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
As a noncontact strategy with flexible tools and high efficiency,laser precision engineering is a significant advanced processing way for high-quality micro-/nanostructure fabrication,especially to achieve novel funct...As a noncontact strategy with flexible tools and high efficiency,laser precision engineering is a significant advanced processing way for high-quality micro-/nanostructure fabrication,especially to achieve novel functional photoelectric structures and devices.For the microscale creation,several femtosecond laser fabrication methods,including multiphoton absorption,laserinduced plasma-assisted ablation,and incubation effect have been developed.Meanwhile,the femtosecond laser can be combined with microlens arrays and interference lithography techniques to achieve the structures in submicron scales.Down to nanoscale feature sizes,advanced processing strategies,such as near-field scanning optical microscope,atomic force microscope,and microsphere,are applied in femtosecond laser processing and the minimum nanostructure creation has been pushed down to~25 nm due to near-field effect.The most fascinating femtosecond laser precision engineering is the possibility of large-area,high-throughput,and far-field nanofabrication.In combination with special strategies,including dual femtosecond laser beam irradiation,~15 nm nanostructuring can be achieved directly on silicon surfaces in far field and in ambient air.The challenges and perspectives in the femtosecond laser precision engineering are also discussed.展开更多
As a new energy source,hydrogen(H_(2))detection is a hot topic in recent years.Because of the weak absorption characteristic,laser spectroscopy-based H_(2)detection is challenging.In this paper,a highly sensitive H_(2...As a new energy source,hydrogen(H_(2))detection is a hot topic in recent years.Because of the weak absorption characteristic,laser spectroscopy-based H_(2)detection is challenging.In this paper,a highly sensitive H_(2)sensor based on light-induced thermoelastic spectroscopy(LITES)technique is demonstrated for the first time.A continuous-wave,distributed feedback diode laser with emission in the 2.1μm region was adopted as the excitation source to target the strongest H_(2)absorption line of 4,712.90 cm^(−1).A Herriott multipass cell with an optical length of 10.1 m was chosen to further improve the H_(2)absorption.With the feature of processing the raw input data without data preprocessing and extracting the desired features automatically,the robust shallow neural network(SNN)fitting algorithm was brought in to denoise the sensor.For the LITES-based H_(2)sensor,the concentration response was tested,and an excellent linear response to H_(2)concentration levels was achieved.A minimum detection limit(MDL)of~80 ppm was obtained.On the basis of implementation of the H_(2)-LITES sensor,a heterodyne H_(2)-LITES sensor was further constructed to realize a fast measurement of resonance frequency of quartz tuning fork and H_(2)concentration simultaneously.The resonance frequency can be retrieved in several hundred milliseconds with the measurement accuracy of±0.2 Hz,and the result of 30,713.76 Hz is exactly same as the experimentally determined value of 30,713.69 Hz.After the SNN algorithm was applied,an MDL of~45 ppm was achieved for this heterodyne H_(2)-LITES sensor.展开更多
Recent advancements in photonic bound states in the continuum(BICs)have opened up exciting new possibilities for the design of optoelectronic devices with improved performance.In this perspective article,we provide an...Recent advancements in photonic bound states in the continuum(BICs)have opened up exciting new possibilities for the design of optoelectronic devices with improved performance.In this perspective article,we provide an overview of recent progress in photonic BICs based on metamaterials and photonic crystals,focusing on both the underlying physics and their practical applications.The first part of this article introduces 2 different interpretations of BICs,based on far-field interference of multipoles and near-field analysis of topological charges.We then discuss recent research on manipulating the far-field radiation properties of BICs through engineering topological charges.The second part of the article summarizes recent developments in the applications of BICs,including chiral light and vortex beam generation,nonlinear optical frequency conversion,sensors,and nanolasers.Finally,we conclude with a discussion of the potential of photonic BICs to advance terahertz applications in areas such as generation and detection,modulation,sensing,and isolation.Webelieve that continued researchinthis area will lead to exciting new advancements in optoelectronics,particularly in the field of terahertz devices.展开更多
In the recent decade,single-shot ultrafast optical imaging by active detection,called single-shot active ultrafast optical imaging(SS-AUOI)here,has made great progress,e.g.,with a temporal resolution of 50 fs and a fr...In the recent decade,single-shot ultrafast optical imaging by active detection,called single-shot active ultrafast optical imaging(SS-AUOI)here,has made great progress,e.g.,with a temporal resolution of 50 fs and a frame rate beyond 10 trillion frames per second.Now,it has become indispensable for charactering the nonrepeatable and difficult-to-reproduce events and revealing the underlying physical,chemical,and biological mechanisms.On the basis of this delightful status,we would like to make a review of SS-AUOI.On the basis of a brief introduction of SS-AUOI,our review starts with discussing its characteristics and then focuses on the survey and prospect of SS-AUOI technology.展开更多
Matters are generally classified within four states:solid,liquid,gas,and plasma.Three of the four states of matter(solid,gas,and plasma)have been used for THz wave generation with short laser pulse excitation for deca...Matters are generally classified within four states:solid,liquid,gas,and plasma.Three of the four states of matter(solid,gas,and plasma)have been used for THz wave generation with short laser pulse excitation for decades,including the recent vigorous development of THz photonics in gases(air plasma).However,the demonstration of THz generation from liquids was conspicuously absent.It is well known that water,the most common liquid,is a strong absorber in the far infrared range.Therefore,liquid water has historically been sworn off as a source for THz radiation.Recently,broadband THz wave generation from a flowing liquid target has been experimentally demonstrated through laser-induced microplasma.The liquid target as the THz source presents unique properties.Specifically,liquids have the comparable material density to that of solids,meaning that laser pulses over a certain area will interact with three orders more molecules than an equivalent cross-section of gases.In contrast with solid targets,the fluidity of liquid allows every laser pulse to interact with a fresh area on the target,meaning that material damage or degradation is not an issue with the high-repetition rate intense laser pulses.These make liquids very promising candidates for the investigation of high-energy-density plasma,as well as the possibility of being the next generation of THz sources.展开更多
Remote or standoff detection of greenhouse gases,air pollutants,and biological agents with innovative ultrafast laser technology attracts growing interests in recent years.Hybrid femtosecond/picosecond coherent Raman ...Remote or standoff detection of greenhouse gases,air pollutants,and biological agents with innovative ultrafast laser technology attracts growing interests in recent years.Hybrid femtosecond/picosecond coherent Raman spectroscopy is considered as one of the most versatile techniques due to its great advantages in terms of detection sensitivity and chemical specificity.However,the simultaneous requirement for the femtosecond pump and the picosecond probe increases the complexity of optical system.Herein,we demonstrate that air lasing naturally created inside a filament can serve as an ideal light source to probe Raman coherence excited by the femtosecond pump,producing coherent Raman signal with molecular vibrational signatures.The combination of pulse self-compression effect and air lasing action during filamentation improves Raman excitation efficiency and greatly simplifies the experimental setup.The air-lasing-assisted Raman spectroscopy was applied to quantitatively detect greenhouse gases mixed in air,and it was found that the minimum detectable concentrations of CO_(2) and SF_(6) can reach 0.1%and 0.03%,respectively.The ingenious designs,especially the optimization of pump-seed delay and the choice of perpendicular polarization,ensure a high detection sensitivity and signal stability.Moreover,it is demonstrated that this method can be used for simultaneously measuring CO_(2) and SF_(6) gases and distinguishing ^(12)CO_(2) and ^(13)CO_(2).The developed scheme provides a new route for high-sensitivity standoff detection and combustion diagnosis.展开更多
Femtosecond laser ablation(FLA)has been playing a prominent role in precision fabrication of material because of its circumvention of thermal effect and extremely high spatial resolution.Molecular dynamics modeling,as...Femtosecond laser ablation(FLA)has been playing a prominent role in precision fabrication of material because of its circumvention of thermal effect and extremely high spatial resolution.Molecular dynamics modeling,as a powerful tool to study the mechanism of femtosecond laser ablation,still lacks the connection between its simulation results and experimental observations at present.Here we combine a single-shot chirped spectral mapping ultrafast photography(CSMUP)technique in experiment and a three-dimensional two-temperature model-based molecular dynamics(3D TTM-MD)method in theory to jointly investigate the FLA process of bulky gold.Our experimental and simulated results show quite high consistency in time-resolved morphologic dynamics.According to the highly accurate simulations,the FLA process of gold at the high laser fluence is dominated by the phase explosion,which shows drastic vaporized cluster eruption and pressure dynamics,while the FLA process at the low laser fluence mainly results from the photomechanical spallation,which shows moderate temperature and pressure dynamics.This study reveals the ultrafast dynamics of gold with different ablation schemes,which has a guiding significance for the applications of FLA on various kinds of materials.展开更多
One of the main constraints for reducing the temporal duration of attosecond pulses is the attochirp inherent to the process of high-order harmonic generation(HHG).Though the attochirp can be compensated in the extrem...One of the main constraints for reducing the temporal duration of attosecond pulses is the attochirp inherent to the process of high-order harmonic generation(HHG).Though the attochirp can be compensated in the extreme-ultraviolet using dispersive materials,this is unfeasible toward x-rays,where the shortest attosecond or even sub-attosecond pulses could be obtained.We theoretically demonstrate that HHG driven by a circularly polarized infrared pulse while assisted by an strong oscillating ultrafast intense magnetic field enables the generation of few-cycle Fourier-limited few attosecond pulses.In such a novel scenario,the magnetic field transversally confines the ionized electron during the HHG process,analogously to a nanowire trapping.Once the electron is ionized,the transverse electron dynamics is excited by the magnetic field,acting as a high-energy reservoir to be released in the form of phase-locked spectrally wide high-frequency harmonic radiation during the electron recollision with the parent ion.In addition,the transverse breathing dynamics of the electron wavepacket,introduced by the magnetic trapping,strongly modulates the recollision efficiency of the electronic trajectories,thus the attosecond pulse emissions.The aftermath is the possibility of producing high-frequency(hundreds of eV)attosecond isolated few-cycle pulses,almost Fourier limited.The isolated intense magnetic fields considered in our simulations,of tens of kT,can be produced in finite spatial volumes considering structured beams or stationary configurations of counter-propagating state-of-the-art multi-terawatt/petawatt lasers.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support from Academic Research Fund Tier 2,Ministry of Education-Singapore(MOE2019-T2-2-147).
文摘As a noncontact strategy with flexible tools and high efficiency,laser precision engineering is a significant advanced processing way for high-quality micro-/nanostructure fabrication,especially to achieve novel functional photoelectric structures and devices.For the microscale creation,several femtosecond laser fabrication methods,including multiphoton absorption,laserinduced plasma-assisted ablation,and incubation effect have been developed.Meanwhile,the femtosecond laser can be combined with microlens arrays and interference lithography techniques to achieve the structures in submicron scales.Down to nanoscale feature sizes,advanced processing strategies,such as near-field scanning optical microscope,atomic force microscope,and microsphere,are applied in femtosecond laser processing and the minimum nanostructure creation has been pushed down to~25 nm due to near-field effect.The most fascinating femtosecond laser precision engineering is the possibility of large-area,high-throughput,and far-field nanofabrication.In combination with special strategies,including dual femtosecond laser beam irradiation,~15 nm nanostructuring can be achieved directly on silicon surfaces in far field and in ambient air.The challenges and perspectives in the femtosecond laser precision engineering are also discussed.
基金the National Natural Science Foundation of China(grant nos.62275065,62022032,61875047,and 61505041)Fundamental Research Funds for the Central Universities.
文摘As a new energy source,hydrogen(H_(2))detection is a hot topic in recent years.Because of the weak absorption characteristic,laser spectroscopy-based H_(2)detection is challenging.In this paper,a highly sensitive H_(2)sensor based on light-induced thermoelastic spectroscopy(LITES)technique is demonstrated for the first time.A continuous-wave,distributed feedback diode laser with emission in the 2.1μm region was adopted as the excitation source to target the strongest H_(2)absorption line of 4,712.90 cm^(−1).A Herriott multipass cell with an optical length of 10.1 m was chosen to further improve the H_(2)absorption.With the feature of processing the raw input data without data preprocessing and extracting the desired features automatically,the robust shallow neural network(SNN)fitting algorithm was brought in to denoise the sensor.For the LITES-based H_(2)sensor,the concentration response was tested,and an excellent linear response to H_(2)concentration levels was achieved.A minimum detection limit(MDL)of~80 ppm was obtained.On the basis of implementation of the H_(2)-LITES sensor,a heterodyne H_(2)-LITES sensor was further constructed to realize a fast measurement of resonance frequency of quartz tuning fork and H_(2)concentration simultaneously.The resonance frequency can be retrieved in several hundred milliseconds with the measurement accuracy of±0.2 Hz,and the result of 30,713.76 Hz is exactly same as the experimentally determined value of 30,713.69 Hz.After the SNN algorithm was applied,an MDL of~45 ppm was achieved for this heterodyne H_(2)-LITES sensor.
基金supported by the National Natural Science Foundation of China (Award No.:62175099)the Guangdong Basic and Applied Basic Research Foundation (Award No.:2023A1515011085)+1 种基金the Stable Support Program for Higher Education Institutions from Shenzhen Science,Technology&Innovation Commission (Award No.:20220815151149004)startup funding of Southern University of Science and Technology。
文摘Recent advancements in photonic bound states in the continuum(BICs)have opened up exciting new possibilities for the design of optoelectronic devices with improved performance.In this perspective article,we provide an overview of recent progress in photonic BICs based on metamaterials and photonic crystals,focusing on both the underlying physics and their practical applications.The first part of this article introduces 2 different interpretations of BICs,based on far-field interference of multipoles and near-field analysis of topological charges.We then discuss recent research on manipulating the far-field radiation properties of BICs through engineering topological charges.The second part of the article summarizes recent developments in the applications of BICs,including chiral light and vortex beam generation,nonlinear optical frequency conversion,sensors,and nanolasers.Finally,we conclude with a discussion of the potential of photonic BICs to advance terahertz applications in areas such as generation and detection,modulation,sensing,and isolation.Webelieve that continued researchinthis area will lead to exciting new advancements in optoelectronics,particularly in the field of terahertz devices.
基金National Natural Science Foundation of China(92050203,62075138,62275163,and 12174264)Natural Science Foundation of Guangdong Province(2021A1515011909 and 2022A1515011457)Shenzhen Fundamental Research Program(JCYJ20200109105606426,JCYJ20190808164007485,JCYJ20210324095213037,JCYJ20190808121817100,JCYJ20190808143419622,JSGG20191231144201722,and JCYJ20190808115601653).
文摘In the recent decade,single-shot ultrafast optical imaging by active detection,called single-shot active ultrafast optical imaging(SS-AUOI)here,has made great progress,e.g.,with a temporal resolution of 50 fs and a frame rate beyond 10 trillion frames per second.Now,it has become indispensable for charactering the nonrepeatable and difficult-to-reproduce events and revealing the underlying physical,chemical,and biological mechanisms.On the basis of this delightful status,we would like to make a review of SS-AUOI.On the basis of a brief introduction of SS-AUOI,our review starts with discussing its characteristics and then focuses on the survey and prospect of SS-AUOI technology.
基金supported by the Army Research Office(Grant no.W911NF-17-1-0428)Air Force Office of Scientific Research(Grant no.FA9550-18-1-0357),and National Science Foundation(Grant no.ECCS1916068)+2 种基金A.Tcypkin and S.Kozlov are supported by the Russian Science Foundation(Grant no.19-12-00097).L.Zhang and C.Zhang are supported by the Beijing Natural Science Foundation(Grant no.JQ18015)the National Natural Science Foundation of China(Grant no.12074272).
文摘Matters are generally classified within four states:solid,liquid,gas,and plasma.Three of the four states of matter(solid,gas,and plasma)have been used for THz wave generation with short laser pulse excitation for decades,including the recent vigorous development of THz photonics in gases(air plasma).However,the demonstration of THz generation from liquids was conspicuously absent.It is well known that water,the most common liquid,is a strong absorber in the far infrared range.Therefore,liquid water has historically been sworn off as a source for THz radiation.Recently,broadband THz wave generation from a flowing liquid target has been experimentally demonstrated through laser-induced microplasma.The liquid target as the THz source presents unique properties.Specifically,liquids have the comparable material density to that of solids,meaning that laser pulses over a certain area will interact with three orders more molecules than an equivalent cross-section of gases.In contrast with solid targets,the fluidity of liquid allows every laser pulse to interact with a fresh area on the target,meaning that material damage or degradation is not an issue with the high-repetition rate intense laser pulses.These make liquids very promising candidates for the investigation of high-energy-density plasma,as well as the possibility of being the next generation of THz sources.
基金supported by the National Natural Science Foundation of China(11822410,12034013,12074063)Key Research Program of Frontier Sciences of Chinese Academy of Sciences(QYZDJ-SSW-SLH010)+2 种基金Program of Shanghai Academic Research Leader(20XD1424200)Shanghai Municipal Science and Technology Major Project(2019SHZDZX01)Youth Innovation Promotion Association of CAS(2018284).
文摘Remote or standoff detection of greenhouse gases,air pollutants,and biological agents with innovative ultrafast laser technology attracts growing interests in recent years.Hybrid femtosecond/picosecond coherent Raman spectroscopy is considered as one of the most versatile techniques due to its great advantages in terms of detection sensitivity and chemical specificity.However,the simultaneous requirement for the femtosecond pump and the picosecond probe increases the complexity of optical system.Herein,we demonstrate that air lasing naturally created inside a filament can serve as an ideal light source to probe Raman coherence excited by the femtosecond pump,producing coherent Raman signal with molecular vibrational signatures.The combination of pulse self-compression effect and air lasing action during filamentation improves Raman excitation efficiency and greatly simplifies the experimental setup.The air-lasing-assisted Raman spectroscopy was applied to quantitatively detect greenhouse gases mixed in air,and it was found that the minimum detectable concentrations of CO_(2) and SF_(6) can reach 0.1%and 0.03%,respectively.The ingenious designs,especially the optimization of pump-seed delay and the choice of perpendicular polarization,ensure a high detection sensitivity and signal stability.Moreover,it is demonstrated that this method can be used for simultaneously measuring CO_(2) and SF_(6) gases and distinguishing ^(12)CO_(2) and ^(13)CO_(2).The developed scheme provides a new route for high-sensitivity standoff detection and combustion diagnosis.
基金National Natural Science Foundation of China(91850202,92150301,12074121,62105101,62175066,11727810,12034008)Science and Technology Commission of Shanghai Municipality(21XD1400900,20ZR1417100,21JM0010700).
文摘Femtosecond laser ablation(FLA)has been playing a prominent role in precision fabrication of material because of its circumvention of thermal effect and extremely high spatial resolution.Molecular dynamics modeling,as a powerful tool to study the mechanism of femtosecond laser ablation,still lacks the connection between its simulation results and experimental observations at present.Here we combine a single-shot chirped spectral mapping ultrafast photography(CSMUP)technique in experiment and a three-dimensional two-temperature model-based molecular dynamics(3D TTM-MD)method in theory to jointly investigate the FLA process of bulky gold.Our experimental and simulated results show quite high consistency in time-resolved morphologic dynamics.According to the highly accurate simulations,the FLA process of gold at the high laser fluence is dominated by the phase explosion,which shows drastic vaporized cluster eruption and pressure dynamics,while the FLA process at the low laser fluence mainly results from the photomechanical spallation,which shows moderate temperature and pressure dynamics.This study reveals the ultrafast dynamics of gold with different ablation schemes,which has a guiding significance for the applications of FLA on various kinds of materials.
基金funding from the European Research Council (ERC)under the European Union's Horizon 2020 research and innovation program (Grant Agreement No.851201)We acknowledge support from Ministerio de Ciencia e Innovacion (PID2019-106910GB-I00)+2 种基金Junta de Castilla y Leon FEDER funds (Project No.SA287P18)C.H.-G.acknowledges Ministerio de Ciencia,Innovaciony Universidades for a Ramon y Cajal contract (RYC-2017-22745)co-funded by the European Social Fund.H.H.and A.B.acknowledge support from the Austrian Science Fund (FWF)under ZK 9100-N and FWFI 4566.
文摘One of the main constraints for reducing the temporal duration of attosecond pulses is the attochirp inherent to the process of high-order harmonic generation(HHG).Though the attochirp can be compensated in the extreme-ultraviolet using dispersive materials,this is unfeasible toward x-rays,where the shortest attosecond or even sub-attosecond pulses could be obtained.We theoretically demonstrate that HHG driven by a circularly polarized infrared pulse while assisted by an strong oscillating ultrafast intense magnetic field enables the generation of few-cycle Fourier-limited few attosecond pulses.In such a novel scenario,the magnetic field transversally confines the ionized electron during the HHG process,analogously to a nanowire trapping.Once the electron is ionized,the transverse electron dynamics is excited by the magnetic field,acting as a high-energy reservoir to be released in the form of phase-locked spectrally wide high-frequency harmonic radiation during the electron recollision with the parent ion.In addition,the transverse breathing dynamics of the electron wavepacket,introduced by the magnetic trapping,strongly modulates the recollision efficiency of the electronic trajectories,thus the attosecond pulse emissions.The aftermath is the possibility of producing high-frequency(hundreds of eV)attosecond isolated few-cycle pulses,almost Fourier limited.The isolated intense magnetic fields considered in our simulations,of tens of kT,can be produced in finite spatial volumes considering structured beams or stationary configurations of counter-propagating state-of-the-art multi-terawatt/petawatt lasers.
