We present a comprehensive study on the role of various excited states in high-order harmonic generation of hydrogen atoms driven by a long-wavelength(1500 nm)laser field.By numerically solving the time-dependent Schr...We present a comprehensive study on the role of various excited states in high-order harmonic generation of hydrogen atoms driven by a long-wavelength(1500 nm)laser field.By numerically solving the time-dependent Schrodinger equation(TDSE)and performing a time-frequency analysis,we investigate the influence of individual excited states on the harmonic spectrum.Our results reveal that the 2s excited state primarily contributes to the enhancement of high-energy harmonic yields by facilitating long electron trajectories,while the 2p excited state predominantly suppresses harmonic yields in the lower-energy region(20th-50th orders)by altering the contributions of electron trajectories.Our results highlight the critical role of the excited states in the HHG process,even at longer laser wavelengths.展开更多
We present a graphics processing units(GPU)parallelization based three-dimensional time-dependent Schrödinger equation(3D-TDSE)code to simulate the interaction between single-active-electron atom/molecule and arb...We present a graphics processing units(GPU)parallelization based three-dimensional time-dependent Schrödinger equation(3D-TDSE)code to simulate the interaction between single-active-electron atom/molecule and arbitrary types of laser pulses with either velocity gauge or length gauge in Cartesian coordinates.Split-operator method combined with fast Fourier transforms(FFT)is used to perform the time evolution.Sample applications in different scenarios,such as stationary state energies,photon ionization spectra,attosecond clocks,and high-order harmonic generation(HHG),are given for the hydrogen atom.Repeatable results can be obtained with the benchmark program PCTDSE,which is a 3DTDSE Fortran solver parallelized using message passing interface(MPI)library.With the help of GPU acceleration and vectorization strategy,our code running on a single NVIDIA 3090 RTX GPU can achieve about 10 times faster computation speed than PCTDSE running on a 144 Intel Xeon CPU cores server with the same accuracy.In addition,3D-GTDSE can also be modified slightly to simulate non-adiabatic dynamics involving the coupling of nuclear and electronic wave packets,as well as pure nuclear wave packet dynamics in the presence of strong laser fields within 3 dimensions.Additionally,we have also discussed the limitations and shortcomings of our code in utilizing GPU memory.The 3D-GTDSE code provides an alternative tool for studying the ultrafast nonlinear dynamics under strong laser fields.展开更多
The high harmonic generation(HHG)by few-cycle laser pulses is essential for research in strong-field solid-state physics.Through comparison of high harmonic spectra of solids generated by laser pulses with varying dur...The high harmonic generation(HHG)by few-cycle laser pulses is essential for research in strong-field solid-state physics.Through comparison of high harmonic spectra of solids generated by laser pulses with varying durations,we discovered that lasers with good dispersion compensation are capable of producing a broad spectrum of high harmonics.As the pulse duration is further compressed,several interference peaks appear in the broad spectrum.Moreover,we conducted simulations using the semiconductor Bloch equation,considering the effect of Berry curvature,to better understand this process.Our work provides a valuable approach for studying HHG by few-cycle laser pulses in solid materials,expanding the application of HHG in attosecond physics.展开更多
The Chinese Academy of Engineering Physics Terahertz Free Electron Laser Facility(CAEP THz FEL,CTFEL)is the only high-average power free electron laser terahertz source based on superconducting accelerators in China.T...The Chinese Academy of Engineering Physics Terahertz Free Electron Laser Facility(CAEP THz FEL,CTFEL)is the only high-average power free electron laser terahertz source based on superconducting accelerators in China.The update of the CTFEL is now undergoing and will expand the frequency range from 0.1–4.2 THz to 0.1–125 THz.Two experimental stations for material spectroscopy and biomedicine will be built.A high harmonic generation(HHG)lightsource based beamline at the material spectroscopy experimental station for time-resolved angle-resolved photoemission spectroscopy(ARPES)research will be constructed and the optical design is presented.The HHG lightsource covers the extreme ultraviolet(XUV)photon energy range of 20–50 eV.A Czerny–Turner monochromator with two plane gratings worked in conical diffraction configuration is employed to maintain the transmission efficiency and preserve the pulse time duration.The calculated beamline transmission efficiency is better than 5%in the whole photon energy range.To our knowledge,this is the first time in China to combine THz-infrared FEL with HHG light source,and this experimental station will be a powerful and effective instrument that will give new research opportunities in the future for users doing research on the dynamic evolution of the excited electron band structure of a material’s surface.展开更多
The average output power and peak power scalability are the key motivation of the development of ultrafast laser systems,enabling them for a wide range of applications.The thin-disk ultrafast lasers stand out due to t...The average output power and peak power scalability are the key motivation of the development of ultrafast laser systems,enabling them for a wide range of applications.The thin-disk ultrafast lasers stand out due to their advantageous geometric design.The SESAM and Kerr-lens thin disk mode-locked oscillators represent the foremost configurations available in this field.They facilitate the direct generation of high average power and high peak power ultrafast pulses at high repetition rates.These compact tabletop systems offer a compelling alternative to bulky amplifier setups and have recently achieved>0.5 kW average power and>100 MW peak power at a megahertz repetition rate.With the continuous pursuit of shorter pulse durations and high peak power,the significance of these oscillators is rapidly expanding.This review focuses on the recent advancements and operational trade-offs in different parameters of thin-disk mode-locked oscillators.With this,we will delve into their capabilities for generating few-cycle pulses and achieving gigawatt-level peak powers,particularly investigating their suitability for post-pulse compression.Furthermore,we will explore the potential of these laser systems for generating broadband few-cycle mid-infrared laser sources and optical parametric chirped amplification.The review will also highlight the application of thin disk oscillators for efficient high-harmonic generation and discuss the possible implementation of dual comb TD-oscillators to enable dual comb spectroscopy in less explored spectral regions such as UV and XUV.展开更多
The symmetry of the target system plays a decisive role in the polarization of high harmonic generation(HHG).Molecules breaking the isotropic symmetry can be utilized to manipulate HHG polarization,but it has long bee...The symmetry of the target system plays a decisive role in the polarization of high harmonic generation(HHG).Molecules breaking the isotropic symmetry can be utilized to manipulate HHG polarization,but it has long been believed that prealignment is necessary to manifest the microscopic molecular structural effect within the macroscopic ensemble.In this work,we show that the molecular structural effect can be exploited in nonaligned molecular ensembles with appropriate 2-dimensional driving fields,despite the ensembles exhibiting isotropic macroscopic symmetry.The feasibility of this scheme is comprehensively elaborated with a multiscale theory from the perspective of symmetry breaking and is experimentally validated employing bichromatic counterrotating circularly polarized driving fields as an example.By varying the intensity ratio of the bichromatic components,substantially chiral high harmonics are generated from nonaligned molecules associated with the highest HHG efficiency,where,by contrast,the spectral chirality is nearly zero from the reference atom.Remarkably,we observe a simultaneous enhancement of both the chirality and yield of the harmonics from CO_(2),overcoming a commonly observed trade-off of the HHG efficiency for higher spectral chirality.Our findings hold the potential for a straightforward and robust pathway toward attosecond light sources with high brightness and large ellipticity.展开更多
Table-top extreme ultraviolet(EUV)microscopy offers unique opportunities for label-free investigation of biological samples.Here,we demonstrate ptychographic EUV imaging of two dried,unstained model specimens:germling...Table-top extreme ultraviolet(EUV)microscopy offers unique opportunities for label-free investigation of biological samples.Here,we demonstrate ptychographic EUV imaging of two dried,unstained model specimens:germlings of a fungus(Aspergillus nidulans),and bacteria(Escherichia coli)cells at 13.5 nm wavelength.We find that the EUV spectral region,which to date has not received much attention for biological imaging,offers sufficient penetration depths for the identification of intracellular features.By implementing a position-correlated ptychography approach,we demonstrate a millimeter-squared field of view enabled by infrared illumination combined with sub-60 nm spatial resolution achieved with EUV illumination on selected regions of interest.The strong element contrast at 13.5 nm wavelength enables the identification of the nanoscale material composition inside the specimens.Our work will advance and facilitate EUV imaging applications and enable further possibilities in life science.展开更多
We present a method to generate broadband isolated attosecond pulses. Using a two-color laser field, which is synthesized by a mid-infrared （12.5 fs, 2000 nm） and a weaker （12 fs, 800 nm） pulse in the x direction,...We present a method to generate broadband isolated attosecond pulses. Using a two-color laser field, which is synthesized by a mid-infrared （12.5 fs, 2000 nm） and a weaker （12 fs, 800 nm） pulse in the x direction, a modulated supercontinuum from 290 to 430 eV is obtainable. By properly adding a second-harmonic control field of the driving pulse in the y direction, the short quantum path is well selected and a smooth supercontinuum from 290 to 440 eV is generated. The bandwidth of the supercontinuum can be controlled by adjusting the electric field of the control pulse in the x direction. When the electric field increases to 0.051 a.u., a smooth supercontinuum from 295 to 520 eV is obtained. Using this method we expect that isolated 63-as attosecond pulses with tunable central wavelengths are straightforwardly obtained.We present a method to generate broadband isolated attosecond pulses. Using a two-color laser field, which is synthesized by a mid-infrared （12.5 fs, 2000 nm） and a weaker （12 fs, 800 nm） pulse in the x direction, a modulated supercontinuum from 290 to 430 eV is obtainable. By properly adding a second-harmonic control field of the driving pulse in the y direction, the short quantum path is well selected and a smooth supercontinuum from 290 to 440 eV is generated. The bandwidth of the supercontinuum can be controlled by adjusting the electric field of the control pulse in the x direction. When the electric field increases to 0.051 a.u., a smooth supercontinuum from 295 to 520 eV is obtained. Using this method we expect that isolated 63-as attosecond pulses with tunable central wavelengths are straightforwardly obtained.展开更多
Using nonperturbative quantum electrodynamics, we develop a scattering theory for high harmonic generation （HHG）. A transition rate formula for HHG is obtained. Applying this formula, we cal- culate the spectra of h...Using nonperturbative quantum electrodynamics, we develop a scattering theory for high harmonic generation （HHG）. A transition rate formula for HHG is obtained. Applying this formula, we cal- culate the spectra of high harmonics generated from different noble gases shined by strong laser light. We study the cutoff property of the spectra. The data show that the cutoff orders of high harmonics are greater than that predicted by the ＂3.17＂ cutoff law. As a numerical experiment, the data obtained from our repeated calculations support the newly derived theoretical expression of the cutoff law. The cutoff energy of high harmonics described by the new cutoff law, in terms of the ponderomotive energy Up and the ionization potential energy Ip, is 3.34Up 1.83Ip. The higher cutoff orders predicted by this theory are due to the absorption of the extra photons, which participate only the photon-mode up-conversion and do nothing in the photoionization process.展开更多
We propose a theoretical scheme to generate a broadband supercontinuum using a modulated chirped polarization gating technique. By this technique, a broadband continuum of 155 eV can be obtained at microscopic level. ...We propose a theoretical scheme to generate a broadband supercontinuum using a modulated chirped polarization gating technique. By this technique, a broadband continuum of 155 eV can be obtained at microscopic level. The modulations on the supercontinuum can be eliminated after propagation. Then a smooth broadband supercontinuum with the bandwidth of 155 eV can be generated. As a result, isolated sub-100-attosecond pulses with tunable central wavelengths could be obtained straightforwardly. Our simulations also reveal that an isolated attosecond pulse can still be generated by using multicycle driving laser pulses, and the central wave- length of isolated attosecond pulse can be controlled by adjusting the delay rj （ra is the delay of the two counter-rotating circularly polarized pulses.）.展开更多
基金supported by the Scientific and Technological Innovation Programs of Higher Education Institutions in Shanxi。
文摘We present a comprehensive study on the role of various excited states in high-order harmonic generation of hydrogen atoms driven by a long-wavelength(1500 nm)laser field.By numerically solving the time-dependent Schrodinger equation(TDSE)and performing a time-frequency analysis,we investigate the influence of individual excited states on the harmonic spectrum.Our results reveal that the 2s excited state primarily contributes to the enhancement of high-energy harmonic yields by facilitating long electron trajectories,while the 2p excited state predominantly suppresses harmonic yields in the lower-energy region(20th-50th orders)by altering the contributions of electron trajectories.Our results highlight the critical role of the excited states in the HHG process,even at longer laser wavelengths.
基金supported by the GHfund A(Grant No.ghfund202407013663)the Fundamental Research Funds for the Central Universities(Grant No.GK202207012)+4 种基金Shaanxi Province(Grant No.QCYRCXM-2022-241)the National Key Research and Development Program of China(Grant No.2022YFE0134200)Guangdong Basic and Applied Basic Research Foundation(Grant No.2025A1515011117)the Natural Science Foundation of Jilin Province(Grant No.20220101016JC)the National Natural Science Foundation of China(Grant Nos.12374238,11934004,and 11974230)。
文摘We present a graphics processing units(GPU)parallelization based three-dimensional time-dependent Schrödinger equation(3D-TDSE)code to simulate the interaction between single-active-electron atom/molecule and arbitrary types of laser pulses with either velocity gauge or length gauge in Cartesian coordinates.Split-operator method combined with fast Fourier transforms(FFT)is used to perform the time evolution.Sample applications in different scenarios,such as stationary state energies,photon ionization spectra,attosecond clocks,and high-order harmonic generation(HHG),are given for the hydrogen atom.Repeatable results can be obtained with the benchmark program PCTDSE,which is a 3DTDSE Fortran solver parallelized using message passing interface(MPI)library.With the help of GPU acceleration and vectorization strategy,our code running on a single NVIDIA 3090 RTX GPU can achieve about 10 times faster computation speed than PCTDSE running on a 144 Intel Xeon CPU cores server with the same accuracy.In addition,3D-GTDSE can also be modified slightly to simulate non-adiabatic dynamics involving the coupling of nuclear and electronic wave packets,as well as pure nuclear wave packet dynamics in the presence of strong laser fields within 3 dimensions.Additionally,we have also discussed the limitations and shortcomings of our code in utilizing GPU memory.The 3D-GTDSE code provides an alternative tool for studying the ultrafast nonlinear dynamics under strong laser fields.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.91850209 and 11974416)。
文摘The high harmonic generation(HHG)by few-cycle laser pulses is essential for research in strong-field solid-state physics.Through comparison of high harmonic spectra of solids generated by laser pulses with varying durations,we discovered that lasers with good dispersion compensation are capable of producing a broad spectrum of high harmonics.As the pulse duration is further compressed,several interference peaks appear in the broad spectrum.Moreover,we conducted simulations using the semiconductor Bloch equation,considering the effect of Berry curvature,to better understand this process.Our work provides a valuable approach for studying HHG by few-cycle laser pulses in solid materials,expanding the application of HHG in attosecond physics.
基金supported by Major Instrument Projects of Sichuan Province.
文摘The Chinese Academy of Engineering Physics Terahertz Free Electron Laser Facility(CAEP THz FEL,CTFEL)is the only high-average power free electron laser terahertz source based on superconducting accelerators in China.The update of the CTFEL is now undergoing and will expand the frequency range from 0.1–4.2 THz to 0.1–125 THz.Two experimental stations for material spectroscopy and biomedicine will be built.A high harmonic generation(HHG)lightsource based beamline at the material spectroscopy experimental station for time-resolved angle-resolved photoemission spectroscopy(ARPES)research will be constructed and the optical design is presented.The HHG lightsource covers the extreme ultraviolet(XUV)photon energy range of 20–50 eV.A Czerny–Turner monochromator with two plane gratings worked in conical diffraction configuration is employed to maintain the transmission efficiency and preserve the pulse time duration.The calculated beamline transmission efficiency is better than 5%in the whole photon energy range.To our knowledge,this is the first time in China to combine THz-infrared FEL with HHG light source,and this experimental station will be a powerful and effective instrument that will give new research opportunities in the future for users doing research on the dynamic evolution of the excited electron band structure of a material’s surface.
基金the Development Program of China(No.2022YFB3605800)the National Key Research and Natural Science Foundation of China(Nos.62275174,62105225,62105225,61975136,and 61935014)+3 种基金Shenzhen University Stability Support Project(Nos.20220719104008001 and 20220718173849001)Shenzhen major Scientific and Technological projects(No.KZD20240903100205008)the Natural Science Foundation of Top Talent of Shenzhen Technology University(No.GDRC202106)Guangdong Provincial Engineering Technology Research Center for Materials for Advanced MEMS Sensor Chip(No.2022GCZX005).
文摘The average output power and peak power scalability are the key motivation of the development of ultrafast laser systems,enabling them for a wide range of applications.The thin-disk ultrafast lasers stand out due to their advantageous geometric design.The SESAM and Kerr-lens thin disk mode-locked oscillators represent the foremost configurations available in this field.They facilitate the direct generation of high average power and high peak power ultrafast pulses at high repetition rates.These compact tabletop systems offer a compelling alternative to bulky amplifier setups and have recently achieved>0.5 kW average power and>100 MW peak power at a megahertz repetition rate.With the continuous pursuit of shorter pulse durations and high peak power,the significance of these oscillators is rapidly expanding.This review focuses on the recent advancements and operational trade-offs in different parameters of thin-disk mode-locked oscillators.With this,we will delve into their capabilities for generating few-cycle pulses and achieving gigawatt-level peak powers,particularly investigating their suitability for post-pulse compression.Furthermore,we will explore the potential of these laser systems for generating broadband few-cycle mid-infrared laser sources and optical parametric chirped amplification.The review will also highlight the application of thin disk oscillators for efficient high-harmonic generation and discuss the possible implementation of dual comb TD-oscillators to enable dual comb spectroscopy in less explored spectral regions such as UV and XUV.
基金supported by the National Key Research and Development Program(Grant No.2023YFA1406800)the National Natural Science Foundation of China(NSFC)(Grant Nos.12174134,12021004,12104389,and 12225406).
文摘The symmetry of the target system plays a decisive role in the polarization of high harmonic generation(HHG).Molecules breaking the isotropic symmetry can be utilized to manipulate HHG polarization,but it has long been believed that prealignment is necessary to manifest the microscopic molecular structural effect within the macroscopic ensemble.In this work,we show that the molecular structural effect can be exploited in nonaligned molecular ensembles with appropriate 2-dimensional driving fields,despite the ensembles exhibiting isotropic macroscopic symmetry.The feasibility of this scheme is comprehensively elaborated with a multiscale theory from the perspective of symmetry breaking and is experimentally validated employing bichromatic counterrotating circularly polarized driving fields as an example.By varying the intensity ratio of the bichromatic components,substantially chiral high harmonics are generated from nonaligned molecules associated with the highest HHG efficiency,where,by contrast,the spectral chirality is nearly zero from the reference atom.Remarkably,we observe a simultaneous enhancement of both the chirality and yield of the harmonics from CO_(2),overcoming a commonly observed trade-off of the HHG efficiency for higher spectral chirality.Our findings hold the potential for a straightforward and robust pathway toward attosecond light sources with high brightness and large ellipticity.
基金Strategy and Innovation Grant from the Free State of Thuringia(41-5507-2016)Innovation Pool of the Research Field Matter of the Helmholtz Association of German Research Centers(project FISCOV)+5 种基金Leibniz Research Cluster InfectoOptics(SAS-2015-HKI-LWC)Thüringer Ministerium für Bildung,Wissenschaft und Kultur(2018 FGR 0080)Helmholtz Association(incubator project Ptychography 4.0)Fraunhofer-Gesellschaft(Cluster of Excellence Advanced Photon Sources)German Research Foundation(Deutsche Forschungsgemeinschaft,DFG)under Germany’s Excellence Strategy–EXC 2051–Project-ID 390713860S.H.is supported by the German Research Foundation(Deutsche Forschungs-gemeinschaft,DFG)–SFB 1127/2 ChemBioSys–239748522.
文摘Table-top extreme ultraviolet(EUV)microscopy offers unique opportunities for label-free investigation of biological samples.Here,we demonstrate ptychographic EUV imaging of two dried,unstained model specimens:germlings of a fungus(Aspergillus nidulans),and bacteria(Escherichia coli)cells at 13.5 nm wavelength.We find that the EUV spectral region,which to date has not received much attention for biological imaging,offers sufficient penetration depths for the identification of intracellular features.By implementing a position-correlated ptychography approach,we demonstrate a millimeter-squared field of view enabled by infrared illumination combined with sub-60 nm spatial resolution achieved with EUV illumination on selected regions of interest.The strong element contrast at 13.5 nm wavelength enables the identification of the nanoscale material composition inside the specimens.Our work will advance and facilitate EUV imaging applications and enable further possibilities in life science.
基金supported by the National Natural Science Foundation of China (Grant Nos. 110775069, 91026021, 11075068 and 10875054)the Fundamental Research Funds for the Central Universities (Grant No.lzujbky-2010-k08)the Scholarship Award for Excellent Doctoral Student granted by Ministry of Education
文摘We present a method to generate broadband isolated attosecond pulses. Using a two-color laser field, which is synthesized by a mid-infrared （12.5 fs, 2000 nm） and a weaker （12 fs, 800 nm） pulse in the x direction, a modulated supercontinuum from 290 to 430 eV is obtainable. By properly adding a second-harmonic control field of the driving pulse in the y direction, the short quantum path is well selected and a smooth supercontinuum from 290 to 440 eV is generated. The bandwidth of the supercontinuum can be controlled by adjusting the electric field of the control pulse in the x direction. When the electric field increases to 0.051 a.u., a smooth supercontinuum from 295 to 520 eV is obtained. Using this method we expect that isolated 63-as attosecond pulses with tunable central wavelengths are straightforwardly obtained.We present a method to generate broadband isolated attosecond pulses. Using a two-color laser field, which is synthesized by a mid-infrared （12.5 fs, 2000 nm） and a weaker （12 fs, 800 nm） pulse in the x direction, a modulated supercontinuum from 290 to 430 eV is obtainable. By properly adding a second-harmonic control field of the driving pulse in the y direction, the short quantum path is well selected and a smooth supercontinuum from 290 to 440 eV is generated. The bandwidth of the supercontinuum can be controlled by adjusting the electric field of the control pulse in the x direction. When the electric field increases to 0.051 a.u., a smooth supercontinuum from 295 to 520 eV is obtained. Using this method we expect that isolated 63-as attosecond pulses with tunable central wavelengths are straightforwardly obtained.
文摘Using nonperturbative quantum electrodynamics, we develop a scattering theory for high harmonic generation （HHG）. A transition rate formula for HHG is obtained. Applying this formula, we cal- culate the spectra of high harmonics generated from different noble gases shined by strong laser light. We study the cutoff property of the spectra. The data show that the cutoff orders of high harmonics are greater than that predicted by the ＂3.17＂ cutoff law. As a numerical experiment, the data obtained from our repeated calculations support the newly derived theoretical expression of the cutoff law. The cutoff energy of high harmonics described by the new cutoff law, in terms of the ponderomotive energy Up and the ionization potential energy Ip, is 3.34Up 1.83Ip. The higher cutoff orders predicted by this theory are due to the absorption of the extra photons, which participate only the photon-mode up-conversion and do nothing in the photoionization process.
基金supported by the National Natural Science Foundation of China (Grant Nos.91026021,11075068,10875054,11175076 and 10975065)the Fundamental Research Funds for the Central Universities(Grant No.lzujbky-2010-k08)Scholarship Award for Excellent Doctoral Students Granted by Ministry of Education
文摘We propose a theoretical scheme to generate a broadband supercontinuum using a modulated chirped polarization gating technique. By this technique, a broadband continuum of 155 eV can be obtained at microscopic level. The modulations on the supercontinuum can be eliminated after propagation. Then a smooth broadband supercontinuum with the bandwidth of 155 eV can be generated. As a result, isolated sub-100-attosecond pulses with tunable central wavelengths could be obtained straightforwardly. Our simulations also reveal that an isolated attosecond pulse can still be generated by using multicycle driving laser pulses, and the central wave- length of isolated attosecond pulse can be controlled by adjusting the delay rj （ra is the delay of the two counter-rotating circularly polarized pulses.）.
