The mechanism of lightning that ignites a forest fire and the lightning that occurs above a forest fire are explained at the molecular level. It is based on two phenomena, namely, internal charge separation inside the...The mechanism of lightning that ignites a forest fire and the lightning that occurs above a forest fire are explained at the molecular level. It is based on two phenomena, namely, internal charge separation inside the atmospheric cloud particles and the existence of a layer of positively charged hydrogen atoms sticking out of the surface of the liquid layer of water on the surface of rimers. Strong turbulence-driven collisions of the ice particles and water droplets with the rimers give rise to breakups of the ice particles and water droplets into positively and negatively charged fragments leading to charge separation. Hot weather in a forest contributes to the updraft of hot and humid air, which follows the same physical/chemical processes of normal lightning proposed and explained recently[1]. Lightning would have a high probability of lighting up and burning the dry biological materials in the ground of the forest, leading to a forest (wild) fire. The burning of trees and other plants would release a lot of heat and moisture together with a lot of smoke particles (aerosols) becoming a strong updraft. The condition for creating lightning is again satisfied which would result in further lightning high above the forest wild fire.展开更多
In order to verify the feasibility of semi-automatic garlic planter with inclined belt program and determine its reasonable operating parameters, the semi-automatic test-bed with inclined belt of garlic transplanting ...In order to verify the feasibility of semi-automatic garlic planter with inclined belt program and determine its reasonable operating parameters, the semi-automatic test-bed with inclined belt of garlic transplanting machine was designed, and the garlic box experiments were conducted. The angle of inclined belt on the test-bed and its running speed were adjustable. Single factor test results showed that the program of the semi-automatic garlic planter with inclined belt was feasible, and the angle of inclined belt and the test bed running speed affected the indicators. Orthogonal experiment results showed that the angle of inclined belt was the main factor affecting the test indicators. It is also found that the best angle was 30 degrees, while the most reasonable running speed was 0.75 Km/h.展开更多
After reaching a world record of 10 PW,the peak power development of the titanium-sapphire(Ti:sapphire)PW ultraintense lasers has hit a bottleneck,and it seems to be difficult to continue increasing due to the difficu...After reaching a world record of 10 PW,the peak power development of the titanium-sapphire(Ti:sapphire)PW ultraintense lasers has hit a bottleneck,and it seems to be difficult to continue increasing due to the difficulty of manufacturing larger Ti:sapphire crystals and the limitation of parasitic lasing that can consume stored pump energy.Unlike coherent beam combining,coherent Ti:sapphire tiling is a viable solution for expanding Ti:sapphire crystal sizes,truncating transverse amplified spontaneous emission,suppressing parasitic lasing,and,importantly,not requiring complex space-time tiling control.A theoretical analysis of the above features and an experimental demonstration of high-quality laser amplification are reported.The results show that the addition of a 2×2 tiled Ti:sapphire amplifier to today’s 10 PW ultraintense laser is a viable technique to break the 10 PW limit and directly increase the highest peak power recorded by a factor of 4,further approaching the exawatt class.展开更多
Compressing all the energy of a laser pulse into a spatiotemporal focal cube edged by the laser center wavelength will realize the highest intensity of an ultra-intense ultrashort laser,which is called theλ^(3) regim...Compressing all the energy of a laser pulse into a spatiotemporal focal cube edged by the laser center wavelength will realize the highest intensity of an ultra-intense ultrashort laser,which is called theλ^(3) regime or theλ^(3) laser.Herein,we introduced a rotational hyperbolic mirror—an important rotational conic section mirror with two foci—that is used as a secondary focusing mirror after a rotational parabolic mirror to reduce the focal spot size from several wavelengths to a single wavelength by significantly increasing the focusing angular aperture.Compared with the rotational ellipsoidal mirror,the first focal spot with a high intensity,as well as some unwanted strong-field effects,is avoided.The optimal focusing condition of this method is presented and the enhanced tight focusing for a femtosecond petawatt laser and theλ3 laser is numerically simulated,which can enhance the focused intensities of ultra-intense ultrashort lasers for laser physics.展开更多
Lead halide hybrid perovskites(LHP)have emerged as one of the most promising photovoltaic materials for their remarkable solar energy conversion ability.The transportation of the photoinduced carriers in LHP could scr...Lead halide hybrid perovskites(LHP)have emerged as one of the most promising photovoltaic materials for their remarkable solar energy conversion ability.The transportation of the photoinduced carriers in LHP could screen the defect recombination with the help of the large polaron formation.However,the physical insight of the relationship between the superior optical-electronic performance of perovskite and its polaron dynamics related to the electron-lattice strong coupling induced by the substitution engineering is still lack of investigation.Here,the bandgap modulated thin films ofα-FAPbI_(3)with different element substitution is investigated by the time resolved Terahertz spectroscopy.We find the polaron recombination dynamics could be prolonged in LHP with a relatively smaller bandgap,even though the formation of polaron will not be affected apparently.Intuitively,the large polaron mobility in(FAPb I_(3))0.95(MAPbI_(3))0.05thin film is~30%larger than that in(FAPb I_(3))0.85(MAPbBr_(3))0.15.The larger mobility in(FAPb I_(3))0.95(MAPb I_(3))0.05could be assigned to the slowing down of the carrier scattering time.Therefore,the physical origin of the higher carrier mobility in the(FAPb I_(3))0.95(MAPbI_(3))0.05should be related with the lattice distortion and enhanced electron–phonon coupling induced by the substitution.In addition,(FAPbI_(3))0.95(MAPbI_(3))0.05will lose fewer active carriers during the polaron cooling process than that in(FAPb I_(3))0.85(MAPbBr_(3)),indicating lower thermal dissipation in(FAPbI_(3))0.95(MAPbI_(3))0.05.Our results suggest that besides the smaller bandgap,the higher polaron mobility improved by the substitution engineering inα-FAPbI_(3)can also be an important factor for the high PCE of the black phaseα-FAPbI_(3)based solar cell devices.展开更多
A supercontinuum white laser with ultrabroad bandwidth,intense pulse energy,and high spectral flatness can be accomplished via synergic action of third-order nonlinearity(3rd-NL)and second-order nonlinearity.In this w...A supercontinuum white laser with ultrabroad bandwidth,intense pulse energy,and high spectral flatness can be accomplished via synergic action of third-order nonlinearity(3rd-NL)and second-order nonlinearity.In this work,we employ an intense Ti:sapphire femtosecond laser with a pulse duration of 50 fs and pulse energy up to 4 mJ to ignite the supercontinuum white laser.Remarkably,we use water instead of the usual solid materials as the 3rd-NL medium exhibiting both strong self-phase modulation and stimulated Raman scattering effect to create a supercontinuum laser with significantly broadened bandwidth and avoid laser damage and destruction.Then the supercontinuum laser is injected into a water-embedded chirped periodically poled lithium niobate crystal that enables broadband and high-efficiency second-harmonic generation.The output white laser has a 10 dB bandwidth encompassing 413 to 907 nm,more than one octave,and a pulse energy of 0.6 mJ.This methodology would open up an efficient route to creating a long-lived,high-stability,and inexpensive white laser with intense pulse energy,high spectral flatness,and ultrabroad bandwidth for application to various areas of basic science and high technology.展开更多
Cloud electrification is one of the oldest unresolved puzzles in the atmospheric sciences. Though many mechanisms for charge separation in clouds have been proposed, a quantitative understanding of their respective co...Cloud electrification is one of the oldest unresolved puzzles in the atmospheric sciences. Though many mechanisms for charge separation in clouds have been proposed, a quantitative understanding of their respective contribution in a given meteorological situation is lacking. Here we suggest and analyze a hitherto little discussed process. A qualitative picture at the molecular level of the charge separation mechanism of lightning in a thundercloud is proposed. It is based on two key physical/chemical natural phenomena, namely, internal charge separation of the atmospheric impurities/aerosols inside an atmospheric water cluster/droplet/ice particle and the existence of liquid water layers on rimers (graupels and hailstones) forming a layer of dipoles with H<sup>+</sup> pointing out from the air-water interface. Charge separation is achieved through strong collisions among ice particles and water droplets with the rimers in the turbulence of the thundercloud. This work would have significant contribution to cloud electrification and lightning formation.展开更多
Castor(Ricinus communis L.)is one of the top 10 oil crops in the world,and inflorescence is a trait that directly affects its yield.Phospholipase C(PLCs)is involved in many plant activities and metabolic processes.To ...Castor(Ricinus communis L.)is one of the top 10 oil crops in the world,and inflorescence is a trait that directly affects its yield.Phospholipase C(PLCs)is involved in many plant activities and metabolic processes.To study the functions of PLC family genes in the regulation of the inflorescence development of the female line of Lm-type castor aLmAB2,we determined the expression levels of six PLC family genes of three types of inflorescences of aLmAB2(isofemale line,female line,bisexual line)at different developmental stages.The results showed that the 6 genes of the castor PLC family had relative expression levels at different developmental stages of the three types of inflorescences.The subcellular location of all six protein products was the cell membrane.The six genes were heterologously overexpressed in Arabidopsis thaliana to obtain the T3 generation-resistant Arabidopsis thaliana plants.The results showed that the overexpression of six genes significantly promoted the maturation of Arabidopsis thaliana,the growth of lateral moss,and the development of flowers and pods,but the development of basal leaves and stem leaves of Arabidopsis thaliana was significantly inhibited.According to homology analysis,it is speculated that PLC2,PLC2M,PLC2N,PLC4,PLC4X2,and PLC6 genes have the same regulatory function.展开更多
We propose a novel approach for generating a high-density,spatially periodic narrow electron beam comb(EBC)from a plasma grating induced by the interference of two intense laser pulses in subcritical-density plasma.We...We propose a novel approach for generating a high-density,spatially periodic narrow electron beam comb(EBC)from a plasma grating induced by the interference of two intense laser pulses in subcritical-density plasma.We employ particle-in-cell(PIC)simulations to investigate the effects of cross-propagating laser pulses with specific angles overlapping in a subcritical plasma.This overlap results in the formation of a transverse standing wave,leading to a spatially periodic high-density modulation known as a plasma grating.The electron density peak within the grating can reach several times the background plasma density.The charge imbalance between electrons and ions in the electron density peaks causes mutual repulsion among the electrons,resulting in Coulomb expansion and acceleration of the electrons.As a result,some electrons expand into vacuum,forming a periodic narrow EBC with an individual beam width in the nanoscale range.To further explore the formation of the nanoscale EBC,we conduct additional PIC simulations to study the dependence on various laser parameters.Overall,our proposed method offers a promising and controlled approach to generate tunable narrow EBCs with high density.展开更多
High-order harmonics and attosecond pulse generation with coherent wake emission are theoretically investigated for the effect of pulse duration and carrier envelope phase(CEP)of few-cycle laser pulse.We find that sho...High-order harmonics and attosecond pulse generation with coherent wake emission are theoretically investigated for the effect of pulse duration and carrier envelope phase(CEP)of few-cycle laser pulse.We find that short pulse duration will cause the negative chirp for the high harmonics.When the laser pulse is shortened to a few cycles,the influence of the laser CEP on the chirp of the harmonics will also become more prominent.展开更多
In this paper,promising but simple schemes are investigated to enhance the micro-bunching of relativistic electron beams for coherent harmonic generation(CHG)by using phase merging effects.In contrast to the standard ...In this paper,promising but simple schemes are investigated to enhance the micro-bunching of relativistic electron beams for coherent harmonic generation(CHG)by using phase merging effects.In contrast to the standard CHG scheme,two specially designed dispersion sections(DSs)are adopted with the DS-modulator–DS configuration.The phase space of the e beam is appropriately coupled in the first DS,and the electrons within one seed wavelength can merge to the same phase with a matched second DS.Micro-bunching of the e beam can thus be enhanced by a large margin with much higher-harmonic components.Taking e beams from laser wakefield accelerators(LWFAs)as an example,start-to-end simulations are performed to show the effectiveness and robustness of the proposed schemes with several configurations.The beam current can be optimized to several tens to hundreds of kiloamperes,and the radiation power reaches hundreds of megawatts in the extreme ultraviolet regime within a 3.5 m-long beamline.The proposed schemes offer new opportunities for future compact free-electron lasers driven by LWFAs and provides prospects for truly compact and widely applicable systems.展开更多
The high-order harmonic generation(HHG)in solids permits the exploration of the ultrafast electron dynamics in strong-field light–matter interaction.In particular,the laser ellipticity dependence of HHG provides insi...The high-order harmonic generation(HHG)in solids permits the exploration of the ultrafast electron dynamics in strong-field light–matter interaction.In particular,the laser ellipticity dependence of HHG provides insight into the energy band structure and the electron dynamics.Here,we report the harmonics up to the 10th order generated from monolayer MoS2in experiment.The perpendicular components of even harmonics display unreported enhanced yield at a finite ellipticity,which is sensitive to the crystal orientations.The abnormal ellipticity dependence indicates a novel mechanism that the Berry curvature distributed in a two-dimensional structure manipulates the subcycle electron dynamics during harmonics generation.So far,the research of the BC is limited to the theoretical configuration or one-dimensional experimental measurement,lacking a comprehensive characterization of the BC in the whole Brillouin zone.Our experiment provides a potential experimental scheme to characterize the complex BC structure in two-or three-dimensional materials and a new way to control the subcycle electron dynamics based on the Berry curvature field.展开更多
A deep convolutional neural network is employed to simultaneously measure the beam-pointing and phase difference of sub-beams from a single far-field interference fringe for coherent beam combining systems.The amplitu...A deep convolutional neural network is employed to simultaneously measure the beam-pointing and phase difference of sub-beams from a single far-field interference fringe for coherent beam combining systems.The amplitudes of sub-beams in the measurement path are modulated in order to prevent measuring mistakes caused by the symmetry of beam-pointing.This method is able to measure beam-pointing and phase difference with an RMS accuracy of about 0.2μrad andλ/250,respectively,in a two-beam coherent beam combining system.展开更多
A femtosecond mid-infrared optical vortex laser can be used for high harmonic generation to extend cutoff energy to the kilo-electron-volt range with orbital angular momentum,as well as other secondary radiations.For ...A femtosecond mid-infrared optical vortex laser can be used for high harmonic generation to extend cutoff energy to the kilo-electron-volt range with orbital angular momentum,as well as other secondary radiations.For these,we demonstrate a high-energy femtosecond 4μm optical vortex laser based on optical parametric chirped pulse amplification(OPCPA)for the first time.The optical vortex seed is generated from a femtosecond 4μm laser by a silicon spiral phase plate with the topological charge l of 1 before the stretcher.Through using a two-stage collinear OPCPA amplifier,the chirped vortex pulse is amplified to 12.4 m J with 200 nm full width at half-maximum bandwidth.After compression,the vortex laser pulse with 9.53 m J,119 fs can be obtained.Furthermore,the vortex characteristics of the laser beam are investigated and evaluated.This demonstration can scale to generate a higher-peak-power vortex mid-IR laser and pave a new way for high field physics.展开更多
Supercontinuum(SC)light source has advanced ultrafast laser spectroscopy in condensed matter science,biology,physics,and chemistry.Compared to the frequently used photonic crystal fibers and bulk materials,femtosecond...Supercontinuum(SC)light source has advanced ultrafast laser spectroscopy in condensed matter science,biology,physics,and chemistry.Compared to the frequently used photonic crystal fibers and bulk materials,femtosecond laser filamentation in gases is damage-immune for supercontinuum generation.A bottleneck problem is the strong jitters from filament induced self-heating at kHz repetition rate level.We demonstrated stable kHz supercontinuum generation directly in air with multiple mJ level pulse energy.This was achieved by applying an external DC electric field to the air plasma filament.Beam pointing jitters of the 1 kHz air filament induced SC light were reduced by more than 2 fold.The stabilized high repetition rate laser filament offers the opportunity for stable intense SC generation and its applications in air.展开更多
In this paper,we report the recent progress on the 1 PW/0.1 Hz laser beamline of Shanghai Superintense Ultrafast Laser Facility(SULF).The SULF-1 PW laser beamline is based on the double chirped pulse amplification(CPA...In this paper,we report the recent progress on the 1 PW/0.1 Hz laser beamline of Shanghai Superintense Ultrafast Laser Facility(SULF).The SULF-1 PW laser beamline is based on the double chirped pulse amplification(CPA)scheme,which can generate laser pulses of 50.8 J at 0.1 Hz after the final amplifier;the shot-to-shot energy fluctuation of the amplified pulse is as low as 1.2%(std).After compression,the pulse duration of 29.6 fs is achieved,which can support a maximal peak power of 1 PW.The contrast ratio at-80 ps before main pulse is measured to be 2.5×10^-11.The focused peak intensity is improved by optimizing the angular dispersion in the grating compressor.The maximal focused peak intensity can reach 2.7×10^19W/cm2 even with an f/26.5 off-axis parabolic mirror.The horizontal and vertical angular pointing fluctuations in 1 h are measured to be 1.89 and 2.45μrad,respectively.The moderate repetition rate and the good stability are desirable characteristics for lasermatter interactions.The SULF-1 PW laser beamline is now in the phase of commissioning,and preliminary experiments of particle acceleration and secondary radiation under 300–400 TW/0.1 Hz laser condition have been implemented.The progress on the experiments and the daily stable operation of the laser demonstrate the availability of the SULF-1 PW beamline.展开更多
We present a velocity-gauge model for the generation of even-order high harmonics, and reveal that the even-order harmonics originate from the multiple-step transitions among the energy bands in momentum space, while ...We present a velocity-gauge model for the generation of even-order high harmonics, and reveal that the even-order harmonics originate from the multiple-step transitions among the energy bands in momentum space, while the odd-order harmonics are mainly from direct transitions. The lower valence band is found vital for the generation of even harmonics. Relative intensity of even-order harmonics versus the odd orders is calculated and shows a growing trend as the laser field amplitude increases.展开更多
We report on a simultaneous generation of double white light lasers through filamentation by focusing a femtosecond laser pulse. The appearance of the two white light lasers can be controlled by tilting the focusing l...We report on a simultaneous generation of double white light lasers through filamentation by focusing a femtosecond laser pulse. The appearance of the two white light lasers can be controlled by tilting the focusing lens. The spectral bandwidth and the pulse energy of the double white light lasers were controlled by tuning laser filamenting pulse energy and polarization. Two white light lasers with pulse energies of 1.54 m J and 1.84 m J,respectively, were generated with the pump laser energy of 7.43 m J. Besides being beneficial in understanding the multiple white light lasers generation process through multiple filamentation and its control, the results are also valuable for white light laser-based applications.展开更多
We demonstrate an ultra-broadband high temporal contrast infrared laser source based on cascaded optical parametric amplification,hollow-core fiber(HCF)and second harmonic generation processes.In this setup,the spectr...We demonstrate an ultra-broadband high temporal contrast infrared laser source based on cascaded optical parametric amplification,hollow-core fiber(HCF)and second harmonic generation processes.In this setup,the spectrum of an approximately 1.8μm laser pulse has near 1μm full bandwidth by employing an argon gas-filled HCF.Subsequently,after frequency doubling with cascaded crystals and dispersion compensation by a fused silica wedge pair,9.6 fs(~3cycles)and 150μJ pulses centered at 910 nm with full bandwidth of over 300 nm can be generated.The energy stability of the output laser pulse is excellent with 0.8%(root mean square)over 20 min,and the temporal contrast is>10^(12)at-10 ps before the main pulse.The excellent temporal and spatial characteristics and stability make this laser able to be used as a good seed source for ultra-intense and ultrafast laser systems.展开更多
Free-electron light sources feature extraordinary luminosity,directionality,and coherence,which has enabled significant scientific progress in fields including physics,chemistry,and biology.The next generation of ligh...Free-electron light sources feature extraordinary luminosity,directionality,and coherence,which has enabled significant scientific progress in fields including physics,chemistry,and biology.The next generation of light sources has aimed at compact radiation sources driven by free electrons,with the advantages of reduction in both space and cost.With the rapid development of ultra-intense and ultrashort lasers,great effort has been devoted to the quest for compact free-electron lasers(FELs).This review focuses on the current efforts and advancements in the development of compact FELs,with a particular emphasis on two notable paths:the development of compact accelerators and the construction of micro undulators based on innovative materials/structures or optical modulation of electrons.In addition,the physical essence of inverse Compton scattering is discussed,which offers remarkable capability to develop an optical undulator with a spatial period that matches the optical wavelength.Recent scientific developments and future directions for miniaturized and integrated free-electron coherent light sources are also reviewed.In the future,the prospect of generating ultrashort electron pulses will provide fascinating means of producing superradiant radiation,promising high brilliance and coherence even on a micro scale using optical micro undulators.展开更多
文摘The mechanism of lightning that ignites a forest fire and the lightning that occurs above a forest fire are explained at the molecular level. It is based on two phenomena, namely, internal charge separation inside the atmospheric cloud particles and the existence of a layer of positively charged hydrogen atoms sticking out of the surface of the liquid layer of water on the surface of rimers. Strong turbulence-driven collisions of the ice particles and water droplets with the rimers give rise to breakups of the ice particles and water droplets into positively and negatively charged fragments leading to charge separation. Hot weather in a forest contributes to the updraft of hot and humid air, which follows the same physical/chemical processes of normal lightning proposed and explained recently[1]. Lightning would have a high probability of lighting up and burning the dry biological materials in the ground of the forest, leading to a forest (wild) fire. The burning of trees and other plants would release a lot of heat and moisture together with a lot of smoke particles (aerosols) becoming a strong updraft. The condition for creating lightning is again satisfied which would result in further lightning high above the forest wild fire.
文摘In order to verify the feasibility of semi-automatic garlic planter with inclined belt program and determine its reasonable operating parameters, the semi-automatic test-bed with inclined belt of garlic transplanting machine was designed, and the garlic box experiments were conducted. The angle of inclined belt on the test-bed and its running speed were adjustable. Single factor test results showed that the program of the semi-automatic garlic planter with inclined belt was feasible, and the angle of inclined belt and the test bed running speed affected the indicators. Orthogonal experiment results showed that the angle of inclined belt was the main factor affecting the test indicators. It is also found that the best angle was 30 degrees, while the most reasonable running speed was 0.75 Km/h.
基金supported by the National Key R&D Program of China(Grant No.2022YFA1604401)the Shanghai Science and Technology Committee Program(Grant Nos.22560780100 and 23560750200)the National Natural Science Foundation of China(Grant No.61925507).
文摘After reaching a world record of 10 PW,the peak power development of the titanium-sapphire(Ti:sapphire)PW ultraintense lasers has hit a bottleneck,and it seems to be difficult to continue increasing due to the difficulty of manufacturing larger Ti:sapphire crystals and the limitation of parasitic lasing that can consume stored pump energy.Unlike coherent beam combining,coherent Ti:sapphire tiling is a viable solution for expanding Ti:sapphire crystal sizes,truncating transverse amplified spontaneous emission,suppressing parasitic lasing,and,importantly,not requiring complex space-time tiling control.A theoretical analysis of the above features and an experimental demonstration of high-quality laser amplification are reported.The results show that the addition of a 2×2 tiled Ti:sapphire amplifier to today’s 10 PW ultraintense laser is a viable technique to break the 10 PW limit and directly increase the highest peak power recorded by a factor of 4,further approaching the exawatt class.
基金supported by the National Key R&D Program of China(Grant No.2022YFA1604401)the Shanghai Science and Technology Committee Program(Grant Nos.22560780100 and 23560750200)the National Natural Science Foundation of China(Grant No.61925507)。
文摘Compressing all the energy of a laser pulse into a spatiotemporal focal cube edged by the laser center wavelength will realize the highest intensity of an ultra-intense ultrashort laser,which is called theλ^(3) regime or theλ^(3) laser.Herein,we introduced a rotational hyperbolic mirror—an important rotational conic section mirror with two foci—that is used as a secondary focusing mirror after a rotational parabolic mirror to reduce the focal spot size from several wavelengths to a single wavelength by significantly increasing the focusing angular aperture.Compared with the rotational ellipsoidal mirror,the first focal spot with a high intensity,as well as some unwanted strong-field effects,is avoided.The optimal focusing condition of this method is presented and the enhanced tight focusing for a femtosecond petawatt laser and theλ3 laser is numerically simulated,which can enhance the focused intensities of ultra-intense ultrashort lasers for laser physics.
基金supported by the National Natural Science Foundation of China(Nos.92050203,61905264,61925507,61875211,61674023,62005296,and 62105347)the National Key R&D Program of China 2017YFE0123700+1 种基金Shanghai Pilot Program for Basic Research(22JC1403200)the CAS Interdisciplinary Innovation Team。
文摘Lead halide hybrid perovskites(LHP)have emerged as one of the most promising photovoltaic materials for their remarkable solar energy conversion ability.The transportation of the photoinduced carriers in LHP could screen the defect recombination with the help of the large polaron formation.However,the physical insight of the relationship between the superior optical-electronic performance of perovskite and its polaron dynamics related to the electron-lattice strong coupling induced by the substitution engineering is still lack of investigation.Here,the bandgap modulated thin films ofα-FAPbI_(3)with different element substitution is investigated by the time resolved Terahertz spectroscopy.We find the polaron recombination dynamics could be prolonged in LHP with a relatively smaller bandgap,even though the formation of polaron will not be affected apparently.Intuitively,the large polaron mobility in(FAPb I_(3))0.95(MAPbI_(3))0.05thin film is~30%larger than that in(FAPb I_(3))0.85(MAPbBr_(3))0.15.The larger mobility in(FAPb I_(3))0.95(MAPb I_(3))0.05could be assigned to the slowing down of the carrier scattering time.Therefore,the physical origin of the higher carrier mobility in the(FAPb I_(3))0.95(MAPbI_(3))0.05should be related with the lattice distortion and enhanced electron–phonon coupling induced by the substitution.In addition,(FAPbI_(3))0.95(MAPbI_(3))0.05will lose fewer active carriers during the polaron cooling process than that in(FAPb I_(3))0.85(MAPbBr_(3)),indicating lower thermal dissipation in(FAPbI_(3))0.95(MAPbI_(3))0.05.Our results suggest that besides the smaller bandgap,the higher polaron mobility improved by the substitution engineering inα-FAPbI_(3)can also be an important factor for the high PCE of the black phaseα-FAPbI_(3)based solar cell devices.
基金supported by the Science and Technology Project of Guangdong (Grant No.2020B010190001)the National Natural Science Foundation of China (Grant No.11974119)+1 种基金the Guangdong Innovative and Entrepreneurial Research Team Program (Grant No.2016ZT06C594)the National Key R&D Program of China (Grant No.2018YFA 0306200).
文摘A supercontinuum white laser with ultrabroad bandwidth,intense pulse energy,and high spectral flatness can be accomplished via synergic action of third-order nonlinearity(3rd-NL)and second-order nonlinearity.In this work,we employ an intense Ti:sapphire femtosecond laser with a pulse duration of 50 fs and pulse energy up to 4 mJ to ignite the supercontinuum white laser.Remarkably,we use water instead of the usual solid materials as the 3rd-NL medium exhibiting both strong self-phase modulation and stimulated Raman scattering effect to create a supercontinuum laser with significantly broadened bandwidth and avoid laser damage and destruction.Then the supercontinuum laser is injected into a water-embedded chirped periodically poled lithium niobate crystal that enables broadband and high-efficiency second-harmonic generation.The output white laser has a 10 dB bandwidth encompassing 413 to 907 nm,more than one octave,and a pulse energy of 0.6 mJ.This methodology would open up an efficient route to creating a long-lived,high-stability,and inexpensive white laser with intense pulse energy,high spectral flatness,and ultrabroad bandwidth for application to various areas of basic science and high technology.
文摘Cloud electrification is one of the oldest unresolved puzzles in the atmospheric sciences. Though many mechanisms for charge separation in clouds have been proposed, a quantitative understanding of their respective contribution in a given meteorological situation is lacking. Here we suggest and analyze a hitherto little discussed process. A qualitative picture at the molecular level of the charge separation mechanism of lightning in a thundercloud is proposed. It is based on two key physical/chemical natural phenomena, namely, internal charge separation of the atmospheric impurities/aerosols inside an atmospheric water cluster/droplet/ice particle and the existence of liquid water layers on rimers (graupels and hailstones) forming a layer of dipoles with H<sup>+</sup> pointing out from the air-water interface. Charge separation is achieved through strong collisions among ice particles and water droplets with the rimers in the turbulence of the thundercloud. This work would have significant contribution to cloud electrification and lightning formation.
基金the following agencies:National Natural Science Foundation of China(31860071)New Agricultural Research and Reform Practice Project of the Ministry of Education(2020114)+8 种基金Grassland Talent Innovation Team of Inner Mongolia Autonomous Region-Castor Molecular Breeding Research Innovative Talent Team(2022)Inner Mongolia University for Nationalities 2022 Basic Research Business Funds for Universities Directly under the Autonomous Region(237)the Natural Science Foundation of Inner Mongolia Autonomous Region(2021 MS03008)In 2023,the Department of Science and Technology of Inner Mongolia Autonomous Region Approved the Construction Project of Inner Mongolia Autonomous Region Key Laboratory of Castor Breeding and Comprehensive UtilizationInner Mongolia Autonomous Region Castor Industry Collaborative Innovation Center Open Fund Project(MDK2021011,MDK2022014)the Natural Science Foundation of Inner Mongolia Autonomous Region(2021BS03036)Inner Mongolia University for Nationalities Doctoral Research Start-Up Fund(BS672)Castor Industry Technology Innovation Inner Mongolia Autonomous Region Engineering Research Center Open Project(MDK2021004)Inner Mongolia Autonomous Region Castor Industry Collaborative Innovation Center Open Project(MDK2022016).
文摘Castor(Ricinus communis L.)is one of the top 10 oil crops in the world,and inflorescence is a trait that directly affects its yield.Phospholipase C(PLCs)is involved in many plant activities and metabolic processes.To study the functions of PLC family genes in the regulation of the inflorescence development of the female line of Lm-type castor aLmAB2,we determined the expression levels of six PLC family genes of three types of inflorescences of aLmAB2(isofemale line,female line,bisexual line)at different developmental stages.The results showed that the 6 genes of the castor PLC family had relative expression levels at different developmental stages of the three types of inflorescences.The subcellular location of all six protein products was the cell membrane.The six genes were heterologously overexpressed in Arabidopsis thaliana to obtain the T3 generation-resistant Arabidopsis thaliana plants.The results showed that the overexpression of six genes significantly promoted the maturation of Arabidopsis thaliana,the growth of lateral moss,and the development of flowers and pods,but the development of basal leaves and stem leaves of Arabidopsis thaliana was significantly inhibited.According to homology analysis,it is speculated that PLC2,PLC2M,PLC2N,PLC4,PLC4X2,and PLC6 genes have the same regulatory function.
基金This work was supported by the National Natural Science Foundation of China(Grant Nos.12174410,11991072,11991074,12225411,and 12105353)the CAS Project for Young Scientists in Basic Research(Grant No.YSBR060)the State Key Laboratory Program of the Chinese Ministry of Science and Technology,and the CAS Youth Innovation Promotion Association(Grant Nos.Y201952 and 2022242).
文摘We propose a novel approach for generating a high-density,spatially periodic narrow electron beam comb(EBC)from a plasma grating induced by the interference of two intense laser pulses in subcritical-density plasma.We employ particle-in-cell(PIC)simulations to investigate the effects of cross-propagating laser pulses with specific angles overlapping in a subcritical plasma.This overlap results in the formation of a transverse standing wave,leading to a spatially periodic high-density modulation known as a plasma grating.The electron density peak within the grating can reach several times the background plasma density.The charge imbalance between electrons and ions in the electron density peaks causes mutual repulsion among the electrons,resulting in Coulomb expansion and acceleration of the electrons.As a result,some electrons expand into vacuum,forming a periodic narrow EBC with an individual beam width in the nanoscale range.To further explore the formation of the nanoscale EBC,we conduct additional PIC simulations to study the dependence on various laser parameters.Overall,our proposed method offers a promising and controlled approach to generate tunable narrow EBCs with high density.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.91950203,11874374,and 61690223)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB16).
文摘High-order harmonics and attosecond pulse generation with coherent wake emission are theoretically investigated for the effect of pulse duration and carrier envelope phase(CEP)of few-cycle laser pulse.We find that short pulse duration will cause the negative chirp for the high harmonics.When the laser pulse is shortened to a few cycles,the influence of the laser CEP on the chirp of the harmonics will also become more prominent.
基金supported by the National Natural Science Foundation of China(Grant Nos.12388102,12225411,12105353,11991072,and 12174410)the CAS Project for Young Scientists in Basic Research(Grant No.YSBR060)+1 种基金the Program of Shanghai Academic Research Leader(Grant No.22XD1424200)the State Key Laboratory Program of the Chinese Ministry of Science and Technology and CAS Youth Innovation Promotion Association(Y201952 and 2022242).
文摘In this paper,promising but simple schemes are investigated to enhance the micro-bunching of relativistic electron beams for coherent harmonic generation(CHG)by using phase merging effects.In contrast to the standard CHG scheme,two specially designed dispersion sections(DSs)are adopted with the DS-modulator–DS configuration.The phase space of the e beam is appropriately coupled in the first DS,and the electrons within one seed wavelength can merge to the same phase with a matched second DS.Micro-bunching of the e beam can thus be enhanced by a large margin with much higher-harmonic components.Taking e beams from laser wakefield accelerators(LWFAs)as an example,start-to-end simulations are performed to show the effectiveness and robustness of the proposed schemes with several configurations.The beam current can be optimized to several tens to hundreds of kiloamperes,and the radiation power reaches hundreds of megawatts in the extreme ultraviolet regime within a 3.5 m-long beamline.The proposed schemes offer new opportunities for future compact free-electron lasers driven by LWFAs and provides prospects for truly compact and widely applicable systems.
基金Zhangjiang LaboratoryNational Natural Science Foundation of China(91950203,11874374)。
文摘The high-order harmonic generation(HHG)in solids permits the exploration of the ultrafast electron dynamics in strong-field light–matter interaction.In particular,the laser ellipticity dependence of HHG provides insight into the energy band structure and the electron dynamics.Here,we report the harmonics up to the 10th order generated from monolayer MoS2in experiment.The perpendicular components of even harmonics display unreported enhanced yield at a finite ellipticity,which is sensitive to the crystal orientations.The abnormal ellipticity dependence indicates a novel mechanism that the Berry curvature distributed in a two-dimensional structure manipulates the subcycle electron dynamics during harmonics generation.So far,the research of the BC is limited to the theoretical configuration or one-dimensional experimental measurement,lacking a comprehensive characterization of the BC in the whole Brillouin zone.Our experiment provides a potential experimental scheme to characterize the complex BC structure in two-or three-dimensional materials and a new way to control the subcycle electron dynamics based on the Berry curvature field.
基金supported by the National Natural Science Foundation of China(NSFC)(Nos.61775223 and11974367)the Strategic Priority Research Program of Chinese Academy of Sciences(No.XDB1603)。
文摘A deep convolutional neural network is employed to simultaneously measure the beam-pointing and phase difference of sub-beams from a single far-field interference fringe for coherent beam combining systems.The amplitudes of sub-beams in the measurement path are modulated in order to prevent measuring mistakes caused by the symmetry of beam-pointing.This method is able to measure beam-pointing and phase difference with an RMS accuracy of about 0.2μrad andλ/250,respectively,in a two-beam coherent beam combining system.
基金Strategic Priority Research Program of the Chinese Academy of Sciences(XDB1603)International ST Cooperation Program of China(2016YFE0119300)+2 种基金Program of Shanghai Academic/Technology Research Leader(18XD1404200)Shanghai Municipal Science and Technology Major Project(2017SHZDZX02)National Natural Science Foundation of China(11127901,61925507)。
文摘A femtosecond mid-infrared optical vortex laser can be used for high harmonic generation to extend cutoff energy to the kilo-electron-volt range with orbital angular momentum,as well as other secondary radiations.For these,we demonstrate a high-energy femtosecond 4μm optical vortex laser based on optical parametric chirped pulse amplification(OPCPA)for the first time.The optical vortex seed is generated from a femtosecond 4μm laser by a silicon spiral phase plate with the topological charge l of 1 before the stretcher.Through using a two-stage collinear OPCPA amplifier,the chirped vortex pulse is amplified to 12.4 m J with 200 nm full width at half-maximum bandwidth.After compression,the vortex laser pulse with 9.53 m J,119 fs can be obtained.Furthermore,the vortex characteristics of the laser beam are investigated and evaluated.This demonstration can scale to generate a higher-peak-power vortex mid-IR laser and pave a new way for high field physics.
基金This work was supported in part by NSAF(Grant No.U2130123)the International Partnership Program of Chinese Academy of Sciences(Grant Nos.181231KYSB20200033 and 181231KYSB20200040)Shanghai Science and Technology Program(Grant No.21511105000).S.L.C.acknowledges the support of COPL,Laval University,Quebec City,Canada.We thank Dr.Hao Guo,Ms.Na Chen,Mr.Xuan Zhang,Dr.Haiyi Sun from SIOM for help in the experiments and Prof.Howard M.Milchberg from the University of Maryland for the fruitful discussions and his reading of the manuscript.
文摘Supercontinuum(SC)light source has advanced ultrafast laser spectroscopy in condensed matter science,biology,physics,and chemistry.Compared to the frequently used photonic crystal fibers and bulk materials,femtosecond laser filamentation in gases is damage-immune for supercontinuum generation.A bottleneck problem is the strong jitters from filament induced self-heating at kHz repetition rate level.We demonstrated stable kHz supercontinuum generation directly in air with multiple mJ level pulse energy.This was achieved by applying an external DC electric field to the air plasma filament.Beam pointing jitters of the 1 kHz air filament induced SC light were reduced by more than 2 fold.The stabilized high repetition rate laser filament offers the opportunity for stable intense SC generation and its applications in air.
基金the support from the electronacceleration team led by Wentao Wang,Rong Qithe proton-acceleration team led by Hui Zhang+4 种基金supported by the National Natural Science Foundation of China(Nos.11127901,61521093 and 61505234)International S&T Cooperation Program of China(No.2016YFE 0119300)Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDB160301)Technology Commission of Shanghai Municipality(No.2017SHZDZX02)Youth Innovation Promotion Association of the Chinese Academy of Sciences。
文摘In this paper,we report the recent progress on the 1 PW/0.1 Hz laser beamline of Shanghai Superintense Ultrafast Laser Facility(SULF).The SULF-1 PW laser beamline is based on the double chirped pulse amplification(CPA)scheme,which can generate laser pulses of 50.8 J at 0.1 Hz after the final amplifier;the shot-to-shot energy fluctuation of the amplified pulse is as low as 1.2%(std).After compression,the pulse duration of 29.6 fs is achieved,which can support a maximal peak power of 1 PW.The contrast ratio at-80 ps before main pulse is measured to be 2.5×10^-11.The focused peak intensity is improved by optimizing the angular dispersion in the grating compressor.The maximal focused peak intensity can reach 2.7×10^19W/cm2 even with an f/26.5 off-axis parabolic mirror.The horizontal and vertical angular pointing fluctuations in 1 h are measured to be 1.89 and 2.45μrad,respectively.The moderate repetition rate and the good stability are desirable characteristics for lasermatter interactions.The SULF-1 PW laser beamline is now in the phase of commissioning,and preliminary experiments of particle acceleration and secondary radiation under 300–400 TW/0.1 Hz laser condition have been implemented.The progress on the experiments and the daily stable operation of the laser demonstrate the availability of the SULF-1 PW beamline.
基金supported by the National Natural Science Foundation of China (NSFC) (Nos. 11127901, 11134010, 61221064, and 61405222)the Strategic Priority Research Program of Chinese Academy of Sciences (CAS) (No. XDB16000000)。
文摘We present a velocity-gauge model for the generation of even-order high harmonics, and reveal that the even-order harmonics originate from the multiple-step transitions among the energy bands in momentum space, while the odd-order harmonics are mainly from direct transitions. The lower valence band is found vital for the generation of even harmonics. Relative intensity of even-order harmonics versus the odd orders is calculated and shows a growing trend as the laser field amplitude increases.
基金the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDB16010400)the International Partnership Program of Chinese Academy of Sciences(No.181231KYSB20160045).
文摘We report on a simultaneous generation of double white light lasers through filamentation by focusing a femtosecond laser pulse. The appearance of the two white light lasers can be controlled by tilting the focusing lens. The spectral bandwidth and the pulse energy of the double white light lasers were controlled by tuning laser filamenting pulse energy and polarization. Two white light lasers with pulse energies of 1.54 m J and 1.84 m J,respectively, were generated with the pump laser energy of 7.43 m J. Besides being beneficial in understanding the multiple white light lasers generation process through multiple filamentation and its control, the results are also valuable for white light laser-based applications.
基金supported by the National Key R&D Program of China(2017YFE0123700)the Strategic Priority Research Program of the Chinese Academy of Sciences(XDB1603)+3 种基金the National Natural Science Foundation of China(61925507,62075227,12004402,61635012)the Program of Shanghai Academic/Technology Research Leader(18XD1404200)the Shanghai Municipal Science and Technology Major Project(2017SHZDZX02)the Youth Innovation Promotion Association CAS(2020248)
文摘We demonstrate an ultra-broadband high temporal contrast infrared laser source based on cascaded optical parametric amplification,hollow-core fiber(HCF)and second harmonic generation processes.In this setup,the spectrum of an approximately 1.8μm laser pulse has near 1μm full bandwidth by employing an argon gas-filled HCF.Subsequently,after frequency doubling with cascaded crystals and dispersion compensation by a fused silica wedge pair,9.6 fs(~3cycles)and 150μJ pulses centered at 910 nm with full bandwidth of over 300 nm can be generated.The energy stability of the output laser pulse is excellent with 0.8%(root mean square)over 20 min,and the temporal contrast is>10^(12)at-10 ps before the main pulse.The excellent temporal and spatial characteristics and stability make this laser able to be used as a good seed source for ultra-intense and ultrafast laser systems.
基金supported by the Shanghai Pilot Program for Basic Research-Chinese Academy of Sciences,ShanghaiBranchNational Natural Science Foundation of China(Nos.12104471,U226720057,and 62105346)+3 种基金Key Research Program of Frontier Sciences,Chinese Academy of SciencesYouth Innovation Promotion Association of Chinese Academy of SciencesCAS Project for Young Scientists in Basic Research(No.YSBRO60)Shanghai Sailing Program(No.21YF1453900).
文摘Free-electron light sources feature extraordinary luminosity,directionality,and coherence,which has enabled significant scientific progress in fields including physics,chemistry,and biology.The next generation of light sources has aimed at compact radiation sources driven by free electrons,with the advantages of reduction in both space and cost.With the rapid development of ultra-intense and ultrashort lasers,great effort has been devoted to the quest for compact free-electron lasers(FELs).This review focuses on the current efforts and advancements in the development of compact FELs,with a particular emphasis on two notable paths:the development of compact accelerators and the construction of micro undulators based on innovative materials/structures or optical modulation of electrons.In addition,the physical essence of inverse Compton scattering is discussed,which offers remarkable capability to develop an optical undulator with a spatial period that matches the optical wavelength.Recent scientific developments and future directions for miniaturized and integrated free-electron coherent light sources are also reviewed.In the future,the prospect of generating ultrashort electron pulses will provide fascinating means of producing superradiant radiation,promising high brilliance and coherence even on a micro scale using optical micro undulators.
