Within the framework of plane-wave angular spectrum analysis of the electromagnetic field structure, a solution valid for tightly focused radially polarized few-cycle laser pulses propagating in vacuum is presented. T...Within the framework of plane-wave angular spectrum analysis of the electromagnetic field structure, a solution valid for tightly focused radially polarized few-cycle laser pulses propagating in vacuum is presented. The resulting field distribution is significantly different from that based on the paraxial approximation for pulses with either small or large beam diameters. We compare the electron accelerations obtained with the two solutions and find that the energy gain obtained with our new solution is usually much larger than that with the paraxial approximation solution.展开更多
A Fourier analysis method is used to accurately determine not only the absolute phase but also the tempuralpulse phase of an isolated few-cycle (chirped) laser pulse. This method is independent of the pulse shape an...A Fourier analysis method is used to accurately determine not only the absolute phase but also the tempuralpulse phase of an isolated few-cycle (chirped) laser pulse. This method is independent of the pulse shape and can fully characterize the light wave even though only a few samples per optical cycle are available. It pavas the way for investigating the absolute phase-dependent extreme nonlinear optics, and the evolutions of the absolute phase and the temporal-pulse phase of few-cycle laser pulses.展开更多
The asymmetric photoionization of atoms irradiated by intense, few-cycle laser pulses is studied numerically. The results show that the pulse intensity affects the asymmetric photoionization in three aspects. First, a...The asymmetric photoionization of atoms irradiated by intense, few-cycle laser pulses is studied numerically. The results show that the pulse intensity affects the asymmetric photoionization in three aspects. First, at higher intensities, the asymmetry becomes distinctive for few-cycle pulses of longer durations. Second, as the laser intensity increases, the maximal asymmetry first decreases then increases after it has reached a minimal value. Last, the value of the carrier-envelope phase corresponding to the maximal asymmetry varies with the pulse intensity. This study reveals that the increasing of pulse intensity is helpful for observing the asymmetric photoionization.展开更多
The above-threshold detachment of F- ions induced by a linearly polarized few-cycle laser pulse is investigated theoretically using the strong-field approximation model without considering the rescattering mechanism. ...The above-threshold detachment of F- ions induced by a linearly polarized few-cycle laser pulse is investigated theoretically using the strong-field approximation model without considering the rescattering mechanism. We first derive an analytical form of transition amplitude for describing the strong-field photodetachment of F- ions. The integration over time in transition amplitude can be performed using the numerical integration method or the saddle-point (SP) method of Shearer et al. [Phys. Rev. A 88 (2013) 033415]. The validity of the SP method is carefully examined by comparing the energy spectra and photoelectron angular distributions (PADs) with those obtained from the numerical integration method. By considering the volume effect of a focused laser beam, both the energy spectra and the low-energy PADs calculated by the numerical integration method agree very well with the experimental results.展开更多
The high harmonic generation(HHG)by few-cycle laser pulses is essential for research in strong-field solid-state physics.Through comparison of high harmonic spectra of solids generated by laser pulses with varying dur...The high harmonic generation(HHG)by few-cycle laser pulses is essential for research in strong-field solid-state physics.Through comparison of high harmonic spectra of solids generated by laser pulses with varying durations,we discovered that lasers with good dispersion compensation are capable of producing a broad spectrum of high harmonics.As the pulse duration is further compressed,several interference peaks appear in the broad spectrum.Moreover,we conducted simulations using the semiconductor Bloch equation,considering the effect of Berry curvature,to better understand this process.Our work provides a valuable approach for studying HHG by few-cycle laser pulses in solid materials,expanding the application of HHG in attosecond physics.展开更多
We theoretically investigate the characteristics of terahertz(THz) radiation from monolayer graphene exposed to normal incident few-cycle laser pulses, by numerically solving the extended semiconductor Bloch equations...We theoretically investigate the characteristics of terahertz(THz) radiation from monolayer graphene exposed to normal incident few-cycle laser pulses, by numerically solving the extended semiconductor Bloch equations. Our simulations show that the THz spectra in low frequency regions are highly dependent on the carrier envelope phase(CEP) of driving laser pulses. Using an optimal CEP of few-cycle laser pulses, we can obtain broadband strong THz waves, due to the symmetry breaking of the laser-graphene system. Our results also show that the strength of the THz spectra depend on both the intensity and central wavelength of the laser pulses. The intensity dependence of the THz wave can be described by the excitation rate of graphene, while wavelength dependence can be traced back to the band velocity and the population of graphene. We find that a near single-cycle THz pulse can be obtained from graphene driven by a mid-infrared laser pulse.展开更多
In this paper, the generalized nonlinear Schrodinger equation (GNLSE) is solved by an adaptive split-step Fourier method (ASSFM). It is found that ASSFM must be used to solve GNLSE to ensure precision when the sol...In this paper, the generalized nonlinear Schrodinger equation (GNLSE) is solved by an adaptive split-step Fourier method (ASSFM). It is found that ASSFM must be used to solve GNLSE to ensure precision when the soliton selffrequency shift is remarkable and the photonic crystal fibre (PCF) parameters vary with the frequency considerably. The precision of numerical simulation by using ASSFM is higher than that by using split-step Fourier method in the process of laser pulse propagation in PCFs due to the fact that the variation of fibre parameters with the peak frequency in the pulse spectrum can be taken into account fully.展开更多
The simulations of three-dimensional particle dynamics show that when irradiated by an ultrashort intense laser pulse, the deuterated methane cluster expands and the majority of deuterons overrun the more slowly expan...The simulations of three-dimensional particle dynamics show that when irradiated by an ultrashort intense laser pulse, the deuterated methane cluster expands and the majority of deuterons overrun the more slowly expanding carbon ions, resulting in the creation of two separated subelusters. The enhanced deuteron kinetic energy and a narrow peak around the energy maximum in the deuteron energy distribution make a considerable contribution to the efficiency of nuclear fusion compared with the ease of homonuelear deuterium clusters. With the intense laser irradiation, the nuclear fusion yield increases with the increase of the cluster size, so that deuterated heteronuelear clusters with larger sizes are required to achieve a greater neutron yield.展开更多
The laser-induced vibrational state-selectivity of product HF in photoassociation reaction H+F→HF is theoret- ically investigated by using the time-dependent quantum wave packet method. The population transfer proce...The laser-induced vibrational state-selectivity of product HF in photoassociation reaction H+F→HF is theoret- ically investigated by using the time-dependent quantum wave packet method. The population transfer process from the continuum state down to the bound vibrational states can be controlled by the driving laser. The effects of laser pulse parameters and the initial momentum of the two collision atoms on the vibrational population of the product HF are discussed in detail. Photodissociation accompanied with the photoassociation process is also described.展开更多
We have studied the plasma generation through collecting the charged particles produced in laser-induced break-down in atmospheric air.This breakdovn is produced by ultrashort laser pulses with various durations rangi...We have studied the plasma generation through collecting the charged particles produced in laser-induced break-down in atmospheric air.This breakdovn is produced by ultrashort laser pulses with various durations ranging from 200fs to 2ps at a fixed pulse energy of 8mJ.We found that the plasma yield increases first with the increment of pulse duration and then reaches a plateau at a duration longer than 500fs.The generated plasma temperature is estimated to be higher than 5x 10^(5)K.展开更多
We propose a nanotube-based erbium-doped fiber laser that can deliver conventional soliton (CS) and stretched pulse (SP) based on D-shaped fiber saturable absorber (DF-SA) where evanescent-field interaction works. The...We propose a nanotube-based erbium-doped fiber laser that can deliver conventional soliton (CS) and stretched pulse (SP) based on D-shaped fiber saturable absorber (DF-SA) where evanescent-field interaction works. The novel Nanotube-based Fiber Laser can generate SP or CS by tuning pump power and polarization controller (PC) properly. The net cavity dispersion of laser is slightly negative. In our experiment, by optimizing the PC in the cavity, CS and SP can be obtained at the central wavelengths of 1530.6 nm and 1530.3 nm due to on carbon nanotubes and the spectral filtering effect induced by nonlinear polarization rotation. Although the acquired CS and SP nearly have the same central wavelengths, they show distinct optical spectra, 3-dB bandwidths. The proposed fiber laser with switchable CS and SP is attractive for ultrashort pulse generation and fast measurements in practical applications.展开更多
The efficient production of energetic γ photons is a significant physical process in the relativistic ultrashortpulse laser-plasma inducing photonuclear action. Based on the interaction of laser-solid-target, an anal...The efficient production of energetic γ photons is a significant physical process in the relativistic ultrashortpulse laser-plasma inducing photonuclear action. Based on the interaction of laser-solid-target, an analytical theory onstimulated γ photon emission from a hot electron firing the target-nucleus is developed by a relativistic full quantummethod. The emitting power or probability of γ photon in arbitrary space direction can be calculated for laser irradiatingsolid-target normally. It is valid only if the scatter-centre is immovable or its motion can be neglected compared withthat of the scattered electrons.展开更多
Chirped wideband pump and seed pulses are usually considered for backward Raman amplification(BRA) in plasmas to achieve an extremely high-power laser pulse. However, current theoretical models only contain either a...Chirped wideband pump and seed pulses are usually considered for backward Raman amplification(BRA) in plasmas to achieve an extremely high-power laser pulse. However, current theoretical models only contain either a chirped pump or a chirped seed. In this paper, modified three-wave coupling equations are proposed for the BRA in the plasmas with both chirped wideband pump and seed. The simulation results can more precisely describe the experiments, such as the Princeton University experiment. The optimized chirp and bandwidth are determined based on the simulation to enhance the output intensity and efficiency.展开更多
A set of exact one-dlmensional solutions to coupled nonlinear equations describing the propagation of a relativistic ultrashort circularly polarized laser pulse in a cold collisionless and bounded plasma where electro...A set of exact one-dlmensional solutions to coupled nonlinear equations describing the propagation of a relativistic ultrashort circularly polarized laser pulse in a cold collisionless and bounded plasma where electrons have an initial velocity in the laser propagating direction is presented. The solutions investigated here are in the form of quickly moving envelop solitons at a propagation velocity comparable to the light speed. The features of solitons in both underdense and overdense plasmas with electrons having different given initial velocities in the laser propagating direction are described. It is found that the amplitude of solitons is larger and soliton width shorter in plasmas where electrons have a larger initial velocity. In overdense plasmas, soliton duration is shorter, the amplitude higher than that in underdense plasmas where electrons have the same initial velocity.展开更多
A direct Kerr-lens mode-locked Tm:LuYO_(3)ceramic laser without the aid of any mode-locked starting element is reported for the first time. A pulse duration as short as 259 fs and a maximum average output power of 326...A direct Kerr-lens mode-locked Tm:LuYO_(3)ceramic laser without the aid of any mode-locked starting element is reported for the first time. A pulse duration as short as 259 fs and a maximum average output power of 326 m W are obtained at a repetition rate of 97.1 MHz. The corresponding optical spectrum centered at 2053 nm exhibits a bandwidth of 19.8 nm,which indicates the presence of nearly Fourier transform-limited pulses. Such a Kerr-lens mode-locked Tm:LuYO_(3)ceramic laser is a promising ultrashort pulse source, with both the excellent laser characteristics of Tm:LuYO3and the high-power 790 nm laser diode pumping scheme.展开更多
The behavior of population transfcr in an excited-doublet four-level system driven by linear polarized few-cycle ultrashort laser pulses is investigated numerically. It is shown that almost complete population transfe...The behavior of population transfcr in an excited-doublet four-level system driven by linear polarized few-cycle ultrashort laser pulses is investigated numerically. It is shown that almost complete population transfer can be achieved even when the adiabatic criterion is not fulfilled. Moreover, the robustness of this scheme in terms of the Rabi frequencies and chirp rates of the pulses is explored.展开更多
A classical ensemble method is used to investigate nonsequential double ionization(NSDI) of Ar atoms irradiated by linearly polarized few-cycle laser pulses. The correlated-electron momentum distribution(CMD) exhi...A classical ensemble method is used to investigate nonsequential double ionization(NSDI) of Ar atoms irradiated by linearly polarized few-cycle laser pulses. The correlated-electron momentum distribution(CMD) exhibits a strong dependence on the carrier-envelope phase(CEP). When the pulse duration is four cycles, the CMD shows a cross-like structure, which is consistent with experimental results. The CEP dependence is more notable when the laser pulse duration is decreased to two cycles and a special L-shaped structure appears in CMD. Recollision time of returning electrons greatly depends on CEP, which plays a significant role in accounting for the appearance of this structure.展开更多
Previous research shows that few-cycle laser(FCL) pulses with low energy and without a bias field can be used to coherently detect terahertz(THz) pulses. As we know, it is very difficult to stabilize the carrier e...Previous research shows that few-cycle laser(FCL) pulses with low energy and without a bias field can be used to coherently detect terahertz(THz) pulses. As we know, it is very difficult to stabilize the carrier envelope phase(CEP) of FCL pulses, i.e., there are some random fluctuations for the CEP. Here we theoretically investigate the influence of such instability on the accuracy of THz detection. Our results show that although there is an optimum CEP for THz detection, the fluctuations of the CEP will lead to terrible thorns on the detected THz waveform. In order to solve this problem, we propose an approach using two few-cycle laser pulses with opposite CEPs, i.e., their CEPs are differed by π.展开更多
基金supported by the National Natural Science Foundation of China (Grant Nos.10734130,10935002,and 11075105)the National Basic Research Program of China (Grant No.2009GB105002)
文摘Within the framework of plane-wave angular spectrum analysis of the electromagnetic field structure, a solution valid for tightly focused radially polarized few-cycle laser pulses propagating in vacuum is presented. The resulting field distribution is significantly different from that based on the paraxial approximation for pulses with either small or large beam diameters. We compare the electron accelerations obtained with the two solutions and find that the energy gain obtained with our new solution is usually much larger than that with the paraxial approximation solution.
基金Project supported by the National Natural Science Foundation of China (Grant No 60478002), and the Basic Research Key Foundation of Shanghai (Grant Nos 04JC14036 and 05DJ14003).
文摘A Fourier analysis method is used to accurately determine not only the absolute phase but also the tempuralpulse phase of an isolated few-cycle (chirped) laser pulse. This method is independent of the pulse shape and can fully characterize the light wave even though only a few samples per optical cycle are available. It pavas the way for investigating the absolute phase-dependent extreme nonlinear optics, and the evolutions of the absolute phase and the temporal-pulse phase of few-cycle laser pulses.
基金supported by the National Natural Science Foundation of China (Grant Nos 60408008 and 10774153)the Natural Science Key Foundation of Shanghai (Grant No 04JC14036)+1 种基金the National Basic Research Program of China (Grant No 2006CD806000)the Rising Star Program of Shanghai,China (Grant No 08QH1402400)
文摘The asymmetric photoionization of atoms irradiated by intense, few-cycle laser pulses is studied numerically. The results show that the pulse intensity affects the asymmetric photoionization in three aspects. First, at higher intensities, the asymmetry becomes distinctive for few-cycle pulses of longer durations. Second, as the laser intensity increases, the maximal asymmetry first decreases then increases after it has reached a minimal value. Last, the value of the carrier-envelope phase corresponding to the maximal asymmetry varies with the pulse intensity. This study reveals that the increasing of pulse intensity is helpful for observing the asymmetric photoionization.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11647150,11464026,11664035 and 11364038the Young Talents Program of Gansu Province in 2016+1 种基金the Scientific Research Program of the Higher Education Institutions of Gansu Province under Grant No 2016A-068the Doctoral Scientific Research Foundation of Lanzhou City University under Grant No LZCU-BS2015-04
文摘The above-threshold detachment of F- ions induced by a linearly polarized few-cycle laser pulse is investigated theoretically using the strong-field approximation model without considering the rescattering mechanism. We first derive an analytical form of transition amplitude for describing the strong-field photodetachment of F- ions. The integration over time in transition amplitude can be performed using the numerical integration method or the saddle-point (SP) method of Shearer et al. [Phys. Rev. A 88 (2013) 033415]. The validity of the SP method is carefully examined by comparing the energy spectra and photoelectron angular distributions (PADs) with those obtained from the numerical integration method. By considering the volume effect of a focused laser beam, both the energy spectra and the low-energy PADs calculated by the numerical integration method agree very well with the experimental results.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.91850209 and 11974416)。
文摘The high harmonic generation(HHG)by few-cycle laser pulses is essential for research in strong-field solid-state physics.Through comparison of high harmonic spectra of solids generated by laser pulses with varying durations,we discovered that lasers with good dispersion compensation are capable of producing a broad spectrum of high harmonics.As the pulse duration is further compressed,several interference peaks appear in the broad spectrum.Moreover,we conducted simulations using the semiconductor Bloch equation,considering the effect of Berry curvature,to better understand this process.Our work provides a valuable approach for studying HHG by few-cycle laser pulses in solid materials,expanding the application of HHG in attosecond physics.
基金Supported by the National Natural Science Foundation of China (Grant Nos.11764038,11864037,11765018,and 91850209)。
文摘We theoretically investigate the characteristics of terahertz(THz) radiation from monolayer graphene exposed to normal incident few-cycle laser pulses, by numerically solving the extended semiconductor Bloch equations. Our simulations show that the THz spectra in low frequency regions are highly dependent on the carrier envelope phase(CEP) of driving laser pulses. Using an optimal CEP of few-cycle laser pulses, we can obtain broadband strong THz waves, due to the symmetry breaking of the laser-graphene system. Our results also show that the strength of the THz spectra depend on both the intensity and central wavelength of the laser pulses. The intensity dependence of the THz wave can be described by the excitation rate of graphene, while wavelength dependence can be traced back to the band velocity and the population of graphene. We find that a near single-cycle THz pulse can be obtained from graphene driven by a mid-infrared laser pulse.
文摘In this paper, the generalized nonlinear Schrodinger equation (GNLSE) is solved by an adaptive split-step Fourier method (ASSFM). It is found that ASSFM must be used to solve GNLSE to ensure precision when the soliton selffrequency shift is remarkable and the photonic crystal fibre (PCF) parameters vary with the frequency considerably. The precision of numerical simulation by using ASSFM is higher than that by using split-step Fourier method in the process of laser pulse propagation in PCFs due to the fact that the variation of fibre parameters with the peak frequency in the pulse spectrum can be taken into account fully.
基金Project supported by the National Natural Science Foundation of China (Grant Nos 10535070 and 10674145)the National Basic Research Program of China (Grant No 2006CB806000)the Shanghai Supercomputer Center (SSC)
文摘The simulations of three-dimensional particle dynamics show that when irradiated by an ultrashort intense laser pulse, the deuterated methane cluster expands and the majority of deuterons overrun the more slowly expanding carbon ions, resulting in the creation of two separated subelusters. The enhanced deuteron kinetic energy and a narrow peak around the energy maximum in the deuteron energy distribution make a considerable contribution to the efficiency of nuclear fusion compared with the ease of homonuelear deuterium clusters. With the intense laser irradiation, the nuclear fusion yield increases with the increase of the cluster size, so that deuterated heteronuelear clusters with larger sizes are required to achieve a greater neutron yield.
基金Project supported by the National Natural Science Foundation of China (Grant Nos 10674022 and 20633070).
文摘The laser-induced vibrational state-selectivity of product HF in photoassociation reaction H+F→HF is theoret- ically investigated by using the time-dependent quantum wave packet method. The population transfer process from the continuum state down to the bound vibrational states can be controlled by the driving laser. The effects of laser pulse parameters and the initial momentum of the two collision atoms on the vibrational population of the product HF are discussed in detail. Photodissociation accompanied with the photoassociation process is also described.
基金the National Climbing Project of China,and the National Natural Science Foundation of China under Grant Nos.19884001 and 19525412.
文摘We have studied the plasma generation through collecting the charged particles produced in laser-induced break-down in atmospheric air.This breakdovn is produced by ultrashort laser pulses with various durations ranging from 200fs to 2ps at a fixed pulse energy of 8mJ.We found that the plasma yield increases first with the increment of pulse duration and then reaches a plateau at a duration longer than 500fs.The generated plasma temperature is estimated to be higher than 5x 10^(5)K.
文摘We propose a nanotube-based erbium-doped fiber laser that can deliver conventional soliton (CS) and stretched pulse (SP) based on D-shaped fiber saturable absorber (DF-SA) where evanescent-field interaction works. The novel Nanotube-based Fiber Laser can generate SP or CS by tuning pump power and polarization controller (PC) properly. The net cavity dispersion of laser is slightly negative. In our experiment, by optimizing the PC in the cavity, CS and SP can be obtained at the central wavelengths of 1530.6 nm and 1530.3 nm due to on carbon nanotubes and the spectral filtering effect induced by nonlinear polarization rotation. Although the acquired CS and SP nearly have the same central wavelengths, they show distinct optical spectra, 3-dB bandwidths. The proposed fiber laser with switchable CS and SP is attractive for ultrashort pulse generation and fast measurements in practical applications.
文摘The efficient production of energetic γ photons is a significant physical process in the relativistic ultrashortpulse laser-plasma inducing photonuclear action. Based on the interaction of laser-solid-target, an analytical theory onstimulated γ photon emission from a hot electron firing the target-nucleus is developed by a relativistic full quantummethod. The emitting power or probability of γ photon in arbitrary space direction can be calculated for laser irradiatingsolid-target normally. It is valid only if the scatter-centre is immovable or its motion can be neglected compared withthat of the scattered electrons.
基金Project supported by the National Natural Science Foundation of China(Grant No.11305157)the Development Foundation of China Academy of Engineering Physics Laboratory(CAEPL)(Grant No.2013A0401019)
文摘Chirped wideband pump and seed pulses are usually considered for backward Raman amplification(BRA) in plasmas to achieve an extremely high-power laser pulse. However, current theoretical models only contain either a chirped pump or a chirped seed. In this paper, modified three-wave coupling equations are proposed for the BRA in the plasmas with both chirped wideband pump and seed. The simulation results can more precisely describe the experiments, such as the Princeton University experiment. The optimized chirp and bandwidth are determined based on the simulation to enhance the output intensity and efficiency.
基金Project supported by the National Natural Science Foundation of China (Grant No 10335020).
文摘A set of exact one-dlmensional solutions to coupled nonlinear equations describing the propagation of a relativistic ultrashort circularly polarized laser pulse in a cold collisionless and bounded plasma where electrons have an initial velocity in the laser propagating direction is presented. The solutions investigated here are in the form of quickly moving envelop solitons at a propagation velocity comparable to the light speed. The features of solitons in both underdense and overdense plasmas with electrons having different given initial velocities in the laser propagating direction are described. It is found that the amplitude of solitons is larger and soliton width shorter in plasmas where electrons have a larger initial velocity. In overdense plasmas, soliton duration is shorter, the amplitude higher than that in underdense plasmas where electrons have the same initial velocity.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 62165012 and 61665010)Key research and development projects in Gansu Province (Grant No. 21YFIGE300)+5 种基金Gansu Province College Industry Support Plan Project (Grant Nos. 2020C-23 and 2022CYZC-59)Department of Education of Gansu Province: The Education Project of Open Competition for the Best Candidates (Grant No. 2021jyjbgs-06)Gansu Provincial University Innovation Fund Project (Grant No. 2021B-190)Qinzhou District Science and Technology Plan Project (Grant No. 2021-SHFZG1442)Gansu Province College Young Doctor Support Project (Grant No. 2023QB-013)Gansu Province Excellent Graduate Innovation Star Project (Grant No. 2022CXZX796)。
文摘A direct Kerr-lens mode-locked Tm:LuYO_(3)ceramic laser without the aid of any mode-locked starting element is reported for the first time. A pulse duration as short as 259 fs and a maximum average output power of 326 m W are obtained at a repetition rate of 97.1 MHz. The corresponding optical spectrum centered at 2053 nm exhibits a bandwidth of 19.8 nm,which indicates the presence of nearly Fourier transform-limited pulses. Such a Kerr-lens mode-locked Tm:LuYO_(3)ceramic laser is a promising ultrashort pulse source, with both the excellent laser characteristics of Tm:LuYO3and the high-power 790 nm laser diode pumping scheme.
基金The work was supported by the National Natural Sci-ence Foundation of China (No. 10234030 and 60478002)and the Natural Science Foundation of Shanghai (No.04JC14036 and 03ZR14102)
文摘The behavior of population transfcr in an excited-doublet four-level system driven by linear polarized few-cycle ultrashort laser pulses is investigated numerically. It is shown that almost complete population transfer can be achieved even when the adiabatic criterion is not fulfilled. Moreover, the robustness of this scheme in terms of the Rabi frequencies and chirp rates of the pulses is explored.
基金supported by the National Natural Science Foundation of China(No.61275103)the Natural Science Foundation of Shanghai(No.18ZR1413600)
文摘A classical ensemble method is used to investigate nonsequential double ionization(NSDI) of Ar atoms irradiated by linearly polarized few-cycle laser pulses. The correlated-electron momentum distribution(CMD) exhibits a strong dependence on the carrier-envelope phase(CEP). When the pulse duration is four cycles, the CMD shows a cross-like structure, which is consistent with experimental results. The CEP dependence is more notable when the laser pulse duration is decreased to two cycles and a special L-shaped structure appears in CMD. Recollision time of returning electrons greatly depends on CEP, which plays a significant role in accounting for the appearance of this structure.
基金supported by the National Natural Science Foundation of China(Nos. 61475054 and 11574105)the Fundamental Research Funds for the Central Universities (No. 2017KFYXJJ029)
文摘Previous research shows that few-cycle laser(FCL) pulses with low energy and without a bias field can be used to coherently detect terahertz(THz) pulses. As we know, it is very difficult to stabilize the carrier envelope phase(CEP) of FCL pulses, i.e., there are some random fluctuations for the CEP. Here we theoretically investigate the influence of such instability on the accuracy of THz detection. Our results show that although there is an optimum CEP for THz detection, the fluctuations of the CEP will lead to terrible thorns on the detected THz waveform. In order to solve this problem, we propose an approach using two few-cycle laser pulses with opposite CEPs, i.e., their CEPs are differed by π.