The size of compression gratings has become a crucial factor in achieving 100-PW level super-intense ultrafast lasers,in view of the laser-induced damage of grating compressor.To improve the output laser energy within...The size of compression gratings has become a crucial factor in achieving 100-PW level super-intense ultrafast lasers,in view of the laser-induced damage of grating compressor.To improve the output laser energy within the damage threshold of grating compressor and therefore obtain higher laser peak power,we proposed the full-aperture grating compressor(FAGC).In this work,the spatiotemporal characteristics of the output pulses from FAGC are investigated,based on the SULF-10 PW laser facility with~400-mm beam diameter.The simulation and proof-of-principle experiment show that the pulse duration and the focusing quality of the output pulses from an FAGC are basically identical with those from a conventional 4-grating compressor;meanwhile,no evident diffractions are induced by the spectral clipping of FAGC.Thus,there is no marked influence of FAGC on the spatiotemporal characteristics of output compressed pulses.This work further demonstrates the feasibility of FAGC efficiently,which should be a promising scheme for realizing single-channel 100-PW level super-intense ultrafast lasers.展开更多
We present theoretical results on the generation of short-wavelength vortex beams in semiconductors through their interaction with an intense Laguerre-Gauss(LG)beam,in the regime where nonperturbative high-order harmo...We present theoretical results on the generation of short-wavelength vortex beams in semiconductors through their interaction with an intense Laguerre-Gauss(LG)beam,in the regime where nonperturbative high-order harmonics are generated.Our approach leverages key aspects of the microscopic mechanism for high-order harmonic generation(HHG)in condensed matter,including the incorporation of dephasing time in the semiconductor Bloch equations(SBEs),the integration of the SBE model with the thin-slab model,and the application of experimentally validated scaling laws for different harmonic orders.For our simulations,we use a zinc oxide crystal interacting with an LG vortex beam characterized by a topological charge of I=1.Time-domain analysis reveals that this is a feasible route,by synthesizing several harmonics,toward the generation of twisted attosecond pulse trains.These findings contribute to advancing the understanding of solid-state media interacting with structured light.展开更多
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
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
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
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
The ultimate feature size is key in ultrafast laser material processing.A capacity to substantially exceed optical limits and to structure below 100 nm is essential to advance ultrafast processing into the field of me...The ultimate feature size is key in ultrafast laser material processing.A capacity to substantially exceed optical limits and to structure below 100 nm is essential to advance ultrafast processing into the field of metamaterials.Such achievement requires combining the control of optical near-fields and of material reactions while preserving the flexibility of long working distances,compatible with a mature laser process.Using subpicosecond and picosecond nondiffractive Bessel beams,we demonstrate unprecedented feature sizes below a hundredth of the incident 1-um wavelength over an extended focus depth of tens of micrometers.Record features sizes,down to 7 nm,result from self-generated near-field light components initiated by cavities induced by far-field radiation in a back-surface illumination geometry.This sustains the generation of more confined near-field evanescent components along the laser scan with a nanometer pitch,perpendicular to the incident field direction,driving a superresolved laser structuring process via local thermal ablation.The near-field pattern is replicated with high robustness,advancing toward a 10-nm nanoscribing tool with a micrometer-sized laser pen.The process is controllable by the field orientation.The nondiffractive irradiation develops evanescent fields over the focusing length,resulting in high-aspect-ratio trenching with a nanometer section and a micrometer depth.Higher energy doses trigger the self-organization of quasi-periodic patterns seeded by spatially modulated scattering,similarly to optical modelocking.A predictive multipulse simulation method validates the far-field-induced near-field electromagnetic scenario of void nanochannel growth and replication,indicating the processing range and resolution on the surface and in the depth.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
Ultrafast dynamics observed at low energies carry insightful information about the complex many-body interactions in solid-state materials.Here,we present a highly sensitive and robust setup for asymmetric 2-dimension...Ultrafast dynamics observed at low energies carry insightful information about the complex many-body interactions in solid-state materials.Here,we present a highly sensitive and robust setup for asymmetric 2-dimensional spectroscopy performing 2-pulse visible excitation combined with probing in the 15-to 35-THz frequency range.This experimental setup is ideal for targeting the interplay of high-and low-energy correlations in functional materials with femtosecond temporal and millielectronvolt energy resolution.In addition,the sub-cycle field resolution of mid-infrared pulses enables tracking nonthermal interactions in the complex dielectric function.Prototypical measurements benchmark ultrafast carrier dynamics in thin-film graphite,showing in detail the interplay of direct and indirect optical transitions in the transient excited state.We further investigate the photo-induced collapse of the superconducting condensate in the high-temperature superconductor Bi_(2)Sr_(2)CaCu_(2)O_(8+x)at energies resonant to the optical bandgap,revealing a nontrivial instantaneous nonlinearity related to the excited quasiparticles in the material.Optical pump–terahertz probe experiments build the foundation for this evolutionary step in 2-dimensional spectroscopy as well as for terahertz 4-wave mixing with resonant driving and readout of the superconducting state.Our results offer exciting perspectives in the study of strong correlations and enable precise investigations of nontrivial many-body interactions in few-layer samples and nanostructures.展开更多
The Fano line shape,arising from the interference of pathways for the excitation of discrete and continuum states,plays a fundamental role in many branches of physics,chemistry,and materials science.Exciting the reson...The Fano line shape,arising from the interference of pathways for the excitation of discrete and continuum states,plays a fundamental role in many branches of physics,chemistry,and materials science.Exciting the resonance with a high harmonic provides naturally a phase delay between the pathways leading to a complex asymmetry parameter.We demonstrate that its amplitude and phase can be controlled on the femtosecond and attosecond time scales,respectively.With our high-energy-resolution(10-meV)experiment,we dynamically image a resonance-enhanced electron wave packet during its temporal evolution,extracting both the amplitude and the phase.Calculations reproduce our experimental results.Our approach constitutes a method for measuring the photoionization delays of a resonance and enables the reconstruction of the electron wave packet in the time domain.This concept of an interferencecontrolled Fano line shape is a step toward attosecond quantum optics with potential ramifications into nanoscience and next-generation optical materials.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
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
Nonlinear Cherenkov radiation(NCR),an intriguing noncollinear second harmonic generation process satisfying versatile longitudinal phase matching and its diffraction in space,has been realized in periodically poled li...Nonlinear Cherenkov radiation(NCR),an intriguing noncollinear second harmonic generation process satisfying versatile longitudinal phase matching and its diffraction in space,has been realized in periodically poled lithium niobate(PPLN)nonlinear grating and other engineered nonlinear photonic structures.Here,we report on the observation of unprecedented ultrabroadband NCR(with a 1.3-octave bandwidth ranging from 363 to 900 nm)from a single PPLN nonlinear grating plate driven by a high-peak-power ultrashort femtosecond pump white laser that covers 2.2-octave bandwidth ranging from 400 to 1,850 nm and possesses a maximum pulse energy of 1.7mJ.Multiple colored NCR patterns along the direction of Cherenkov conical angles simultaneously appear and superimpose in space,leading to a beautifully colorful red-violet rainbow picture dispersed in space clearly observable by the naked eye that has never been reported before.The experiments would enrich the basic physical and optical understanding of nonlinear optical interaction and diffraction characteristics of ultrabroadband high-peak-power white laser sources with engineered nonlinear microstructures.展开更多
We propose a novel scheme for generating and accelerating simultaneously a dozen-GeVisolated attosecond electron bunch via phase-compressed injection in a radiative-wakefield-breaking process from an electron beam-dri...We propose a novel scheme for generating and accelerating simultaneously a dozen-GeVisolated attosecond electron bunch via phase-compressed injection in a radiative-wakefield-breaking process from an electron beam-driven hollow-channel plasma target.During the beam-target interaction,transverse oscillations of plasma electrons are induced,and subsequently,a radiative wakefield is generated.Meanwhile,a large number of plasma electrons of close to the speed of light are injected transversely toward the center of the hollow channel from the position of the transverse electric field of radiative wakefield,forming an isolated attosecond electron bunch due to the phase compression in the radiative-wakefield-breaking process.The injected attosecond electron bunch is then located just in the acceleration phase of the longitudinal electric field of the radiative wakefield and is importantly accelerated to high energies by the radiative wakefield.It is demonstrated theoretically and numerically that this scheme can efficiently generate an isolated attosecond electron bunch with a charge of more than 2 nC,a peak energy up to 13 GeV of more than 2 times that of the driving electron beam,a peak divergence angle of less than 5 mrad,a duration of 276 as,and an energy conversion efficiency of 36.7%as well as a high stability as compared with the laser-beam drive case.Such an isolated attosecond electron bunch in the range of GeV would provide critical applications in ultrafast physics and high-energy physics.展开更多
Pulse contrast stands as a crucial performance metric for intense lasers,and its accurate characterization is indispensable for improving laser system and evaluating strong-field physics experiments.However,traditiona...Pulse contrast stands as a crucial performance metric for intense lasers,and its accurate characterization is indispensable for improving laser system and evaluating strong-field physics experiments.However,traditional methods for ultrahigh-dynamic-range pulse-contrast characterization based on third-order cross-correlation necessitate single-photon detection sensitivity,rendering them susceptible to shot noise and resulting in significant fluctuations in measuring results between shots.In this study,we demonstrate that the impact of shot noise can be considerably reduced by employing an optical parametric amplification correlator(OPAC).The OPAC offers photon gain that counteracts the photon loss incurred during nonlinear conversion and along the propagation path while simultaneously generating parametric super-fluorescence to enhance the number of photons that ultimately reach the detector.These combined effects effectively mitigate shot noise even when the pulse under test contains only a few photons.Consequently,the OPAC facilitates reliable,ultrahigh-dynamic-range,single-shot characterization on pulse contrast of intense lasers,marked by improved shot-to-shot reproducibility.展开更多
An attosecond light source provides an advanced tool for investigating electron motion using time-resolvedspectroscopy techniques.Isolated attosecond pulses,especially,will significantlyadvance the study of electron d...An attosecond light source provides an advanced tool for investigating electron motion using time-resolvedspectroscopy techniques.Isolated attosecond pulses,especially,will significantlyadvance the study of electron dynamics.However,achieving high-intensity isolated attosecond pulses is still challenging at the present stage.In this paper,we propose a novel scheme for generating high-intensity,isolated attosecond soft x-ray free-electron lasers(FELs)using a mid-infrared(MiR)subcycle modulation laser from gas-filled hollow capillary fibers.The multi-cycle MlR pulses are first compressed to subcycles using a krypton-filled hollow capillary fiber with a decreasing pressure gradient due to the soliton self-compression effect.By utilizing such subcycle MlR laser pulses to modulate an electron beam,we can obtain a quasi-isolated current peak,which can then produce an isolated FEL pulse with a high signal-to-noise ratio,naturally synchronizing with the subcycle MiR laser pulse.Numerical simulations have been carried out,including subcycle pulse generation,electron beam modulation,and FEL radiation processes.The simulation results indicate that an isolated attosecond pulse with a wavelength of 1 nm,a peak power of~28 GW,a pulse duration of~580 as,and a signal-to-noise ratio of~96.2%can be generated by our proposed method.The numerical results demonstrated here pave a new way for generating a high-intensity isolated attosecond soft x-ray pulse,which may have many applications in nonlinear spectroscopy and atomic-site electronic processes.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
Sustained mutual coherence between 2 combs over extended periods is a prerequisite for dual-comb spectroscopy(DCS),particularly in achieving high-resolution molecular spectroscopy and precise spectral measurements.How...Sustained mutual coherence between 2 combs over extended periods is a prerequisite for dual-comb spectroscopy(DCS),particularly in achieving high-resolution molecular spectroscopy and precise spectral measurements.However,achieving long coherence times remains a challenge for Yb-doped frequency combs.This work introduces an experimental approach for phase-stable DCS using Yb-doped frequency combs at 1.03μm with a novel feed-forward method,combatting the limitations of mutual coherence.Without relying on postprocessing or self-correction algorithms,we achieve a coherence time of 1,000 s-3 orders of magnitude longer than the current state of the art for DCS.This extended coherence enables time-domain averaging,resulting in a signal-to-noise ratio(SNR)of 2,045.We demonstrate high-resolution monitoring of weak overtone transitions in the P and R branches of C_(2)H_(2),achieving good agreement with simulated spectra based on HITRAN parameters.The phase-locked multiheterodyne system also enables phase spectrum measurements with a scatter down to 7 mrad.Furthermore,we successfully extend our technique to the visible spectral region using second harmonic generation,achieving high-resolution spectra of NO_(2)with excellent SNR.The method offers high-frequency accuracy and demonstrates the potential of Yb-doped systems for multiplexed metrology,effectively extending the capabilities of DCS as a powerful tool for multi-disciplinary applications.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
基金supported by the National Key R&D Program of China(2020YFA0714500,2019YFF01014401)The National Natural Science Foundation of China(12388102)+2 种基金Strategic Priority Research Program of Chinese Academy of Sciences(XDB0890102)Shanghai Science and Technology Committee Program(22DZ1100300,22560780100,23560750200)The Youth Innovation Promotion Association of the Chinese Academy of Sciences.
文摘The size of compression gratings has become a crucial factor in achieving 100-PW level super-intense ultrafast lasers,in view of the laser-induced damage of grating compressor.To improve the output laser energy within the damage threshold of grating compressor and therefore obtain higher laser peak power,we proposed the full-aperture grating compressor(FAGC).In this work,the spatiotemporal characteristics of the output pulses from FAGC are investigated,based on the SULF-10 PW laser facility with~400-mm beam diameter.The simulation and proof-of-principle experiment show that the pulse duration and the focusing quality of the output pulses from an FAGC are basically identical with those from a conventional 4-grating compressor;meanwhile,no evident diffractions are induced by the spectral clipping of FAGC.Thus,there is no marked influence of FAGC on the spatiotemporal characteristics of output compressed pulses.This work further demonstrates the feasibility of FAGC efficiently,which should be a promising scheme for realizing single-channel 100-PW level super-intense ultrafast lasers.
基金financial support from the National Key Research and Development Program of China(grant no.2023YFA1407100)Guangdong Province Science and Technology Major Project(Future functional materials under extreme conditions—2021B0301030005)+1 种基金the Guangdong Natural Science Foundation(General Program project no.2023A1-515010871)support by the U.S.Department of Energy,Offi ce of Science,Basic Energy Sciences,Chemical Sciences,Geosciences,and Biosciences Division through the AMOS program.
文摘We present theoretical results on the generation of short-wavelength vortex beams in semiconductors through their interaction with an intense Laguerre-Gauss(LG)beam,in the regime where nonperturbative high-order harmonics are generated.Our approach leverages key aspects of the microscopic mechanism for high-order harmonic generation(HHG)in condensed matter,including the incorporation of dephasing time in the semiconductor Bloch equations(SBEs),the integration of the SBE model with the thin-slab model,and the application of experimentally validated scaling laws for different harmonic orders.For our simulations,we use a zinc oxide crystal interacting with an LG vortex beam characterized by a topological charge of I=1.Time-domain analysis reveals that this is a feasible route,by synthesizing several harmonics,toward the generation of twisted attosecond pulse trains.These findings contribute to advancing the understanding of solid-state media interacting with structured light.
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 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 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 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The National Key R&D Program of China(2022YFB4600200)the Natural Science Basic Research Program of Shaanxi Province(2022JQ-648)partially supported by the French National Research Agency(ANR)with grants ANR-19-CE30-0036 and ANR-21-CE08-0005.
文摘The ultimate feature size is key in ultrafast laser material processing.A capacity to substantially exceed optical limits and to structure below 100 nm is essential to advance ultrafast processing into the field of metamaterials.Such achievement requires combining the control of optical near-fields and of material reactions while preserving the flexibility of long working distances,compatible with a mature laser process.Using subpicosecond and picosecond nondiffractive Bessel beams,we demonstrate unprecedented feature sizes below a hundredth of the incident 1-um wavelength over an extended focus depth of tens of micrometers.Record features sizes,down to 7 nm,result from self-generated near-field light components initiated by cavities induced by far-field radiation in a back-surface illumination geometry.This sustains the generation of more confined near-field evanescent components along the laser scan with a nanometer pitch,perpendicular to the incident field direction,driving a superresolved laser structuring process via local thermal ablation.The near-field pattern is replicated with high robustness,advancing toward a 10-nm nanoscribing tool with a micrometer-sized laser pen.The process is controllable by the field orientation.The nondiffractive irradiation develops evanescent fields over the focusing length,resulting in high-aspect-ratio trenching with a nanometer section and a micrometer depth.Higher energy doses trigger the self-organization of quasi-periodic patterns seeded by spatially modulated scattering,similarly to optical modelocking.A predictive multipulse simulation method validates the far-field-induced near-field electromagnetic scenario of void nanochannel growth and replication,indicating the processing range and resolution on the surface and in the depth.
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 by the FEDER Program(Grant No.2017-03-022-19“Lux-Ultra-Fast”and Grant No.2023-01-04“Lux-Ultra-Fast 2”).
文摘Ultrafast dynamics observed at low energies carry insightful information about the complex many-body interactions in solid-state materials.Here,we present a highly sensitive and robust setup for asymmetric 2-dimensional spectroscopy performing 2-pulse visible excitation combined with probing in the 15-to 35-THz frequency range.This experimental setup is ideal for targeting the interplay of high-and low-energy correlations in functional materials with femtosecond temporal and millielectronvolt energy resolution.In addition,the sub-cycle field resolution of mid-infrared pulses enables tracking nonthermal interactions in the complex dielectric function.Prototypical measurements benchmark ultrafast carrier dynamics in thin-film graphite,showing in detail the interplay of direct and indirect optical transitions in the transient excited state.We further investigate the photo-induced collapse of the superconducting condensate in the high-temperature superconductor Bi_(2)Sr_(2)CaCu_(2)O_(8+x)at energies resonant to the optical bandgap,revealing a nontrivial instantaneous nonlinearity related to the excited quasiparticles in the material.Optical pump–terahertz probe experiments build the foundation for this evolutionary step in 2-dimensional spectroscopy as well as for terahertz 4-wave mixing with resonant driving and readout of the superconducting state.Our results offer exciting perspectives in the study of strong correlations and enable precise investigations of nontrivial many-body interactions in few-layer samples and nanostructures.
基金funding from the European Union’s Horizon 2020 research and innovation program under the Marie Skłodowska-Curie grant agreement no.801459-FP-RESOMUSfunding by the Chemical Sciences,Geosciences and Biosciences Division,Office of Basic Energy Sciences,Office of Science,US Department of Energy,grant no.DE-FG02-86ER13491supported by ETH Zurich and the Swiss National Science Foundation through projects 200021_172946 and the NCCR-MUST.
文摘The Fano line shape,arising from the interference of pathways for the excitation of discrete and continuum states,plays a fundamental role in many branches of physics,chemistry,and materials science.Exciting the resonance with a high harmonic provides naturally a phase delay between the pathways leading to a complex asymmetry parameter.We demonstrate that its amplitude and phase can be controlled on the femtosecond and attosecond time scales,respectively.With our high-energy-resolution(10-meV)experiment,we dynamically image a resonance-enhanced electron wave packet during its temporal evolution,extracting both the amplitude and the phase.Calculations reproduce our experimental results.Our approach constitutes a method for measuring the photoionization delays of a resonance and enables the reconstruction of the electron wave packet in the time domain.This concept of an interferencecontrolled Fano line shape is a step toward attosecond quantum optics with potential ramifications into nanoscience and next-generation optical materials.
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 Science and Technology Project of Guangdong(2020B010190001)the National Natural Science Foundation of China(12434016)+1 种基金the National Key R&D Program of China(2023YFA1406900)the National Funded Postdoctoral Researcher Program(GZB20240785).
文摘Nonlinear Cherenkov radiation(NCR),an intriguing noncollinear second harmonic generation process satisfying versatile longitudinal phase matching and its diffraction in space,has been realized in periodically poled lithium niobate(PPLN)nonlinear grating and other engineered nonlinear photonic structures.Here,we report on the observation of unprecedented ultrabroadband NCR(with a 1.3-octave bandwidth ranging from 363 to 900 nm)from a single PPLN nonlinear grating plate driven by a high-peak-power ultrashort femtosecond pump white laser that covers 2.2-octave bandwidth ranging from 400 to 1,850 nm and possesses a maximum pulse energy of 1.7mJ.Multiple colored NCR patterns along the direction of Cherenkov conical angles simultaneously appear and superimpose in space,leading to a beautifully colorful red-violet rainbow picture dispersed in space clearly observable by the naked eye that has never been reported before.The experiments would enrich the basic physical and optical understanding of nonlinear optical interaction and diffraction characteristics of ultrabroadband high-peak-power white laser sources with engineered nonlinear microstructures.
基金supported by Project of Gamma-Gamma Collider and Integrated Beam Flow Facility(Phase I)Validation Device at SYSU(2403-000000-05-03-714165)Guangdong Provincial Key Laboratory of Advanced Particle Detection Technology(2024B1212010005)+3 种基金Guangdong Provincial Key Laboratory of Gamma-Gamma Collider and Its Comprehensiv Applications(2024KSY001)Research Project of SYSU(74140-71020003 and 74140-71020006)National Natural Science Foundation of China(grant nos.12375244 and 12135009)Natural Science Foundation of Hunan Province of China(grant no.2025JJ30002).
文摘We propose a novel scheme for generating and accelerating simultaneously a dozen-GeVisolated attosecond electron bunch via phase-compressed injection in a radiative-wakefield-breaking process from an electron beam-driven hollow-channel plasma target.During the beam-target interaction,transverse oscillations of plasma electrons are induced,and subsequently,a radiative wakefield is generated.Meanwhile,a large number of plasma electrons of close to the speed of light are injected transversely toward the center of the hollow channel from the position of the transverse electric field of radiative wakefield,forming an isolated attosecond electron bunch due to the phase compression in the radiative-wakefield-breaking process.The injected attosecond electron bunch is then located just in the acceleration phase of the longitudinal electric field of the radiative wakefield and is importantly accelerated to high energies by the radiative wakefield.It is demonstrated theoretically and numerically that this scheme can efficiently generate an isolated attosecond electron bunch with a charge of more than 2 nC,a peak energy up to 13 GeV of more than 2 times that of the driving electron beam,a peak divergence angle of less than 5 mrad,a duration of 276 as,and an energy conversion efficiency of 36.7%as well as a high stability as compared with the laser-beam drive case.Such an isolated attosecond electron bunch in the range of GeV would provide critical applications in ultrafast physics and high-energy physics.
基金supported by the National Key Research&Development Program of China(2023YFA1608503)National Natural Science Foundation of China(62375165 and 62122049).
文摘Pulse contrast stands as a crucial performance metric for intense lasers,and its accurate characterization is indispensable for improving laser system and evaluating strong-field physics experiments.However,traditional methods for ultrahigh-dynamic-range pulse-contrast characterization based on third-order cross-correlation necessitate single-photon detection sensitivity,rendering them susceptible to shot noise and resulting in significant fluctuations in measuring results between shots.In this study,we demonstrate that the impact of shot noise can be considerably reduced by employing an optical parametric amplification correlator(OPAC).The OPAC offers photon gain that counteracts the photon loss incurred during nonlinear conversion and along the propagation path while simultaneously generating parametric super-fluorescence to enhance the number of photons that ultimately reach the detector.These combined effects effectively mitigate shot noise even when the pulse under test contains only a few photons.Consequently,the OPAC facilitates reliable,ultrahigh-dynamic-range,single-shot characterization on pulse contrast of intense lasers,marked by improved shot-to-shot reproducibility.
基金supported by the National Natural Science Foundation of China(Nos.12435011,11905275,11775294,12122514,and 62205353)the Youth Innovation Promotion Association CAS,the National Postdoctoral Program for Innovative Talents(No.BX2021328)+1 种基金the China Postdoctoral Science Foundation(No.2021M703325)the CAS Project for Young Scientists in Basic Research(YSBR-115).
文摘An attosecond light source provides an advanced tool for investigating electron motion using time-resolvedspectroscopy techniques.Isolated attosecond pulses,especially,will significantlyadvance the study of electron dynamics.However,achieving high-intensity isolated attosecond pulses is still challenging at the present stage.In this paper,we propose a novel scheme for generating high-intensity,isolated attosecond soft x-ray free-electron lasers(FELs)using a mid-infrared(MiR)subcycle modulation laser from gas-filled hollow capillary fibers.The multi-cycle MlR pulses are first compressed to subcycles using a krypton-filled hollow capillary fiber with a decreasing pressure gradient due to the soliton self-compression effect.By utilizing such subcycle MlR laser pulses to modulate an electron beam,we can obtain a quasi-isolated current peak,which can then produce an isolated FEL pulse with a high signal-to-noise ratio,naturally synchronizing with the subcycle MiR laser pulse.Numerical simulations have been carried out,including subcycle pulse generation,electron beam modulation,and FEL radiation processes.The simulation results indicate that an isolated attosecond pulse with a wavelength of 1 nm,a peak power of~28 GW,a pulse duration of~580 as,and a signal-to-noise ratio of~96.2%can be generated by our proposed method.The numerical results demonstrated here pave a new way for generating a high-intensity isolated attosecond soft x-ray pulse,which may have many applications in nonlinear spectroscopy and atomic-site electronic processes.
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 HORIZON EUROPE European Research Council(947288)Austrian Science Fund(FWF)(Y1254)funding from the European Union(grant agreement 101076933 EUVORAM).
文摘Sustained mutual coherence between 2 combs over extended periods is a prerequisite for dual-comb spectroscopy(DCS),particularly in achieving high-resolution molecular spectroscopy and precise spectral measurements.However,achieving long coherence times remains a challenge for Yb-doped frequency combs.This work introduces an experimental approach for phase-stable DCS using Yb-doped frequency combs at 1.03μm with a novel feed-forward method,combatting the limitations of mutual coherence.Without relying on postprocessing or self-correction algorithms,we achieve a coherence time of 1,000 s-3 orders of magnitude longer than the current state of the art for DCS.This extended coherence enables time-domain averaging,resulting in a signal-to-noise ratio(SNR)of 2,045.We demonstrate high-resolution monitoring of weak overtone transitions in the P and R branches of C_(2)H_(2),achieving good agreement with simulated spectra based on HITRAN parameters.The phase-locked multiheterodyne system also enables phase spectrum measurements with a scatter down to 7 mrad.Furthermore,we successfully extend our technique to the visible spectral region using second harmonic generation,achieving high-resolution spectra of NO_(2)with excellent SNR.The method offers high-frequency accuracy and demonstrates the potential of Yb-doped systems for multiplexed metrology,effectively extending the capabilities of DCS as a powerful tool for multi-disciplinary applications.
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.
