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| 1 | Femtosecond Laser Precision Engineering: From Micron, Submicron, to Nanoscale显示文摘As a noncontact strategy with flexible tools and high efficiency,laser precision engineering is a significant advanced processing way for high-quality micro-/nanostructure fabrication,especially to achieve novel functional photoelectric structures and devices.For the microscale creation,several femtosecond laser fabrication methods,including multiphoton absorption,laserinduced plasma-assisted ablation,and incubation effect have been developed.Meanwhile,the femtosecond laser can be combined with microlens arrays and interference lithography techniques to achieve the structures in submicron scales.Down to nanoscale feature sizes,advanced processing strategies,such as near-field scanning optical microscope,atomic force microscope,and microsphere,are applied in femtosecond laser processing and the minimum nanostructure creation has been pushed down to~25 nm due to near-field effect.The most fascinating femtosecond laser precision engineering is the possibility of large-area,high-throughput,and far-field nanofabrication.In combination with special strategies,including dual femtosecond laser beam irradiation,~15 nm nanostructuring can be achieved directly on silicon surfaces in far field and in ambient air.The challenges and perspectives in the femtosecond laser precision engineering are also discussed. | Zhenyuan Lin Minghui Hong | 2021 | Ultrafast Science2021，，1： | 13 |
| 2 | High-Sensitivity Gas Detection with Air-Lasing-Assisted Coherent Raman Spectroscopy显示文摘Remote or standoff detection of greenhouse gases,air pollutants,and biological agents with innovative ultrafast laser technology attracts growing interests in recent years.Hybrid femtosecond/picosecond coherent Raman spectroscopy is considered as one of the most versatile techniques due to its great advantages in terms of detection sensitivity and chemical specificity.However,the simultaneous requirement for the femtosecond pump and the picosecond probe increases the complexity of optical system.Herein,we demonstrate that air lasing naturally created inside a filament can serve as an ideal light source to probe Raman coherence excited by the femtosecond pump,producing coherent Raman signal with molecular vibrational signatures.The combination of pulse self-compression effect and air lasing action during filamentation improves Raman excitation efficiency and greatly simplifies the experimental setup.The air-lasing-assisted Raman spectroscopy was applied to quantitatively detect greenhouse gases mixed in air,and it was found that the minimum detectable concentrations of CO_(2) and SF_(6) can reach 0.1%and 0.03%,respectively.The ingenious designs,especially the optimization of pump-seed delay and the choice of perpendicular polarization,ensure a high detection sensitivity and signal stability.Moreover,it is demonstrated that this method can be used for simultaneously measuring CO_(2) and SF_(6) gases and distinguishing ^(12)CO_(2) and ^(13)CO_(2).The developed scheme provides a new route for high-sensitivity standoff detection and combustion diagnosis. | Zhihao Zhang Fangbo Zhang Bo Xu Hongqiang Xie Botao Fu Xu Lu Ning Zhang Shupeng Yu Jinping Yao Ya Cheng Zhizhan Xu | 2022 | Ultrafast Science2022，，2： | 4 |
| 3 | Broadband THz Sources from Gases to Liquids显示文摘Matters are generally classified within four states:solid,liquid,gas,and plasma.Three of the four states of matter(solid,gas,and plasma)have been used for THz wave generation with short laser pulse excitation for decades,including the recent vigorous development of THz photonics in gases(air plasma).However,the demonstration of THz generation from liquids was conspicuously absent.It is well known that water,the most common liquid,is a strong absorber in the far infrared range.Therefore,liquid water has historically been sworn off as a source for THz radiation.Recently,broadband THz wave generation from a flowing liquid target has been experimentally demonstrated through laser-induced microplasma.The liquid target as the THz source presents unique properties.Specifically,liquids have the comparable material density to that of solids,meaning that laser pulses over a certain area will interact with three orders more molecules than an equivalent cross-section of gases.In contrast with solid targets,the fluidity of liquid allows every laser pulse to interact with a fresh area on the target,meaning that material damage or degradation is not an issue with the high-repetition rate intense laser pulses.These make liquids very promising candidates for the investigation of high-energy-density plasma,as well as the possibility of being the next generation of THz sources. | Yiwen E Liangliang Zhang Anton Tcypkin Sergey Kozlov Cunlin Zhang X.-C.Zhang | 2021 | Ultrafast Science2021，，1： | 3 |
| 4 | Highly Sensitive and Fast Hydrogen Detection Based on Light-Induced Thermoelastic Spectroscopy显示文摘As a new energy source,hydrogen(H_(2))detection is a hot topic in recent years.Because of the weak absorption characteristic,laser spectroscopy-based H_(2)detection is challenging.In this paper,a highly sensitive H_(2)sensor based on light-induced thermoelastic spectroscopy(LITES)technique is demonstrated for the first time.A continuous-wave,distributed feedback diode laser with emission in the 2.1μm region was adopted as the excitation source to target the strongest H_(2)absorption line of 4,712.90 cm^(−1).A Herriott multipass cell with an optical length of 10.1 m was chosen to further improve the H_(2)absorption.With the feature of processing the raw input data without data preprocessing and extracting the desired features automatically,the robust shallow neural network(SNN)fitting algorithm was brought in to denoise the sensor.For the LITES-based H_(2)sensor,the concentration response was tested,and an excellent linear response to H_(2)concentration levels was achieved.A minimum detection limit(MDL)of~80 ppm was obtained.On the basis of implementation of the H_(2)-LITES sensor,a heterodyne H_(2)-LITES sensor was further constructed to realize a fast measurement of resonance frequency of quartz tuning fork and H_(2)concentration simultaneously.The resonance frequency can be retrieved in several hundred milliseconds with the measurement accuracy of±0.2 Hz,and the result of 30,713.76 Hz is exactly same as the experimentally determined value of 30,713.69 Hz.After the SNN algorithm was applied,an MDL of~45 ppm was achieved for this heterodyne H_(2)-LITES sensor. | Yufei Ma Tiantian Liang Shunda Qiao Xiaonan Liu Ziting Lang | 2023 | Ultrafast Science2023，3，3： | 2 |
| 5 | Anti-Correlated Plasma and THz Pulse Generation during Two-Color Laser Filamentation in Air显示文摘The THz generation efficiency and the plasma density generated by a filament in air have been found anti-correlated when pumped by 800 nm+1600 nm two-color laser field.The plasma density near zero delay of two laser pulses has a minimum value,which is opposite to the trend of THz generation eficiency and contradicts common sense.The lower plasma density cannot be explained by the static tunneling model according to the conventional photocurrent model,but it might be attributed to the electron trapping by the excited states of nitrogen molecule.The present work also clarifies the dominant role of the drifting velocity accelerated by the two-color laser field during the THz pulse generation process.The results promote our understanding on the optimization of the THz generation efficiency by the two-color laser filamentation. | Zhiqiang Yu Lu Sun Nan Zhang Jianxin Wang Pengfei Qi Lanjun Guo Quan Sun Weiwei Liu Hiroaki Misawa | 2022 | Ultrafast Science2022，，6： | 2 |
| 6 | 13.4 fs,0.1 Hz OPCPA Front End for the 100 PW-Class Laser Facility显示文摘Here,we report the recent progress on the front end developed for the 100 PW-class laser facility.Using 3 stages of optical parametric chirped-pulse amplification(OPCPA)based on lithium triborate(LBO)crystals,we realized a 5.26 J/0.1 Hz amplified output with a bandwidth over 200 nm near the center wavelength of 925 nm.After the compressor,we obtained a pulse duration of 13.4 fs.As the compression efficiency reached 67%,this OPCPA front end could potentially support a peak power of 263 TW at a repetition rate of 0.1 Hz.To the best of our knowledge,among all the 100 TW-level OPCPA systems,it shows the widest spectral width,the shortest pulse duration,and it is also the first OPCPA system working at a repetition-rate mode. | Xinliang Wang Xingyan Liu Xiaoming Lu Junchi Chen Yingbin Long Wenkai Li Haidong Chen Xun Chen Peile Bai Yanyan Li Yujie Peng Yanqi Liu Fenxiang Wu Cheng Wang Zhaoyang Li Yi Xu Xiaoyan Liang Yuxin Leng Ruxin Li | 2022 | Ultrafast Science2022，，3： | 1 |
| 7 | High-Harmonic Generation and Correlated Electron Emission from Relativistic Plasma Mirrors at 1 kHz Repetition Rate显示文摘We report evidence for the first generation of XUV spectra from relativistic surface high-harmonic generation(SHHG)on plasma mirrors at a kilohertz repetition rate,emitted simultaneously with energetic electrons.SHHG spectra and electron angular distributions are measured as a function of the experimentally controlled plasma density gradient scale length Lg for three increasingly short and intense driving pulses:24 fs and a0=1:1,8 fs and a0=1:6,and finally 4 fs and a0≈2:1,where a0 is the peak vector potential normalized by mec/e with the elementary charge e,the electron rest mass me,and the vacuum light velocity c.For all driver pulses,we observe correlated relativistic SHHG and electron emission in the range Lg∈½λ/20,λ/4,with an optimum gradient scale length of Lg≈λ/10.This universal optimal Lg-range is rationalized by deriving a direct intensity-independent link between the scale length Lg and an effective similarity parameter for relativistic laser-plasma interactions. | Stefan Haessler Marie Ouillé Jaismeen Kaur Maïmouna Bocoum Frederik Böhle Dan Levy Louis Daniault Aline Vernier Jérôme Faure Rodrigo Lopez-Martens | 2022 | Ultrafast Science2022，，3： | 1 |
| 8 | Birefringence-Managed Normal-Dispersion Fiber Laser Delivering Energy-Tunable Chirp-Free Solitons显示文摘Chirp-free solitons have been mainly achieved with anomalous-dispersion fiber lasers by the balance of dispersive and nonlinear effects,and the single-pulse energy is constrained within a relatively small range.Here,we report a class of chirp-free pulse in normal-dispersion erbium-doped fiber lasers,termed birefringence-managed soliton,in which the birefringence-related phasematching effect dominates the soliton evolution.Controllable harmonic mode locking from 5 order to 85 order is obtained at the same pump level of~10 mW with soliton energy fully tunable beyond ten times,which indicates a new birefringencerelated soliton energy law,which fundamentally differs from the conventional soliton energy theorem.The unique transformation behavior between birefringence-managed solitons and dissipative solitons is directly visualized via the singleshot spectroscopy.The results demonstrate a novel approach of engineering fiber birefringence to create energy-tunable chirpfree solitons in normal-dispersion regime and open new research directions in fields of optical solitons,ultrafast lasers,and theirapplications. | Dong Mao Zhiwen He Qun Gao Chao Zeng Ling Yun Yueqing Du Hua Lu Zhipei Sun Jianlin Zhao | 2022 | Ultrafast Science2022，，4： | 1 |
| 9 | Two-Beam Ultrafast Laser Scribing of Graphene Patterns with 90-nm Subdiffraction Feature Size显示文摘The fabrication of high-resolution laser-scribed graphene devices is crucial to achieving large surface areas and thus performance breakthroughs.However,since the investigation mainly focuses on the laser-induced reduction of graphene oxide,the single-beam scribing provides a tremendous challenge to realizing subdiffraction features of graphene patterns.Here,we present an innovative 2-beam laser scribing pathway for the fabrication of subdiffraction graphene patterns.First,an oxidation reaction of highly reduced graphene oxide can be controllably driven by irradiation of a 532-nm femtosecond laser beam.Based on the oxidation mechanism,a 2-beam laser scribing was performed on graphene oxide thin films,in which a doughnut-shaped 375-nm beam reduces graphene oxide and a spherical 532-nm ultrafast beam induces the oxidation of laser-reduced graphene oxide.The spherical beam turns the highly reduced graphene oxide(reduced by the doughnut-shaped beam)to an oxidized state,splitting the laser-scribed graphene oxide line into 2 subdiffraction featured segments and thus forming a laserscribed graphene/oxidized laser-scribed graphene/laser-scribed graphene line.Through the adjustment of the oxidation beam power,the minimum linewidth of laser-scribed graphene was measured to be 90 nm.Next,we fabricated patterned supercapacitor electrodes containing parallel laser-scribed graphene lines with subdiffraction widths and spacings.An outstanding gravimetric capacitance of 308 F/g,which is substantially higher than those of reported graphene-based supercapacitors,has been delivered.The results offer a broadly accessible strategy for the fabrication of high-performance graphene-based devices including high-capacity energy storage,high-resolution holograms,high-sensitivity sensors,triboelectric nanogenerators with high power densities,and artificial intelligence devices with high neuron densities. | Xi Chen Min Gu | 2023 | Ultrafast Science2023，3，1： | 1 |
| 10 | Probing Molecular Frame Wigner Time Delay and Electron Wavepacket Phase Structure of CO Molecule显示文摘The time delay of photoelectron emission serves as a fundamental building block to understand the ultrafast electron emission dynamics in strong-field physics.Here,we study the photoelectron angular streaking of CO molecules by using two-color(400+800nm)corotating circularly polarized fields.By coincidently measuring photoelectrons with the dissociative ions,we present molecular frame photoelectron angular distributions with respect to the instantaneous driving electric field signatures.We develop a semiclassical nonadiabatic molecular quantum-trajectory Monte Carlo(MO-QTMC)model that fully captures the experimental observations and further ab initio simulations.We disentangle the orientation-resolved contribution of the anisotropic ionic potential and the molecular orbital structure on the measured photoelectron angular distributions.Furthermore,by analyzing the photoelectron interference patterns,we extract the sub-Coulomb-barrier phase distribution of the photoelectron wavepacket and reconstruct the orientation-and energy-resolved Wigner time delay in the molecular frame.Holographic angular streaking with bicircular fields can be used for probing polyatomic molecules in the future. | Zhenning Guo Peipei Ge Yiqi Fang Yankun Dou Xiaoyang Yu Jiguo Wang Qihuang Gong Yunquan Liu | 2022 | Ultrafast Science2022，，2： | 1 |
| 11 | Exploring Femtosecond Laser Ablation by Snapshot Ultrafast Imaging and Molecular Dynamics Simulation显示文摘Femtosecond laser ablation(FLA)has been playing a prominent role in precision fabrication of material because of its circumvention of thermal effect and extremely high spatial resolution.Molecular dynamics modeling,as a powerful tool to study the mechanism of femtosecond laser ablation,still lacks the connection between its simulation results and experimental observations at present.Here we combine a single-shot chirped spectral mapping ultrafast photography(CSMUP)technique in experiment and a three-dimensional two-temperature model-based molecular dynamics(3D TTM-MD)method in theory to jointly investigate the FLA process of bulky gold.Our experimental and simulated results show quite high consistency in time-resolved morphologic dynamics.According to the highly accurate simulations,the FLA process of gold at the high laser fluence is dominated by the phase explosion,which shows drastic vaporized cluster eruption and pressure dynamics,while the FLA process at the low laser fluence mainly results from the photomechanical spallation,which shows moderate temperature and pressure dynamics.This study reveals the ultrafast dynamics of gold with different ablation schemes,which has a guiding significance for the applications of FLA on various kinds of materials. | Jiali Yao Dalong Qi Hongtao Liang Yilin He Yunhua Yao Tianqing Jia Yang Yang Zhenrong Sun Shian Zhang | 2022 | Ultrafast Science2022，，5： | 1 |
| 12 | Research Article Focusing Properties of High-Order Harmonics显示文摘Many applications of the extreme ultraviolet(XUV)radiation obtained by high-order harmonic generation(HHG)in gases require a small focus area in order to enable attosecond pulses to reach a high intensity.Here,high-order harmonics generated in Ar with a multiterawatt laser system in a loose focusing geometry are focused to a few micrometers using two toroidal mirrors in a Wolter configuration with a high demagnification factor.Using a knife-edge measurement technique,we determine the position and size of the XUV foci as a function of harmonic order.We show that the focus properties vary with harmonic order and the generation conditions.Simulations,based on a classical description of the harmonic dipole phase and assuming that the individual harmonics can be described as Gaussian beams,reproduce the experimental behavior.We discuss how the generation geometry affects the intensity and duration of the focused attosecond pulses. | Maria Hoflund Jasper Peschel Marius Plach Hugo Dacasa Kévin Veyrinas Eric Constant Peter Smorenburg Hampus Wikmark Sylvain Maclot Chen Guo Cord Arnold Anne L'Huillier Per Eng-Johnsson | 2021 | Ultrafast Science2021，，1： | 1 |
| 13 | A Custom-Tailored Multi-TW Optical Electric Field for Gigawatt Soft-X-Ray Isolated Attosecond Pulses显示文摘Since the first isolated attosecond pulse was demonstrated through high-order harmonics generation(HHG)in 2001,researchers’interest in the ultrashort time region has expanded.However,one realizes a limitation for related research such as attosecond spectroscopy.The bottleneck is concluded to be the lack of a high-peak-power isolated attosecond pulse source.Therefore,currently,generating an intense attosecond pulse would be one of the highest priority goals.In this paper,we review our recent work of a TW-class parallel three-channel waveform synthesizer for generating a gigawatt-scale soft-X-ray isolated attosecond pulse(IAP)using HHG.By employing several stabilization methods,we have achieved a stable 50 mJ three-channel opticalwaveform synthesizer with a peak power at the multi-TW level.This optical-waveform synthesizer is capable of creating a stable intense optical field for generating an intense continuum harmonic beam thanks to the successful stabilization of all the parameters.Furthermore,the precision control of shot-to-shot reproducible synthesized waveforms is achieved.Through the HHG process employing a loose-focusing geometry,an intense shot-to-shot stable supercontinuum(50–70 eV)is generated in an argon gas cell.This continuum spectrum supports an IAP with a transform-limited duration of 170 as and a submicrojoule pulse energy,which allows the generation of a GW-scale IAP.Another supercontinuum in the soft-X-ray region with higher photon energy of approximately 100–130 eV is also generated in neon gas from the synthesizer.The transform-limited pulse duration is 106 as.Thus,the enhancement of HHG output through optimized waveform synthesis is experimentally proved. | Bing Xue Yuuki Tamaru Yuxi Fu Hua Yuan Pengfei Lan Oliver D.Mücke Akira Suda Katsumi Midorikawa Eiji J.Takahashi | 2021 | Ultrafast Science2021，，1： | 1 |
| 14 | THz-Enhanced DC Ultrafast Electron Diffractometer显示文摘Terahertz-(THz-)based electron manipulation has recently been shown to hold tremendous promise as a technology for manipulating and driving the next generation of compact ultrafast electron sources.Here,we demonstrate an ultrafast electron diffractometer with THz-driven pulse compression.The electron bunches from a conventional DC gun are compressed by a factor of 10 and reach a duration of~180 fs(FWHM)with 10,000 electrons/pulse at a 1 kHz repetition rate.The resulting ultrafast electron source is used in a proof-of-principle experiment to probe the photoinduced dynamics of single-crystal silicon.The THz-compressed electron beams produce high-quality diffraction patterns and enable the observation of the ultrafast structural dynamics with improved time resolution.These results validate the maturity of THz-driven ultrafast electron sources for use in precision applications. | Dongfang Zhang Tobias Kroh Felix Ritzkowsky Timm Rohwer Moein Fakhari Huseyin Cankaya Anne-Laure Calendron Nicholas H.Matlis Franz X.Kärtner | 2021 | Ultrafast Science2021，，1： | 1 |
| 15 | Ultrafast Hole Deformation Revealed by Molecular Attosecond Interferometry显示文摘Understanding the evolution of molecular electronic structures is the key to explore and control photochemical reactions and photobiological processes.Subjected to strong laser fields,electronic holes are formed upon ionization and evolve in the attosecond timescale.It is crucial to probe the electronic dynamics in real time with attosecond-temporal and atomic-spatial precision.Here,we present molecular attosecond interferometry that enables the in situ manipulation of holes in carbon dioxide molecules via the interferometry of the phase-locked electrons(propagating in opposite directions)of a laser-triggered rotational wave packet.The joint measurement on high-harmonic and terahertz spectroscopy(HATS)provides a unique tool for understanding electron dynamics from picoseconds to attoseconds.The optimum phases of two-color pulses for controlling the electron wave packet are precisely determined owing to the robust reference provided with the terahertz pulse generation.It is noteworthy that the contribution of HOMO-1 and HOMO-2 increases reflecting the deformation of the hole as the harmonic order increases.Our method can be applied to study hole dynamics of complex molecules and electron correlations during the strong-field process.The threefold control through molecular alignment,laser polarization,and the two-color pulse phase delay allows the precise manipulation of the transient hole paving the way for new advances in attochemistry. | Yindong Huang Jing Zhao Zheng Shu Yalei Zhu Jinlei Liu Wenpu Dong Xiaowei Wang Zhihui Lü Dongwen Zhang Jianmin Yuan Jing Chen Zengxiu Zhao | 2021 | Ultrafast Science2021，，1： | 1 |
| 16 | Neighboring Atom Collisions in Solid-State High Harmonic Generation显示文摘High harmonic generation(HHG)from solids shows great application prospects in compact short-wavelength light sources and as a tool for imaging the dynamics in crystals with subnanometer spatial and attosecond temporal resolution.However,the underlying collision dynamics behind solid HHG is still intensively debated and no direct mapping relationship between the collision dynamics with band structure has been built.Here,we show that the electron and its associated hole can be elastically scattered by neighboring atoms when their wavelength approaches the atomic size.We reveal that the elastic scattering of electron/hole from neighboring atoms can dramatically influence the electron recombination with its left-behind hole,which turns out to be the fundamental reason for the anisotropic interband HHG observed recently in bulk crystals.Our findings link the electron/hole backward scattering with Van Hove singularities and forward scattering with critical lines in the band structure and thus build a clear mapping between the band structure and the harmonic spectrum.Our work provides a unifying picture for several seemingly unrelated experimental observations and theoretical predictions,including the anisotropic harmonic emission in MgO,the atomic-like recollision mechanism of solid HHG,and the delocalization of HHG in ZnO.This strongly improved understanding will pave the way for controlling the solid-state HHG and visualizing the structure-dependent electron dynamics in solids. | Ruixin Zuo Alexander Trautmann Guifang Wang Wolf-Rüdiger Hannes Shidong Yang Xiaohong Song Torsten Meier Marcelo Ciappina Huynh Thanh Duc Weifeng Yang | 2021 | Ultrafast Science2021，，1： | 0 |
| 17 | Polarization Flipping of Even-Order Harmonics in Monolayer Transition-Metal Dichalcogenides显示文摘We present a systematic study of the crystal-orientation dependence of high-harmonic generation in monolayer transition-metal dichalcogenides,WS2 and MoSe2,subjected to intense linearly polarized midinfrared laser fields.The measured spectra consist of both odd-and even-order harmonics,with a high-energy cutoff extending beyond the 15th order for a laser-field strength around~1 V/nm.In WS2,we find that the polarization direction of the odd-order harmonics smoothly follows that of the laser field irrespective of the crystal orientation,whereas the direction of the even-order harmonics is fixed by the crystal mirror planes.Furthermore,the polarization of the even-order harmonics shows a flip in the course of crystal rotation when the laser field lies between two of the crystal mirror planes.By numerically solving the semiconductor Bloch equations for a gapped-graphene model,we qualitatively reproduce these experimental features and find the polarization flipping to be associated with a significant contribution from interband polarization.In contrast,high-harmonic signals from MoSe2 exhibit deviations from the laser-field following of oddorder harmonics and crystal-mirror-plane following of even-order harmonics.We attribute these differences to the competing roles of the intraband and interband contributions,including the deflection of the electron-hole trajectories by nonparabolic crystal bands. | Yuki Kobayashi Christian Heide Hamed Koochaki Kelardeh Amalya Johnson Fang Liu Tony F.Heinz David A.Reis Shambhu Ghimire | 2021 | Ultrafast Science2021，，1： | 0 |
| 18 | Ultrafast Science to Capture Ultrafast Motions显示文摘To reflect blooming interest in ultrafast dynamics,we are launching a new journal to publish top-quality research in the field.Ultrafast Science is now open for your submissions.We are living in a dynamic world,where all matter is in a vibrant process,whether it is a giant celestial body or a small atom.Being able to observe,analyze,and manipulate these dynamic processes is undoubtedly essential for scientific discoveries and technical innovations.The evolution of any physical quantity(e.g.,displacement,mass,electromagnetic fields,intensity,phase,and spectra)with time gives rise to different time-varying phenomena—some are slow,some are fast,and some are ultrafast,in view of what human beings can sense.With the modern smartphone or camera,fast motions within the microsecond time scale can now be recorded in daily life.However,when we enter into the micro/nanoscale world,what happens often becomes ultrafast.For example,atomic diffusion occurs in a nanosecond(10–9 s)time scale.Molecular rotation,charge transfer relaxation,and magnetization reversal happen in picoseconds(10–12s). | Qihuang Gong Wei Zhao | 2021 | Ultrafast Science2021，，1： | 0 |
| 19 | High-Flux 1ookHz Attosecond Pulse Source Driven by a High-Average Power Annular Laser Beam显示文摘High-repetition rate attosecond pulse sources are indispensable tools for time-resolved studies of electron dynamics,such as coincidence spectroscopy and experiments with high demands on statistics or signal-to-noise ratio,especilly in the case of solid and big molecule samples in chemistry and biology.Although with the high-repetition rate lasers,such attosecond pulses in a pump-probe configuration are possible to achieve,until now,only a few such light sources have been demonstrated.Here,by shaping the driving laser to an annular beam,a 100 kHz attosecond pulse train(APT)is reported with the highest energy so far(51 pl/shot)on target(269 pJat generation)among the high-repetition rate systems(>10 kHz)in which the attosecond pulses were temporally characterized.The on-target pulse energy is maximized by reducing the losses from the reflections and filtering of the high harmonics,and an unprecedented 19%transmission rate from the generation point to the target position is achieved.At the same time,the probe beam is also annular and low loss of this beam is reached by using another holey mirror to combine with the APT.The advantages of using an annular beam to generate attosecond pulses with a high-average power laser are demonstrated experimentally and theoretically,The effect of nonlinear propagation in the generation medium on the annular-beam generation concept is also analyzed in detail. | Peng Ye Lenard Gulyas Oldal Tamas Csizmadia Zoltan Filus Timea Grosz Peter Jojart Imre Seres Zsolt Bengery Barnabas Gilicze Subhendu Kahaly Katalin Varju Balazs Major | 2022 | Ultrafast Science2022，，1： | 0 |
| 20 | Bessel Terahertz Pulses from Superluminal Laser Plasma Filaments显示文摘Terahertz radiation with a Bessel beam profile is demonstrated experimentally from a two-color laser filament in air,which is induced by tailored femtosecond laser pulses with an axicon.The temporal and spatial distributions of Bessel rings of the terahertz radiation are retrieved after being collected in the far field.A theoretical model is proposed,which suggests that such Bessel terahertz pulses are produced due to the combined effects of the inhomogeneous superluminal flament structure and the phase change of the two-color laser components inside the plasma channel.These two efects lead to wavefront crossover and constructive/destructive interference of terahertz radiation from different plasma sources along the laser flament,respectively.Compared with other methods,our technique can support the generation of Bessel pulses with broad spectral bandwidth.Such Bessel pulses can propagate to the far field without significant spatial spreading,which shall provide new opportunities for terahertz applications. | Zhelin Zhang Jiayang Zhang Yanping Chen Tianhao Xia Linzheng Wang Bonan Han Feng He Zhengming Sheng Jie Zhang | 2022 | Ultrafast Science2022，，1： | 0 |
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