Valleytronic devices based on all-optical ultrafast control are expected to increase the speed of information processing to petahertz and serve a new generation of quantum computers.However,the current difficulty in r...Valleytronic devices based on all-optical ultrafast control are expected to increase the speed of information processing to petahertz and serve a new generation of quantum computers.However,the current difficulty in realizing this vision is the lack of a nondamaging means suitable for ultrafast lasers.We propose a robust scheme to control the valley polarization of monolayer materials,achieved through the quantum interference between 1-and 2-photon transition pathways.The scheme reveals that conventional circularly polarized light is unnecessary for resonantly induced valley polarization and,instead,only a parallel-polarized 2-color field is required.The interference dynamics enables the switch of valley to be manipulated within few femtoseconds without the necessity for extremely strong or single-cycle pulses.The disclosure of this interference scheme enables repetitive operations in valley devices for signal processing at petahertz clock rates without causing material damage.It sheds light on the practical manufacture of high-speed valleytronic devices.展开更多
Recent advancements in high-energy terahertz(THz)sources,driven by powerful laser systems,now enable the generation of ultrashort THz pulses with energies up to several millijoules,spanning frequencies from 1 to 30 TH...Recent advancements in high-energy terahertz(THz)sources,driven by powerful laser systems,now enable the generation of ultrashort THz pulses with energies up to several millijoules,spanning frequencies from 1 to 30 THz.A key breakthrough is developing a reliable single-shot detection method,essential for measuring the electric field of these broadband,low-repetition-rate pulses,which is vital for exploring the complex dynamics of THz emission and studying extreme nonlinear material responses in this range.Existing detection methods have been limited to lower frequencies.Here,we introduce the first potentially single-shot-capable THz detection technique for capturing ultra-broadband waveforms.Utilizing a 1-μm-thick SiN detection chip,we exploit THz field-induced second harmonic generation to achieve real-time monitoring of THz waveforms with frequency content up to 30 THz.By adjusting the angle between the THz and optical probe beams,we can fine-tune the detection window for enhanced flexibility.Our novel THz detector is ideally suited for high-energy,low-repetition-rate sources,unlocking new frontiers in THz research.展开更多
Dissipative Kerr solitons in optical microcavities enable various stable states involving multi-soliton and perfect soliton crystal(PSC),leading to widespread applications.However,the triggering condition and switchin...Dissipative Kerr solitons in optical microcavities enable various stable states involving multi-soliton and perfect soliton crystal(PSC),leading to widespread applications.However,the triggering condition and switching dynamics of the PSC and multi-soliton states(MSs)remain unexplored,which makes it challenging to selectively trigger the PSC/MS state for distinct area.Here,we theoretically and experimentally investigate the realization and switching of multi-/single-soliton and PSC states by engineering the periodic intracavity potential field constructed by control laser in a high-Q microrod cavity.We show that,by varying the parameters of the control laser,the PSC and multi-/single-soliton states can be selectively excited,and the soliton dynamics depends on the chaotic regime.We establish a fundamental link between the PSC switching behavior with the transient chaotic regime.Using such relation,we also demonstrate the switching and dynamical phenomena involving the conversion between PSC and MS,and soliton crystal melting and recrystallization.Our work provides additional routes for manipulation of soliton temporal and spectral profiles in optical microcavity systems and enables soliton generation on demand with desired states inside a single device.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
Dual-comb spectroscopy provides a marked advantage over single-comb techniques for molecular fingerprinting,particularly in terms of scanning speed.The single-cavity dual-comb system is a simpler approach to dual-comb...Dual-comb spectroscopy provides a marked advantage over single-comb techniques for molecular fingerprinting,particularly in terms of scanning speed.The single-cavity dual-comb system is a simpler approach to dual-comb operation.This system utilized a single free-running oscillator to generate both combs,eliminating the complex setups with multiple lasers.Here,we report a high-power deep ultraviolet(DUV)dual comb driven by a thin-disk single-cavity(TDSC)Yb:YAG dual-comb laser.A TDSC Yb:YAG oscillator generates 2 comb beams with repetition rates near 76 MHz,differing by a few kilohertz and tunable by adjusting one cavity arm.Both combs operate at a central wavelength of 1,030 nm with pulse durations of 431 and 411 fs,respectively,and achieve average output powers of 5 W each.We employed the TDSC as a light source for a ranging system,demonstrating a measurement difference accuracy of 1.23μm for a target at 6.5 m with an average acquisition time of 330 ms.To extend the dual comb to DUV region,we generated the second and fourth harmonics using LBO and BBO crystals,respectively,with conversion efficiencies exceeding 40%and 10%for both comb beams.With over 300 mW of power at 258 nm for each comb,we successfully demonstrated DUV dual-comb operation with a frequency difference of 20 kHz.This represents the first DUV dual comb generated by a TDSC laser.Finally,we discussed the prospect of extending the dual-comb range to extreme UV and terahertz dual combs based on the TDSC Yb:YAG laser platform.展开更多
Laser-induced melting plays a crucial role in advanced manufacturing technology and ultrafast science;however,its atomic processes and microscopic mechanisms,especially in a wide-gap ceramic,remain elusive due to comp...Laser-induced melting plays a crucial role in advanced manufacturing technology and ultrafast science;however,its atomic processes and microscopic mechanisms,especially in a wide-gap ceramic,remain elusive due to complex interplays between many degrees of freedom within a timescale of~100 fs.We report here that laser melting is greatly accelerated by intense laser-induced tunnel ionization,instead of a priori multiphoton absorption,in the archetypal ceramic magnesium oxide(MgO).The tunneling processes generate a large number of photocarriers and results in intense energy absorption,instantaneously altering the potential energy surface of lattice configuration.The strong electron–phonon couplings and fast carrier relaxation enable efficient energy transfer between electrons and the lattice.These results account well for the latest ultrafast melting experiments and provide atomistic details and nonequilibrium mechanism of photoinduced ultrafast phase transitions in wide-gap materials.The laser modulation of melting thresholds and phase boundary demonstrate the possibility of manipulating phase transition on demand.A shock wave curve is also obtained at moderate conditions(P=2 GPa),extending Hugoniot curve to new regimes.展开更多
In this paper,a series of calibration-free temperature measurement methods based on light-induced thermoelastic spectroscopy(LITES)are proposed for the first time.These techniques utilize the steady-state and transien...In this paper,a series of calibration-free temperature measurement methods based on light-induced thermoelastic spectroscopy(LITES)are proposed for the first time.These techniques utilize the steady-state and transient response characteristics of the quartz tuning fork(QTF),namely,the calibration-free LITES(CF-LITES)and calibration-free heterodyne LITES(CF-H-LITES)methods.Four methods,first harmonic(1f)difference signal to normalize the second harmonic(2f)fundamental signal(method Ⅰ,2f_(fund)/1f_(diff)),1f overtone signal to normalize the 2f fundamental signal(method Ⅱ,2f_(fund)/1f_(over)),1f heterodyne difference signal to normalize the 2f heterodyne fundamental signal(method Ⅲ,2f-H_(fund)/1f-H_(diff)),and 1f heterodyne overtone signal to normalize the 2f heterodyne fundamental signal(method Ⅳ,2f-H_(fund)/1f-H_(over)),for simultaneously detecting 1f and 2f within the frequency response range of the QTF are proposed to achieve calibration-free measurement.A self-designed T-shaped QTF with low fundamental and overtone frequencies was used to increase the energy accumulation time,thereby enhancing the sensor signal level.A 3-stage tube furnace was adopted to verify the performance of these 4 methods.Experimental results showed that the errors for the 4 methods were less than 4%,with a standard deviation below 11℃.Furthermore,the calibration-free method,which employs normalization of the 2f signal with the 1f signal,effectively mitigates the impact of laser beam jitter and power fluctuations on detection performance.A superior performance can be obtained by adopting the CF-H-LITES technique based on method Ⅳ.It not only has excellent detection performance but also reduces the measurement period to 4 s,which is about 5 times faster.This development shows substantial promise for expanding the application of the CF-LITES and CF-H-LITES techniques in harsh environments.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
Coherent control has been achieved in atoms and small molecules in gas phase during the past few decades.An intriguing demonstration of coherent control is a so-called“dark pulse”that cancels 2-photon transition pro...Coherent control has been achieved in atoms and small molecules in gas phase during the past few decades.An intriguing demonstration of coherent control is a so-called“dark pulse”that cancels 2-photon transition probabilities despite exposing the target to the full power spectrum of transform-limited laser pulses.However,for larger functional molecules in condensed phase at room temperature,ensemble measurements do typically not allow exerting full control over competing pathways due to the unavoidable influence of the surrounding(mostly complex)environment.Here,we demonstrate room-temperature coherent control exploiting a nonresonant 2-photon transition into a higher excited state of single conjugated polymer chains embedded in a disordered matrix,including proof-of-principle experiments on bulk films.To manipulate the 2-photon transition probability,we exploit complex pulse sequences,created by a systematically varied cosinusoidal spectral phase applied to the excitation laser spectrum.For single molecules,the phase-dependent response varies from molecule to molecule,which reflects the spectral heterogeneity(position,linewidth)of their 2-photon transitions.These data indicate that coherent control of single molecules requires optimization of parameters for each individual molecule.The experimental data are reproduced by a simple model that allows to directly retrieve the 2-photon absorption spectrum of each single molecule.Our coherent-control approach is a powerful and robust way to obtain spectral characteristics of higher excited states of single molecules and to manipulate the excited-state dynamics in condensed phase at room temperature.It holds the potential to be useful for the characterization of complex organic functional materials.展开更多
Femtosecond laser ablation-driven periodic surface structuring offers a promising method for large-scale and high-throughput nanolithography technique.However,the self-organized periodic structures typically manifest ...Femtosecond laser ablation-driven periodic surface structuring offers a promising method for large-scale and high-throughput nanolithography technique.However,the self-organized periodic structures typically manifest constraints in terms of tunable period and depth,as well as suboptimal regularity,which restricts their broader application potential.Here,in terms of a rarely explored laser-induced photochemical mechanism for nonablative structuring,we demonstrate manufacturing of sub-wavelength oxidative grating structures on silicon films with active structural modulation.In this scenario,the plasmonic field plays a pivotal role in dragging oxygen ions from surface into the silicon,greatly speeding up oxidation rates.While high oxygen doping levels can already be achieved with single-pulse exposure,far superior results are obtained with the application of 40-MHz burst mode pulse trains,mitigating the formation of excessively large nanocrystallites.Furthermore,it is revealed that the periodicity and modulation depth of laser-writing nanograting are both dependent on the number of pulse per burst.This offers a convenient scheme for actively controlling laser plasmonic lithography.展开更多
The field of ultrafast science is dependent on either ultrashort laser pulse technology or ultrafast passive detection.While there exists a plethora of sub-picosecond laser pulse solutions,streak cameras are singular ...The field of ultrafast science is dependent on either ultrashort laser pulse technology or ultrafast passive detection.While there exists a plethora of sub-picosecond laser pulse solutions,streak cameras are singular in providing sub-picosecond passive imaging capabilities.Therefore,their use in fields ranging from medicine to physics is prevalent.Streak cameras attain such temporal resolutions by converting signal photons to electrons.However,the Coulomb repulsion force spreads these electrons spatiotemporally aggravating streak cameras’temporal resolution and dynamic range—an effect that increases in severity in ultrafast applications where electrons are generated nearly instantaneously.While many electro-optical solutions have been proposed and successfully implemented,this issue remains as a challenge for all sub-picosecond streak camera technology.Instead of resorting to electro-optical solutions,in this work,we present an all-optical approach based on the combination of photon tagging and spatial lock-in detection with a technique called periodic shadowing—that is directly applicable to all generations of streak cameras.We have demonstrated that this accessible all-optical solution,consisting of a single externally applied optical component,results in(a)a>3×improvement in dynamic range,(b)a 25%increase in temporal resolution,and(c)a reduction of background noise levels by a factor of 50,which,when combined,allows for a markedly improved accuracy in the measurement of ultrafast signals.展开更多
Quantum interference occurs frequently in the interaction of laser radiation with materials,leading to a series of fascinating effects such as lasing without inversion,electromagnetically induced transparency,Fano res...Quantum interference occurs frequently in the interaction of laser radiation with materials,leading to a series of fascinating effects such as lasing without inversion,electromagnetically induced transparency,Fano resonance,etc.Such quantum interference effects are mostly enabled by single-photon resonance with transitions in the matter,regardless of how many optical frequencies are involved.Here,we report on quantum interference driven by multiple photons in the emission spectroscopy of nitrogen ions that are resonantly pumped by ultrafast infrared laser pulses.In the spectral domain,Fano resonance is observed in the emission spectrum,where a laser-assisted dynamic Stark effect creates the continuum.In the time domain,the fast-evolving emission is measured,revealing the nature of free-induction decay arising from quantum radiation and molecular cooperativity.These findings clarify the mechanism of coherent emission of nitrogen ions pumped with mid-infrared pump laser and are found to be universal.The present work opens a route to explore the important role of quantum interference during the interaction of intense laser pulses with materials near multiple photon resonance.展开更多
Photoelectron spectroscopy in intense laser fields has proven to be a powerful tool for providing detailed insights into molecular structure.The ionizing molecular orbital,however,has not been reconstructed from the p...Photoelectron spectroscopy in intense laser fields has proven to be a powerful tool for providing detailed insights into molecular structure.The ionizing molecular orbital,however,has not been reconstructed from the photoelectron spectra,because its phase information is difficult to access.Here,we propose a method to retrieve the phase information of the ionizing molecular orbital.By analyzing the interference pattern in the photoelectron spectrum,the weighted coefficients and the relative phases of the constituent atomic orbitals for a molecular orbital can be extracted.With this information,we reconstruct the highest occupied molecular orbital of N2.Our work provides a reliable and straightforward approach for reconstructing molecular orbitals with the photoelectron spectroscopy.展开更多
Atomic time scale imaging,opening a new era for studying dynamics in microcosmos,is presently attracting immense research interest on the global level due to its powerful ability.On the atom level,physics,chemistry,an...Atomic time scale imaging,opening a new era for studying dynamics in microcosmos,is presently attracting immense research interest on the global level due to its powerful ability.On the atom level,physics,chemistry,and biology are identical for researching atom motion and atomic state change.The light possesses twoness,the information carrier and the research resource.The most fundamental principle of this imaging is that light records the event-modulated light field by itself,so-called all-optical imaging.This paper can answer what is the essential standard to develop and evaluate atomic time scale imaging,what is the optimal imaging system,and what are the typical techniques to implement this imaging,up to now.At present,the best record in the experiment,made by multistage optical parametric amplification(MOPA),is realizing 50-fs resolved optical imaging with a spatial resolution of~83 lp/mm at an effective framing rate of 15×10^(12)fps for recording an ultrafast optical lattice with its rotating speed up to 13.5×10^(12)rad/s.展开更多
We investigate the spatial characteristics of high-order harmonic radiation generated in argon and observe cross-like patterns in the far field.An analytical model describing harmonics from an astigmatic driving beam ...We investigate the spatial characteristics of high-order harmonic radiation generated in argon and observe cross-like patterns in the far field.An analytical model describing harmonics from an astigmatic driving beam reveals that these patterns result from the order and generation position-dependent divergence of harmonics.Even small amounts of driving field astigmatism may result in cross-like patterns,coming from the superposition of individual harmonics with spatial profiles elongated in different directions.By correcting the aberrations using a deformable mirror,we show that fine-tuning the driving wavefront is essential for optimal spatial quality of the harmonics.展开更多
Single-shot 2-dimensional optical imaging of transient phenomena is indispensable for numerous areas of study.Among existing techniques,compressed ultrafast photography(CUP)using a chirped ultrashort pulse as active i...Single-shot 2-dimensional optical imaging of transient phenomena is indispensable for numerous areas of study.Among existing techniques,compressed ultrafast photography(CUP)using a chirped ultrashort pulse as active illumination can acquire nonrepetitive time-evolving events at hundreds of trillions of frames per second.However,the bulky size and conventional configurations limit its reliability and application scopes.Superdispersive metalenses offer a promising solution for an ultracompact design with a stable performance by integrating the functions of a focusing lens and dispersive optical components into a single device.Nevertheless,existing metalens designs,typically optimized for the full visible spectrum with a relatively low spectral resolution,cannot be readily applied to active-illumination CUP.To address these limitations,here,we propose single-shot compressed ultracompact femtophotography(CUF)that synergically combines the fields of nanophotonics,optical imaging,compressed sensing,and deep learning.We develop the theory of CUF’s data acquisition composed of temporal–spectral mapping,spatial encoding,temporal shearing,and spatiotemporal integration.We also develop CUF’s image reconstruction via deep learning.Moreover,we design and evaluate CUF’s crucial components—a static binary transmissive mask,a superdispersive metalens,and a 2-dimensional sensor.Finally,using numerical simulations,CUF’s feasibility is verified using 2 synthetic scenes:an ultrafast beam sweeping across a surface and the propagation of a terahertz Cherenkov wave.展开更多
The exploration of optical and photonic phenomena,particularly the modulation of pulse signals and the ultrafast control of light fields at extreme temporal and spatial scales,substantially enhances our understanding ...The exploration of optical and photonic phenomena,particularly the modulation of pulse signals and the ultrafast control of light fields at extreme temporal and spatial scales,substantially enhances our understanding of light-matter interactions and broadens the scope of potential applications inspired by metamaterials and metasurfaces.In this perspective,we highlight advancements in ultrafast metaphotonics by introducing ultrafast pulse shaping and control using metadevices.We begin with a detailed exposition of the principles of metasurfaces and evaluate their role in manipulating light fields in high-frequency and terahertz bands,emphasizing the importance of metasurfaces in ultrafast optics.We then present several methods for controlling the output response of metadevices using external physical fields or phase-change materials to achieve active metadevices.Finally,we anticipate the prospects of this field in terms of fundamental research and practical applications.The integration of these 2 disciplines will drive vibrant developments across multiple fields,including biology,chemistry,and materials science.展开更多
Advancements in light engineering have led to the creation of pulsed laser sources capable of delivering high-repetition-rate,high-power few-cycle laser pulses across a wide spectral range,enabling exploration of many...Advancements in light engineering have led to the creation of pulsed laser sources capable of delivering high-repetition-rate,high-power few-cycle laser pulses across a wide spectral range,enabling exploration of many fascinating nonlinear processes occurring in all states of matter.High-harmonic generation,one such process,which converts the low-frequency photons of the driver laser field into soft x-rays,has revolutionized atomic,molecular,and optical physics,leading to progress in attosecond science and ultrafast optoelectronics.The Extreme Light Infrastructure,Attosecond Light Pulse Source(ELI ALPS)facility pioneers state-of-the-art tools for research in these areas.This paper outlines the design rationale,capabilities,and applications of plasma-and gas-based high-repetition-rate(1 kHz to 100 kHz)attosecond extreme ultraviolet(XUV)beamlines developed at ELI ALPS,highlighting their potential for advancing various research fields.展开更多
基金supported by the Hubei Provincial Natural Science Foundation of China(Grant No.2024AFA029)the National Natural Science Foundation of China(Grant No.12204492)the CAS Project for Young Scientists in Basic Research(Grant No.YSBR-059).
文摘Valleytronic devices based on all-optical ultrafast control are expected to increase the speed of information processing to petahertz and serve a new generation of quantum computers.However,the current difficulty in realizing this vision is the lack of a nondamaging means suitable for ultrafast lasers.We propose a robust scheme to control the valley polarization of monolayer materials,achieved through the quantum interference between 1-and 2-photon transition pathways.The scheme reveals that conventional circularly polarized light is unnecessary for resonantly induced valley polarization and,instead,only a parallel-polarized 2-color field is required.The interference dynamics enables the switch of valley to be manipulated within few femtoseconds without the necessity for extremely strong or single-cycle pulses.The disclosure of this interference scheme enables repetitive operations in valley devices for signal processing at petahertz clock rates without causing material damage.It sheds light on the practical manufacture of high-speed valleytronic devices.
基金supported by the Independent Research Fund Denmark(project THz-GRIP:2035-00365B).
文摘Recent advancements in high-energy terahertz(THz)sources,driven by powerful laser systems,now enable the generation of ultrashort THz pulses with energies up to several millijoules,spanning frequencies from 1 to 30 THz.A key breakthrough is developing a reliable single-shot detection method,essential for measuring the electric field of these broadband,low-repetition-rate pulses,which is vital for exploring the complex dynamics of THz emission and studying extreme nonlinear material responses in this range.Existing detection methods have been limited to lower frequencies.Here,we introduce the first potentially single-shot-capable THz detection technique for capturing ultra-broadband waveforms.Utilizing a 1-μm-thick SiN detection chip,we exploit THz field-induced second harmonic generation to achieve real-time monitoring of THz waveforms with frequency content up to 30 THz.By adjusting the angle between the THz and optical probe beams,we can fine-tune the detection window for enhanced flexibility.Our novel THz detector is ideally suited for high-energy,low-repetition-rate sources,unlocking new frontiers in THz research.
基金supported in part by the National Natural Science Foundation of China(NSFC)(grant number 52375534,52175503,and 51975179)the National Key Research and Development Program of China(grant number 2019YFE010747)the Fundamental Research Funds for the Central Universities(JZ2024HGTG0306).
文摘Dissipative Kerr solitons in optical microcavities enable various stable states involving multi-soliton and perfect soliton crystal(PSC),leading to widespread applications.However,the triggering condition and switching dynamics of the PSC and multi-soliton states(MSs)remain unexplored,which makes it challenging to selectively trigger the PSC/MS state for distinct area.Here,we theoretically and experimentally investigate the realization and switching of multi-/single-soliton and PSC states by engineering the periodic intracavity potential field constructed by control laser in a high-Q microrod cavity.We show that,by varying the parameters of the control laser,the PSC and multi-/single-soliton states can be selectively excited,and the soliton dynamics depends on the chaotic regime.We establish a fundamental link between the PSC switching behavior with the transient chaotic regime.Using such relation,we also demonstrate the switching and dynamical phenomena involving the conversion between PSC and MS,and soliton crystal melting and recrystallization.Our work provides additional routes for manipulation of soliton temporal and spectral profiles in optical microcavity systems and enables soliton generation on demand with desired states inside a single device.
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supported by the Project of Aerosapce Information Research Institute,Chinese Academy of Sciences(E1Z1D101 and E2Z2D101)the Project of Chinese Academy of Sciences(E33310030D)the National Natural Science Foundation of China(62335009).
文摘Dual-comb spectroscopy provides a marked advantage over single-comb techniques for molecular fingerprinting,particularly in terms of scanning speed.The single-cavity dual-comb system is a simpler approach to dual-comb operation.This system utilized a single free-running oscillator to generate both combs,eliminating the complex setups with multiple lasers.Here,we report a high-power deep ultraviolet(DUV)dual comb driven by a thin-disk single-cavity(TDSC)Yb:YAG dual-comb laser.A TDSC Yb:YAG oscillator generates 2 comb beams with repetition rates near 76 MHz,differing by a few kilohertz and tunable by adjusting one cavity arm.Both combs operate at a central wavelength of 1,030 nm with pulse durations of 431 and 411 fs,respectively,and achieve average output powers of 5 W each.We employed the TDSC as a light source for a ranging system,demonstrating a measurement difference accuracy of 1.23μm for a target at 6.5 m with an average acquisition time of 330 ms.To extend the dual comb to DUV region,we generated the second and fourth harmonics using LBO and BBO crystals,respectively,with conversion efficiencies exceeding 40%and 10%for both comb beams.With over 300 mW of power at 258 nm for each comb,we successfully demonstrated DUV dual-comb operation with a frequency difference of 20 kHz.This represents the first DUV dual comb generated by a TDSC laser.Finally,we discussed the prospect of extending the dual-comb range to extreme UV and terahertz dual combs based on the TDSC Yb:YAG laser platform.
基金National Key Research and Development Program of China(no.2021YFA1400200)National Natural Science Foundation of China(nos.12025407,11934003,and 12204513)“Strategic Priority Research Program(B)”of Chinese Academy of Sciences(grant nos.XDB330301 and YSBR047).
文摘Laser-induced melting plays a crucial role in advanced manufacturing technology and ultrafast science;however,its atomic processes and microscopic mechanisms,especially in a wide-gap ceramic,remain elusive due to complex interplays between many degrees of freedom within a timescale of~100 fs.We report here that laser melting is greatly accelerated by intense laser-induced tunnel ionization,instead of a priori multiphoton absorption,in the archetypal ceramic magnesium oxide(MgO).The tunneling processes generate a large number of photocarriers and results in intense energy absorption,instantaneously altering the potential energy surface of lattice configuration.The strong electron–phonon couplings and fast carrier relaxation enable efficient energy transfer between electrons and the lattice.These results account well for the latest ultrafast melting experiments and provide atomistic details and nonequilibrium mechanism of photoinduced ultrafast phase transitions in wide-gap materials.The laser modulation of melting thresholds and phase boundary demonstrate the possibility of manipulating phase transition on demand.A shock wave curve is also obtained at moderate conditions(P=2 GPa),extending Hugoniot curve to new regimes.
基金supported by the National Natural Science Foundation of China(Grant Nos.62335006,62022032,62275065,62405078,and 61875047)the Key Laboratory of Opto-Electronic Information Acquisition and Manipulation(Anhui University),the Ministry of Education(Grant No.OEIAM202202)the Fundamental Research Funds for the Central Universities(Grant No.HIT.OCEF.2023011).
文摘In this paper,a series of calibration-free temperature measurement methods based on light-induced thermoelastic spectroscopy(LITES)are proposed for the first time.These techniques utilize the steady-state and transient response characteristics of the quartz tuning fork(QTF),namely,the calibration-free LITES(CF-LITES)and calibration-free heterodyne LITES(CF-H-LITES)methods.Four methods,first harmonic(1f)difference signal to normalize the second harmonic(2f)fundamental signal(method Ⅰ,2f_(fund)/1f_(diff)),1f overtone signal to normalize the 2f fundamental signal(method Ⅱ,2f_(fund)/1f_(over)),1f heterodyne difference signal to normalize the 2f heterodyne fundamental signal(method Ⅲ,2f-H_(fund)/1f-H_(diff)),and 1f heterodyne overtone signal to normalize the 2f heterodyne fundamental signal(method Ⅳ,2f-H_(fund)/1f-H_(over)),for simultaneously detecting 1f and 2f within the frequency response range of the QTF are proposed to achieve calibration-free measurement.A self-designed T-shaped QTF with low fundamental and overtone frequencies was used to increase the energy accumulation time,thereby enhancing the sensor signal level.A 3-stage tube furnace was adopted to verify the performance of these 4 methods.Experimental results showed that the errors for the 4 methods were less than 4%,with a standard deviation below 11℃.Furthermore,the calibration-free method,which employs normalization of the 2f signal with the 1f signal,effectively mitigates the impact of laser beam jitter and power fluctuations on detection performance.A superior performance can be obtained by adopting the CF-H-LITES technique based on method Ⅳ.It not only has excellent detection performance but also reduces the measurement period to 4 s,which is about 5 times faster.This development shows substantial promise for expanding the application of the CF-LITES and CF-H-LITES techniques in harsh environments.
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.
基金supported by the China Scholarship Council(no.202006170068).
文摘Coherent control has been achieved in atoms and small molecules in gas phase during the past few decades.An intriguing demonstration of coherent control is a so-called“dark pulse”that cancels 2-photon transition probabilities despite exposing the target to the full power spectrum of transform-limited laser pulses.However,for larger functional molecules in condensed phase at room temperature,ensemble measurements do typically not allow exerting full control over competing pathways due to the unavoidable influence of the surrounding(mostly complex)environment.Here,we demonstrate room-temperature coherent control exploiting a nonresonant 2-photon transition into a higher excited state of single conjugated polymer chains embedded in a disordered matrix,including proof-of-principle experiments on bulk films.To manipulate the 2-photon transition probability,we exploit complex pulse sequences,created by a systematically varied cosinusoidal spectral phase applied to the excitation laser spectrum.For single molecules,the phase-dependent response varies from molecule to molecule,which reflects the spectral heterogeneity(position,linewidth)of their 2-photon transitions.These data indicate that coherent control of single molecules requires optimization of parameters for each individual molecule.The experimental data are reproduced by a simple model that allows to directly retrieve the 2-photon absorption spectrum of each single molecule.Our coherent-control approach is a powerful and robust way to obtain spectral characteristics of higher excited states of single molecules and to manipulate the excited-state dynamics in condensed phase at room temperature.It holds the potential to be useful for the characterization of complex organic functional materials.
基金supported by the National Natural Science Foundation of China(12474317 and 62105269).
文摘Femtosecond laser ablation-driven periodic surface structuring offers a promising method for large-scale and high-throughput nanolithography technique.However,the self-organized periodic structures typically manifest constraints in terms of tunable period and depth,as well as suboptimal regularity,which restricts their broader application potential.Here,in terms of a rarely explored laser-induced photochemical mechanism for nonablative structuring,we demonstrate manufacturing of sub-wavelength oxidative grating structures on silicon films with active structural modulation.In this scenario,the plasmonic field plays a pivotal role in dragging oxygen ions from surface into the silicon,greatly speeding up oxidation rates.While high oxygen doping levels can already be achieved with single-pulse exposure,far superior results are obtained with the application of 40-MHz burst mode pulse trains,mitigating the formation of excessively large nanocrystallites.Furthermore,it is revealed that the periodicity and modulation depth of laser-writing nanograting are both dependent on the number of pulse per burst.This offers a convenient scheme for actively controlling laser plasmonic lithography.
基金funded by European Research Council(803634 and 852394)Vetenskapsradet(2019-05183,2021-04506).
文摘The field of ultrafast science is dependent on either ultrashort laser pulse technology or ultrafast passive detection.While there exists a plethora of sub-picosecond laser pulse solutions,streak cameras are singular in providing sub-picosecond passive imaging capabilities.Therefore,their use in fields ranging from medicine to physics is prevalent.Streak cameras attain such temporal resolutions by converting signal photons to electrons.However,the Coulomb repulsion force spreads these electrons spatiotemporally aggravating streak cameras’temporal resolution and dynamic range—an effect that increases in severity in ultrafast applications where electrons are generated nearly instantaneously.While many electro-optical solutions have been proposed and successfully implemented,this issue remains as a challenge for all sub-picosecond streak camera technology.Instead of resorting to electro-optical solutions,in this work,we present an all-optical approach based on the combination of photon tagging and spatial lock-in detection with a technique called periodic shadowing—that is directly applicable to all generations of streak cameras.We have demonstrated that this accessible all-optical solution,consisting of a single externally applied optical component,results in(a)a>3×improvement in dynamic range,(b)a 25%increase in temporal resolution,and(c)a reduction of background noise levels by a factor of 50,which,when combined,allows for a markedly improved accuracy in the measurement of ultrafast signals.
基金supported in part by the National Natural Science Foundation of China(Grant Nos.12034013,12234020,12204308,12174011,and 12104380)the Shanghai Science and Technology Commission(Grant No.22ZR1444100)+1 种基金the Early Career Scheme(No.9048216)NSFC/RGC Collaborative Research Scheme(No.9054901)from the Research Grants Council of Hong Kong.
文摘Quantum interference occurs frequently in the interaction of laser radiation with materials,leading to a series of fascinating effects such as lasing without inversion,electromagnetically induced transparency,Fano resonance,etc.Such quantum interference effects are mostly enabled by single-photon resonance with transitions in the matter,regardless of how many optical frequencies are involved.Here,we report on quantum interference driven by multiple photons in the emission spectroscopy of nitrogen ions that are resonantly pumped by ultrafast infrared laser pulses.In the spectral domain,Fano resonance is observed in the emission spectrum,where a laser-assisted dynamic Stark effect creates the continuum.In the time domain,the fast-evolving emission is measured,revealing the nature of free-induction decay arising from quantum radiation and molecular cooperativity.These findings clarify the mechanism of coherent emission of nitrogen ions pumped with mid-infrared pump laser and are found to be universal.The present work opens a route to explore the important role of quantum interference during the interaction of intense laser pulses with materials near multiple photon resonance.
基金supported by the National Key Program for S&T Research and Development(grant no.2019YFA0307702)the National Natural Science Foundation of China(grant nos.11834015,11922413,12121004,12274420,and 12004394)+3 种基金the Strategic Priority Research Program of the Chinese Academy of Sciences(grant no.XDB210i0400)CAS Project for Young Scientists in Basic Research(grant no.YSBR-055)the Science and Technology Department of Hubei Province(grant nos.2020CFA029 and 2021CFA078)K.C.Wong Education Foundation.
文摘Photoelectron spectroscopy in intense laser fields has proven to be a powerful tool for providing detailed insights into molecular structure.The ionizing molecular orbital,however,has not been reconstructed from the photoelectron spectra,because its phase information is difficult to access.Here,we propose a method to retrieve the phase information of the ionizing molecular orbital.By analyzing the interference pattern in the photoelectron spectrum,the weighted coefficients and the relative phases of the constituent atomic orbitals for a molecular orbital can be extracted.With this information,we reconstruct the highest occupied molecular orbital of N2.Our work provides a reliable and straightforward approach for reconstructing molecular orbitals with the photoelectron spectroscopy.
基金supported by financial supports from the National major scientific research instrument research projects of the Nationai Natural Science Foundation of China(61827815).
文摘Atomic time scale imaging,opening a new era for studying dynamics in microcosmos,is presently attracting immense research interest on the global level due to its powerful ability.On the atom level,physics,chemistry,and biology are identical for researching atom motion and atomic state change.The light possesses twoness,the information carrier and the research resource.The most fundamental principle of this imaging is that light records the event-modulated light field by itself,so-called all-optical imaging.This paper can answer what is the essential standard to develop and evaluate atomic time scale imaging,what is the optimal imaging system,and what are the typical techniques to implement this imaging,up to now.At present,the best record in the experiment,made by multistage optical parametric amplification(MOPA),is realizing 50-fs resolved optical imaging with a spatial resolution of~83 lp/mm at an effective framing rate of 15×10^(12)fps for recording an ultrafast optical lattice with its rotating speed up to 13.5×10^(12)rad/s.
基金support from the Swedish Research Council(2013-8185,2021-04691,2017-04106,and 2021-05992)the European Research Council(advanced grant QPAP,884900)the Knut and Alice Wallenberg Foundation(KAW 2020.0111).
文摘We investigate the spatial characteristics of high-order harmonic radiation generated in argon and observe cross-like patterns in the far field.An analytical model describing harmonics from an astigmatic driving beam reveals that these patterns result from the order and generation position-dependent divergence of harmonics.Even small amounts of driving field astigmatism may result in cross-like patterns,coming from the superposition of individual harmonics with spatial profiles elongated in different directions.By correcting the aberrations using a deformable mirror,we show that fine-tuning the driving wavefront is essential for optimal spatial quality of the harmonics.
基金supported in part by Natural Sciences and Engineering Research Council of Canada(RGPIN-2017-05959,RGPAS-2017-507845,I2IPJ-555593-20,RGPIN-2018-06217,RGPAS-2018-522650,and RGPIN-2019-06138)Canada Foundation for Innovation and Ministere de P'Economie et de P'Innovation du Quebec(37146)+1 种基金Fonds de Recherche du Quebec-Nature et Technologies(203345-Centre d'Optique,Photonique,et Lasers)Canada Research Chairs Program(CRC-2022-00119)。
文摘Single-shot 2-dimensional optical imaging of transient phenomena is indispensable for numerous areas of study.Among existing techniques,compressed ultrafast photography(CUP)using a chirped ultrashort pulse as active illumination can acquire nonrepetitive time-evolving events at hundreds of trillions of frames per second.However,the bulky size and conventional configurations limit its reliability and application scopes.Superdispersive metalenses offer a promising solution for an ultracompact design with a stable performance by integrating the functions of a focusing lens and dispersive optical components into a single device.Nevertheless,existing metalens designs,typically optimized for the full visible spectrum with a relatively low spectral resolution,cannot be readily applied to active-illumination CUP.To address these limitations,here,we propose single-shot compressed ultracompact femtophotography(CUF)that synergically combines the fields of nanophotonics,optical imaging,compressed sensing,and deep learning.We develop the theory of CUF’s data acquisition composed of temporal–spectral mapping,spatial encoding,temporal shearing,and spatiotemporal integration.We also develop CUF’s image reconstruction via deep learning.Moreover,we design and evaluate CUF’s crucial components—a static binary transmissive mask,a superdispersive metalens,and a 2-dimensional sensor.Finally,using numerical simulations,CUF’s feasibility is verified using 2 synthetic scenes:an ultrafast beam sweeping across a surface and the propagation of a terahertz Cherenkov wave.
基金supported by the National Program on Key Basic Research Project of China(2022YFA1404300)National Natural Science Foundation of China(nos.12325411,62288101,and 11774162)+4 种基金The Open Research Fund of the State Key Laboratory of Transient Optics and Photonics,Chinese Academy of Sciences(SKLST202218)Fundamental Research Funds for the Central Universities(020414380175)Postgraduate Research&Practice Innovation Program of Jiangsu Province(KYCX23_0096)G.H.acknowledges the Nanyang Assistant Professorship Start-up Grant,Ministry of Education(Singapore)under AcRF TIER1(RG61/23)National Research Foundation of Singapore through the Competitive Research Program(NRF-CRP29-2022-0003).
文摘The exploration of optical and photonic phenomena,particularly the modulation of pulse signals and the ultrafast control of light fields at extreme temporal and spatial scales,substantially enhances our understanding of light-matter interactions and broadens the scope of potential applications inspired by metamaterials and metasurfaces.In this perspective,we highlight advancements in ultrafast metaphotonics by introducing ultrafast pulse shaping and control using metadevices.We begin with a detailed exposition of the principles of metasurfaces and evaluate their role in manipulating light fields in high-frequency and terahertz bands,emphasizing the importance of metasurfaces in ultrafast optics.We then present several methods for controlling the output response of metadevices using external physical fields or phase-change materials to achieve active metadevices.Finally,we anticipate the prospects of this field in terms of fundamental research and practical applications.The integration of these 2 disciplines will drive vibrant developments across multiple fields,including biology,chemistry,and materials science.
基金The ELI ALPS project(GINOP-2.3.6-15-2015-00001)is supported by the European Union,and it is co-financed by the European Regional Development Fund.supported by the IMPULSE project,which receives funding from the European Union Framework Programme for Research and Innovation Horizon 2020 under grant agreement no.871161.S.K.and M.U.K.also acknowledges project no.2019-2.1.13-TET-IN-2020-00059+2 种基金support provided by the National Research,Development and Innovation Fund of Hungary,and financed under the 2019-2.1.13-TET-IN funding scheme.D.C.acknowledges support of this work by the Hellenic Foundation for Research and Innovation(HFRI)and the General Secretariat for Research and Technology(GSRT)under the grant no.NEA-APS HFRIFM17-3173support from the Swedish Research Council,the European Research Council(advanced grant QPAP,884900)the Knut and Alice Wallenberg Foundation,including the Wallenberg Center for Quantum Technology(WACQT).
文摘Advancements in light engineering have led to the creation of pulsed laser sources capable of delivering high-repetition-rate,high-power few-cycle laser pulses across a wide spectral range,enabling exploration of many fascinating nonlinear processes occurring in all states of matter.High-harmonic generation,one such process,which converts the low-frequency photons of the driver laser field into soft x-rays,has revolutionized atomic,molecular,and optical physics,leading to progress in attosecond science and ultrafast optoelectronics.The Extreme Light Infrastructure,Attosecond Light Pulse Source(ELI ALPS)facility pioneers state-of-the-art tools for research in these areas.This paper outlines the design rationale,capabilities,and applications of plasma-and gas-based high-repetition-rate(1 kHz to 100 kHz)attosecond extreme ultraviolet(XUV)beamlines developed at ELI ALPS,highlighting their potential for advancing various research fields.
