X-ray free-electron lasers(XFELs)can generate bright X-ray pulses with short durations and narrow bandwidths,leading to extensive applica-tions in many disciplines such as biology,materials science,and ultrafast scien...X-ray free-electron lasers(XFELs)can generate bright X-ray pulses with short durations and narrow bandwidths,leading to extensive applica-tions in many disciplines such as biology,materials science,and ultrafast science.Recently,there has been a growing demand for X-ray pulses with high photon energy,especially from developments in“diffraction-before-destruction”applications and in dynamic mesoscale materials science.Here,we propose utilizing the electron beams at XFELs to drive a meter-scale two-bunch plasma wakefield accelerator and double the energy of the accelerated beam in a compact and inexpensive way.Particle-in-cell simulations are performed to study the beam quality degradation under different beam loading scenarios and nonideal issues,and the results show that more than half of the accelerated beam can meet the requirements of XFELs.After its transport to the undulator,the accelerated beam can improve the photon energy to 22 keV by a factor of around four while maintaining the peak power,thus offering a promising pathway toward high-photon-energy XFELs.展开更多
Generation of intense, fully coherent radiation with wide spectral coverage has been a long-standing challenge for laser technologies. Several techniques have been developed in recent years to extend the spectral cove...Generation of intense, fully coherent radiation with wide spectral coverage has been a long-standing challenge for laser technologies. Several techniques have been developed in recent years to extend the spectral coverage in optical physics, but none of them hold the potential to produce X-ray laser pulses with very high-peak power. Urgent demands for intense X-ray light sources have prompted the development of free-electron lasers(FELs), which have been proved to be very useful tools in many scientific areas. In this paper, we give an overview of the basic principle of FELs, techniques for realizing fully coherent FELs, and the development of fully coherent FEL facilities in China.展开更多
X-ray beams carrying orbital angular momentum(OAM)are an emerging tool for probing matter.Optical elements,such as spiral phase plates and zone plates,have been widely used to generate OAM light.However,due to the hig...X-ray beams carrying orbital angular momentum(OAM)are an emerging tool for probing matter.Optical elements,such as spiral phase plates and zone plates,have been widely used to generate OAM light.However,due to the high impinging intensities,these optics are challenging to use at X-ray free-electron lasers(XFELs).Here,we propose a self-seeded free-electron laser(FEL)method to produce intense X-ray vortices.Unlike passive filtering after amplification,an optical element will be used to introduce the helical phase to the radiation pulse in the linear regime,significantly reducing thermal load on the optical element.The generated OAM pulse is then used as a seed and significantly amplified.Theoretical analysis and numerical simulations demonstrate that the power of the OAM seed pulse can be amplified by more than two orders of magnitude,reaching peak powers of several tens of gigawatts.The proposed method paves the way for high-power and high-repetition-rate OAM pulses of XFEL light.展开更多
A three-dimensional simulation of a steady-state amplifier model of a long-wavelength free-electron laser （FEL） with realizable helical wiggler and ion-channel guiding is presented. The set of coupled nonlinear diff...A three-dimensional simulation of a steady-state amplifier model of a long-wavelength free-electron laser （FEL） with realizable helical wiggler and ion-channel guiding is presented. The set of coupled nonlinear differential equations for electron orbits and fields of TE 11 mode in a cylindrical waveguide are solved numerically by the Runge–Kutta algorithm with averages calculated by the Gaussian quadrature technique. Self-fields and space-charge effects are neglected, and the electron beam is assumed to be cold and slippage is ignored. The parameters correspond to the Compton regime. Evolution of the radiation power and growth rate along the wiggler is studied. Ion-channel density is chosen to obtain optimum efficiency. Simulations are preformed for the FEL operating in the neighborhood of 35 GHz and 16.5 GHz for the electron beam energies of 250 keV and 400 keV, respectively. The result of the saturated efficiency was found to be in good agreement with the simple estimation based on the phase-trapping model.展开更多
The effects of self-fields on electron trajectories and gain in planar wiggler free-electron lasers with two-stream and ion-channel guiding are investigated. An analysis of the two-stream quasi-steady-state electron t...The effects of self-fields on electron trajectories and gain in planar wiggler free-electron lasers with two-stream and ion-channel guiding are investigated. An analysis of the two-stream quasi-steady-state electron trajectories is given by solving the equation of motion in the presence of ion-channel guiding and the planar wiggler. The electron trajectories and the gain are derived. The stability of the trajectories, the characteristics of the linear gain, and the normalized maximum gain are studied numerically. The numerical calculations show that there are eight group trajectories rather than the two groups reported in the absence of the self-fields. It is also shown that the normalized gain group seven （G7） decreases while the rest increases with the increase in normalized ion-channel frequency. The two-stream instability and the self-field lead to a decrease in the maximum gain, except for G7.展开更多
X-ray free-electron lasers(FELs)provide cutting-edge tools for fundamental researches to study nature down to the atomic level at a time-scale that fits this resolution.A precise knowledge of temporal information of F...X-ray free-electron lasers(FELs)provide cutting-edge tools for fundamental researches to study nature down to the atomic level at a time-scale that fits this resolution.A precise knowledge of temporal information of FEL pulses is the central issue for its applications.Here we proposed and demonstrated a novel method to determine the FEL temporal profiles online.This robust method,designed for ultrafast FELs,allows researchers to acquire real-time longitudinal profiles of FEL pulses as well as their arrive times with respect to the external optical laser with a resolution better than 6 fs.Based on this method,we can also directly measure various properties of FEL pulses and correlations between them online.This helps us to further understand the FEL lasing processes and realize the generation of stable,nearly fully coherent soft X-ray laser pulses at the Shanghai Soft X-ray FEL facility.This method will enhance the experimental opportunities for ultrafast science in various areas.展开更多
A super-radiant terahertz free-electron laser(THz-FEL)light source was developed for the first time in Thailand and Southeast Asia at the PBP-CMU Electron Linac Laboratory(PCELL)of Chiang Mai University.This radiation...A super-radiant terahertz free-electron laser(THz-FEL)light source was developed for the first time in Thailand and Southeast Asia at the PBP-CMU Electron Linac Laboratory(PCELL)of Chiang Mai University.This radiation source requires relatively ultrashort electron bunches to produce intense coherent THz pulses.Three electron bunch compression processes are utilized in the PCELL accelerator system comprising pre-bunch compression in an alpha magnet,velocity bunching in a radio-frequency(RF)linear accelerator(linac),and magnetic bunch compression in a 180°acromat system.Electron bunch compression in the magnetic compressor system poses considerable challenges,which are addressed through the use of three quadrupole doublets.The strengths of the quadrupole fields significantly influence the rotation of the beam line longitudinal phase space distribution along the bunch compressor.Start-to-end beam dynamics simulations using the ASTRA code were performed to optimize the electron beam properties for generating super-radiant THz-FEL radiation.The operational parameters considered in the simulations comprise the alpha magnet gradient,linac RF phase,and quadrupole field strengths.The optimization results show that 10-16MeV femtosecond electron bunches with a low energy spread(~0.2%),small normalized emittance(~15πmm·mrad),and high peak current(165-247A)can be produced by the PCELL accelerator system at the optimal parameters.A THz-FEL with sub-microjoule pulse energies can thus be obtained at the optimized electron beam parameters.The physical and conceptual design of the THz-FEL beamline were completed based on the beam dynamics simulation results.The construction and installation of this beamline are currently underway and expected to be completed by mid-2024.The commissioning of the beamline will then commence.展开更多
Broad area quantum cascade lasers(BA QCLs)have significant applications in many areas,but suffer from demanding pulse operating conditions and poor beam quality due to heat accumulation and generation of high order mo...Broad area quantum cascade lasers(BA QCLs)have significant applications in many areas,but suffer from demanding pulse operating conditions and poor beam quality due to heat accumulation and generation of high order modes.A structure of mini-array is adopted to improve the heat dissipation capacity and beam quality of BA QCLs.The active region is etched to form a multi-emitter and the channels are filled with In P:Fe,which acts as a lateral heat dissipation channel to improve the lateral heat dissipation efficiency.A device withλ~4.8μm,a peak output power of 122 W at 1.2%duty cycle with a pulse of 1.5μs is obtained in room temperature,with far-field single-lobed distribution.This result allows BA QCLs to obtain high peak power at wider pump pulse widths and higher duty cycle conditions,promotes the application of the mid-infrared laser operating in pulsed mode in th e field of standoff photoacoustic chemical detection,space optical communication,and so on.展开更多
Objective The use of lasers has been an important part of urology in the treatment of stone and prostate disease.The thermal effects of lasers in lithotripsy have been a subject of debate over the years.The objective ...Objective The use of lasers has been an important part of urology in the treatment of stone and prostate disease.The thermal effects of lasers in lithotripsy have been a subject of debate over the years.The objective of this review was to assess the current state of knowledge available on the thermal effects of lasers in lithotripsy,as well as explore any new areas where studies are needed.Methods In August 2022,a keyword search on Google Scholar,PubMed,and Scopus for all papers containing the phrases“thermal effects”AND“laser”AND“lithotripsy”AND“urology”was done followed by citation jumping to other studies pertaining to the topic and 35 relevant papers were included in our study.The data from relevant papers were segregated into five groups according to the factor studied and type of study,and tables were created for a comparison of data.Results Temperature above the threshold of 43℃ was reached only when the power was>40 W and when there was adequate irrigation(at least 15–30 mL/min).Shorter lasing time divided by lithotripsy time or operator duty cycles less than 70%also resulted in a smaller temperature rise.Conclusion At least eight factors modify the thermal effects of lasers,and most importantly,the use of chilled irrigation at higher perfusion rates,lower power settings of<40 W,and with a shorter operator duty cycle will help to prevent thermal injuries from occurring.Stones impacted in the ureter or pelvi-ureteric junction further increase the probability of thermal injuries during laser firing.展开更多
Development of on-chip coherent light sources with desired single-mode operation and straightforward spectral tunability has attracted intense interest due to ever-increasing demand for photonic devices and optoelectr...Development of on-chip coherent light sources with desired single-mode operation and straightforward spectral tunability has attracted intense interest due to ever-increasing demand for photonic devices and optoelectronic integration,but still faces serious challenges.Herein,we propose a facile method to synthesize cesium lead halide(CsPbX3)microstructures with well-defined morphologies,sizes,and constituent element gradient.The scheme is conducted using a chemical vapor deposition(CVD),which is subsequently associated with annealing-assisted solid-solid anion exchange.For the plate-shaped structures,the controllability on the cross-sectional dimension enables to precisely modulate the lasing modes,thus achieving single-mode operation;while tuning the stoichiometric of the halogen anion components in the plate-shaped CsPbI_(x)Br_(3−x) alloy samples,the lasing wavelengths are straightforwardly varied to span the entire visible spectrum.By comparison,the experimental scheme on synthesizing alloyed CsPbI_(x)Br_(3−x) perovskites is conducted using an in-situ approach,thereby achieving precise modulation of bandgap-controlled microlasers by controlling the reaction time.Such laser properties like controllable microcavity modes and broad stoichiometry-dependent tunability of light-emitting/lasing colors,associated with the facile synthesizing method of monocrystalline CsPbI_(x)Br_(3−x) structures,make lead halide perovskites ideal materials for the development of wavelength-controlled microlasers toward practical photonic integration.展开更多
External seeded free-electron lasers(FELs) have exhibited substantial progress in diverse applications over the last decade. However, the frequency up-conversion efficiency in single-stage seeded FELs, particularly in...External seeded free-electron lasers(FELs) have exhibited substantial progress in diverse applications over the last decade. However, the frequency up-conversion efficiency in single-stage seeded FELs, particularly in high-gain harmonic generation(HGHG), remains constrained to a modest level. This limitation restricts its capability to conduct experiments within the ‘water window'. This paper presents a novel method for generating coherent X-ray FEL pulses in the water window region based on the HGHG scheme with multi-stage harmonic cascade. Without any additional modifications to the HGHG configuration, simulation results demonstrate the generation of intense 3 nm coherent FEL radiation using an external ultraviolet seed laser. This indicates an increase of the harmonic conversion number to approximately 90.A preliminary experiment is performed to evaluate the feasibility of this method. The proposed approach could potentially serve as an efficient method to broaden the wavelength coverage accessible to both existing and planned seeded X-ray FEL facilities.展开更多
Linear accelerator-based free-electron lasers(FELs)are the leading source of fully coherent X-rays with ultra-high peak powers and ultrashort pulse lengths.Current X-ray FEL facilities have proved their worth as usefu...Linear accelerator-based free-electron lasers(FELs)are the leading source of fully coherent X-rays with ultra-high peak powers and ultrashort pulse lengths.Current X-ray FEL facilities have proved their worth as useful tools for diverse scientific applications.In this paper,we present an overview of the features and future prospects of X-ray FELs,including the working principles and properties of X-ray FELs,the operational status of different FEL facilities worldwide,the applications supported by such facilities,and the current developments and outlook for X-ray FEL-based research.展开更多
As a representative transition metal dichalcogenides(TMD),NiTe_(2)has an ultra-fast optical response,high carrier mobility,and excellent environmental stability.It has a broad application prospect in the fields of ene...As a representative transition metal dichalcogenides(TMD),NiTe_(2)has an ultra-fast optical response,high carrier mobility,and excellent environmental stability.It has a broad application prospect in the fields of ener-gy,biomedicine,optoelectronic devices,and so on.At present,there have been scant reports on the application of NiTe_(2)in the field of ultrafast photonics.In this work,NiTe_(2)was synthesized by chemical vapor deposition(CVD)and integrated with a tapered optical fiber to achieve mode-locking in an erbium-doped fiber laser(EDFL)and a thu-lium-doped fiber laser(TDFL).The mode-locked EDFL exhibited a pulse width of 678 fs and an output power of 3.92 mW.The pulse width of mode-locked TDFL was estimated to have a pulse width of 694 fs with an output power of 21.64 mW.These results demonstrate that NiTe_(2)is an effective saturable absorber material with potential applica-tions in the field of ultrafast optics.展开更多
Introduction:Surgeons typically prefer 270μm and 272μm laser probes in retrograde intrarenal surgery(RIRS)due to the reduced deflection capacity of flexible ureterorenoscopes when using larger probe diameters.This s...Introduction:Surgeons typically prefer 270μm and 272μm laser probes in retrograde intrarenal surgery(RIRS)due to the reduced deflection capacity of flexible ureterorenoscopes when using larger probe diameters.This study aims to investigate the effects of 272 and 365μm holmium laser probes on operative time,clinical efficacy,and complication rates in RIRS.Materials and Methods:A total of 285 patients with proximal ureteral or kidney stones who met the inclusion criteria were enrolled in the study.Patients were divided into two groups based on laser probe thickness:272μm and 365μm.Stone-free rates,operative time,and complication rates were compared between the groups.Factors affecting stone-free rates were analyzed using multivariate logistic regression analysis.Results:Patient and stone characteristics were similar between the two groups.No significant differences were found in stone-free or complication rates.However,operative time was significantly shorter in the 365μm probe group.In univariate analysis,risk factors for postoperative residual stones included multi-calyceal stones,lower pole stones,high Hounsfield unit(HU)values on noncontrast computed tomography,and larger stone size.In multivariate analysis,independent prognostic factors for residual stones were identified as multi-calycal stones,lower pole stones,and high HU values.Conclusion:Compared to 272μm laser probes,operative time was shorter in surgeries performed with 365μm laser probes.The 365μm holmium laser can be effectively and safely used in the treatment of proximal ureteral and renal stones,demonstrating high clinical efficacy and safety.展开更多
Photonic crystal surface emitting lasers(PCSELs)utilize the Bragg diffraction of two-dimensional photonic crystals to achieve a single-mode output with a high power and a small divergence angle,and has recently attrac...Photonic crystal surface emitting lasers(PCSELs)utilize the Bragg diffraction of two-dimensional photonic crystals to achieve a single-mode output with a high power and a small divergence angle,and has recently attracted much attention^([1−3]).In 2023,Kyoto University reported GaAs-based 945 nm PCSELs with a continuous-wave(CW)single-mode output power of exceeding 50 W,and a narrow beam divergence angle of 0.05°,demonstrating a brightness of 1 GW·cm^(−2)·sr^(−1),which rivals those of the existing bulky lasers^([4]).展开更多
Perovskite materials have emerged as promising candidates for various optoelectronic applications owing to their remarkable optoelectronic properties and easy solution processing.Metal halide perovskites,as direct-ban...Perovskite materials have emerged as promising candidates for various optoelectronic applications owing to their remarkable optoelectronic properties and easy solution processing.Metal halide perovskites,as direct-bandgap semiconductors,show an excellent class of optical gain media,which makes them applicable to the development of low-threshold or even thresholdless lasers.This mini review explores recent advances in perovskite-based laser technology,which have led to chiral single-mode microlasers,low-threshold,external-cavity-free lasing devices at room temperature,and other innovative device architectures.Including self-assembled CsPbBr3 microwires that enable edge lasing.Realized continuous-wave(CW)pumped lasing by perovskite material pushes the research of electrically driven perovskite lasers.The capacity to regulate charge transport in halide perovskites further enhances their applicability in optoelectronic systems.The ongoing integration of perovskite materials with advanced photonic structures holds excellent potential for future innovations in laser technology and photovoltaics.We also highlight the transformative potential of perovskite materials in advancing the next generation of efficient and integrated optoelectronic devices.展开更多
Rotational dynamics simulations of neutral O_(2)molecules driven by linearly,elliptically and circularly polarized femtosecond pulsed lasers are carried out using a full quantum time-dependent wave packet evolution me...Rotational dynamics simulations of neutral O_(2)molecules driven by linearly,elliptically and circularly polarized femtosecond pulsed lasers are carried out using a full quantum time-dependent wave packet evolution method.Here,the direction of laser propagation is set along the z axis,and the polarization plane is restricted to the xy plane.The results indicate that the alignment of O_(2)molecules in the z direction is weakly affected by varying the ellipticity when the total laser intensity is held constant.For rotation within the xy plane,the linearly polarized laser significantly excites rotational motion,with the degree of excitation increasing as the ellipticity increases.In contrast,under the influence of a circularly polarized laser,the angular distribution of O_(2)molecules in the xy plane remains isotropic.Additionally,the effects of the initial rotational quantum number,the temperature of the O_(2)molecules and the nuclear spin on laser-induced alignment are discussed.展开更多
Perovskite semiconductors show great promise as gain media for all-solution-processed single-mode microlasers.However,despite the recent efforts to improve their lasing performance,achieving tunable single-mode microl...Perovskite semiconductors show great promise as gain media for all-solution-processed single-mode microlasers.However,despite the recent efforts to improve their lasing performance,achieving tunable single-mode microlasers remains challenging.In this work,we address this challenge by demonstrating a tunable vertical cavity surface emitting laser(VCSEL)employing a tunable gain medium of halide phase-change perovskites-specifically MAPbI_(3) perovskite,sandwiched between two highly reflective mirrors composed of bottom-distributed Bragg reflectors(DBRs).This VCSEL possesses single-mode lasing emission with a low threshold of 23.5μJ cm^(−2) under 160 K,attributed to strong optical confinement in the high-quality(Q)cavity.Upon the phase change of MAPbI_(3) perovskite,both its gain and dielectric constant changes dramatically,enabling a wide(Δλ>9 nm)and temperature-sensitive(0.30 nm K^(−1) rate)spectral tunability of lasing mode in the near-infrared(N-IR)region.The laser displays excellent stability,demonstrating an 80%lifetime of>2.4×107 pulses excitation.Our findings may provide a versatile platform for the next generation of tunable coherent light sources.展开更多
The authors report the development of aλ~4.1μm quantum cascade laser grown by metal-organic chemical vapor deposition using strain-balanced In Ga As/In Al As materials.A device with a 7.5 mm cavity length and 6.5μm...The authors report the development of aλ~4.1μm quantum cascade laser grown by metal-organic chemical vapor deposition using strain-balanced In Ga As/In Al As materials.A device with a 7.5 mm cavity length and 6.5μm ridge width,bonded to an aluminum nitride heatsink,achieves maximum output powers of 3.4 W at 288 K in pulsed mode and 1.6 W at288 K in continuous-wave(CW)operation,with corresponding maximum wall-plug efficiencies of 14.8%and 9.3%.A kink is observed in the power–current curve under CW operation,which is absent in pulsed operation.Near-field results show that in CW operation,the horizontal beam quality factor M2fluctuates with current,indicating mode instability and highorder lateral mode excitation,while in pulsed mode,the horizontal M2remains stable around 1.3 as the current increases from 1.4 A to 1.9 A.展开更多
基金supported by the National Grand Instrument Project No. SQ2019YFF01014400the Natural Science Foundation of China (Grant Nos. 12375147, 12435011, 12075030)+2 种基金the Beijing Outstanding Young Scientist Project, Project for Young Scientists in Basic Research of Chinese Academy of Sciences (YSBR-115)the Beijing Normal University Scientific Research Initiation Fund for Introducing Talents No. 310432104the Fundamental Research Funds for the Central Universities, Peking University
文摘X-ray free-electron lasers(XFELs)can generate bright X-ray pulses with short durations and narrow bandwidths,leading to extensive applica-tions in many disciplines such as biology,materials science,and ultrafast science.Recently,there has been a growing demand for X-ray pulses with high photon energy,especially from developments in“diffraction-before-destruction”applications and in dynamic mesoscale materials science.Here,we propose utilizing the electron beams at XFELs to drive a meter-scale two-bunch plasma wakefield accelerator and double the energy of the accelerated beam in a compact and inexpensive way.Particle-in-cell simulations are performed to study the beam quality degradation under different beam loading scenarios and nonideal issues,and the results show that more than half of the accelerated beam can meet the requirements of XFELs.After its transport to the undulator,the accelerated beam can improve the photon energy to 22 keV by a factor of around four while maintaining the peak power,thus offering a promising pathway toward high-photon-energy XFELs.
基金supported by the National Key Research and Development Program of China(No.2016YFA0401900)the National Natural Science Foundation of China(Nos.11475250 and11775293)+1 种基金the Young Elite Scientist Sponsorship Program of CAST(2015QNRC001)the Ten Thousand Talent Program
文摘Generation of intense, fully coherent radiation with wide spectral coverage has been a long-standing challenge for laser technologies. Several techniques have been developed in recent years to extend the spectral coverage in optical physics, but none of them hold the potential to produce X-ray laser pulses with very high-peak power. Urgent demands for intense X-ray light sources have prompted the development of free-electron lasers(FELs), which have been proved to be very useful tools in many scientific areas. In this paper, we give an overview of the basic principle of FELs, techniques for realizing fully coherent FELs, and the development of fully coherent FEL facilities in China.
文摘X-ray beams carrying orbital angular momentum(OAM)are an emerging tool for probing matter.Optical elements,such as spiral phase plates and zone plates,have been widely used to generate OAM light.However,due to the high impinging intensities,these optics are challenging to use at X-ray free-electron lasers(XFELs).Here,we propose a self-seeded free-electron laser(FEL)method to produce intense X-ray vortices.Unlike passive filtering after amplification,an optical element will be used to introduce the helical phase to the radiation pulse in the linear regime,significantly reducing thermal load on the optical element.The generated OAM pulse is then used as a seed and significantly amplified.Theoretical analysis and numerical simulations demonstrate that the power of the OAM seed pulse can be amplified by more than two orders of magnitude,reaching peak powers of several tens of gigawatts.The proposed method paves the way for high-power and high-repetition-rate OAM pulses of XFEL light.
文摘A three-dimensional simulation of a steady-state amplifier model of a long-wavelength free-electron laser （FEL） with realizable helical wiggler and ion-channel guiding is presented. The set of coupled nonlinear differential equations for electron orbits and fields of TE 11 mode in a cylindrical waveguide are solved numerically by the Runge–Kutta algorithm with averages calculated by the Gaussian quadrature technique. Self-fields and space-charge effects are neglected, and the electron beam is assumed to be cold and slippage is ignored. The parameters correspond to the Compton regime. Evolution of the radiation power and growth rate along the wiggler is studied. Ion-channel density is chosen to obtain optimum efficiency. Simulations are preformed for the FEL operating in the neighborhood of 35 GHz and 16.5 GHz for the electron beam energies of 250 keV and 400 keV, respectively. The result of the saturated efficiency was found to be in good agreement with the simple estimation based on the phase-trapping model.
基金supported by the Plasma Physics Research Center, Science and Research Branch, Islamic Azad University
文摘The effects of self-fields on electron trajectories and gain in planar wiggler free-electron lasers with two-stream and ion-channel guiding are investigated. An analysis of the two-stream quasi-steady-state electron trajectories is given by solving the equation of motion in the presence of ion-channel guiding and the planar wiggler. The electron trajectories and the gain are derived. The stability of the trajectories, the characteristics of the linear gain, and the normalized maximum gain are studied numerically. The numerical calculations show that there are eight group trajectories rather than the two groups reported in the absence of the self-fields. It is also shown that the normalized gain group seven （G7） decreases while the rest increases with the increase in normalized ion-channel frequency. The two-stream instability and the self-field lead to a decrease in the maximum gain, except for G7.
文摘X-ray free-electron lasers(FELs)provide cutting-edge tools for fundamental researches to study nature down to the atomic level at a time-scale that fits this resolution.A precise knowledge of temporal information of FEL pulses is the central issue for its applications.Here we proposed and demonstrated a novel method to determine the FEL temporal profiles online.This robust method,designed for ultrafast FELs,allows researchers to acquire real-time longitudinal profiles of FEL pulses as well as their arrive times with respect to the external optical laser with a resolution better than 6 fs.Based on this method,we can also directly measure various properties of FEL pulses and correlations between them online.This helps us to further understand the FEL lasing processes and realize the generation of stable,nearly fully coherent soft X-ray laser pulses at the Shanghai Soft X-ray FEL facility.This method will enhance the experimental opportunities for ultrafast science in various areas.
基金support from the NSRF via the Program Management Unit for Human Resources&Institutional Development,Research,and Innovation(No.B05F650022),as well as from Chiang Mai University.
文摘A super-radiant terahertz free-electron laser(THz-FEL)light source was developed for the first time in Thailand and Southeast Asia at the PBP-CMU Electron Linac Laboratory(PCELL)of Chiang Mai University.This radiation source requires relatively ultrashort electron bunches to produce intense coherent THz pulses.Three electron bunch compression processes are utilized in the PCELL accelerator system comprising pre-bunch compression in an alpha magnet,velocity bunching in a radio-frequency(RF)linear accelerator(linac),and magnetic bunch compression in a 180°acromat system.Electron bunch compression in the magnetic compressor system poses considerable challenges,which are addressed through the use of three quadrupole doublets.The strengths of the quadrupole fields significantly influence the rotation of the beam line longitudinal phase space distribution along the bunch compressor.Start-to-end beam dynamics simulations using the ASTRA code were performed to optimize the electron beam properties for generating super-radiant THz-FEL radiation.The operational parameters considered in the simulations comprise the alpha magnet gradient,linac RF phase,and quadrupole field strengths.The optimization results show that 10-16MeV femtosecond electron bunches with a low energy spread(~0.2%),small normalized emittance(~15πmm·mrad),and high peak current(165-247A)can be produced by the PCELL accelerator system at the optimal parameters.A THz-FEL with sub-microjoule pulse energies can thus be obtained at the optimized electron beam parameters.The physical and conceptual design of the THz-FEL beamline were completed based on the beam dynamics simulation results.The construction and installation of this beamline are currently underway and expected to be completed by mid-2024.The commissioning of the beamline will then commence.
文摘Broad area quantum cascade lasers(BA QCLs)have significant applications in many areas,but suffer from demanding pulse operating conditions and poor beam quality due to heat accumulation and generation of high order modes.A structure of mini-array is adopted to improve the heat dissipation capacity and beam quality of BA QCLs.The active region is etched to form a multi-emitter and the channels are filled with In P:Fe,which acts as a lateral heat dissipation channel to improve the lateral heat dissipation efficiency.A device withλ~4.8μm,a peak output power of 122 W at 1.2%duty cycle with a pulse of 1.5μs is obtained in room temperature,with far-field single-lobed distribution.This result allows BA QCLs to obtain high peak power at wider pump pulse widths and higher duty cycle conditions,promotes the application of the mid-infrared laser operating in pulsed mode in th e field of standoff photoacoustic chemical detection,space optical communication,and so on.
文摘Objective The use of lasers has been an important part of urology in the treatment of stone and prostate disease.The thermal effects of lasers in lithotripsy have been a subject of debate over the years.The objective of this review was to assess the current state of knowledge available on the thermal effects of lasers in lithotripsy,as well as explore any new areas where studies are needed.Methods In August 2022,a keyword search on Google Scholar,PubMed,and Scopus for all papers containing the phrases“thermal effects”AND“laser”AND“lithotripsy”AND“urology”was done followed by citation jumping to other studies pertaining to the topic and 35 relevant papers were included in our study.The data from relevant papers were segregated into five groups according to the factor studied and type of study,and tables were created for a comparison of data.Results Temperature above the threshold of 43℃ was reached only when the power was>40 W and when there was adequate irrigation(at least 15–30 mL/min).Shorter lasing time divided by lithotripsy time or operator duty cycles less than 70%also resulted in a smaller temperature rise.Conclusion At least eight factors modify the thermal effects of lasers,and most importantly,the use of chilled irrigation at higher perfusion rates,lower power settings of<40 W,and with a shorter operator duty cycle will help to prevent thermal injuries from occurring.Stones impacted in the ureter or pelvi-ureteric junction further increase the probability of thermal injuries during laser firing.
基金supported by the National Natural Science Foundation of China(No.12374257)。
文摘Development of on-chip coherent light sources with desired single-mode operation and straightforward spectral tunability has attracted intense interest due to ever-increasing demand for photonic devices and optoelectronic integration,but still faces serious challenges.Herein,we propose a facile method to synthesize cesium lead halide(CsPbX3)microstructures with well-defined morphologies,sizes,and constituent element gradient.The scheme is conducted using a chemical vapor deposition(CVD),which is subsequently associated with annealing-assisted solid-solid anion exchange.For the plate-shaped structures,the controllability on the cross-sectional dimension enables to precisely modulate the lasing modes,thus achieving single-mode operation;while tuning the stoichiometric of the halogen anion components in the plate-shaped CsPbI_(x)Br_(3−x) alloy samples,the lasing wavelengths are straightforwardly varied to span the entire visible spectrum.By comparison,the experimental scheme on synthesizing alloyed CsPbI_(x)Br_(3−x) perovskites is conducted using an in-situ approach,thereby achieving precise modulation of bandgap-controlled microlasers by controlling the reaction time.Such laser properties like controllable microcavity modes and broad stoichiometry-dependent tunability of light-emitting/lasing colors,associated with the facile synthesizing method of monocrystalline CsPbI_(x)Br_(3−x) structures,make lead halide perovskites ideal materials for the development of wavelength-controlled microlasers toward practical photonic integration.
基金support provided by the Dalian Coherent Light Source.This work was supported by the National Natural Science Foundation of China(Grant Nos.12305359 and 22288201)the Scientific Instrument Developing Project of Chinese Academy of Sciences(Grant No.GJJSTD20220001)
文摘External seeded free-electron lasers(FELs) have exhibited substantial progress in diverse applications over the last decade. However, the frequency up-conversion efficiency in single-stage seeded FELs, particularly in high-gain harmonic generation(HGHG), remains constrained to a modest level. This limitation restricts its capability to conduct experiments within the ‘water window'. This paper presents a novel method for generating coherent X-ray FEL pulses in the water window region based on the HGHG scheme with multi-stage harmonic cascade. Without any additional modifications to the HGHG configuration, simulation results demonstrate the generation of intense 3 nm coherent FEL radiation using an external ultraviolet seed laser. This indicates an increase of the harmonic conversion number to approximately 90.A preliminary experiment is performed to evaluate the feasibility of this method. The proposed approach could potentially serve as an efficient method to broaden the wavelength coverage accessible to both existing and planned seeded X-ray FEL facilities.
基金This work was supported by the National Key Research and Development Program of China(2018YFE0103100,2016YFA0401900)the National Natural Science Foundation of China(11935020,11775293)The SXFEL and SHINE projects are supported by the Chinese Central Government and the Shanghai Government.
文摘Linear accelerator-based free-electron lasers(FELs)are the leading source of fully coherent X-rays with ultra-high peak powers and ultrashort pulse lengths.Current X-ray FEL facilities have proved their worth as useful tools for diverse scientific applications.In this paper,we present an overview of the features and future prospects of X-ray FELs,including the working principles and properties of X-ray FELs,the operational status of different FEL facilities worldwide,the applications supported by such facilities,and the current developments and outlook for X-ray FEL-based research.
基金Supported by Guangdong Basic and Applied Basic Research Fund,China(2024A1515012429)。
文摘As a representative transition metal dichalcogenides(TMD),NiTe_(2)has an ultra-fast optical response,high carrier mobility,and excellent environmental stability.It has a broad application prospect in the fields of ener-gy,biomedicine,optoelectronic devices,and so on.At present,there have been scant reports on the application of NiTe_(2)in the field of ultrafast photonics.In this work,NiTe_(2)was synthesized by chemical vapor deposition(CVD)and integrated with a tapered optical fiber to achieve mode-locking in an erbium-doped fiber laser(EDFL)and a thu-lium-doped fiber laser(TDFL).The mode-locked EDFL exhibited a pulse width of 678 fs and an output power of 3.92 mW.The pulse width of mode-locked TDFL was estimated to have a pulse width of 694 fs with an output power of 21.64 mW.These results demonstrate that NiTe_(2)is an effective saturable absorber material with potential applica-tions in the field of ultrafast optics.
文摘Introduction:Surgeons typically prefer 270μm and 272μm laser probes in retrograde intrarenal surgery(RIRS)due to the reduced deflection capacity of flexible ureterorenoscopes when using larger probe diameters.This study aims to investigate the effects of 272 and 365μm holmium laser probes on operative time,clinical efficacy,and complication rates in RIRS.Materials and Methods:A total of 285 patients with proximal ureteral or kidney stones who met the inclusion criteria were enrolled in the study.Patients were divided into two groups based on laser probe thickness:272μm and 365μm.Stone-free rates,operative time,and complication rates were compared between the groups.Factors affecting stone-free rates were analyzed using multivariate logistic regression analysis.Results:Patient and stone characteristics were similar between the two groups.No significant differences were found in stone-free or complication rates.However,operative time was significantly shorter in the 365μm probe group.In univariate analysis,risk factors for postoperative residual stones included multi-calyceal stones,lower pole stones,high Hounsfield unit(HU)values on noncontrast computed tomography,and larger stone size.In multivariate analysis,independent prognostic factors for residual stones were identified as multi-calycal stones,lower pole stones,and high HU values.Conclusion:Compared to 272μm laser probes,operative time was shorter in surgeries performed with 365μm laser probes.The 365μm holmium laser can be effectively and safely used in the treatment of proximal ureteral and renal stones,demonstrating high clinical efficacy and safety.
基金funded by National Key R&D Program of China(Grant Nos.2024YFB3612200,2023YFB3609601,2022YFB3604300,2022YFB2802801,2022YFB3604802)Natural Science Foundation of China(Grant Nos.U24A20300,62174174,62274177,62275263,62325406,62374172,62304242,62304240,62404241)+4 种基金Youth Innovation Promotion Association of CAS(Grant Nos.2022323 and 2022324)Key R&D Program of Jiangsu Province(Grant No.BE2023018-2)Basic Research Program of Jiangsu(Grant No.BK20240126)Suzhou Science and Technology Program(Grant Nos.SYC2022089,ZXL2024379,and ZXL2024376)Guangdong Basic and Applied Basic Research Foundation(Grant Nos.2022A1515110482 and 2022A1515110004).
文摘Photonic crystal surface emitting lasers(PCSELs)utilize the Bragg diffraction of two-dimensional photonic crystals to achieve a single-mode output with a high power and a small divergence angle,and has recently attracted much attention^([1−3]).In 2023,Kyoto University reported GaAs-based 945 nm PCSELs with a continuous-wave(CW)single-mode output power of exceeding 50 W,and a narrow beam divergence angle of 0.05°,demonstrating a brightness of 1 GW·cm^(−2)·sr^(−1),which rivals those of the existing bulky lasers^([4]).
文摘Perovskite materials have emerged as promising candidates for various optoelectronic applications owing to their remarkable optoelectronic properties and easy solution processing.Metal halide perovskites,as direct-bandgap semiconductors,show an excellent class of optical gain media,which makes them applicable to the development of low-threshold or even thresholdless lasers.This mini review explores recent advances in perovskite-based laser technology,which have led to chiral single-mode microlasers,low-threshold,external-cavity-free lasing devices at room temperature,and other innovative device architectures.Including self-assembled CsPbBr3 microwires that enable edge lasing.Realized continuous-wave(CW)pumped lasing by perovskite material pushes the research of electrically driven perovskite lasers.The capacity to regulate charge transport in halide perovskites further enhances their applicability in optoelectronic systems.The ongoing integration of perovskite materials with advanced photonic structures holds excellent potential for future innovations in laser technology and photovoltaics.We also highlight the transformative potential of perovskite materials in advancing the next generation of efficient and integrated optoelectronic devices.
基金supported by the National Key Research and Development Program of China(Grant No.2022YFA1602502)the National Natural Science Foundation of China(Grant No.12450404).
文摘Rotational dynamics simulations of neutral O_(2)molecules driven by linearly,elliptically and circularly polarized femtosecond pulsed lasers are carried out using a full quantum time-dependent wave packet evolution method.Here,the direction of laser propagation is set along the z axis,and the polarization plane is restricted to the xy plane.The results indicate that the alignment of O_(2)molecules in the z direction is weakly affected by varying the ellipticity when the total laser intensity is held constant.For rotation within the xy plane,the linearly polarized laser significantly excites rotational motion,with the degree of excitation increasing as the ellipticity increases.In contrast,under the influence of a circularly polarized laser,the angular distribution of O_(2)molecules in the xy plane remains isotropic.Additionally,the effects of the initial rotational quantum number,the temperature of the O_(2)molecules and the nuclear spin on laser-induced alignment are discussed.
基金supported by the National Key Research and Development Program of China(2020YFA0714504,2019YFA0709100 to T.C.)the program of the National Natural Science Foundation of China(No.62105054 to T.C.)+1 种基金the New Cornerstone Science Foundation(AoE/P502/20 to S.Z.)the Research Grants Council of Hong Kong(17315522 to S.Z.).
文摘Perovskite semiconductors show great promise as gain media for all-solution-processed single-mode microlasers.However,despite the recent efforts to improve their lasing performance,achieving tunable single-mode microlasers remains challenging.In this work,we address this challenge by demonstrating a tunable vertical cavity surface emitting laser(VCSEL)employing a tunable gain medium of halide phase-change perovskites-specifically MAPbI_(3) perovskite,sandwiched between two highly reflective mirrors composed of bottom-distributed Bragg reflectors(DBRs).This VCSEL possesses single-mode lasing emission with a low threshold of 23.5μJ cm^(−2) under 160 K,attributed to strong optical confinement in the high-quality(Q)cavity.Upon the phase change of MAPbI_(3) perovskite,both its gain and dielectric constant changes dramatically,enabling a wide(Δλ>9 nm)and temperature-sensitive(0.30 nm K^(−1) rate)spectral tunability of lasing mode in the near-infrared(N-IR)region.The laser displays excellent stability,demonstrating an 80%lifetime of>2.4×107 pulses excitation.Our findings may provide a versatile platform for the next generation of tunable coherent light sources.
文摘The authors report the development of aλ~4.1μm quantum cascade laser grown by metal-organic chemical vapor deposition using strain-balanced In Ga As/In Al As materials.A device with a 7.5 mm cavity length and 6.5μm ridge width,bonded to an aluminum nitride heatsink,achieves maximum output powers of 3.4 W at 288 K in pulsed mode and 1.6 W at288 K in continuous-wave(CW)operation,with corresponding maximum wall-plug efficiencies of 14.8%and 9.3%.A kink is observed in the power–current curve under CW operation,which is absent in pulsed operation.Near-field results show that in CW operation,the horizontal beam quality factor M2fluctuates with current,indicating mode instability and highorder lateral mode excitation,while in pulsed mode,the horizontal M2remains stable around 1.3 as the current increases from 1.4 A to 1.9 A.
