In this comprehensive review,tuning the transient electron activation processes,high-rate laser energy deposition,and dynamic evolution of plasma morphology by the temporal/spatial shaping methods have been demonstrated to facilitate the transition from conventional homogeneous transparent material welding to the more intricate realm of transparent/metal heterogeneous material welding.The welding strength and stability are also improvable through the implementation of real-time,in-situ monitoring techniques and the prompt diagnosis of welding defects.The principles of ultrafast laser welding,bottleneck problems in the welding,novel welding methods,advances in welding performance,in-situ monitoring and diagnosis,and various applications are reviewed.Finally,we offer a forward-looking perspective on the fundamental challenges within the field of ultrafast laser welding and identify key areas for future research,underscoring the imperative need for ongoing innovation and exploration.
基金supported by the Guangdong Basic and Applied Basic Research Foundation (No.2023A1515010093)the Shenzhen Fundamental Research Program (Stable Support Plan Program)(Nos.JCYJ20220809170611004, 20231121110828001 and 20231121113641002)the National Taipei University of Technology-Shenzhen University Joint Research Program (No.2024001)。
文摘In this paper, we have demonstrated an Er-doped ultrafast laser with a single mode fiber-gradient index multimode fiber-single mode fiber(SMF-GIMF-SMF, SMS) structure as saturable absorber(SA), which can generate not only stable single-pulse state, but also special mode-locked pulses with the characteristics of high energy and noisy behaviors at proper pump power and cavity polarization state. In addition, we have deeply investigated the real-time spectral evolutions of the mode-locked pulses through the dispersive Fourier transformation(DFT) technique. It can be found that the pulse regime can actually consist of a lot of small noise pulses with randomly varying intensities. We believe that these results will further enrich the nonlinear dynamical processes in the ultrafast lasers.
基金supported from Science and Technology Development Program of Jilin Province(Nos.20240101128JC,20230402058GH)National Natural Science Foundation of China(No.52130101).
文摘Sodium-ion batteries have emerged as competitive substitutes for low-temperature applications due to severe capacity loss and safety concerns of lithium-ion batteries at−20°C or lower.However,the key capability of ultrafast charging at ultralow temperature for SIBs is rarely reported.Herein,a hybrid of Bi nanoparticles embedded in carbon nanorods is demonstrated as an ideal material to address this issue,which is synthesized via a high temperature shock method.Such a hybrid shows an unprecedented rate performance(237.9 mAh g^(−1) at 2 A g^(−1))at−60℃,outperforming all reported SIB anode materials.Coupled with a Na_(3)V_(2)(PO_(4))_(3)cathode,the energy density of the full cell can reach to 181.9 Wh kg^(−1) at−40°C.Based on this work,a novel strategy of high-rate activation is proposed to enhance performances of Bi-based materials in cryogenic conditions by creating new active sites for interfacial reaction under large current.
基金supported by the National Natural Science Foundation of China(No.52122407)the Science and Technology Innovation Program of Hunan Province(No.2022RC3048)。
文摘Nickel-rich cathode materials have received widespread attention due to their high energy density.However,the poor rate capability and inferior cycle stability seriously hinder their large-scale application.The traditional co-precipitation method for preparing them has a long process and easily arises agglomeration leading to inhomogeneous element distribution.Here,a novel precursor containing Li element was prepared by ultrafast spray pyrolysis(SP)in 3–5 s.Then the precursor was used to synthesize pristine LiNi_(0.9)Co_(0.05)Mn_(0.05)O_(2)(NCM90)and 1%Mg modified LiNi_(0.9)Co_(0.05)Mn_(0.05)O_(2)(NCM90-Mg1).This method gets rid of mixing Li/Mg source and the precursor prepared by common co-precipitation,thus could achieve homogeneous lithiation and Mg2+doping.The cell parameter c is expanded,and the cation disorder is reduced after Mg2+doping.Furthermore,the harmful H2-H3 phase transition in NCM90-Mg1 is also well suppressed.As a result,the obtained NCM90-Mg1 shows better electrochemical performance than NCM90.Within 2.8–4.3 V(25℃),the specific discharge capacity of NCM90-Mg1 at 5 C is as high as 169.1m Ah/g,and an outstanding capacity retention of 70.0%(10.0%higher than NCM90)can be obtained after400 cycles at 0.5 C.At 45℃,a capacity retention of 81.9%after 100 cycles at 1 C is recorded for NCM90-Mg1.Moreover,the NCM90-Mg1 also exhibits superior cycle stability when cycled at high cut-off voltage(4.5 V,25℃),possessing the capacity retention of 79.2%after 200 cycles at 1 C.Therefore,SP can be proposed as a powerful method for the preparation of multi-element materials for next-generation high energy density LIBs.
文摘Filter capacitors play an important role in altern-ating current(AC)-line filtering for stabilizing voltage,sup-pressing harmonics,and improving power quality.However,traditional aluminum electrolytic capacitors(AECs)suffer from a large size,short lifespan,low power density,and poor reliability,which limits their use.In contrast,ultrafast supercapacitors(SCs)are ideal for replacing commercial AECs because of their extremely high power densities,fast charging and discharging,and excellent high-frequency re-sponse.We review the design principles and key parameters for ultrafast supercapacitors and summarize research pro-gress in recent years from the aspects of electrode materials,electrolytes,and device configurations.The preparation,structures,and frequency response performance of electrode materials mainly consisting of carbon materials such as graphene and carbon nanotubes,conductive polymers,and transition metal compounds,are focused on.Finally,future research directions for ultrafast SCs are suggested.
基金support by the National Key R&D Program of China(Nos.2020YFA0714603 and 2020YFA0714604)。
文摘The heavy-atom effect of halogen(Br and I)has been widely employed for boosting spin-crossover in organic molecules,while recent investigation indicated halogen-substitution can also enhance fluorescence and even lead to aggregation-induced emission(AIE).In this work,we investigated ultrafast excited state dynamics of a halogen-substituted model system,i.e.squaryliums NSQ-R(R=H,Cl,Br,I),by using femtosecond spectroscopy and theoretical approach.Fast external reorganization(Ex-re,~3 ps)and slow internal reorganization(In-re,5-20 ps)were observed,while quantitative fitting indicated halogen-substitution leads to a slower non-radiative S1→S0 decay(k_(NR)^(s))and subsequently enhanced fluorescence emitting.By analyzing the extracted k_(NR)^(s)within theoretical framework of non-radiative transition in the strong coupling regime,a plausible AIE mechanism of NSQs was revealed.Our work provides a clear picture on non-radiative dynamics of halogen-substituted squaryliums,which might be useful for future development of organic dyes.
基金supported by the National Key R&D Program of China(No.2022YFB4601101)the National Natural Science Foundation of China(No.12075190)+3 种基金the China Postdoctoral Science Foundation(No.2023M741781)the Key Industry Innovation Chain Project of Shaanxi Province(No.2022ZDLSF04-09)the Shaanxi Province Medical Technology Integration High-end Medical Equipment Common Technology Research and Development Plat-form(No.2023GXJS-01)the Shaanxi Fundamental Science Research Project for Mathematics and Physics(No.23JSY019).
文摘Nanomaterials with promising optical,mechanical and electrical properties have garnered significant in-terest in photonics and electronics.However,the integration of nanomaterials with diverse characteristics for potential ultrafast photonics applications has emerged as a focal point.In this study,two-dimensional MXene(Ti_(3)C_(2)T_(x))and CuO nanoparticles were synthesized to create heterostructure materials.The surface morphology,chemical composition and nonlinear absorption properties of the heterostructure materials were investigated.First-principle-based theoretical calculations were performed to explore the electronic and optical properties of the Ti_(3)C_(2)T_(x)/CuO heterojunction,offering insights into its essential properties and supporting the potential optoelectronic applications.Importantly,the Ti_(3)C_(2)T_(x)/CuO heterojunction ef-fectively functioned as saturable absorbers in ultrafast lasers.Incorporating the Ti_(3)C_(2)T_(x)/CuO-based sat-urable absorber into a net-anomalous dispersion fiber cavity generated stable conventional-soliton pulses with duration of 495 fs.Additionally,adjusting cavity dispersion to net-normal allowed the Ti_(3)C_(2)T_(x)/CuO-based saturable absorber to generate dissipative soliton with a pulse width of 22 ps.The performance of Ti_(3)C_(2)T_(x)/CuO-based fiber lasers demonstrates enhancements over previous works.This study confirms that the Ti_(3)C_(2)T_(x)/CuO heterojunction is a promising nonlinear optical material for ultrafast applications and advanced MXene-based photonic devices.
基金supported by the National Natural Science Foundation of China(Nos.82160153,21505162,22074005,and 22101027)Natural Science Foundation of Hunan Province,China(No.2022SK2102)+1 种基金Hunan Provincial Department of Education Scientific Research Project(No.240994)the Natural Science Foundation of Beijing Municipality(No.2202038).
文摘Ultrafast reaction kinetics is essential for rapid detection,synthesis,and process monitoring,but the intrinsic energy barrier as a basic material property is challenging to tailor.With the involvement of nanointerfacial chemistry,we propose a carbonization-based strategy for achieving ultrafast chemical reaction.In a case study,ultrafast Griess reaction within 1 min through the carbonization of N-(1-naphthalene)ethylenediamine(NETH)was realized.The carbonization-mediated ultrafast reaction is attributed to the synergic action of reduced electrostatic repulsion,enriched reactant concentration,and boosted NETH nucleophilicity.The enhanced reaction kinetics in o-phenylenediamine-Cu^(2)+and ophenylenediamine-ascorbic acid systems validate the universality of carbonization-engineered ultrafast chemical reaction strategy.The finding of this work offers a novel and simple tactic for the fabrication of multifunctional nanoparticles as ultrafast and effective nanoreactants and/or reporters in analytical,biological,and material aspects.
基金the support of the National Natural Science Foundation of China(72325006,72488101,and 72293601)the Sze Family Foundationthe Climate Imperative Foundation(#2024-001465)
文摘In China,electric vehicle(EV)fast-charging power has quadrupled in the past five years,progressing toward 10-minute ultrafast charging.This rapid increase raises concerns about the impact on the power grid including increased peak power demand and the need for substantial upgrades to power infrastruc-ture.Here,we introduce an integrated model to assess fast and ultrafast charging impacts for represen-tative charging stations in China,combining real-world charging patterns and detailed station optimization models.We find that larger stations with 12 or more chargers experience modest peak power increases of less than 30%when fast-charging power is doubled,primarily because shorter charg-ing sessions are less likely to overlap.For more typical stations(e.g.,8-9 chargers and 120 kW·charger^(−1)),upgrading chargers to 350-550 kW while allowing managed dynamic waiting strategies(of∼1 minute)can reduce overall charging times to∼9 minutes.At stations,deploying battery storage and/or expanding transformers can help manage future increases in station loads,yet the primary device cost of the former is∼4 times higher than that of the latter.Our results offer insights for charging infrastructure planning,EV-grid interactions,and associated policymaking.
基金supported by the National Key R&D Program of China(No.2022YFB4601601)the Key R&D Program of Guangxi Province,China(No.GKAB23026101)+1 种基金the Base,Talent Special Project of the Guangxi Science and Technology Plan Project(No.Gui Ke AD23026149)Guangxi Natural Science Foundation,China(No.2023GXNSFBA026287)
文摘Ultrafast phenomena induced by femtosecond laser irradiation encompass a range of highly dynamic physical processes,including but not limited to electron excitation,material ablation,plasma generation,and shock wave propagation.Unveiling the dynamics of these ultrafast processes is crucial for effectively controlling laser processing.However,many of these phenomena occur on timescales ranging from femtoseconds(fs) to nanoseconds(ns),which presents significant challenges in monitoring and interpretation;thus,ultrafast optical imaging techniques are often required.This paper comprehensively reviews the ultrafast optical imaging methods employed in recent years to monitor various ultrafast processes such as electron excitation,ultrafast ablation,plasma ejection,and shock wave propagation during femtosecond laser processing of metallic,composite,and ceramic materials.These methods can be categorized into two primary types:pump-probe ultrafast optical imaging and single-shot ultrafast optical imaging techniques.The working principles and key findings associated with each type of ultrafast optical imaging technique are described in detail.Finally,the imaging principles,advantages and disadvantages,and application scenarios of various ultrafast imaging technologies are summarized,along with a discussion of future challenges and development directions in this field.
基金supported by the National Key R&D Program of China(2024YFB4609801)the National Natural Science Foundation of China(52075289)the Tsinghua-Jiangyin Innovation Special Fund(TJISF,2023JYTH0104).
文摘Photonic computing has emerged as a promising technology for the ever-increasing computational demands of machine learning and artificial intelligence.Due to the advantages in computing speed,integrated photonic chips have attracted wide research attention on performing convolutional neural network algorithm.Programmable photonic chips are vital for achieving practical applications of photonic computing.Herein,a programmable photonic chip based on ultrafast laser-induced phase change is fabricated for photonic computing.Through designing the ultrafast laser pulses,the Sb film integrated into photonic waveguides can be reversibly switched between crystalline and amorphous phase,resulting in a large contrast in refractive index and extinction coefficient.As a consequence,the light transmission of waveguides can be switched between write and erase states.To determine the phase change time,the transient laser-induced phase change dynamics of Sb film are revealed at atomic scale,and the time-resolved transient reflectivity is measured.Based on the integrated photonic chip,photonic convolutional neural networks are built to implement machine learning algorithm,and images recognition task is achieved.This work paves a route for fabricating programmable photonic chips by designed ultrafast laser,which will facilitate the application of photonic computing in artificial intelligence.
基金Project supported by the Natural Science Foundation of Chongqing of China(Grant No.CSTB2023NSCQ-LZX0087)the National Natural Science Foundation of China(Grant Nos.62074021 and 12174380)。
文摘Understanding the dynamics of photoexcited carriers is essential for advancing photoelectronic device design.Photon absorption generates electron–hole pairs,and subsequent scatterings can induce ultrafast thermalization within a picosecond,forming a quasi-equilibrium distribution with overheated electrons.The high-energy tail of this distribution enables carriers to overcome energy barriers,thereby enhancing quantum efficiency—a phenomenon known as photothermionic emission(PTE).Despite its importance,the onset and mechanisms of PTE remain under debate.Using real-time timedependent density functional theory(rt-TDDFT),we investigate ultrafast carrier thermalization in two-dimensional(2D)materials graphene and PtTe2,and the results reveal distinct differences.In graphene,both electrons and holes thermalize into Fermi–Dirac distributions with good agreement to experiment,while PtTe2exhibits anomalous high-energy tails for both electrons and holes,deviating significantly from Fermi–Dirac behavior.We attribute this anomaly to differences in orbital coupling between the two materials,from which we derive design principles for identifying optimal PTE candidates and,ultimately,improving photodetector performance.
基金supported by the National Natural Science Foun-dation of China(51975017 and 52405448)the Human Resource Training Project(HRTP-[2022]-53)of Innovation Laboratory for Sciences and Technologies of Energy Materials of Fujian Province(IKKEM)the support by the China Postdoctoral Science Foundation(2024M750149 and GZC20240087).
文摘1.Introduction.In recent decades,the pursuit of miniaturization has been crucial in nanofabrication,fostering innovation,and enabling novel applications in chip manufacturing,nanophotonics,and quantum devices[1,2].Advancements in nanofabrication technology are driven by the demand for higher component density and performance,necessitating precise material processing in atmospheric environments.
基金supported by the National Science Foundation of China(No.12127806,No.62175195 and No.12304382)the International Joint Research Laboratory for Micro/Nano Manufacturing and Measurement Technologies.
文摘Single-shot ultrafast compressed imaging(UCI)is an effective tool for studying ultrafast dynamics in physics,chemistry,or material science because of its excellent high frame rate and large frame number.However,the random code(Rcode)used in traditional UCI will lead to low-frequency noise covering high-frequency information due to its uneven sampling interval,which is a great challenge in the fidelity of large-frame reconstruction.Here,a high-frequency enhanced compressed active photography(H-CAP)is proposed.By uniformizing the sampling interval of R-code,H-CAP capture the ultrafast process with a random uniform sampling mode.This sampling mode makes the high-frequency sampling energy dominant,which greatly suppresses the low-frequency noise blurring caused by R-code and achieves high-frequency information of image enhanced.The superior dynamic performance and large-frame reconstruction ability of H-CAP are verified by imaging optical self-focusing effect and static object,respectively.We applied H-CAP to the spatial-temporal characterization of double-pulse induced silicon surface ablation dynamics,which is performed within 220 frames in a single-shot of 300 ps.H-CAP provides a high-fidelity imaging method for observing ultrafast unrepeatable dynamic processes with large frames.
