Ultrafast fiber lasers are indispensable components in the field of ultrafast optics,and their continuous performance advancements are driving the progress of this exciting discipline.Micro/Nanofibers(MNFs)possess uni...Ultrafast fiber lasers are indispensable components in the field of ultrafast optics,and their continuous performance advancements are driving the progress of this exciting discipline.Micro/Nanofibers(MNFs)possess unique properties,such as a large fractional evanescent field,flexible and controllable dispersion,and high nonlinearity,making them highly valuable for generating ultrashort pulses.Particularly,in tasks involving mode-locking and dispersion and nonlinearity management,MNFs provide an excellent platform for investigating intriguing nonlinear dynamics and related phenomena,thereby promoting the advancement of ultrafast fiber lasers.In this paper,we present an introduction to the mode evolution and characteristics of MNFs followed by a comprehensive review of recent advances in using MNFs for ultrafast optics applications including evanescent field modulation and control,dispersion and nonlinear management techniques,and nonlinear dynamical phenomenon exploration.Finally,we discuss the potential application prospects of MNFs in the realm of ultrafast optics.展开更多
Ultrafast phenomena induced by femtosecond laser irradiation encompass a range of highly dynamic physical processes,including but not limited to electron excitation,material ablation,plasma generation,and shock wave p...Ultrafast phenomena induced by femtosecond laser irradiation encompass a range of highly dynamic physical processes,including but not limited to electron excitation,material ablation,plasma generation,and shock wave propagation.Unveiling the dynamics of these ultrafast processes is crucial for effectively controlling laser processing.However,many of these phenomena occur on timescales ranging from femtoseconds(fs) to nanoseconds(ns),which presents significant challenges in monitoring and interpretation;thus,ultrafast optical imaging techniques are often required.This paper comprehensively reviews the ultrafast optical imaging methods employed in recent years to monitor various ultrafast processes such as electron excitation,ultrafast ablation,plasma ejection,and shock wave propagation during femtosecond laser processing of metallic,composite,and ceramic materials.These methods can be categorized into two primary types:pump-probe ultrafast optical imaging and single-shot ultrafast optical imaging techniques.The working principles and key findings associated with each type of ultrafast optical imaging technique are described in detail.Finally,the imaging principles,advantages and disadvantages,and application scenarios of various ultrafast imaging technologies are summarized,along with a discussion of future challenges and development directions in this field.展开更多
The control of ultrafast optical field is of great interest in developing ultrafast optics as well as the investigation on vari-ous light-matter interactions with ultrashort pulses.However,conventional spatial encodin...The control of ultrafast optical field is of great interest in developing ultrafast optics as well as the investigation on vari-ous light-matter interactions with ultrashort pulses.However,conventional spatial encoding approaches have only lim-ited steerable targets usually neglecting the temporal effect,thus hindering their broad applications.Here we present a new concept for realizing ultrafast modulation of multi-target focal fields based on the facile combination of time-depend-ent vectorial diffraction theory with fast Fourier transform.This is achieved by focusing femtosecond pulsed light carrying vectorial-vortex by a single objective lens under tight focusing condition.It is uncovered that the ultrafast temporal de-gree of freedom within a configurable temporal duration(~400 fs)plays a pivotal role in determining the rich and exotic features of the focused optical field at one time,namely,bright-dark alternation,periodic rotation,and longitudinal/trans-verse polarization conversion.The underlying control mechanisms have been unveiled.Besides being of academic in-terest in diverse ultrafast spectral regimes,these peculiar behaviors of the space-time evolutionary beams may underpin prolific ultrafast-related applications such as multifunctional integrated optical chip,high-efficiency laser trapping,micro-structure rotation,super-resolution optical microscopy,precise optical measurement,and liveness tracking.展开更多
Femtosecond laser technology has attracted significant attention from the viewpoints of fundamental and application;especially femtosecond laser processing materials present the unique mechanism of laser-material inte...Femtosecond laser technology has attracted significant attention from the viewpoints of fundamental and application;especially femtosecond laser processing materials present the unique mechanism of laser-material interaction.Under the extreme nonequilibrium conditions imposed by femtosecond laser irradiation,many fundamental questions concerning the physical origin of the material removal process remain unanswered.In this review,cutting-edge ultrafast dynamic observation techniques for investigating the fundamental questions,including timeresolved pump-probe shadowgraphy,ultrafast continuous optical imaging,and four-dimensional ultrafast scanning electron microscopy,are comprehensively surveyed.Each technique is described in depth,beginning with its basic principle,followed by a description of its representative applications in laser-material interaction and its strengths and limitations.The consideration of temporal and spatial resolutions and panoramic measurement at different scales are two major challenges.Hence,the prospects for technical advancement in this field are discussed finally.展开更多
The third-order optical nonlinearity of two sandwich-type phthalocyaninato and porphyrinato europium com- plexes, including double- and triple-deckers （Eu[Pc（OC5H11）8]2, Eu2（Pc）（TPP）2, Pc=phthalocyanine, TPP=5,...The third-order optical nonlinearity of two sandwich-type phthalocyaninato and porphyrinato europium com- plexes, including double- and triple-deckers （Eu[Pc（OC5H11）8]2, Eu2（Pc）（TPP）2, Pc=phthalocyanine, TPP=5, 10, 15, 20- tetraphenylporphyrinate）, was investigated by using the femtosecond time-resolved optical Kerr gate method at 830 nm wavelength. Their second-order hyperpolarizability is estimated to be 0.74× 10^-30esu and 3.0× 10^-3esu respectively. This exhibits an evident enhancement in comparison with 0.47×10^-30esu for one-decker Eu（Pc）（acac） （acac=acetylacetonate）, which is also measured under the same conditions. The enhancement is attributed to the introduction of lanthanide metal to the large π-conjugated system, intermacrocycle interaction and two-photon resonance etc.展开更多
Ultrafast optical nonlinearities of N,N-dimethylformamide(DMF)are studied by using polarized light at 400 nm.Both nonlinear refraction(NLR)and stimulated Rayleigh-wing scattering(SRWS)depend on the polarization state ...Ultrafast optical nonlinearities of N,N-dimethylformamide(DMF)are studied by using polarized light at 400 nm.Both nonlinear refraction(NLR)and stimulated Rayleigh-wing scattering(SRWS)depend on the polarization state of incident beam,while two-photon absorption(TPA)changes negligibly with polarization state.The polarization dependence of SRWS originates from that of NLR via self-focusing effect.Third-order susceptibility elements of DMF were determined,and a method to distinguish the multi-photon absorption signal from SRWS in Z-scan is provided.These results are helpful for the nonlinear optical research of the novel materials dissolved in DMF.展开更多
Strong-field terahertz waves not only have high peak power but also possess strong electromagnetic field components.When electrons encounters strong-field terahertz waves,a series of novel changes are induced,which ha...Strong-field terahertz waves not only have high peak power but also possess strong electromagnetic field components.When electrons encounters strong-field terahertz waves,a series of novel changes are induced,which have attracted extensive attention.This review first introduces common optical sources for strong-field terahertz emission,such as photoconductive antennas,optical rectification crystals,and air plasmas.Subsequently,recent applications of strong-field terahertz technology in material state modulation are presented,mainly including strong-field terahertz wave-driven hot carrier motion,coherent phonon control,spintronics,electron acceleration,and biomedicine.展开更多
High-order harmonic generation（HHG） driven by two non-collinear beams including a fundamental and its weak second harmonic is numerically studied. The interference of harmonics from adjacent electron quantum paths i...High-order harmonic generation（HHG） driven by two non-collinear beams including a fundamental and its weak second harmonic is numerically studied. The interference of harmonics from adjacent electron quantum paths is found to be dependent on the relative delay of the driving pulse, and the dependences are different for different harmonic orders.This frequency dependence of the interference is attributed to the spatial frequency chirp in the HHG beam resulting from the harmonic dipole phase, which in turn provides a potential way to gain an insight into the generation of high-order harmonics. As an example, the intensity dependent dipole phase coefficient α is retrieved from the interference fringe.展开更多
We propose a kind of spectral polarization-encoding(SPE)for broadband light pulses,which is realized by inducing optical rotatory dispersion(ORD),and decoded by compensating ORD.Combining with polarization-sensitive d...We propose a kind of spectral polarization-encoding(SPE)for broadband light pulses,which is realized by inducing optical rotatory dispersion(ORD),and decoded by compensating ORD.Combining with polarization-sensitive devices,SPE can not only work to control polarization-dependent transmission for central wavelength or bandwidth-tunable filtering,but also can be used for broadband regenerative or multi-pass amplification with a polarization-dependent gain medium to improve output bandwidth.SPE is entirely passive thus very simple to be designed and aligned.By using an ORD crystal with a good transmission beyond 3-μm mid-infrared region,e.g.,Ag Ga S_(2),SPE promises to be applied for the wavelength tuning lasers in mid-infrared region,where the tunning devices are rather under developed compared with those in visible and near-infrared region.展开更多
We present a high-dispersive multilayer mirror for pulse stretching in a femtosecond fiber laser amplification system.The designed mirror contains 54 layers with a total physical thickness of 7.3 μm, which can provid...We present a high-dispersive multilayer mirror for pulse stretching in a femtosecond fiber laser amplification system.The designed mirror contains 54 layers with a total physical thickness of 7.3 μm, which can provide a positive group delay dispersion(GDD) of 600 fs2and a high reflectance over 99.9% from 1010 to 1070 nm. The samples were prepared by dual ion beam sputtering. The measured transmittance matches well with the theoretical result. The GDD characteristics of samples were tested by home-made white light interferometer. The measured GDD is higher than the design results,an average GDD of +722 fs2from 1010 nm to 1070 nm. The mirrors were employed in a Yb-doped large-mode-area photonic crystal fiber amplification system. An input pulse compressed by the gratings with autocorrelation function of83 fs is obtained with a stretched FWHM of 1.29 ps after 28 bounces between the dispersive mirrors. The results show that the multilayer dispersive mirror could be an effective and promising technique for pulse stretching in femtosecond amplification systems.展开更多
Optical parametric chirped pulse amplification(OPCPA)shows great potential in producing ultrashort high-intensity pulses because of its large gain bandwidth.Quasi-parametric chirped pulse amplification(QPCPA)may furth...Optical parametric chirped pulse amplification(OPCPA)shows great potential in producing ultrashort high-intensity pulses because of its large gain bandwidth.Quasi-parametric chirped pulse amplification(QPCPA)may further extend the bandwidth.However,behavior of QPCPA at a limited pump intensity(e.g.,≤5 GW/cm^(2) in a nanosecond pumped QPCPA)has not yet been investigated fully.We discuss detailedly the ultra-broadband amplification and the noncollinear phasematching geometry in QPCPA,model and develop a novel noncollinear geometry in QPCPA,namely triple-wavelength phase-matching geometry,which provides two additional phase-matching points around the phase-matching point at the central wavelength.Our analysis demonstrates that the triple-wavelength phase-matching geometry can support stable,ultra-broadband amplification in QPCPA.The numerical simulation results show that ultrashort pulse with a pulse duration of 7.92 fs can be achieved in QPCPA when the pump intensity is limited to 5 GW/cm^(2),calculated using the nonlinear coefficient of YCa;O(BO;);.展开更多
We theoretically investigate high-order harmonic generation(HHG)in crystals induced by linearly polarized laser fields.We obtain the HHG spectra by solving the semiconductor Bloch equations and analyze the radiation p...We theoretically investigate high-order harmonic generation(HHG)in crystals induced by linearly polarized laser fields.We obtain the HHG spectra by solving the semiconductor Bloch equations and analyze the radiation process by different models.Here we propose a multiple collision model,in which the electrons and holes are produced at different times and places.It is found that the multiple collision trajectories can help us comprehensively and better explain the results of the quantum calculation.Moreover,we find that the harmonic suppression occurs due to the overlap of multiple collision trajectories.展开更多
The generation of high-repetition rate(frep≥10 GHz)ultra-broadband optical frequency combs(OFCs)at 1550 nm and 1310 nm is investigated by seeding two types of highly nonlinear fibers(HNLFs)with 10 GHz picosecond puls...The generation of high-repetition rate(frep≥10 GHz)ultra-broadband optical frequency combs(OFCs)at 1550 nm and 1310 nm is investigated by seeding two types of highly nonlinear fibers(HNLFs)with 10 GHz picosecond pulses at the pump wavelength of 1550 nm.When pumped near the zero dispersion wavelength(ZDW)in the normal dispersion region of a HNLF,10 GHz flat-topped OFC with 43 nm bandwidth within 5 dB power variation is generated by self-phase modulation(SPM)-based OFC spectral broadening at 26.5 dBm pump power,and 291 fs pulse trains with 10 GHz repetition rate are obtained at 18 dBm pump power without complicated pulse shaping methods.Furthermore,when pumped in the abnormal dispersion region of a HNLF,OFCs with dispersive waves around 1310 nm are studied using a common HNLF and fluorotellurite fibers,which maintain the good coherence of the pump light at 1550 nm.At the same time,sufficient tunability of the generated dispersive waves is achieved when tuning the pump power or ZDW.展开更多
A complete theoretical modeling, avoiding any priori-assumption, is deduced and demonstrated for ultra-fast femtosecond optical pulses in silicon-on-insulator optical waveguides which includes the group velocity dispe...A complete theoretical modeling, avoiding any priori-assumption, is deduced and demonstrated for ultra-fast femtosecond optical pulses in silicon-on-insulator optical waveguides which includes the group velocity dispersion, third-order dispersion, self-phase and cross-phase modulations, self-steepening and shock formation, Raman depletion, propagation loss, two-photon absorption, free-carrier absorption, and free-carrier dispersion. Finally, the temporal and spectral characteristics of 100 fs optical pulses at 1.55 μm are numerically observed in 5-mm-long waveguides while considering different initial chirps and incident peak intensity levels.展开更多
We present a novel all-fiber ultrahigh-repetition-rate pulse(UHRP)source based on ultrafast pulse-stimulated dissipative four-wave mixing(FWM).By injecting an ultrafast seed pulse into a dissipative ring cavity equipp...We present a novel all-fiber ultrahigh-repetition-rate pulse(UHRP)source based on ultrafast pulse-stimulated dissipative four-wave mixing(FWM).By injecting an ultrafast seed pulse into a dissipative ring cavity equipped with a spectral shaper,a comb-like nonlinear response is generated.The high peak power of the seed pulse reaches the FWM threshold,stimulating a 0.275 THz pulse with an output power of 0.5 W.The gain and spectral shaper in the fiber ring cavity form a dissipative system that modifies the initial field both temporally and spectrally,ensuring UHRP stability even after the pulse is turned off.展开更多
Featured with high thermal decomposition temperature and layered structure,violet phosphorus(VP)offers an unparalleled stable allotrope of phosphorus to demonstrate the optoelectronic device and photonics elements wit...Featured with high thermal decomposition temperature and layered structure,violet phosphorus(VP)offers an unparalleled stable allotrope of phosphorus to demonstrate the optoelectronic device and photonics elements with high performance at the nanoscale.Here,we report few-layer and hundreds of nanometer-sized VP with robust stability in different solvents and ambient conditions by ultrasound-assisted liquid phase exfoliation approach.For the first time,the ultrafast carrier dynamics and thirdorder nonlinear optical response of VP were investigated.Sub-picosecond timescale ultrafast carrier dynamic and ultrafast nonlinear saturable absorption of VP were demonstrated.Our findings demonstrated that VP possessed a promising potential for use in ultrafast nonlinear photonic applications such as saturable absorbers and optical switches.展开更多
The generation of power-and wavelength-scalable few optical cycle pulses remains one of the major challenges in modern laser physics.Over the past decade,the development of table-top optical parametric chirped pulse a...The generation of power-and wavelength-scalable few optical cycle pulses remains one of the major challenges in modern laser physics.Over the past decade,the development of table-top optical parametric chirped pulse amplificationbased systems was progressing at amazing speed,demonstrating excellent performance characteristics in terms of pulse duration,energy,peak power and repetition rate,which place them at the front line of modern ultrafast laser technology.At present,table-top optical parametric chirped pulse amplifiers comprise a unique class of ultrafast light sources,which currently amplify octave-spanning spectra and produce carrier-envelope phase-stable,few optical cycle pulses with multi-gigawatt to multi-terawatt peak powers and multi-watt average powers,with carrier wavelengths spanning a considerable range of the optical spectrum.This article gives an overview on the state of the art of table-top optical parametric chirped pulse amplifiers,addressing their relevant scientific and technological aspects,and provides a short outlook of practical applications in the growing field of ultrafast science.展开更多
We report the generation of 207-fs pulses with 1.2 mW average power at 1036 nm directly from a passively modelocked Yb-doped fibre laser with a nonlinear optical loop mirror for mode-locking and pairs of diffraction g...We report the generation of 207-fs pulses with 1.2 mW average power at 1036 nm directly from a passively modelocked Yb-doped fibre laser with a nonlinear optical loop mirror for mode-locking and pairs of diffraction gratings for intracavity dispersion compensation. These results imply a 4-fold reduction in pulse duration over previously reported figure-of-eight cavity passively mode-locked Yb-doped fibre lasers. Stable pulse trains are produced at the fundamental repetition rate of the resonator, 24.0 MHz. On the other hand, this laser offers a cleaner spectrum and greater stability and is completely self-starting.展开更多
The propagation of femtosecond laser pulses in N2-filled hollow fibers is studied both theoretically and experimentally. The laser pulse aligns the N2 molecules and changes the refractive index, which meanwhile modula...The propagation of femtosecond laser pulses in N2-filled hollow fibers is studied both theoretically and experimentally. The laser pulse aligns the N2 molecules and changes the refractive index, which meanwhile modulates the spectrum of the pulse in turn. The dependence of the spectral modulation on the gas temperature is investigated. We find that both spectral broadening and frequency red-shift are enhanced at low temperature. The degree of enhancement is found to be dependent on the pulse duration. Based on our findings, we propose a method for femtosecond pulse spectral broadening and few-cycle pulse generation via the molecular alignment.展开更多
We investigate the ultrafast dynamics of the quasi-one-dimensional Kondo lattice CeCo_(2)Ga_(8) using optical pump-probe spectroscopy.Time-resolved pump-probe reflectivity measurements reveal a strong anisotropy in th...We investigate the ultrafast dynamics of the quasi-one-dimensional Kondo lattice CeCo_(2)Ga_(8) using optical pump-probe spectroscopy.Time-resolved pump-probe reflectivity measurements reveal a strong anisotropy in the photoinduced response,which is a direct consequence of the material's unique electronic structure.The temperature dependence of the relaxation dynamics provides evidence for the formation of two distinct hybridization gaps that appear at different temperatures in the heavy fermion state.A direct gap of 2dir~50 meV that persists up to T^(+)≈90 K,well above the coherence temperature T^(*)≈20 K.We attribute this higher-temperature gap to the hybridization fluctuations.An indirect gap of 2△_(ind)≈14 meV opens closer to T^(*),signifying the development of long-range coherence in the heavy fermion state.Furthermore,we find that the hybridization gap can be suppressed with increasing pump fluence,indicating a delicate interplay between photoexcitation and the coherent heavy fermion state.Our results provide insights into the interplay of Kondo physics and low dimensionality in CeCo_(2)Ga_(8),and establish ultrafast optical spectroscopy as a sensitive probe of anisotropic hybridization in heavy fermion materials.展开更多
基金Project supported by the STI 2030-Major Projects,China(No.2021ZD0200401)the National Key Research and Development Program of China(No.2023YFF0613000)+1 种基金the National Natural Science Foundation of China(Nos.62222511 and 62175122)the Natural Science Foundation of Zhejiang Province,China(No.LR22F050006)。
文摘Ultrafast fiber lasers are indispensable components in the field of ultrafast optics,and their continuous performance advancements are driving the progress of this exciting discipline.Micro/Nanofibers(MNFs)possess unique properties,such as a large fractional evanescent field,flexible and controllable dispersion,and high nonlinearity,making them highly valuable for generating ultrashort pulses.Particularly,in tasks involving mode-locking and dispersion and nonlinearity management,MNFs provide an excellent platform for investigating intriguing nonlinear dynamics and related phenomena,thereby promoting the advancement of ultrafast fiber lasers.In this paper,we present an introduction to the mode evolution and characteristics of MNFs followed by a comprehensive review of recent advances in using MNFs for ultrafast optics applications including evanescent field modulation and control,dispersion and nonlinear management techniques,and nonlinear dynamical phenomenon exploration.Finally,we discuss the potential application prospects of MNFs in the realm of ultrafast optics.
基金supported by the National Key R&D Program of China(No.2022YFB4601601)the Key R&D Program of Guangxi Province,China(No.GKAB23026101)+1 种基金the Base,Talent Special Project of the Guangxi Science and Technology Plan Project(No.Gui Ke AD23026149)Guangxi Natural Science Foundation,China(No.2023GXNSFBA026287)
文摘Ultrafast phenomena induced by femtosecond laser irradiation encompass a range of highly dynamic physical processes,including but not limited to electron excitation,material ablation,plasma generation,and shock wave propagation.Unveiling the dynamics of these ultrafast processes is crucial for effectively controlling laser processing.However,many of these phenomena occur on timescales ranging from femtoseconds(fs) to nanoseconds(ns),which presents significant challenges in monitoring and interpretation;thus,ultrafast optical imaging techniques are often required.This paper comprehensively reviews the ultrafast optical imaging methods employed in recent years to monitor various ultrafast processes such as electron excitation,ultrafast ablation,plasma ejection,and shock wave propagation during femtosecond laser processing of metallic,composite,and ceramic materials.These methods can be categorized into two primary types:pump-probe ultrafast optical imaging and single-shot ultrafast optical imaging techniques.The working principles and key findings associated with each type of ultrafast optical imaging technique are described in detail.Finally,the imaging principles,advantages and disadvantages,and application scenarios of various ultrafast imaging technologies are summarized,along with a discussion of future challenges and development directions in this field.
基金supported by the National Natural Science Foundation of China (Nos. 11974258, 11604236, 61575139)Key Research and Development (R&D) Projects of Shanxi Province (201903D121127)+2 种基金Scientific and Technological Innovation Programs of Higher Education Institutions in Shanxi (2019L0151)the Natural Sciences Foundation in Shanxi Province (201901D111117)the financial support from the Australian Research Council (Australian Research Council (DP190103186, IC180100005)
文摘The control of ultrafast optical field is of great interest in developing ultrafast optics as well as the investigation on vari-ous light-matter interactions with ultrashort pulses.However,conventional spatial encoding approaches have only lim-ited steerable targets usually neglecting the temporal effect,thus hindering their broad applications.Here we present a new concept for realizing ultrafast modulation of multi-target focal fields based on the facile combination of time-depend-ent vectorial diffraction theory with fast Fourier transform.This is achieved by focusing femtosecond pulsed light carrying vectorial-vortex by a single objective lens under tight focusing condition.It is uncovered that the ultrafast temporal de-gree of freedom within a configurable temporal duration(~400 fs)plays a pivotal role in determining the rich and exotic features of the focused optical field at one time,namely,bright-dark alternation,periodic rotation,and longitudinal/trans-verse polarization conversion.The underlying control mechanisms have been unveiled.Besides being of academic in-terest in diverse ultrafast spectral regimes,these peculiar behaviors of the space-time evolutionary beams may underpin prolific ultrafast-related applications such as multifunctional integrated optical chip,high-efficiency laser trapping,micro-structure rotation,super-resolution optical microscopy,precise optical measurement,and liveness tracking.
基金supported by the National Natural Science Foundation of China under Grant Nos.51975054,61605140 and 11704028the National Key R&D Program of China(2017YFB1104300)。
文摘Femtosecond laser technology has attracted significant attention from the viewpoints of fundamental and application;especially femtosecond laser processing materials present the unique mechanism of laser-material interaction.Under the extreme nonequilibrium conditions imposed by femtosecond laser irradiation,many fundamental questions concerning the physical origin of the material removal process remain unanswered.In this review,cutting-edge ultrafast dynamic observation techniques for investigating the fundamental questions,including timeresolved pump-probe shadowgraphy,ultrafast continuous optical imaging,and four-dimensional ultrafast scanning electron microscopy,are comprehensively surveyed.Each technique is described in depth,beginning with its basic principle,followed by a description of its representative applications in laser-material interaction and its strengths and limitations.The consideration of temporal and spatial resolutions and panoramic measurement at different scales are two major challenges.Hence,the prospects for technical advancement in this field are discussed finally.
基金Project supported by the National Key Research Program of China （Grant No TG1999075209） and the National Natural Science Foundation of China （Grant Nos 10434020, 90206003 and 60378012）.
文摘The third-order optical nonlinearity of two sandwich-type phthalocyaninato and porphyrinato europium com- plexes, including double- and triple-deckers （Eu[Pc（OC5H11）8]2, Eu2（Pc）（TPP）2, Pc=phthalocyanine, TPP=5, 10, 15, 20- tetraphenylporphyrinate）, was investigated by using the femtosecond time-resolved optical Kerr gate method at 830 nm wavelength. Their second-order hyperpolarizability is estimated to be 0.74× 10^-30esu and 3.0× 10^-3esu respectively. This exhibits an evident enhancement in comparison with 0.47×10^-30esu for one-decker Eu（Pc）（acac） （acac=acetylacetonate）, which is also measured under the same conditions. The enhancement is attributed to the introduction of lanthanide metal to the large π-conjugated system, intermacrocycle interaction and two-photon resonance etc.
基金the National Natural Science Foundation of China(No.12074202)the Natural Science Foundation of Tianjin City(Nos.22JCYBJC00390 and 20JCQNJC00020)。
文摘Ultrafast optical nonlinearities of N,N-dimethylformamide(DMF)are studied by using polarized light at 400 nm.Both nonlinear refraction(NLR)and stimulated Rayleigh-wing scattering(SRWS)depend on the polarization state of incident beam,while two-photon absorption(TPA)changes negligibly with polarization state.The polarization dependence of SRWS originates from that of NLR via self-focusing effect.Third-order susceptibility elements of DMF were determined,and a method to distinguish the multi-photon absorption signal from SRWS in Z-scan is provided.These results are helpful for the nonlinear optical research of the novel materials dissolved in DMF.
基金supported by the National Natural Science Foundation of China(No.12204251)。
文摘Strong-field terahertz waves not only have high peak power but also possess strong electromagnetic field components.When electrons encounters strong-field terahertz waves,a series of novel changes are induced,which have attracted extensive attention.This review first introduces common optical sources for strong-field terahertz emission,such as photoconductive antennas,optical rectification crystals,and air plasmas.Subsequently,recent applications of strong-field terahertz technology in material state modulation are presented,mainly including strong-field terahertz wave-driven hot carrier motion,coherent phonon control,spintronics,electron acceleration,and biomedicine.
基金Project supported by the National Key Basic Research Program of China(Grant Nos.2013CB922401 and 2013CB922402)the National Key Scientific Instrument and Equipment Development Projects,China(Grant No.2012YQ12004704)+1 种基金the National Natural Science Foundation of China(Grant No.11374356)the International Joint Research Program of National Natural Science Foundation of China(Grant No.61210017)
文摘High-order harmonic generation（HHG） driven by two non-collinear beams including a fundamental and its weak second harmonic is numerically studied. The interference of harmonics from adjacent electron quantum paths is found to be dependent on the relative delay of the driving pulse, and the dependences are different for different harmonic orders.This frequency dependence of the interference is attributed to the spatial frequency chirp in the HHG beam resulting from the harmonic dipole phase, which in turn provides a potential way to gain an insight into the generation of high-order harmonics. As an example, the intensity dependent dipole phase coefficient α is retrieved from the interference fringe.
基金the National Natural Science Foundation of China(Grant Nos.92050203,62075138,61827815,and 61775142)Shenzhen Fundamental Research Project(Grant Nos.JCYJ20190808164007485,JCYJ20190808121817100,JSGG20191231144201722,and JCYJ20190808115601653)。
文摘We propose a kind of spectral polarization-encoding(SPE)for broadband light pulses,which is realized by inducing optical rotatory dispersion(ORD),and decoded by compensating ORD.Combining with polarization-sensitive devices,SPE can not only work to control polarization-dependent transmission for central wavelength or bandwidth-tunable filtering,but also can be used for broadband regenerative or multi-pass amplification with a polarization-dependent gain medium to improve output bandwidth.SPE is entirely passive thus very simple to be designed and aligned.By using an ORD crystal with a good transmission beyond 3-μm mid-infrared region,e.g.,Ag Ga S_(2),SPE promises to be applied for the wavelength tuning lasers in mid-infrared region,where the tunning devices are rather under developed compared with those in visible and near-infrared region.
基金Project supported by the National Natural Science Foundation of China(Grant No.61705194)。
文摘We present a high-dispersive multilayer mirror for pulse stretching in a femtosecond fiber laser amplification system.The designed mirror contains 54 layers with a total physical thickness of 7.3 μm, which can provide a positive group delay dispersion(GDD) of 600 fs2and a high reflectance over 99.9% from 1010 to 1070 nm. The samples were prepared by dual ion beam sputtering. The measured transmittance matches well with the theoretical result. The GDD characteristics of samples were tested by home-made white light interferometer. The measured GDD is higher than the design results,an average GDD of +722 fs2from 1010 nm to 1070 nm. The mirrors were employed in a Yb-doped large-mode-area photonic crystal fiber amplification system. An input pulse compressed by the gratings with autocorrelation function of83 fs is obtained with a stretched FWHM of 1.29 ps after 28 bounces between the dispersive mirrors. The results show that the multilayer dispersive mirror could be an effective and promising technique for pulse stretching in femtosecond amplification systems.
基金supported by the National Natural Science Foundation of China(Grant No.51832009)the Fundamental Research Funds for the Central Universities,China(Grant No.2019YJS209)。
文摘Optical parametric chirped pulse amplification(OPCPA)shows great potential in producing ultrashort high-intensity pulses because of its large gain bandwidth.Quasi-parametric chirped pulse amplification(QPCPA)may further extend the bandwidth.However,behavior of QPCPA at a limited pump intensity(e.g.,≤5 GW/cm^(2) in a nanosecond pumped QPCPA)has not yet been investigated fully.We discuss detailedly the ultra-broadband amplification and the noncollinear phasematching geometry in QPCPA,model and develop a novel noncollinear geometry in QPCPA,namely triple-wavelength phase-matching geometry,which provides two additional phase-matching points around the phase-matching point at the central wavelength.Our analysis demonstrates that the triple-wavelength phase-matching geometry can support stable,ultra-broadband amplification in QPCPA.The numerical simulation results show that ultrashort pulse with a pulse duration of 7.92 fs can be achieved in QPCPA when the pump intensity is limited to 5 GW/cm^(2),calculated using the nonlinear coefficient of YCa;O(BO;);.
基金Project supported by the National Natural Science Foundation of China(Grant No.91850121)the K.C.Wong Education Foundation(Grant No.GJTD-2019-15)
文摘We theoretically investigate high-order harmonic generation(HHG)in crystals induced by linearly polarized laser fields.We obtain the HHG spectra by solving the semiconductor Bloch equations and analyze the radiation process by different models.Here we propose a multiple collision model,in which the electrons and holes are produced at different times and places.It is found that the multiple collision trajectories can help us comprehensively and better explain the results of the quantum calculation.Moreover,we find that the harmonic suppression occurs due to the overlap of multiple collision trajectories.
基金We are grateful for financial supports from the National Natural Science Foundation of China(Grant No.61527823)the National Key R&D Program of China(Grant No.2017YFB0405301).
文摘The generation of high-repetition rate(frep≥10 GHz)ultra-broadband optical frequency combs(OFCs)at 1550 nm and 1310 nm is investigated by seeding two types of highly nonlinear fibers(HNLFs)with 10 GHz picosecond pulses at the pump wavelength of 1550 nm.When pumped near the zero dispersion wavelength(ZDW)in the normal dispersion region of a HNLF,10 GHz flat-topped OFC with 43 nm bandwidth within 5 dB power variation is generated by self-phase modulation(SPM)-based OFC spectral broadening at 26.5 dBm pump power,and 291 fs pulse trains with 10 GHz repetition rate are obtained at 18 dBm pump power without complicated pulse shaping methods.Furthermore,when pumped in the abnormal dispersion region of a HNLF,OFCs with dispersive waves around 1310 nm are studied using a common HNLF and fluorotellurite fibers,which maintain the good coherence of the pump light at 1550 nm.At the same time,sufficient tunability of the generated dispersive waves is achieved when tuning the pump power or ZDW.
基金National Natural Science Foundation of China(60677023)
文摘A complete theoretical modeling, avoiding any priori-assumption, is deduced and demonstrated for ultra-fast femtosecond optical pulses in silicon-on-insulator optical waveguides which includes the group velocity dispersion, third-order dispersion, self-phase and cross-phase modulations, self-steepening and shock formation, Raman depletion, propagation loss, two-photon absorption, free-carrier absorption, and free-carrier dispersion. Finally, the temporal and spectral characteristics of 100 fs optical pulses at 1.55 μm are numerically observed in 5-mm-long waveguides while considering different initial chirps and incident peak intensity levels.
基金supported by the National Natural Science Foundation of China(Nos.62175007 and 62305018)the Chinese Postdoctoral Science Foundation(No.2022M720363)。
文摘We present a novel all-fiber ultrahigh-repetition-rate pulse(UHRP)source based on ultrafast pulse-stimulated dissipative four-wave mixing(FWM).By injecting an ultrafast seed pulse into a dissipative ring cavity equipped with a spectral shaper,a comb-like nonlinear response is generated.The high peak power of the seed pulse reaches the FWM threshold,stimulating a 0.275 THz pulse with an output power of 0.5 W.The gain and spectral shaper in the fiber ring cavity form a dissipative system that modifies the initial field both temporally and spectrally,ensuring UHRP stability even after the pulse is turned off.
基金the financial support from the National Natural Science Foundation of China(Nos.61874141,62275275,and 11904239)the Nature Science Foundation of Hunan Province(Nos.2021JJ40709 and 2022JJ20080)the High Performance Computing Center of Central South University,and the Open Sharing Found for the Large-scale Instruments and Equipment of Central South University.
文摘Featured with high thermal decomposition temperature and layered structure,violet phosphorus(VP)offers an unparalleled stable allotrope of phosphorus to demonstrate the optoelectronic device and photonics elements with high performance at the nanoscale.Here,we report few-layer and hundreds of nanometer-sized VP with robust stability in different solvents and ambient conditions by ultrasound-assisted liquid phase exfoliation approach.For the first time,the ultrafast carrier dynamics and thirdorder nonlinear optical response of VP were investigated.Sub-picosecond timescale ultrafast carrier dynamic and ultrafast nonlinear saturable absorption of VP were demonstrated.Our findings demonstrated that VP possessed a promising potential for use in ultrafast nonlinear photonic applications such as saturable absorbers and optical switches.
基金We are grateful to Dr.D.Kaškelytėfor building a comprehensive literature database on OPCPA.We also would like to add the following dedication at the very end of the paper:This article is dedicated to the memory of Professor Algis Petras Piskarskas(1942-2022).
文摘The generation of power-and wavelength-scalable few optical cycle pulses remains one of the major challenges in modern laser physics.Over the past decade,the development of table-top optical parametric chirped pulse amplificationbased systems was progressing at amazing speed,demonstrating excellent performance characteristics in terms of pulse duration,energy,peak power and repetition rate,which place them at the front line of modern ultrafast laser technology.At present,table-top optical parametric chirped pulse amplifiers comprise a unique class of ultrafast light sources,which currently amplify octave-spanning spectra and produce carrier-envelope phase-stable,few optical cycle pulses with multi-gigawatt to multi-terawatt peak powers and multi-watt average powers,with carrier wavelengths spanning a considerable range of the optical spectrum.This article gives an overview on the state of the art of table-top optical parametric chirped pulse amplifiers,addressing their relevant scientific and technological aspects,and provides a short outlook of practical applications in the growing field of ultrafast science.
基金Project supported by the National Natural Science Foundation of China （Grant Nos 60537060 and 10390160）.
文摘We report the generation of 207-fs pulses with 1.2 mW average power at 1036 nm directly from a passively modelocked Yb-doped fibre laser with a nonlinear optical loop mirror for mode-locking and pairs of diffraction gratings for intracavity dispersion compensation. These results imply a 4-fold reduction in pulse duration over previously reported figure-of-eight cavity passively mode-locked Yb-doped fibre lasers. Stable pulse trains are produced at the fundamental repetition rate of the resonator, 24.0 MHz. On the other hand, this laser offers a cleaner spectrum and greater stability and is completely self-starting.
基金Project supported by the National Natural Science Foundation of China(Grants Nos.11074014 and 11121091)
文摘The propagation of femtosecond laser pulses in N2-filled hollow fibers is studied both theoretically and experimentally. The laser pulse aligns the N2 molecules and changes the refractive index, which meanwhile modulates the spectrum of the pulse in turn. The dependence of the spectral modulation on the gas temperature is investigated. We find that both spectral broadening and frequency red-shift are enhanced at low temperature. The degree of enhancement is found to be dependent on the pulse duration. Based on our findings, we propose a method for femtosecond pulse spectral broadening and few-cycle pulse generation via the molecular alignment.
基金supported by the National Natural Science Foundation of China(Grant Nos.12074436,U22A6005,and U2032204)the National Key Research and Development Program of China(Grant No.2022YFA1604204)+1 种基金the Science and Technology Innovation Program of Hunan Province(No.2022RC3068)the Natural Science Foundation of Changsha(No.kq2208254).
文摘We investigate the ultrafast dynamics of the quasi-one-dimensional Kondo lattice CeCo_(2)Ga_(8) using optical pump-probe spectroscopy.Time-resolved pump-probe reflectivity measurements reveal a strong anisotropy in the photoinduced response,which is a direct consequence of the material's unique electronic structure.The temperature dependence of the relaxation dynamics provides evidence for the formation of two distinct hybridization gaps that appear at different temperatures in the heavy fermion state.A direct gap of 2dir~50 meV that persists up to T^(+)≈90 K,well above the coherence temperature T^(*)≈20 K.We attribute this higher-temperature gap to the hybridization fluctuations.An indirect gap of 2△_(ind)≈14 meV opens closer to T^(*),signifying the development of long-range coherence in the heavy fermion state.Furthermore,we find that the hybridization gap can be suppressed with increasing pump fluence,indicating a delicate interplay between photoexcitation and the coherent heavy fermion state.Our results provide insights into the interplay of Kondo physics and low dimensionality in CeCo_(2)Ga_(8),and establish ultrafast optical spectroscopy as a sensitive probe of anisotropic hybridization in heavy fermion materials.
