The scattering matrices of e+N^(+)with J^(π)=1.5^(+)in discrete energy regions are calculated using the eigenchannel R-matrix method.We obtain good parameters of multichannel quantum defect theory(MQDT)that vary smoo...The scattering matrices of e+N^(+)with J^(π)=1.5^(+)in discrete energy regions are calculated using the eigenchannel R-matrix method.We obtain good parameters of multichannel quantum defect theory(MQDT)that vary smoothly as the function of the energy resulting from the analytical continuation property of the scattering matrices.By employing the MQDT,all discrete energy levels for N could be calculated accurately without missing anyone.The MQDT parameters(i.e.,scattering matrices)can be calibrated with the available precise spectroscopy values.In this work,the optical oscillator strengths for the transition between the ground state and Rydberg series are obtained,which provide rich data for the diagnostic analysis of plasma.展开更多
High-power tunable lasers are intensely pursued due to their vast application potential such as in telecom,ranging,and molecular sensing.Integrated photonics,however,is usually considered not suitable for high-power a...High-power tunable lasers are intensely pursued due to their vast application potential such as in telecom,ranging,and molecular sensing.Integrated photonics,however,is usually considered not suitable for high-power applications mainly due to its small size which limits the energy storage capacity and,therefore,the output power.In the late 90s,to improve the beam quality and increase the stored energy,large-mode-area(LMA)fibers were introduced in which the optical mode area is substantially large.Such LMA fibers have transformed the high-power capability of fiber systems ever since.Introducing such an LMA technology at the chip-scale can play an equally disruptive role with high power signal generation from an integrated photonics system.To this end,in this work we demonstrate such a technology,and show a very high-power tunable laser with the help of a silicon photonics based LMA power amplifier.We show output power reaching 1.8 W over a tunability range of 60 nm,spanning from 1.83μm to 1.89μm,limited only by the seed laser.Such an integrated LMA device can be used to substantially increase the power of the existing integrated tunable lasers currently limited to a few tens of milliwatts.The power levels demonstrated here reach and surpass that of many benchtop systems which truly makes the silicon photonics based integrated LMA device poised towards mass deployment for high power applications without relying on benchtop systems.展开更多
Optical frequency synthesizers have widespread applications in optical spectroscopy,frequency metrology,and many other fields.However,their applicability is currently limited by size,cost,and power consumption.Silicon...Optical frequency synthesizers have widespread applications in optical spectroscopy,frequency metrology,and many other fields.However,their applicability is currently limited by size,cost,and power consumption.Silicon photonics technology,which is compatible with complementary-metal-oxide-semiconductor fabrication processes,provides a low-cost,compact size,lightweight,and low-power-consumption solution.In this work,we demonstrate an optical frequency synthesizer using a fully integrated silicon-based tunable laser.The synthesizer can be self-calibrated by tuning the repetition rate of the internal mode-locked laser.A 20 nm tuning range from 1544 to 1564 nm is achieved with~10−13 frequency instability at 10 s averaging time.Its flexibility and fast reconfigurability are also demonstrated by fine tuning the synthesizer and generating arbitrary specified patterns over time-frequency coordinates.This work promotes the frequency stability of silicon-based integrated tunable lasers and paves the way toward chip-scale lowcost optical frequency synthesizers.展开更多
Synchronous laser-microwave networks delivering attosecond timing precision are highly desirable in many advanced applications,such as geodesy,very-long-baseline interferometry,high-precision navigation and multi-tele...Synchronous laser-microwave networks delivering attosecond timing precision are highly desirable in many advanced applications,such as geodesy,very-long-baseline interferometry,high-precision navigation and multi-telescope arrays.In particular,rapidly expanding photon-science facilities like X-ray free-electron lasers and intense laser beamlines require system-wide attosecond-level synchronization of dozens of optical and microwave signals up to kilometer distances.Once equipped with such precision,these facilities will initiate radically new science by shedding light on molecular and atomic processes happening on the attosecond timescale,such as intramolecular charge transfer,Auger processes and their impacts on X-ray imaging.Here we present for the first time a complete synchronous laser-microwave network with attosecond precision,which is achieved through new metrological devices and careful balancing of fiber nonlinearities and fundamental noise contributions.We demonstrate timing stabilization of a 4.7-km fiber network and remote optical–optical synchronization across a 3.5-km fiber link with an overall timing jitter of 580 and 680 attoseconds root-mean-square,respectively,for over 40 h.Ultimately,we realize a complete laser-microwave network with 950-attosecond timing jitter for 18 h.This work can enable nextgeneration attosecond photon-science facilities to revolutionize many research fields from structural biology to material science and chemistry to fundamental physics.展开更多
We present possible conceptual designs of a laser system for driving table-top free-electron lasers based on terahertz acceleration. After discussing the achievable performances of laser amplifiers with Yb:YAG at cryo...We present possible conceptual designs of a laser system for driving table-top free-electron lasers based on terahertz acceleration. After discussing the achievable performances of laser amplifiers with Yb:YAG at cryogenic and room temperature and Yb:YLF at cryogenic temperature, we present amplification modules with available results and concepts of amplifier chains based on these laser media. Their performances are discussed in light of the specifications for the tasks within the table-top light source. Technical and engineering challenges, such as cooling, control, synchronization and diagnostics, are outlined. Three concepts for the laser layout feeding the accelerator are eventually derived and presented.展开更多
Irradiating solids with ultrashort laser pulses is known to initiate femtosecond timescale magnetization dynamics.However,sub-femtosecond spin dynamics have not yet been observed or predicted.Here,we explore ultrafast...Irradiating solids with ultrashort laser pulses is known to initiate femtosecond timescale magnetization dynamics.However,sub-femtosecond spin dynamics have not yet been observed or predicted.Here,we explore ultrafast light-driven spin dynamics in a highly nonresonant strong-field regime.Through state-of-the-art ab initio calculations,we predict that a nonmagnetic material can transiently transform into a magnetic one via dynamical extremely nonlinear spin-flipping processes,which occur on attosecond timescales and are mediated by cascaded multi-photon and spin–orbit interactions.These are nonperturbative nonresonant analogs to the inverse Faraday effect,allowing the magnetization to evolve in very high harmonics of the laser frequency(e.g.here up to the 42nd,oscillating at~100 attoseconds),and providing control over the speed of magnetization by tuning the laser power and wavelength.Remarkably,we show that even for linearly polarized driving,where one does not intuitively expect the onset of an induced magnetization,the magnetization transiently oscillates as the system interacts with light.This response is enabled by transverse light-driven currents in the solid,and typically occurs on timescales of~500 attoseconds(with the slower femtosecond response suppressed).An experimental setup capable of measuring these dynamics through pump–probe transient absorption spectroscopy is simulated.Our results pave the way for attosecond regimes of manipulation of magnetism.展开更多
The advancement of laser technology,producing increasingly shorter and more intricate optical pulses,has elevated the significance of precise characterization of a transient electric field,including the carrierenvelop...The advancement of laser technology,producing increasingly shorter and more intricate optical pulses,has elevated the significance of precise characterization of a transient electric field,including the carrierenvelope phase.This characterization must cover progressively larger spectral bands and be performed as close as possible to the experimental site to enable a detailed understanding of the coherent light–matter interaction.Furthermore,in many experiments,two(or more)different ultrashort pulses are used,calling for a technique capable of characterizing multiple electric fields simultaneously.Here,we introduce the TREX(third-order reconstruction of electric fields via cross(X)-correlation)method,which allows the alloptical,in situ characterization of the complete electric fields of 2 broadband pulses with different central wavelengths.The method relies on the measurement of the perturbative third-order nonlinear response generated in a noble gas target while varying the delay between 2 pulses.The resulting spectrograms can be reconstructed using a custom evolutionary algorithm.The technique is demonstrated by retrieving the complete electric field,including the carrier-envelope phase,generated by the coherent synthesis of 2 ultrashort pulses.These synthesized waveforms reach time durations below a single optical cycle,demonstrating the ability of TREX to characterize complex multioctave-spanning electric fields.展开更多
Recent developments in the study of ultracold Rydberg gases demand an adwanced level of experimental sophistication, in which high atomic and optical densities must be combined with excellent control of external field...Recent developments in the study of ultracold Rydberg gases demand an adwanced level of experimental sophistication, in which high atomic and optical densities must be combined with excellent control of external fields and sensitive Rydberg atom detection. We describe a tailored experimental system used to produce and study Rydberg-interacting atoms excited from dense ultracold atomic gases. The experiment has been optimized for fast duty cycles using a high flux cold atom source and a three beam optical dipole trap. The latter enables tuning of the atomic density and temperature over several orders of magnitude, all the way to the Bose--Einstein condensation transition. An elec- trode structure surrounding the atoms allows for precise control over electric fields and single-particle sensitive field ionization detection of Rydberg atoms. We review two experiments which highlight the influence of strong Rydberg---Rydberg interactions on different many-body systems. First, the Rydberg blockade effect is used to pre-structure an atomic gas prior to its spontaneous evolution into an ultracold plasma. Second, hybrid states of photons and atoms called dark-state polaritons are studied. By looking at the statistical distribution of Rydberg excited atoms we reveal correlations between dark-state polaritons. These experiments will ultimately provide a deeper understanding of many-body phenomena in strongly-interacting regimes, including the study of strongly-coupled plasmas and interfaces between atoms and light at the quantum level.展开更多
We generate and measure the versatile vortex linear light bullet, which combines a high-order Bessel beam and an Airy pulse. This three-dimensional optical wave packet propagates without distortion in any medium, whil...We generate and measure the versatile vortex linear light bullet, which combines a high-order Bessel beam and an Airy pulse. This three-dimensional optical wave packet propagates without distortion in any medium, while carrying an orbital angular momentum. Its non-varying feature in linear propagation is verified by a three- dimensional measurement. Such a novel versatile linear light bullet can be useful in various applications such as micromachining.展开更多
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...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.展开更多
The highest resolution of images of soft matter and biological materials is ultimately limited by modification of the structure,induced by the necessarily high energy of short-wavelength radiation.Imaging the inelasti...The highest resolution of images of soft matter and biological materials is ultimately limited by modification of the structure,induced by the necessarily high energy of short-wavelength radiation.Imaging the inelastically scattered X-rays at a photon energy of 60 keV(0.02 nm wavelength)offers greater signal per energy transferred to the sample than coherent-scattering techniques such as phase-contrast microscopy and projection holography.We present images of dried,unstained,and unfixed biological objects obtained by scanning Compton X-ray microscopy,at a resolution of about 70 nm.This microscope was realised using novel wedged multilayer Laue lenses that were fabricated to sub-ångström precision,a new wavefront measurement scheme for hard X rays,and efficient pixel-array detectors.The doses required to form these images were as little as 0.02%of the tolerable dose and 0.05%of that needed for phase-contrast imaging at similar resolution using 17 keV photon energy.The images obtained provide a quantitative map of the projected mass density in the sample,as confirmed by imaging a silicon wedge.Based on these results,we find that it should be possible to obtain radiation damage-free images of biological samples at a resolution below 10 nm.展开更多
In this work,we performed extensive first-principles simulations of high-harmonic generation in the topological Diract semimetal Na_(3)Bi using a first-principles time-dependent density functional theory framework,foc...In this work,we performed extensive first-principles simulations of high-harmonic generation in the topological Diract semimetal Na_(3)Bi using a first-principles time-dependent density functional theory framework,focusing on the effect of spin-orbit coupling(SOC)on the harmonic response.We also derived an analytical model describing the microscopic mechanism of strong-field dynamics in presence of spin-orbit coupling,starting from a locally U(1)×SU(2)gauge-invariant Hamiltonian.Our results reveal that SOC:(i)affects the strong-field excitation of carriers to the conduction bands by modifying the bandstructure of Na_(3)Bi,(ii)makes each spin channel reacts differently to the driven laser by modifying the electron velocity(iii)changes the emission timing of the emitted harmonics.Moreover,we show that the SOC affects the harmonic emission by directly coupling the charge current to the spin currents,paving the way to the high-harmonic spectroscopy of spin currents in solids.展开更多
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 rel...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.展开更多
In a recent article in Nature,Zhou et al.[1]reported an impressive demonstration of Floquet materials engineering.In this field researchers aim at creating properties in materials that they do not usually exhibit in t...In a recent article in Nature,Zhou et al.[1]reported an impressive demonstration of Floquet materials engineering.In this field researchers aim at creating properties in materials that they do not usually exhibit in their equilibrium state.The scope ranges from inducing phase transitions in out-of-equilibrium that can otherwise only be achieved by pressure or doping.展开更多
Multilayer Laue lenses are volume diffraction elements for the efficient focusing of X-rays.With a new manufacturing technique that we introduced,it is possible to fabricate lenses of sufficiently high numerical apert...Multilayer Laue lenses are volume diffraction elements for the efficient focusing of X-rays.With a new manufacturing technique that we introduced,it is possible to fabricate lenses of sufficiently high numerical aperture(NA)to achieve focal spot sizes below 10 nm.The alternating layers of the materials that form the lens must span a broad range of thicknesses on the nanometer scale to achieve the necessary range of X-ray deflection angles required to achieve a high NA.This poses a challenge to both the accuracy of the deposition process and the control of the materials properties,which often vary with layer thickness.We introduced a new pair of materials—tungsten carbide and silicon carbide—to prepare layered structures with smooth and sharp interfaces and with no material phase transitions that hampered the manufacture of previous lenses.Using a pair of multilayer Laue lenses(MLLs)fabricated from this system,we achieved a two-dimensional focus of 8.4×6.8 nm2 at a photon energy of 16.3 keV with high diffraction efficiency and demonstrated scanning-based imaging of samples with a resolution well below 10 nm.The high NA also allowed projection holographic imaging with strong phase contrast over a large range of magnifications.An error analysis indicates the possibility of achieving 1 nm focusing.展开更多
In this work,we report on modeling results obtained with our recently developed simulation tool enabling nanoscopic description of electronic processes in X-ray irradiated ferromagnetic materials.With this tool,we hav...In this work,we report on modeling results obtained with our recently developed simulation tool enabling nanoscopic description of electronic processes in X-ray irradiated ferromagnetic materials.With this tool,we have studied the response of Co/Pt multilayer system irradiated by an ultrafast extreme ultraviolet pulse at the M-edge of Co(photon energy~60 eV).It was previously investigated experimentally at the FERMI free-electron-laser facility,using the magnetic small-angle X-ray scattering technique.Our simulations show that the magnetic scattering signal from cobalt decreases on femtosecond timescales due to electronic excitation,relaxation,and transport processes both in the cobalt and in the platinum layers,following the trend observed in the experimental data.The confirmation of the predominant role of electronic processes for X-ray induced demagnetization in the regime below the structural damage threshold is a step toward quantitative control and manipulation of X-ray induced magnetic processes on femtosecond timescales.展开更多
Ultrafast optical control of ferroelectricity using intense terahertz fields has attracted significant interest.Here we show that the nonlinear interactions between two optical phonons in SnTe,a two-dimensional in-pla...Ultrafast optical control of ferroelectricity using intense terahertz fields has attracted significant interest.Here we show that the nonlinear interactions between two optical phonons in SnTe,a two-dimensional in-plane ferroelectric material,enables a dynamical amplification of the electric polarization within subpicoseconds time domain.Our first-principles time-dependent simulations show that the infrared-active out-of-plane phonon mode,pumped to nonlinear regimes,spontaneously generates in-plane motions,leading to rectified oscillations in the in-plane electric polarization.We suggest that this dynamical control of ferroelectric material,by nonlinear phonon excitation,can be utilized to achieve ultrafast control of the photovoltaic or other nonlinear optical responses.展开更多
Magneto-optical response,i.e.optical response in the presence of a magnetic field,is commonly used for characterization of materials and in optical communications.However,quantum mechanical description of electric and...Magneto-optical response,i.e.optical response in the presence of a magnetic field,is commonly used for characterization of materials and in optical communications.However,quantum mechanical description of electric and magnetic fields in crystals is not straightforward as the position operator is ill defined.We present a reformulation of the density matrix perturbation theory for time-dependent electromagnetic fields under periodic boundary conditions,which allows us to treat the orbital magneto-optical response of solids at the ab initio level.The efficiency of the computational scheme proposed is comparable to standard linearresponse calculations of absorption spectra and the results of tests for molecules and solids agree with the available experimental data.A clear signature of the valley Zeeman effect is revealed in the continuum magneto-optical spectrum of a single layer of hexagonal boron nitride.The present formalism opens the path towards the study of magneto-optical effects in strongly driven low-dimensional systems.展开更多
The idea of using ultrashort X-ray pulses to obtain images of single proteins frozen in time has fascinated and inspired many.It was one of the arguments for building X-ray free-electron lasers.According to theory,the...The idea of using ultrashort X-ray pulses to obtain images of single proteins frozen in time has fascinated and inspired many.It was one of the arguments for building X-ray free-electron lasers.According to theory,the extremely intense pulses provide sufficient signal to dispense with using crystals as an amplifier,and the ultrashort pulse duration permits capturing the diffraction data before the sample inevitably explodes.This was first demonstrated on biological samples a decade ago on the giant mimivirus.Since then,a large collaboration has been pushing the limit of the smallest sample that can be imaged.The ability to capture snapshots on the timescale of atomic vibrations,while keeping the sample at room temperature,may allow probing the entire conformational phase space of macromolecules.Here we show the first observation of an X-ray diffraction pattern from a single protein,that of Escherichia coli GroEL which at 14 nm in diameter is the smallest biological sample ever imaged by X-rays,and demonstrate that the concept of diffraction before destruction extends to single proteins.From the pattern,it is possible to determine the approximate orientation of the protein.Our experiment demonstrates the feasibility of ultrafast imaging of single proteins,opening the way to single-molecule time-resolved studies on the femtosecond timescale.展开更多
Coherent x-ray imaging and scattering from accelerator based sources such as synchrotrons continue to impact biology,medicine,technology,and materials science.Many synchrotrons around the world are currently undergoin...Coherent x-ray imaging and scattering from accelerator based sources such as synchrotrons continue to impact biology,medicine,technology,and materials science.Many synchrotrons around the world are currently undergoing major upgrades to increase their available coherent x-ray flux by approximately two orders of magnitude.The improvement of synchrotrons may enable imaging of materials in operando at the atomic scale which may revolutionize battery and catalysis technologies.Current algorithms used for phase retrieval in coherent x-ray imaging are based on the projection onto sets method.These traditional iterative phase retrieval methods will become more computationally expensive as they push towards atomic resolution and may struggle to converge.Additionally,these methods do not incorporate physical information that may additionally constrain the solution.In this work,we present an algorithm which incorporates molecular dynamics into Bragg coherent diffraction imaging(BCDI).This algorithm,which we call PRAMMol(Phase Retrieval with Atomic Modeling and Molecular Dynamics)combines statistical techniques with molecular dynamics to solve the phase retrieval problem.We present several examples where our algorithm is applied to simulated coherent diffraction from 3D crystals and show convergence to the correct solution at the atomic scale.展开更多
基金Project supported by the Science Challenge Project(Grant No.TZ2016005)the National Key Research and Development Program of China(Grant Nos.2017YFA0403200 and 2017YFA0402300)the CAEP Foundation(Grant No.CX2019022)。
文摘The scattering matrices of e+N^(+)with J^(π)=1.5^(+)in discrete energy regions are calculated using the eigenchannel R-matrix method.We obtain good parameters of multichannel quantum defect theory(MQDT)that vary smoothly as the function of the energy resulting from the analytical continuation property of the scattering matrices.By employing the MQDT,all discrete energy levels for N could be calculated accurately without missing anyone.The MQDT parameters(i.e.,scattering matrices)can be calibrated with the available precise spectroscopy values.In this work,the optical oscillator strengths for the transition between the ground state and Rydberg series are obtained,which provide rich data for the diagnostic analysis of plasma.
基金supported by EU Horizon 2020 Framework Programme—Grant Agreement No.:965124(FEMTOCHIP)Deutsche Forschungsgemeinschaft(SP2111)contract number PACE:Ka908/10-1Open Access funding enabled and organized by Projekt DEAL.
文摘High-power tunable lasers are intensely pursued due to their vast application potential such as in telecom,ranging,and molecular sensing.Integrated photonics,however,is usually considered not suitable for high-power applications mainly due to its small size which limits the energy storage capacity and,therefore,the output power.In the late 90s,to improve the beam quality and increase the stored energy,large-mode-area(LMA)fibers were introduced in which the optical mode area is substantially large.Such LMA fibers have transformed the high-power capability of fiber systems ever since.Introducing such an LMA technology at the chip-scale can play an equally disruptive role with high power signal generation from an integrated photonics system.To this end,in this work we demonstrate such a technology,and show a very high-power tunable laser with the help of a silicon photonics based LMA power amplifier.We show output power reaching 1.8 W over a tunability range of 60 nm,spanning from 1.83μm to 1.89μm,limited only by the seed laser.Such an integrated LMA device can be used to substantially increase the power of the existing integrated tunable lasers currently limited to a few tens of milliwatts.The power levels demonstrated here reach and surpass that of many benchtop systems which truly makes the silicon photonics based integrated LMA device poised towards mass deployment for high power applications without relying on benchtop systems.
基金financial support by the Defense Advanced Research Projects Agency(DARPA)Direct On-Chip Digital Optical Synthesizer(DODOS)project(HR0011-15-C-0056,program manager:Dr.Gordon Keeler)the Deutsche Forschungsgemeinschaft through Priority Program SPP-1221,DFG 18-17 PACE+1 种基金the Deutsches Elektronen Synchrotron-DESYsupported by a National Science Scholarship(NSS)from the Agency for Science,Technology and Research(A*STAR),Singapore.
文摘Optical frequency synthesizers have widespread applications in optical spectroscopy,frequency metrology,and many other fields.However,their applicability is currently limited by size,cost,and power consumption.Silicon photonics technology,which is compatible with complementary-metal-oxide-semiconductor fabrication processes,provides a low-cost,compact size,lightweight,and low-power-consumption solution.In this work,we demonstrate an optical frequency synthesizer using a fully integrated silicon-based tunable laser.The synthesizer can be self-calibrated by tuning the repetition rate of the internal mode-locked laser.A 20 nm tuning range from 1544 to 1564 nm is achieved with~10−13 frequency instability at 10 s averaging time.Its flexibility and fast reconfigurability are also demonstrated by fine tuning the synthesizer and generating arbitrary specified patterns over time-frequency coordinates.This work promotes the frequency stability of silicon-based integrated tunable lasers and paves the way toward chip-scale lowcost optical frequency synthesizers.
基金support by the European Research Council under the European Union's Seventh Framework Program(FP/2007-2013)/ERC Grant Agreement No.609920the Cluster of Excellence:The Hamburg Centre for Ultrafast Imaging-Structure,Dynamics and Control of Matter at the Atomic Scale of the Deutsche Forschungsgemeinschaft.
文摘Synchronous laser-microwave networks delivering attosecond timing precision are highly desirable in many advanced applications,such as geodesy,very-long-baseline interferometry,high-precision navigation and multi-telescope arrays.In particular,rapidly expanding photon-science facilities like X-ray free-electron lasers and intense laser beamlines require system-wide attosecond-level synchronization of dozens of optical and microwave signals up to kilometer distances.Once equipped with such precision,these facilities will initiate radically new science by shedding light on molecular and atomic processes happening on the attosecond timescale,such as intramolecular charge transfer,Auger processes and their impacts on X-ray imaging.Here we present for the first time a complete synchronous laser-microwave network with attosecond precision,which is achieved through new metrological devices and careful balancing of fiber nonlinearities and fundamental noise contributions.We demonstrate timing stabilization of a 4.7-km fiber network and remote optical–optical synchronization across a 3.5-km fiber link with an overall timing jitter of 580 and 680 attoseconds root-mean-square,respectively,for over 40 h.Ultimately,we realize a complete laser-microwave network with 950-attosecond timing jitter for 18 h.This work can enable nextgeneration attosecond photon-science facilities to revolutionize many research fields from structural biology to material science and chemistry to fundamental physics.
基金supported by the European Research Council under the European Union’s Seventh Framework Programme(FP/2007-2013)/ERC Grant Agreement n.609920the excellence cluster’The Hamburg Centre for Ultrafast Imaging-Structure,Dynamics and Control of Matter at the Atomic Scale’of the Deutsche Forschungsgemeinschaftsupport by a Helmholtz Postdoctoral grant
文摘We present possible conceptual designs of a laser system for driving table-top free-electron lasers based on terahertz acceleration. After discussing the achievable performances of laser amplifiers with Yb:YAG at cryogenic and room temperature and Yb:YLF at cryogenic temperature, we present amplification modules with available results and concepts of amplifier chains based on these laser media. Their performances are discussed in light of the specifications for the tasks within the table-top light source. Technical and engineering challenges, such as cooling, control, synchronization and diagnostics, are outlined. Three concepts for the laser layout feeding the accelerator are eventually derived and presented.
基金This work was supported by the Cluster of Excellence Advanced Imaging of Matter(AIM),Grupos Consolidados(IT1249-19),SFB925“Light induced dynamics and control of correlated quantum systems”and has received funding from the European Union’s Horizon 2020 research and innovation program under the Marie Skłodowska-Curie grant agreement No.860553.The Flatiron Institute is a division of the Simons Foundation.O.N.gratefully acknowledges the generous support of a Schmidt Science Fellowship。
文摘Irradiating solids with ultrashort laser pulses is known to initiate femtosecond timescale magnetization dynamics.However,sub-femtosecond spin dynamics have not yet been observed or predicted.Here,we explore ultrafast light-driven spin dynamics in a highly nonresonant strong-field regime.Through state-of-the-art ab initio calculations,we predict that a nonmagnetic material can transiently transform into a magnetic one via dynamical extremely nonlinear spin-flipping processes,which occur on attosecond timescales and are mediated by cascaded multi-photon and spin–orbit interactions.These are nonperturbative nonresonant analogs to the inverse Faraday effect,allowing the magnetization to evolve in very high harmonics of the laser frequency(e.g.here up to the 42nd,oscillating at~100 attoseconds),and providing control over the speed of magnetization by tuning the laser power and wavelength.Remarkably,we show that even for linearly polarized driving,where one does not intuitively expect the onset of an induced magnetization,the magnetization transiently oscillates as the system interacts with light.This response is enabled by transverse light-driven currents in the solid,and typically occurs on timescales of~500 attoseconds(with the slower femtosecond response suppressed).An experimental setup capable of measuring these dynamics through pump–probe transient absorption spectroscopy is simulated.Our results pave the way for attosecond regimes of manipulation of magnetism.
基金supported by the Helmholtz Asso ciation Program MML-Matter,by the Cluster of Excellence“CUI:Advanced Imaging of Matter”of the Deutsche Forschungsgemeinschaft(DFG)(EXC 2056-project ID 390715994)by PIER,the partnership of Universit鋞Hamburg and DESY(grant ID PIF-2022-07).
文摘The advancement of laser technology,producing increasingly shorter and more intricate optical pulses,has elevated the significance of precise characterization of a transient electric field,including the carrierenvelope phase.This characterization must cover progressively larger spectral bands and be performed as close as possible to the experimental site to enable a detailed understanding of the coherent light–matter interaction.Furthermore,in many experiments,two(or more)different ultrashort pulses are used,calling for a technique capable of characterizing multiple electric fields simultaneously.Here,we introduce the TREX(third-order reconstruction of electric fields via cross(X)-correlation)method,which allows the alloptical,in situ characterization of the complete electric fields of 2 broadband pulses with different central wavelengths.The method relies on the measurement of the perturbative third-order nonlinear response generated in a noble gas target while varying the delay between 2 pulses.The resulting spectrograms can be reconstructed using a custom evolutionary algorithm.The technique is demonstrated by retrieving the complete electric field,including the carrier-envelope phase,generated by the coherent synthesis of 2 ultrashort pulses.These synthesized waveforms reach time durations below a single optical cycle,demonstrating the ability of TREX to characterize complex multioctave-spanning electric fields.
文摘Recent developments in the study of ultracold Rydberg gases demand an adwanced level of experimental sophistication, in which high atomic and optical densities must be combined with excellent control of external fields and sensitive Rydberg atom detection. We describe a tailored experimental system used to produce and study Rydberg-interacting atoms excited from dense ultracold atomic gases. The experiment has been optimized for fast duty cycles using a high flux cold atom source and a three beam optical dipole trap. The latter enables tuning of the atomic density and temperature over several orders of magnitude, all the way to the Bose--Einstein condensation transition. An elec- trode structure surrounding the atoms allows for precise control over electric fields and single-particle sensitive field ionization detection of Rydberg atoms. We review two experiments which highlight the influence of strong Rydberg---Rydberg interactions on different many-body systems. First, the Rydberg blockade effect is used to pre-structure an atomic gas prior to its spontaneous evolution into an ultracold plasma. Second, hybrid states of photons and atoms called dark-state polaritons are studied. By looking at the statistical distribution of Rydberg excited atoms we reveal correlations between dark-state polaritons. These experiments will ultimately provide a deeper understanding of many-body phenomena in strongly-interacting regimes, including the study of strongly-coupled plasmas and interfaces between atoms and light at the quantum level.
文摘We generate and measure the versatile vortex linear light bullet, which combines a high-order Bessel beam and an Airy pulse. This three-dimensional optical wave packet propagates without distortion in any medium, while carrying an orbital angular momentum. Its non-varying feature in linear propagation is verified by a three- dimensional measurement. Such a novel versatile linear light bullet can be useful in various applications such as micromachining.
基金supported by the European Research Council under the European Union’s Seventh Framework Programme(FP7/2007-2013)through the Synergy Grant AXSIS(609920)Project KA908-12/1 of the Deutsche Forschungsgemeinschaft,the Cluster of Excellence“CUI:Advanced Imaging of Matter”of the Deutsche Forschungsgemeinschaft(DFG)—EXC 2056—project ID 390715994the Accelerator on a Chip Program(ACHIP)funded by the Gordon and Betty Moore Foundation(GBMF4744).
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.
基金We thank Martin Domaracky,Florian Laucks,Jerome Carnis(CFEL)for support with controls and data acquisition software,Sabrina Bolmer,Harumi Nakatsutsumi,Tjark Delmas(CFEL)for technical work,Christian Hamm(AWI,Bremerhaven,Germany)for the diatom sample,Klara Gregorič(Univ.of Ljubljana,Slovenia)and Iosifina Sarrou for preparing the spirulina sample,and Miriam Barthelmeß(CFEL)for the silicon sample.We also thank X-Spectrum(Hamburg,Germany)for support with CdTe detectors.We acknowledge support by DESY(Hamburg,Germany),a member of the Helmholtz Association HGF and by the Cluster of Excellence‘Advanced Imaging of Matter’of the Deutsche Forschungsgemeinschaft(DFG)-EXC 2056-project ID 390715994.
文摘The highest resolution of images of soft matter and biological materials is ultimately limited by modification of the structure,induced by the necessarily high energy of short-wavelength radiation.Imaging the inelastically scattered X-rays at a photon energy of 60 keV(0.02 nm wavelength)offers greater signal per energy transferred to the sample than coherent-scattering techniques such as phase-contrast microscopy and projection holography.We present images of dried,unstained,and unfixed biological objects obtained by scanning Compton X-ray microscopy,at a resolution of about 70 nm.This microscope was realised using novel wedged multilayer Laue lenses that were fabricated to sub-ångström precision,a new wavefront measurement scheme for hard X rays,and efficient pixel-array detectors.The doses required to form these images were as little as 0.02%of the tolerable dose and 0.05%of that needed for phase-contrast imaging at similar resolution using 17 keV photon energy.The images obtained provide a quantitative map of the projected mass density in the sample,as confirmed by imaging a silicon wedge.Based on these results,we find that it should be possible to obtain radiation damage-free images of biological samples at a resolution below 10 nm.
基金This work was supported by the European Research Council(ERC-2015-AdG694097)the Cluster of Excellence‘Advanced Imaging of Matter’(AIM),Grupos Consolidados(IT1249-19)and SFB925.
文摘In this work,we performed extensive first-principles simulations of high-harmonic generation in the topological Diract semimetal Na_(3)Bi using a first-principles time-dependent density functional theory framework,focusing on the effect of spin-orbit coupling(SOC)on the harmonic response.We also derived an analytical model describing the microscopic mechanism of strong-field dynamics in presence of spin-orbit coupling,starting from a locally U(1)×SU(2)gauge-invariant Hamiltonian.Our results reveal that SOC:(i)affects the strong-field excitation of carriers to the conduction bands by modifying the bandstructure of Na_(3)Bi,(ii)makes each spin channel reacts differently to the driven laser by modifying the electron velocity(iii)changes the emission timing of the emitted harmonics.Moreover,we show that the SOC affects the harmonic emission by directly coupling the charge current to the spin currents,paving the way to the high-harmonic spectroscopy of spin currents in solids.
基金supported,in part,by the Ministry of Education,Culture,Sports,Science and Technology of Japan(MEXT)through grants-in-aid under grants 17H01067,19H05628,and 21H01850in part by the FY 2019 Presidents Discretionary Funds of RIKEN+5 种基金in part by the Matsuo Foundation.B.X.acknowledges financial support from RIKEN for a Special Postdoctoral Researcher.Y.F.acknowledges support by the National Natural Science Foundation of China(92050107 and 61690222)Major Science and Technology Infrastructure Preresearch Program of the CAS(J20-021-III)Key Deployment Research Program of XIOPM(S19-020-III).K.M.acknowledges support by the MEXT Quantum Leap Flagship Program(MEXT Q-LEAP)grant number JP-MXS0118068681.P.L.acknowledges support by the National Key Research and Development Program(2017YFE0116600)the National Natural Science Foundation of China(91950202)the Science and Technology Planning Project of Guangdong Province(2018B090944001)O.D.M.acknowledges support by the priority program QUTIF(SPP1840 SOLSTICE)of Deutsche Forschungsgemeinschaft.
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.
基金supported by the Cluster of Excellence’CUI:Advanced Imaging of Matter’–EXC 2056–project ID 390715994 and SFB-925“Light induced dynamics and control of correlated quantum systems”—project 170620586 of the Deutsche Forschungsgemeinschaft(DFG)and Grupos Consolidados(IT1453-22).The Flatiron Institute is a division of the Simons Foundation.
文摘In a recent article in Nature,Zhou et al.[1]reported an impressive demonstration of Floquet materials engineering.In this field researchers aim at creating properties in materials that they do not usually exhibit in their equilibrium state.The scope ranges from inducing phase transitions in out-of-equilibrium that can otherwise only be achieved by pressure or doping.
基金supported by Joachim Herz Stiftungthe Helmholtz Association through program-oriented funds.
文摘Multilayer Laue lenses are volume diffraction elements for the efficient focusing of X-rays.With a new manufacturing technique that we introduced,it is possible to fabricate lenses of sufficiently high numerical aperture(NA)to achieve focal spot sizes below 10 nm.The alternating layers of the materials that form the lens must span a broad range of thicknesses on the nanometer scale to achieve the necessary range of X-ray deflection angles required to achieve a high NA.This poses a challenge to both the accuracy of the deposition process and the control of the materials properties,which often vary with layer thickness.We introduced a new pair of materials—tungsten carbide and silicon carbide—to prepare layered structures with smooth and sharp interfaces and with no material phase transitions that hampered the manufacture of previous lenses.Using a pair of multilayer Laue lenses(MLLs)fabricated from this system,we achieved a two-dimensional focus of 8.4×6.8 nm2 at a photon energy of 16.3 keV with high diffraction efficiency and demonstrated scanning-based imaging of samples with a resolution well below 10 nm.The high NA also allowed projection holographic imaging with strong phase contrast over a large range of magnifications.An error analysis indicates the possibility of achieving 1 nm focusing.
基金V.T.,A.L.,S.M.,B.Z.acknowledge the funding received from the Collaboration Grant of the European XFEL and the Institute of Nuclear Physics,Polish Academy of SciencesK.J.K.thanks the Polish National Agency for Academic Exchange for funding in the frame of the Bekker programme(PPN/BEK/2020/1/00184)+1 种基金K.J.K.acknowledges also the CFEL-DESY Theory group for the hospitality during his six-month research stay in Hamburg in 2019–2020 financed by the National Science Centre(Poland)under the program SONATINA 1 no.2017/24/C/ST3/00276L.M.and A.P.-K.acknowledge funding by the Deutsche Forschungsgemeinschaft(DFG,German Research Foundation)-SFB-925-project 170620586.
文摘In this work,we report on modeling results obtained with our recently developed simulation tool enabling nanoscopic description of electronic processes in X-ray irradiated ferromagnetic materials.With this tool,we have studied the response of Co/Pt multilayer system irradiated by an ultrafast extreme ultraviolet pulse at the M-edge of Co(photon energy~60 eV).It was previously investigated experimentally at the FERMI free-electron-laser facility,using the magnetic small-angle X-ray scattering technique.Our simulations show that the magnetic scattering signal from cobalt decreases on femtosecond timescales due to electronic excitation,relaxation,and transport processes both in the cobalt and in the platinum layers,following the trend observed in the experimental data.The confirmation of the predominant role of electronic processes for X-ray induced demagnetization in the regime below the structural damage threshold is a step toward quantitative control and manipulation of X-ray induced magnetic processes on femtosecond timescales.
基金We further acknowledge financial support from the European Research Council(ERC-2015-AdG-694097)the Clusters of Excellence Advanced Imaging of Matter(AIM,EXC 2056,ID 390715994)+2 种基金Grupos Consolidados(IT1249-19),and SFB925.D.S.acknowledges the support from National Research Foundation of Korea(NRF-2019R1A6A3A03031296)N.P.was supported by National Research Foundation of Korea(NRF-2019R1A2C2089332)The Flatiron Institute is a division of the Simons Foundation.
文摘Ultrafast optical control of ferroelectricity using intense terahertz fields has attracted significant interest.Here we show that the nonlinear interactions between two optical phonons in SnTe,a two-dimensional in-plane ferroelectric material,enables a dynamical amplification of the electric polarization within subpicoseconds time domain.Our first-principles time-dependent simulations show that the infrared-active out-of-plane phonon mode,pumped to nonlinear regimes,spontaneously generates in-plane motions,leading to rectified oscillations in the in-plane electric polarization.We suggest that this dynamical control of ferroelectric material,by nonlinear phonon excitation,can be utilized to achieve ultrafast control of the photovoltaic or other nonlinear optical responses.
基金We acknowledge the financial support from the European Research Council(ERC-2015-AdG-694097)Grupos Consolidados(IT578-13)+2 种基金European Union’s H2020 program under GA no.646259(MOSTOPHOS)no.676580(NOMAD)Spanish Ministry(MINECO)Grant no.FIS2016-79464-P.
文摘Magneto-optical response,i.e.optical response in the presence of a magnetic field,is commonly used for characterization of materials and in optical communications.However,quantum mechanical description of electric and magnetic fields in crystals is not straightforward as the position operator is ill defined.We present a reformulation of the density matrix perturbation theory for time-dependent electromagnetic fields under periodic boundary conditions,which allows us to treat the orbital magneto-optical response of solids at the ab initio level.The efficiency of the computational scheme proposed is comparable to standard linearresponse calculations of absorption spectra and the results of tests for molecules and solids agree with the available experimental data.A clear signature of the valley Zeeman effect is revealed in the continuum magneto-optical spectrum of a single layer of hexagonal boron nitride.The present formalism opens the path towards the study of magneto-optical effects in strongly driven low-dimensional systems.
基金supported by the Universität Hamburg and DFG grant numbers(INST 152/772-1|152/774-1|152/775-1|152/776-1|152/777-1 FUGG)We acknowledge the support of funding from:Cluster of Excellence‘CUI:Advanced Imaging of Matter’of the Deutsche Forschungsgemeinschaft(DFG)-EXC 2056-project ID 390715994+7 种基金ERC-2013-CoG COMOTION 614507NFR 240770Fellowship from the Joachim Herz Stiftung(P.L.X.)P.L.X.and H.N.C.acknowledge support from the Human Frontiers Science Program(RGP0010/2017)J.H.acknowledges support from the European Development Fund:Structural dynamics of biomolecular systems(ELIBIO)(CZ.02.1.01/0.0/0.0/15_003/0000447)EMBO long-term fellowship(ALTF 356-2018)awarded to L.E.F.the Röntgen-Ångström Cluster(2015-06107 and 2019-06092)the Swedish Research Council(2017-05336,2018-00234 and 2019-03935)the Swedish Foundation for Strategic Research(ITM17-0455).
文摘The idea of using ultrashort X-ray pulses to obtain images of single proteins frozen in time has fascinated and inspired many.It was one of the arguments for building X-ray free-electron lasers.According to theory,the extremely intense pulses provide sufficient signal to dispense with using crystals as an amplifier,and the ultrashort pulse duration permits capturing the diffraction data before the sample inevitably explodes.This was first demonstrated on biological samples a decade ago on the giant mimivirus.Since then,a large collaboration has been pushing the limit of the smallest sample that can be imaged.The ability to capture snapshots on the timescale of atomic vibrations,while keeping the sample at room temperature,may allow probing the entire conformational phase space of macromolecules.Here we show the first observation of an X-ray diffraction pattern from a single protein,that of Escherichia coli GroEL which at 14 nm in diameter is the smallest biological sample ever imaged by X-rays,and demonstrate that the concept of diffraction before destruction extends to single proteins.From the pattern,it is possible to determine the approximate orientation of the protein.Our experiment demonstrates the feasibility of ultrafast imaging of single proteins,opening the way to single-molecule time-resolved studies on the femtosecond timescale.
基金supported by the DOE Office of Science(Office of Basic Energy Sciences)(Award number DE-SC0022133)Argonne National Laboratory operated by DOE Office of Science User Facility operated under Contract No.AC02-06CH11357.
文摘Coherent x-ray imaging and scattering from accelerator based sources such as synchrotrons continue to impact biology,medicine,technology,and materials science.Many synchrotrons around the world are currently undergoing major upgrades to increase their available coherent x-ray flux by approximately two orders of magnitude.The improvement of synchrotrons may enable imaging of materials in operando at the atomic scale which may revolutionize battery and catalysis technologies.Current algorithms used for phase retrieval in coherent x-ray imaging are based on the projection onto sets method.These traditional iterative phase retrieval methods will become more computationally expensive as they push towards atomic resolution and may struggle to converge.Additionally,these methods do not incorporate physical information that may additionally constrain the solution.In this work,we present an algorithm which incorporates molecular dynamics into Bragg coherent diffraction imaging(BCDI).This algorithm,which we call PRAMMol(Phase Retrieval with Atomic Modeling and Molecular Dynamics)combines statistical techniques with molecular dynamics to solve the phase retrieval problem.We present several examples where our algorithm is applied to simulated coherent diffraction from 3D crystals and show convergence to the correct solution at the atomic scale.
