As the fundamental optical properties and novel photophysics of graphene and related two-dimensional （2D） crystals are being extensively investigated and revealed, a range of potential applications in optical and op...As the fundamental optical properties and novel photophysics of graphene and related two-dimensional （2D） crystals are being extensively investigated and revealed, a range of potential applications in optical and optoelectronic devices have been proposed and demonstrated. Of the many possibilities, the use of 2D materials as broadband, cost-effective and versatile ultrafast optical switches （or saturable absorbers） for short-pulsed lasers constitutes a rapidly developing field with not only a good number of publications, but also a promising prospect for commercial exploitation. This review primarily focuses on the recent development of pulsed lasers based on several representative 2D materials. The comparative advantages of these materials are discussed, and challenges to practical exploitation, which represent good future directions of research, are laid out.展开更多
We report on an improved ytterbium-doped yttrium aluminum garnet thin-disk multi-pass amplifier for kilowatt-level ultrafast lasers,showcasing excellent beam quality.At a repetition rate of 800 kHz,the 6.8 ps,276 W se...We report on an improved ytterbium-doped yttrium aluminum garnet thin-disk multi-pass amplifier for kilowatt-level ultrafast lasers,showcasing excellent beam quality.At a repetition rate of 800 kHz,the 6.8 ps,276 W seed laser is amplified up to an average power of 1075 W,corresponding to a pulse energy of 1.34 mJ.The 36-pass amplifier is designed as a compact mirror array in which the beam alternately propagates between the mirrors and the disk by a quasi-collimated state.We adopted a quasi-collimated propagation to confine stray and diffracted light by the slight curvature of the disk,which enables us to achieve an outstanding extraction efficiency of up to 57%with excellent beam quality in stable laser operation at high power.The beam quality at 1075 W was measured to be M^(2)<1.51.Furthermore,stability testing was demonstrated with a root-mean-square power fiuctuation of less than 1.67%for 10 min.展开更多
As one of the greatest inventions in the 20 th century, ultrafast lasers have offered new opportunities in the areas of basic scientific research and industrial manufacturing. Optical modulators are of great importanc...As one of the greatest inventions in the 20 th century, ultrafast lasers have offered new opportunities in the areas of basic scientific research and industrial manufacturing. Optical modulators are of great importance in ultrafast lasers, which directly affect the output laser performances. Over the past decades, significant efforts have been made in the development of compact, controllable, repeatable, as well as integratable optical modulators(i.e., saturable absorbers). In this paper, we review the fundamentals of the most widely studied saturable absorbers, including semiconductor saturable absorber mirrors and low-dimensional nanomaterials. Then, different fabrication technologies for saturable absorbers and their ultrafast laser applications in a wide wavelength range are illustrated. Furthermore, challenges and perspectives for the future development of saturable absorbers are discussed and presented. The development of ultrafast lasers together with the continuous exploration of reliable saturable absorbers will open up new directions for the mass production of the nextgeneration optoelectronic devices.展开更多
The unique characteristics of ultrafast lasers,such as picosecond and femtosecond lasers,have opened up new avenues in materials processing that employ ultrashort pulse widths and extremely high peak intensities.Thus,...The unique characteristics of ultrafast lasers,such as picosecond and femtosecond lasers,have opened up new avenues in materials processing that employ ultrashort pulse widths and extremely high peak intensities.Thus,ultrafast lasers are currently used widely for both fundamental research and practical applications.This review describes the characteristics of ultrafast laser processing and the recent advancements and applications of both surface and volume processing.Surface processing includes micromachining,microand nanostructuring,and nanoablation,while volume processing includes two-photon polymerization and three-dimensional(3D)processing within transparent materials.Commercial and industrial applications of ultrafast laser processing are also introduced,and a summary of the technology with future outlooks are also given.展开更多
Because poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate)(PEDOT:PSS)is water processable,thermally stable,and highly conductive,PEDOT:PSS and its composites have been considered to be one of the most promising f...Because poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate)(PEDOT:PSS)is water processable,thermally stable,and highly conductive,PEDOT:PSS and its composites have been considered to be one of the most promising flexible thermoelectric materials.However,the PEDOT:PSS film prepared from its commercial aqueous dispersion usually has very low conductivity,thus cannot be directly utilized for TE applications.Here,a simple environmental friendly strategy via femtosecond laser irradiation without any chemical dopants and treatments was demonstrated.Under optimal conditions,the electrical conductivity of the treated film is increased to 803.1 S cm^(-1)from 1.2 S cm^(-1)around three order of magnitude higher,and the power factor is improved to 19.0μW m^(-1)K^(-2),which is enhanced more than 200 times.The mechanism for such remarkable enhancement was attributed to the transition of the PEDOT chains from a coil to a linear or expanded coil conformation,reduction of the interplanar stacking distance,and the removal of insulating PSS with increasing the oxidation level of PEDOT,facilitating the charge transportation.This work presents an effective route for fabricating high-performance flexible conductive polymer films and wearable thermoelectric devices.展开更多
Ultrafast laser inscription(ULI)inside semiconductors offers new perspectives for 3D monolithic structures to be fabricated and new functionalities to be added in electronic and photonic microdevices.However,important...Ultrafast laser inscription(ULI)inside semiconductors offers new perspectives for 3D monolithic structures to be fabricated and new functionalities to be added in electronic and photonic microdevices.However,important challenges remain because of nonlinear effects such as strong plasma generation that distort the energy delivery at the focal point when exposing these materials to intense infrared light.Up to now,the successful technological demonstrations have primarily concentrated on silicon(Si).In this paper,we target at another important semiconductor:gallium arsenide(GaAs).With nonlinearities higher than those of Si,3D-machining of GaAs with femtosecond pulses becomes even harder.However,we show that the difficulty can be circumvented by burst-mode irradiation.We generate and apply trains of pulses at terahertz repetition rates for efficient pulse-to-pulse accumulation of laser-induced free carriers in the focal region,while avoiding an overdose of prefocal excitations.The superior performance of burst-mode irradiation is confirmed by a comparative study conducted with infrared luminescence microscopy.The results indicate a successful reduction of the plasma density in the prefocal region so that higher pulse energy reaches the focal spot.The same method is applied to identify optimum irradiation conditions considering particular cases such as asymmetric pulse trains and aberrated beams.With 64-pulse trains,we successfully manage to cross the writing threshold providing a solution for ULI inside GaAs.The application potential is finally illustrated with a stealth dicing demonstration by taking benefit of the burst mode.The irradiation method opens wide possibilities for 3D structuring inside GaAs by ULI.展开更多
We predict ultrafast modulation of the pure molten metal surface stress fields under the irradiation of the single femtosecond laser pulse through the two-temperature model molecular-dynamics simulations. High-resolut...We predict ultrafast modulation of the pure molten metal surface stress fields under the irradiation of the single femtosecond laser pulse through the two-temperature model molecular-dynamics simulations. High-resolution and precision calculations are used to resolve the ultrafast laser-induced anisotropic relaxations of the pressure components on the time-scale comparable to the intrinsic liquid density relaxation time. The magnitudes of the dynamic surface tensions are found being modulated sharply within picoseconds after the irradiation, due to the development of the nanometer scale non-hydrostatic regime behind the exterior atomic layer of the liquid surfaces.The reported novel regulation mechanism of the liquid surface stress field and the dynamic surface tension hints at levitating the manipulation of liquid surfaces, such as ultrafast steering the surface directional transport and patterning.展开更多
Laser processing with high-power ultrashort pulses,which promises high precision and efficiency,is an emerging new tool for material structuring.High repetition rate ultrafast laser highlighting with a higher degree o...Laser processing with high-power ultrashort pulses,which promises high precision and efficiency,is an emerging new tool for material structuring.High repetition rate ultrafast laser highlighting with a higher degree of freedom in its burst mode is believed to be able to create micro/nanostructures with even more variety,which is promising for electrochemical applications.We employ a homemade high repetition rate ultrafast fiber laser for structuring metal nickel(Ni)and thus preparing electrocatalysts for hydrogen evolution reaction(HER)for the first time,we believe.Different processing parameters are designed to create three groups of samples with different micro/nanostructures.The various micro/nanostructures not only increase the surface area of the Ni electrode but also regulate local electric field and help discharge hydrogen bubbles,which offer more favorable conditions for HER.All groups of the laser-structured Ni exhibit enhanced electrocatalytic activity for HER in the alkaline solution.Electrochemical measurements demonstrate that the overpotential at 10 mAcm−2 can be decreased as much as 182 mV compared with the overpotential of the untreated Ni(−457 mV versus RHE).展开更多
The ultrafast thermomechanical coupling problem in a thin gold film irradiated by ultrashort laser pulses with different electron ballistic depths is investigated via the ultrafast thermoelasticity model. The solution...The ultrafast thermomechanical coupling problem in a thin gold film irradiated by ultrashort laser pulses with different electron ballistic depths is investigated via the ultrafast thermoelasticity model. The solution of the problem is obtained by solving finite element governing equations. The comparison between the results of ultrafast thermomechanical coupling responses with different electron ballistic depths is made to show the ballistic electron effect. It is found that the ballistic electrons have a significant influence on the ultrafast thermomechanical coupling behaviors of the gold thin film and the best laser micromachining results can be achieved by choosing the specific laser technology（large or small ballistic range）.In addition, the influence of simplification of the ultrashort laser pulse source on the results is studied, and it is found that the simplification has a great influence on the thermomechanical responses, which implies that care should be taken when the simplified form of the laser source term is applied as the Gaussian heat source.展开更多
Precision sculpting of glass with defined surface microstructures is vital due to the miniaturization and integration of glass-based devices,while it is still challenging as the high brittleness of glass.We here creat...Precision sculpting of glass with defined surface microstructures is vital due to the miniaturization and integration of glass-based devices,while it is still challenging as the high brittleness of glass.We here create a three-dimensional multifocus laser for glass micro-sculpting through a beam-shaping technology based on the superposition of lens and grating phase diagrams.The multi-focus laser modification in tandem with chemical etching enables the fabrication of glass microstructures with highly adjustable profiles.Refractive-index-induced deviations are migrated via algorithm correction to ensure multi-focus positional accuracy.Energy un-uniformity due to equidistant laser spots arrangement is eliminated through their coordinate randomization following the target profiles.Finally,uniform laser spots with a proper point-topoint distance create connected cracks inside glass,enabling efficient etching with enhanced rates along the modified profile and the fabrication of surface microstructures.We demonstrate diverse groove arrays with profiles of trapezoid,semicircle,and triangle,revealing low roughness around 1.3μm,a high depth-width ratio of 3:1,and depth up to 300μm,which underscore broad applications such as fiber packaging.展开更多
The performance of ultrafast semiconductor disk lasers has rapidly advanced in recent decades.The strong interest from industry for inexpensive,compact,and reliable ultrafast laser sources in the picosecond and femtos...The performance of ultrafast semiconductor disk lasers has rapidly advanced in recent decades.The strong interest from industry for inexpensive,compact,and reliable ultrafast laser sources in the picosecond and femtosecond domains has driven this technology toward commercial products.Frequency metrology and biomedical applications would benefit from sub-200-femtosecond pulse durations with peak powers in the kilowatt range.The aim of this review is to briefly describe the market potential and give an overview of the current status of mode-locked semiconductor disk lasers.Particular focus is placed on the ongoing efforts to achieve shorter pulses with higher peak powers.展开更多
We report a high-stability ultrafast ultraviolet(UV)laser source at 352 nm by exploring an all-fiber,all-polarizationmaintaining(all-PM),Yb-doped femtosecond fiber laser at 1060 nm.The output power,pulse width,and opt...We report a high-stability ultrafast ultraviolet(UV)laser source at 352 nm by exploring an all-fiber,all-polarizationmaintaining(all-PM),Yb-doped femtosecond fiber laser at 1060 nm.The output power,pulse width,and optical spectrum width of the fiber laser are 6 W,244 fs,and 17.5 nm,respectively.The UV ultrashort pulses at a repetition rate of 28.9 MHz are generated by leveraging single-pass second-harmonic generation in a 1.3-mm-long BiB_(3)O_(6)(BIBO)and sum frequency generation in a 5.1-mm-long BIBO.The maximum UV output power is 596 mW.The root mean square error of the output power of UV pulses is 0.54%.This laser,with promising stability,is expected to be a nice source for frontier applications in the UV wavelength window.展开更多
To overcome the shortcomings of the single-shot autocorrelation SSA where only one pulse width is obtained when the SSA is applied to measure the pulse width of ultrashort laser pulses a modified SSA for measuring the...To overcome the shortcomings of the single-shot autocorrelation SSA where only one pulse width is obtained when the SSA is applied to measure the pulse width of ultrashort laser pulses a modified SSA for measuring the spatiotemporal characteristics of ultrashort laser pulses at different spatial positions is proposed. The spatiotemporal characteristics of femtosecond laser pulses output from the Ti sapphire regenerative amplifier system are experimentally measured by the proposed method. It was found that the complex spatial characteristics are measured accurately.The pulse widths at different spatial positions are various which obey the Gaussian distribution.The pulse width at the same spatial position becomes narrow with the increase in input average power when femtosecond laser pulses pass through a carbon disulfide CS2 nonlinear medium.The experimental results verify that the proposed method is valid for measuring the spatiotemporal characteristics of ultrashort laser pulses at different spatial positions.展开更多
Infrared to visible upconversion luminescence was demonstrated in trivalent Europium doped Ca2Al2SiO7 crystal （Eu^3＋：Ca2Al2SiO7） irradiated by focused infrared femtosecond laser. The upconversion luminescence orig...Infrared to visible upconversion luminescence was demonstrated in trivalent Europium doped Ca2Al2SiO7 crystal （Eu^3＋：Ca2Al2SiO7） irradiated by focused infrared femtosecond laser. The upconversion luminescence originated from 5D0 to 7Ej （j= 1, 2） transitions of Eu^3＋ The relationship between the upconversion luminescence intensity and the pump power indicated that the upconversion from near-infrared to red is dominated by a two-photon absorption process of Eu^3＋ Analysis suggested that two-photon simultaneous absorption induced population inversion should be the predominant frequency upconversion mechanism.展开更多
Usually,only focused femtosecond(fs)lasers at near-infrared(NIR)range can induce photo-damage to transparent cells,making it difficult to treat large amount of cells by such optical methods for photostimulation.In thi...Usually,only focused femtosecond(fs)lasers at near-infrared(NIR)range can induce photo-damage to transparent cells,making it difficult to treat large amount of cells by such optical methods for photostimulation.In this study,we clarify the mechanism of photodamage to cells that are co-cultured with gold nanorods(GNRs)by fs laser.The pulse duration and repetition rate of the fs laser play a key role in cell damage suggesting that the heat accumulation con-tributes to the major part for the cell damage rather than the high peak power which mainly determines the efficiency of multiphoton excitation.We further show that cellular Ca^(2+)can also be released in this scheme,but the process is more sensitive to peak power.Our results can provide a large-scale GNR-mediated photostimulation for cell signaling modulation.展开更多
Long-term optical data storage(ODS)technology is essential to break the bottleneck of high energy consumption for information storage in the current era of big data.Here,ODS with an ultralong lifetime of 2×10^(7)...Long-term optical data storage(ODS)technology is essential to break the bottleneck of high energy consumption for information storage in the current era of big data.Here,ODS with an ultralong lifetime of 2×10^(7)years is attained with single ultrafast laser pulse induced reduction of Eu^(3+)ions and tailoring of optical properties inside the Eu-doped aluminosilicate glasses.We demonstrate that the induced local modifications in the glass can stand against the temperature of up to 970 K and strong ultraviolet light irradiation with the power density of 100 kW/cm^(2).Furthermore,the active ions of Eu^(2+)exhibit strong and broadband emission with the full width at half maximum reaching 190 nm,and the photoluminescence(PL)is flexibly tunable in the whole visible region by regulating the alkaline earth metal ions in the glasses.The developed technology and materials will be of great significance in photonic applications such as long-term ODS.展开更多
By using first-principles simulations based on time-dependent density functional theory,the chemical reaction of an HCl molecule encapsulated in C60induced by femtosecond laser pulses is observed.The H atom starts to ...By using first-principles simulations based on time-dependent density functional theory,the chemical reaction of an HCl molecule encapsulated in C60induced by femtosecond laser pulses is observed.The H atom starts to leave the Cl atom and is reflected by the C60wall.The coherent nuclear dynamic behaviors of bond breakage and recombination of the HCl molecule occurring in both polarized parallel and perpendicular to the H–Cl bond axis are investigated.The radial oscillation is also found in the two polarization directions of the laser pulse.The relaxation time of the H–Cl bond lengths in transverse polarization is slow in comparison with that in longitudinal polarization.Those results are important for studying the dynamics of the chemical bond at an atomic level.展开更多
A compact all-fiber polarization-maintaining Er:laser using a nonlinear amplifying loop mirror is reported. Fundamental single-pulse mode-locking operation can always self start, with a cavity round-trip decreased fro...A compact all-fiber polarization-maintaining Er:laser using a nonlinear amplifying loop mirror is reported. Fundamental single-pulse mode-locking operation can always self start, with a cavity round-trip decreased from ~ 4.7 m to~ 1.7 m. When the pulse repetition rate is 121.0328 MHz, output pulse is measured to have a center wavelength/3-d B spectral bandwidth/radio frequency signal to noise ratio(SNR)/pulse width of 1571.65 nm/18.70 nm/80 d B/477 fs, respectively. Besides, three states including the exponential growth, damping state, and steady state are investigated through the build-up process both experimentally and numerically. Excellent stability of this compact Er:laser is further evaluated,demonstrating that it can be an easy-fabrication maintenance-free ultrafast candidate for the scientific area of this kind.展开更多
Saturable absorbers(SAs)covering wavelengths from near-infrared(NIR)to mid-infrared(MIR)band are required for mode-locking and Q-switching lasers in muti-band wavelengths.Here,broadband nonlinear optical property was ...Saturable absorbers(SAs)covering wavelengths from near-infrared(NIR)to mid-infrared(MIR)band are required for mode-locking and Q-switching lasers in muti-band wavelengths.Here,broadband nonlinear optical property was discovered in Cs_(x)WO_(3) nanorods(NRs),which as a novel non-stoichiometric SA for realizing ultrafast fiber lasers is first demonstrated.The Cs_(x)WO_(3) NRs based SA exhibited good mode-locking ability in three key wavelengths from NIR to MIR region,which is a key advantage over the most reported broadband SAs.The given Cs_(x)WO_(3) NRs showed a broadband optical absorption from 800 to 3,200 nm,and excellent SA properties at 1-μm,1.5-μm,and 2-μm optical bands.Employing such SA,the ultrashort pulse lasers with a pulse duration/repetition rate of 530 fs/37.42 MHz at 1,567 nm and 5.6 ps/41.50 MHz at 1,965 nm from Er-and Tm-doped fiber lasers(TDFL)were realized separately.In addition,a stable mode locked operation at 1,030 nm with a repetition rate of 48.80 MHz was also achieved from Yb-doped fiber laser(YDFL).This work not only offers a new and reliable broadband mode locker for ultrafast laser generation,but also broadens the application of Cs_(x)WO_(3) materials in the field of nonlinear fiber optics.展开更多
This paper demonstrates an approach that negative uniaxial crystal has a relative anomalous dispersion effect which can compensate group velocity delay, and applies this approach to nonlinear frequency conversion of a...This paper demonstrates an approach that negative uniaxial crystal has a relative anomalous dispersion effect which can compensate group velocity delay, and applies this approach to nonlinear frequency conversion of an ultrafast laser field. High efficiency of the third harmonic generation is experimentally fulfilled by adopting a collinear configuration of doubing-compensation-tripling system. Through finely adjusting the incident angle and optical axis direction of the compensation plate, it obtains ultraviolet （UV） output energy of 0.32 mJ centered at 270 nm with spectral bandwidth of 2 nm when input beam at 800 nm was 70 fs pulse duration and 6 mJ pulse energy which was extracted from Ti：sapphire laser system by a diaphragm, corresponding to an 800-to-270 nm conversion efficiency of 5.3% and a factor-of-l.6 improvement in the third harmonic generation of UV band in comparison with a general conventional configuration. Furthermore, when the full energy of 18 mJ from a Ti：sapphire laser system was used and optimized, the UV emission could reach 0.83 mJ.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61378025 and 61427812)the Shuangchuang Team Program of Jiangsu Province,China,the National Key Basic Research Program of China(Grant No.2014CB921101)the State Key Laboratory of Advanced Optical Communication Systems Networks,China
文摘As the fundamental optical properties and novel photophysics of graphene and related two-dimensional （2D） crystals are being extensively investigated and revealed, a range of potential applications in optical and optoelectronic devices have been proposed and demonstrated. Of the many possibilities, the use of 2D materials as broadband, cost-effective and versatile ultrafast optical switches （or saturable absorbers） for short-pulsed lasers constitutes a rapidly developing field with not only a good number of publications, but also a promising prospect for commercial exploitation. This review primarily focuses on the recent development of pulsed lasers based on several representative 2D materials. The comparative advantages of these materials are discussed, and challenges to practical exploitation, which represent good future directions of research, are laid out.
基金supported by the National Key Research and Development Program of China(2022YFB3605800)National Natural Science Foundation of China(62105225,62275174,61975136,61935014)+3 种基金Shenzhen University Stability Support Project(20220719104008001)Natural Science Foundation of Top Talent of Shenzhen Technology University(GDRC202106)Pingshan Special Funds for Scientific and Technological Innovation(PSKG202003,PSKG202007)Guangdong Provincial Engineering Technology Research Center for Materials for Advanced MEMS Sensor Chip(2022GCZX005)。
文摘We report on an improved ytterbium-doped yttrium aluminum garnet thin-disk multi-pass amplifier for kilowatt-level ultrafast lasers,showcasing excellent beam quality.At a repetition rate of 800 kHz,the 6.8 ps,276 W seed laser is amplified up to an average power of 1075 W,corresponding to a pulse energy of 1.34 mJ.The 36-pass amplifier is designed as a compact mirror array in which the beam alternately propagates between the mirrors and the disk by a quasi-collimated state.We adopted a quasi-collimated propagation to confine stray and diffracted light by the slight curvature of the disk,which enables us to achieve an outstanding extraction efficiency of up to 57%with excellent beam quality in stable laser operation at high power.The beam quality at 1075 W was measured to be M^(2)<1.51.Furthermore,stability testing was demonstrated with a root-mean-square power fiuctuation of less than 1.67%for 10 min.
基金supported by the National Natural Science Foundation of China (Nos.61905148,61775146,and 12074264)the Shenzhen Science and Technology Project (Nos.JCYJ20190808160205460,JCYJ20190808174201658,and JCYJ20190808141011530)。
文摘As one of the greatest inventions in the 20 th century, ultrafast lasers have offered new opportunities in the areas of basic scientific research and industrial manufacturing. Optical modulators are of great importance in ultrafast lasers, which directly affect the output laser performances. Over the past decades, significant efforts have been made in the development of compact, controllable, repeatable, as well as integratable optical modulators(i.e., saturable absorbers). In this paper, we review the fundamentals of the most widely studied saturable absorbers, including semiconductor saturable absorber mirrors and low-dimensional nanomaterials. Then, different fabrication technologies for saturable absorbers and their ultrafast laser applications in a wide wavelength range are illustrated. Furthermore, challenges and perspectives for the future development of saturable absorbers are discussed and presented. The development of ultrafast lasers together with the continuous exploration of reliable saturable absorbers will open up new directions for the mass production of the nextgeneration optoelectronic devices.
文摘The unique characteristics of ultrafast lasers,such as picosecond and femtosecond lasers,have opened up new avenues in materials processing that employ ultrashort pulse widths and extremely high peak intensities.Thus,ultrafast lasers are currently used widely for both fundamental research and practical applications.This review describes the characteristics of ultrafast laser processing and the recent advancements and applications of both surface and volume processing.Surface processing includes micromachining,microand nanostructuring,and nanoablation,while volume processing includes two-photon polymerization and three-dimensional(3D)processing within transparent materials.Commercial and industrial applications of ultrafast laser processing are also introduced,and a summary of the technology with future outlooks are also given.
基金supported by the National Key Research and Development Program of China(2020YFA0715000)the Guangdong Basic and Applied Basic Research Foundation(2020A1515110250,2021B1515120041)+1 种基金the Foshan Xianhu Laboratory of the Advanced Energy Science and Technology Guangdong Laboratory(XHT2020-005)the Fundamental Research Funds for the Central Universities(2020IVA068,2021lll007JC)
文摘Because poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate)(PEDOT:PSS)is water processable,thermally stable,and highly conductive,PEDOT:PSS and its composites have been considered to be one of the most promising flexible thermoelectric materials.However,the PEDOT:PSS film prepared from its commercial aqueous dispersion usually has very low conductivity,thus cannot be directly utilized for TE applications.Here,a simple environmental friendly strategy via femtosecond laser irradiation without any chemical dopants and treatments was demonstrated.Under optimal conditions,the electrical conductivity of the treated film is increased to 803.1 S cm^(-1)from 1.2 S cm^(-1)around three order of magnitude higher,and the power factor is improved to 19.0μW m^(-1)K^(-2),which is enhanced more than 200 times.The mechanism for such remarkable enhancement was attributed to the transition of the PEDOT chains from a coil to a linear or expanded coil conformation,reduction of the interplanar stacking distance,and the removal of insulating PSS with increasing the oxidation level of PEDOT,facilitating the charge transportation.This work presents an effective route for fabricating high-performance flexible conductive polymer films and wearable thermoelectric devices.
基金This research has received funding from the European Research Council(ERC)under the European Union’s Horizon 2020 research and innovation program(Grant Agreement No.724480).
文摘Ultrafast laser inscription(ULI)inside semiconductors offers new perspectives for 3D monolithic structures to be fabricated and new functionalities to be added in electronic and photonic microdevices.However,important challenges remain because of nonlinear effects such as strong plasma generation that distort the energy delivery at the focal point when exposing these materials to intense infrared light.Up to now,the successful technological demonstrations have primarily concentrated on silicon(Si).In this paper,we target at another important semiconductor:gallium arsenide(GaAs).With nonlinearities higher than those of Si,3D-machining of GaAs with femtosecond pulses becomes even harder.However,we show that the difficulty can be circumvented by burst-mode irradiation.We generate and apply trains of pulses at terahertz repetition rates for efficient pulse-to-pulse accumulation of laser-induced free carriers in the focal region,while avoiding an overdose of prefocal excitations.The superior performance of burst-mode irradiation is confirmed by a comparative study conducted with infrared luminescence microscopy.The results indicate a successful reduction of the plasma density in the prefocal region so that higher pulse energy reaches the focal spot.The same method is applied to identify optimum irradiation conditions considering particular cases such as asymmetric pulse trains and aberrated beams.With 64-pulse trains,we successfully manage to cross the writing threshold providing a solution for ULI inside GaAs.The application potential is finally illustrated with a stealth dicing demonstration by taking benefit of the burst mode.The irradiation method opens wide possibilities for 3D structuring inside GaAs by ULI.
基金the National Key R&D Program of China (Grant No. 2019YFA0705000)the National Natural Science Foundation of China (Grant Nos. 11874147, 11933005, and 12134001)+3 种基金the Science and Technology Commission of Shanghai Municipality (Grant No. 21DZ1101500)the Shanghai Municipal Science and Technology Major Project (Grant No. 2019SHZDZX01)the Natural Science Foundation of Chongqing, China (Grant No. cstc2021jcyj-msxm X1144)the State Key Laboratory of Solidification Processing in NWPU (Grant No. SKLSP202105)。
文摘We predict ultrafast modulation of the pure molten metal surface stress fields under the irradiation of the single femtosecond laser pulse through the two-temperature model molecular-dynamics simulations. High-resolution and precision calculations are used to resolve the ultrafast laser-induced anisotropic relaxations of the pressure components on the time-scale comparable to the intrinsic liquid density relaxation time. The magnitudes of the dynamic surface tensions are found being modulated sharply within picoseconds after the irradiation, due to the development of the nanometer scale non-hydrostatic regime behind the exterior atomic layer of the liquid surfaces.The reported novel regulation mechanism of the liquid surface stress field and the dynamic surface tension hints at levitating the manipulation of liquid surfaces, such as ultrafast steering the surface directional transport and patterning.
基金supported by the National Natural Science Foundation of China(Grant Nos.62375087,12374304,and 62235014)the NSFC Development of National Major Scientific Research Instrument(Grant No.61927816)+3 种基金the Mobility Programme of the Sino-German(Grant No.M-0296)the Introduced Innovative Team Project of Guangdong Pearl River Talents Program(Grant No.2021ZT09Z109)the Natural Science Foundation of Guangdong Province(Grant No.2021B1515020074)the Science and Technology Project of Guangdong(Grant No.2020B1212060002).
文摘Laser processing with high-power ultrashort pulses,which promises high precision and efficiency,is an emerging new tool for material structuring.High repetition rate ultrafast laser highlighting with a higher degree of freedom in its burst mode is believed to be able to create micro/nanostructures with even more variety,which is promising for electrochemical applications.We employ a homemade high repetition rate ultrafast fiber laser for structuring metal nickel(Ni)and thus preparing electrocatalysts for hydrogen evolution reaction(HER)for the first time,we believe.Different processing parameters are designed to create three groups of samples with different micro/nanostructures.The various micro/nanostructures not only increase the surface area of the Ni electrode but also regulate local electric field and help discharge hydrogen bubbles,which offer more favorable conditions for HER.All groups of the laser-structured Ni exhibit enhanced electrocatalytic activity for HER in the alkaline solution.Electrochemical measurements demonstrate that the overpotential at 10 mAcm−2 can be decreased as much as 182 mV compared with the overpotential of the untreated Ni(−457 mV versus RHE).
基金Project supported by the National Natural Science Foundation of China(Grant No.11502085)the Natural Science Foundation of Hubei Province,China(Grant No.2016CFB542)+1 种基金the Fundamental Research Funds for the Central Universities,China(Grant No.2016YXMS097)the Research Fund of State Key Laboratory of Mechanics and Control of Mechanical Structures(NUAA),China(Grant No.0315K01)
文摘The ultrafast thermomechanical coupling problem in a thin gold film irradiated by ultrashort laser pulses with different electron ballistic depths is investigated via the ultrafast thermoelasticity model. The solution of the problem is obtained by solving finite element governing equations. The comparison between the results of ultrafast thermomechanical coupling responses with different electron ballistic depths is made to show the ballistic electron effect. It is found that the ballistic electrons have a significant influence on the ultrafast thermomechanical coupling behaviors of the gold thin film and the best laser micromachining results can be achieved by choosing the specific laser technology（large or small ballistic range）.In addition, the influence of simplification of the ultrashort laser pulse source on the results is studied, and it is found that the simplification has a great influence on the thermomechanical responses, which implies that care should be taken when the simplified form of the laser source term is applied as the Gaussian heat source.
基金National Natural Science Foundation of China(Grant No.52375438)Shenzhen Science and Technology Programs(Grant No.JCYJ20220818100408019,JSGG20220831101401003)Jiangyin-SUSTech Innovation Fund.
文摘Precision sculpting of glass with defined surface microstructures is vital due to the miniaturization and integration of glass-based devices,while it is still challenging as the high brittleness of glass.We here create a three-dimensional multifocus laser for glass micro-sculpting through a beam-shaping technology based on the superposition of lens and grating phase diagrams.The multi-focus laser modification in tandem with chemical etching enables the fabrication of glass microstructures with highly adjustable profiles.Refractive-index-induced deviations are migrated via algorithm correction to ensure multi-focus positional accuracy.Energy un-uniformity due to equidistant laser spots arrangement is eliminated through their coordinate randomization following the target profiles.Finally,uniform laser spots with a proper point-topoint distance create connected cracks inside glass,enabling efficient etching with enhanced rates along the modified profile and the fabrication of surface microstructures.We demonstrate diverse groove arrays with profiles of trapezoid,semicircle,and triangle,revealing low roughness around 1.3μm,a high depth-width ratio of 3:1,and depth up to 300μm,which underscore broad applications such as fiber packaging.
基金The authors acknowledge support of the technology and cleanroom facility FIRST of ETH Zurich for advanced micro-and nanotechnologyThis work was financed by the Swiss Confederation Program Nano-Tera.ch,which was scientifically evaluated by the Swiss National Science Foundation(SNSF).
文摘The performance of ultrafast semiconductor disk lasers has rapidly advanced in recent decades.The strong interest from industry for inexpensive,compact,and reliable ultrafast laser sources in the picosecond and femtosecond domains has driven this technology toward commercial products.Frequency metrology and biomedical applications would benefit from sub-200-femtosecond pulse durations with peak powers in the kilowatt range.The aim of this review is to briefly describe the market potential and give an overview of the current status of mode-locked semiconductor disk lasers.Particular focus is placed on the ongoing efforts to achieve shorter pulses with higher peak powers.
基金partially supported by the National Natural Science Foundation of China(NSFC)(Nos.62375087,12374304,U1609219,and 62235014)the NSFC Development of National Major Scientific Research Instrument(No.61927816)+3 种基金the Mobility Programme of the Sino-German(No.M-0296)the Introduced Innovative Team Project of Guangdong Pearl River Talents Program(No.2021ZT09Z109)the Natural Science Foundation of Guangdong Province(No.2021B1515020074)the Science and Technology Project of Guangdong(No.2020B1212060002)。
文摘We report a high-stability ultrafast ultraviolet(UV)laser source at 352 nm by exploring an all-fiber,all-polarizationmaintaining(all-PM),Yb-doped femtosecond fiber laser at 1060 nm.The output power,pulse width,and optical spectrum width of the fiber laser are 6 W,244 fs,and 17.5 nm,respectively.The UV ultrashort pulses at a repetition rate of 28.9 MHz are generated by leveraging single-pass second-harmonic generation in a 1.3-mm-long BiB_(3)O_(6)(BIBO)and sum frequency generation in a 5.1-mm-long BIBO.The maximum UV output power is 596 mW.The root mean square error of the output power of UV pulses is 0.54%.This laser,with promising stability,is expected to be a nice source for frontier applications in the UV wavelength window.
基金The National Natural Science Foundation of China(No.61171081,No.61471164)the Natural Science Foundation of Hunan Province(No.14JJ6043)
文摘To overcome the shortcomings of the single-shot autocorrelation SSA where only one pulse width is obtained when the SSA is applied to measure the pulse width of ultrashort laser pulses a modified SSA for measuring the spatiotemporal characteristics of ultrashort laser pulses at different spatial positions is proposed. The spatiotemporal characteristics of femtosecond laser pulses output from the Ti sapphire regenerative amplifier system are experimentally measured by the proposed method. It was found that the complex spatial characteristics are measured accurately.The pulse widths at different spatial positions are various which obey the Gaussian distribution.The pulse width at the same spatial position becomes narrow with the increase in input average power when femtosecond laser pulses pass through a carbon disulfide CS2 nonlinear medium.The experimental results verify that the proposed method is valid for measuring the spatiotemporal characteristics of ultrashort laser pulses at different spatial positions.
基金Funded by the National Natural Science Foundation of China (No.50672087 and No.60778039)National Basic Research Program of China (No.2006CB806000)National High Technology Program of China (No.2006AA03Z304)
文摘Infrared to visible upconversion luminescence was demonstrated in trivalent Europium doped Ca2Al2SiO7 crystal （Eu^3＋：Ca2Al2SiO7） irradiated by focused infrared femtosecond laser. The upconversion luminescence originated from 5D0 to 7Ej （j= 1, 2） transitions of Eu^3＋ The relationship between the upconversion luminescence intensity and the pump power indicated that the upconversion from near-infrared to red is dominated by a two-photon absorption process of Eu^3＋ Analysis suggested that two-photon simultaneous absorption induced population inversion should be the predominant frequency upconversion mechanism.
基金from National Natural Science Foundation of China(NSFC)81571719,61322502Open Project of State Key Laboratory of Modern Optical Instrumentation,Zhejiang University,and Program for Changjiang Scholars and Innovative Research Team in Uni-versity IRT13033.
文摘Usually,only focused femtosecond(fs)lasers at near-infrared(NIR)range can induce photo-damage to transparent cells,making it difficult to treat large amount of cells by such optical methods for photostimulation.In this study,we clarify the mechanism of photodamage to cells that are co-cultured with gold nanorods(GNRs)by fs laser.The pulse duration and repetition rate of the fs laser play a key role in cell damage suggesting that the heat accumulation con-tributes to the major part for the cell damage rather than the high peak power which mainly determines the efficiency of multiphoton excitation.We further show that cellular Ca^(2+)can also be released in this scheme,but the process is more sensitive to peak power.Our results can provide a large-scale GNR-mediated photostimulation for cell signaling modulation.
基金supports from the National Key R&D Program of China (No. 2021YFB2802000 and 2021YFB2800500)the National Natural Science Foundation of China (Grant Nos. U20A20211, 51902286, 61775192, 61905215, and 62005164)+2 种基金Key Research Project of Zhejiang Labthe State Key Laboratory of High Field Laser Physics (Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences)China Postdoctoral Science Foundation (2021M702799)。
文摘Long-term optical data storage(ODS)technology is essential to break the bottleneck of high energy consumption for information storage in the current era of big data.Here,ODS with an ultralong lifetime of 2×10^(7)years is attained with single ultrafast laser pulse induced reduction of Eu^(3+)ions and tailoring of optical properties inside the Eu-doped aluminosilicate glasses.We demonstrate that the induced local modifications in the glass can stand against the temperature of up to 970 K and strong ultraviolet light irradiation with the power density of 100 kW/cm^(2).Furthermore,the active ions of Eu^(2+)exhibit strong and broadband emission with the full width at half maximum reaching 190 nm,and the photoluminescence(PL)is flexibly tunable in the whole visible region by regulating the alkaline earth metal ions in the glasses.The developed technology and materials will be of great significance in photonic applications such as long-term ODS.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11074176 and 10976019)the Doctoral Program of Higher Education of China(Grant No.20100181110080)
文摘By using first-principles simulations based on time-dependent density functional theory,the chemical reaction of an HCl molecule encapsulated in C60induced by femtosecond laser pulses is observed.The H atom starts to leave the Cl atom and is reflected by the C60wall.The coherent nuclear dynamic behaviors of bond breakage and recombination of the HCl molecule occurring in both polarized parallel and perpendicular to the H–Cl bond axis are investigated.The radial oscillation is also found in the two polarization directions of the laser pulse.The relaxation time of the H–Cl bond lengths in transverse polarization is slow in comparison with that in longitudinal polarization.Those results are important for studying the dynamics of the chemical bond at an atomic level.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61805282,11802339,and 11504420)the Opening Foundation of State Key Laboratory of High Performance Computing,China(Grant No.201601-02)+2 种基金the Open Research Fund of Hunan Provincial Key Laboratory of High Energy Technology,China(Grant No.GNJGJS03)the Opening Foundation of State Key Laboratory of Laser Interaction with Matter,China(Grant No.SKLLIM1702)the China Postdoctoral Innovation Science Foundation(Grant No.BX20180373)
文摘A compact all-fiber polarization-maintaining Er:laser using a nonlinear amplifying loop mirror is reported. Fundamental single-pulse mode-locking operation can always self start, with a cavity round-trip decreased from ~ 4.7 m to~ 1.7 m. When the pulse repetition rate is 121.0328 MHz, output pulse is measured to have a center wavelength/3-d B spectral bandwidth/radio frequency signal to noise ratio(SNR)/pulse width of 1571.65 nm/18.70 nm/80 d B/477 fs, respectively. Besides, three states including the exponential growth, damping state, and steady state are investigated through the build-up process both experimentally and numerically. Excellent stability of this compact Er:laser is further evaluated,demonstrating that it can be an easy-fabrication maintenance-free ultrafast candidate for the scientific area of this kind.
基金This work was supported by the Specialized Fund for the Doctoral Research of Jilin Engineering Normal University under(No.BSKJ201920)the Science and Technology Research Project of Jilin Province's Education Department(No.JJKH20210175KJ)the Project of Science and Technology Plan of Jilin Province(No.YDZJ202101ZYTS178)。
文摘Saturable absorbers(SAs)covering wavelengths from near-infrared(NIR)to mid-infrared(MIR)band are required for mode-locking and Q-switching lasers in muti-band wavelengths.Here,broadband nonlinear optical property was discovered in Cs_(x)WO_(3) nanorods(NRs),which as a novel non-stoichiometric SA for realizing ultrafast fiber lasers is first demonstrated.The Cs_(x)WO_(3) NRs based SA exhibited good mode-locking ability in three key wavelengths from NIR to MIR region,which is a key advantage over the most reported broadband SAs.The given Cs_(x)WO_(3) NRs showed a broadband optical absorption from 800 to 3,200 nm,and excellent SA properties at 1-μm,1.5-μm,and 2-μm optical bands.Employing such SA,the ultrashort pulse lasers with a pulse duration/repetition rate of 530 fs/37.42 MHz at 1,567 nm and 5.6 ps/41.50 MHz at 1,965 nm from Er-and Tm-doped fiber lasers(TDFL)were realized separately.In addition,a stable mode locked operation at 1,030 nm with a repetition rate of 48.80 MHz was also achieved from Yb-doped fiber laser(YDFL).This work not only offers a new and reliable broadband mode locker for ultrafast laser generation,but also broadens the application of Cs_(x)WO_(3) materials in the field of nonlinear fiber optics.
基金Project supported by the National Basic Research Program of China (Grant No 2006CB0806001)the Program for Changjiang and Innovative Research Team in UniversityShanghai Leading Academic Discipline Project (Grant No B408)
文摘This paper demonstrates an approach that negative uniaxial crystal has a relative anomalous dispersion effect which can compensate group velocity delay, and applies this approach to nonlinear frequency conversion of an ultrafast laser field. High efficiency of the third harmonic generation is experimentally fulfilled by adopting a collinear configuration of doubing-compensation-tripling system. Through finely adjusting the incident angle and optical axis direction of the compensation plate, it obtains ultraviolet （UV） output energy of 0.32 mJ centered at 270 nm with spectral bandwidth of 2 nm when input beam at 800 nm was 70 fs pulse duration and 6 mJ pulse energy which was extracted from Ti：sapphire laser system by a diaphragm, corresponding to an 800-to-270 nm conversion efficiency of 5.3% and a factor-of-l.6 improvement in the third harmonic generation of UV band in comparison with a general conventional configuration. Furthermore, when the full energy of 18 mJ from a Ti：sapphire laser system was used and optimized, the UV emission could reach 0.83 mJ.
