In this paper, the nonlinear Schr?dinger equation combining quadratic-cubic nonlinearity is considered, which can be represented by an approximate model of relatively dense quasi-one-dimensional Bose-Einstein condensa...In this paper, the nonlinear Schr?dinger equation combining quadratic-cubic nonlinearity is considered, which can be represented by an approximate model of relatively dense quasi-one-dimensional Bose-Einstein condensate. Based on the bifurcation theory, we proved the existence of solitary and periodic solutions. The methods we take are the trial equation method and the complete discrimination system for polynomial method. Therefore, we obtain the exact chirped solutions, which are more abundant in type and quantity than the existing results, so that the equation has more profound physical significance. These two methods are rigorously mathematical derivation and calculations, rather than based on certain conditional assumptions. In addition, we give some specific parameters to graphing the motion of the solutions, which helps to understand the propagation of nonlinear waves in fiber optic systems.展开更多
To capture the nonlinear dynamics and gain evolution in chirped pulse amplification(CPA)systems,the split-step Fourier method and the fourth-order Runge–Kutta method are integrated to iteratively address the generali...To capture the nonlinear dynamics and gain evolution in chirped pulse amplification(CPA)systems,the split-step Fourier method and the fourth-order Runge–Kutta method are integrated to iteratively address the generalized nonlinear Schrödinger equation and the rate equations.However,this approach is burdened by substantial computational demands,resulting in significant time expenditures.In the context of intelligent laser optimization and inverse design,the necessity for numerous simulations further exacerbates this issue,highlighting the need for fast and accurate simulation methodologies.Here,we introduce an end-to-end model augmented with active learning(E2E-AL)with decent generalization through different dedicated embedding methods over various parameters.On an identical computational platform,the artificial intelligence–driven model is 2000 times faster than the conventional simulation method.Benefiting from the active learning strategy,the E2E-AL model achieves decent precision with only two-thirds of the training samples compared with the case without such a strategy.Furthermore,we demonstrate a multi-objective inverse design of the CPA systems enabled by the E2E-AL model.The E2E-AL framework manifests the potential of becoming a standard approach for the rapid and accurate modeling of ultrafast lasers and is readily extended to simulate other complex systems.展开更多
We investigate theoretically the effects of chirped laser pulses on high-order harmonic generation(HHG)from solids.We find that the harmonic spectra display redshifts for the driving laser pulses with negative chirp a...We investigate theoretically the effects of chirped laser pulses on high-order harmonic generation(HHG)from solids.We find that the harmonic spectra display redshifts for the driving laser pulses with negative chirp and blueshifts for those with positive chirp,which is due to the change in the instantaneous frequency of the driving laser for different chirped pulses.The analysis of crystal-momentum-resolved(k-resolved)HHG reveals that the frequency shifts are equal for the harmonics generated by different crystal momentum channels.The frequency shifts in the cutoff region are larger than those in the plateau region.With the increase of the absolute value of the chirp parameters,the frequency shifts of HHG become more significant,leading to the shifts from odd-to even-order harmonics.We also demonstrate that the frequency shifts of harmonic spectra are related to the duration of the chirped laser field,but are insensitive to the laser intensity and dephasing time.展开更多
The existence and stability of the fundamental, multi-peak, and twisted solitons in Kerr nonlinear media with chirped(amplitude-modulated) lattices are reported. We discover that the chirp rate and lattice depth can d...The existence and stability of the fundamental, multi-peak, and twisted solitons in Kerr nonlinear media with chirped(amplitude-modulated) lattices are reported. We discover that the chirp rate and lattice depth can dramatically change the existence domain of solitons, the energy flow of solitons increases with increasing chirp rate or decreasing lattice depth.We also analyze how the chirp rate and lattice depth affect the stability of solitons. The stable domains of fundamental solitons and twisted solitons exhibit a multi-window distribution, while multi-peak solitons are unstable throughout the entire existence domain.展开更多
Laser frequency combs,which are composed of a series of equally spaced coherent frequency components,have triggered revolutionary progress in precision spectroscopy and optical metrology.Length/distance is of fundamen...Laser frequency combs,which are composed of a series of equally spaced coherent frequency components,have triggered revolutionary progress in precision spectroscopy and optical metrology.Length/distance is of fundamental importance in both science and technology.We describe a ranging scheme based on chirped pulse interferometry.In contrast to the traditional spectral interferometry,the local oscillator is strongly chirped which is able to meet the measurement pulses at arbitrary distances,and therefore,the dead zones can be removed.The distances can be precisely determined via two measurement steps based on the time-of-flight method and synthetic wavelength interferometry,respectively.To overcome the speed limitation of the optical spectrum analyzer,the spectrograms are stretched and detected by a fast photodetector and oscilloscope and consequently mapped into the time domain in real time.The experimental results indicate that the measurement uncertainty can be well within±2μm,compared with the reference distance meter.The Allan deviation can reach 0.4μm at 4 ns averaging time and 25 nm at 1μs and can achieve 2 nm at 100μs averaging time.We also measured a spinning disk with grooves of different depths to verify the measurement speed,and the results show that the grooves with about 150 m∕s line speed can be clearly captured.Our method provides a unique combination of non-dead zones,ultrafast measurement speed,high precision and accuracy,large ambiguity range,and only one single comb source.This system could offer a powerful solution for field measurements in practical applications in the future.展开更多
With a three-dimensional semiclassical ensemble method, we theoretically investigated the nonsequential double ionization of Ar driven by the spatially inhomogeneous few-cycle negatively chirped laser pulses. Our resu...With a three-dimensional semiclassical ensemble method, we theoretically investigated the nonsequential double ionization of Ar driven by the spatially inhomogeneous few-cycle negatively chirped laser pulses. Our results show that the recollision time window can be precisely controlled within an isolated time interval of several hundred attoseconds, which is useful for understanding the subcycle correlated electron dynamics. More interestingly, the correlated electron momentum distribution (CEMD) exhibits a strong dependence on laser intensity. That is, at lower laser intensity, CEMD is located in the first quadrant. As the laser intensity increases,CEMD shifts almost completely to the second and fourth quadrants, and then gradually to the third quadrant.The underlying physics governing the CEMD's dependence on laser intensity is explained.展开更多
This research examines the dynamics of a cosh-Gaussian laser pulse travelling through a vacuum and its impact on electron acceleration. We examine the impact of several critical factors, such as laser electric field a...This research examines the dynamics of a cosh-Gaussian laser pulse travelling through a vacuum and its impact on electron acceleration. We examine the impact of several critical factors, such as laser electric field amplitude, decentered parameter, beam waist, and laser chirp parameter, on the energy gain of electrons using coupled momentum equations. Our results indicate that the energy acquisition of electrons escalates with the amplitude of the laser electric field, decentered parameter, and chirp parameter. An appropriate beam waist is essential for attaining energyefficient electron acceleration in a vacuum. Through the optimization of these parameters, we get a maximum electron energy gain of 2.80 Ge V. This study highlights the significance of customized laser pulse attributes in improving electron acceleration and aids in the progression of high-energy particle physics.展开更多
The photoionization of a hydrogen atom from its ground state with ultra-fast chirped pulses is investigated by numerically solving the time-dependent Schrodinger equation within length,velocity,and Kramers-Henneberger...The photoionization of a hydrogen atom from its ground state with ultra-fast chirped pulses is investigated by numerically solving the time-dependent Schrodinger equation within length,velocity,and Kramers-Henneberger gauges.Converged results for all gauges for chirp-free pulses agree with the prediction of dynamic interference for ground state hydrogen atoms predicted recently by Jiang and Burgdorfer[Opt.Express 26,19921(2018)].In addition,we investigated photoelectron spectra of hydrogen atoms by chirped laser pulses,and showed that dynamic interference effect will be weaken for pulses with increasing linear chirp.Our numerical results can be understood and discussed in terms of an interplay of photoelectron wavepackets from first and second halves of laser enevelop,including the ac Stark energy level shift of the photoelectron final state and atomic stabilization effect at ultra-high intensities.展开更多
This paper theoretically investigates the high-order harmonic generation cutoff extension using intense few-cycle linearly chirped laser pulses. It shows that the cutoff of the harmonic can be extended remarkably by o...This paper theoretically investigates the high-order harmonic generation cutoff extension using intense few-cycle linearly chirped laser pulses. It shows that the cutoff of the harmonic can be extended remarkably by optimising the chirping parameters. The time-frequency characteristics of high-order harmonics with different chirping parameters are analysed by means of wavelet transform of the dipole acceleration. It also gives out the classical three-step model pictures of electron. By superposing a properly selected range of the harmonic spectrum, it obtains an isolated 65as pulse.展开更多
Above-threshold ionization （ATI） of a hydrogen atom exposed to chirped laser fields is investigated theoretically by solving the time-dependent Schrodinger equation. By comparing the energy spectra, the two-dimensio...Above-threshold ionization （ATI） of a hydrogen atom exposed to chirped laser fields is investigated theoretically by solving the time-dependent Schrodinger equation. By comparing the energy spectra, the two-dimensional momentum spectra, and the angular distributions of photoelectron for the laser pulses with different chirp rates, we show a very clear chirp dependence both in the multiphoton and tunneling ionization processes but no chirp dependence in the single-photon ionization. We find that the chirp dependence in the multiphoton ionization based ATI can be attributed to the excited bound states. In the single-photon and tunneling ionization regimes, the electron can be removed directly from the ground state and thus the excited states may not be very important. It indicates that the chirp dependence in the tunneling ionization based ATI processes is mainly due to the laser pulses with different chirp rates,展开更多
In this article, we investigate the nonparaxial propagation properties of the chirped Airy Gaussian vortex（CAiGV）beams in uniaxial crystals orthogonal to the optical axis analytically and numerically. We discuss how...In this article, we investigate the nonparaxial propagation properties of the chirped Airy Gaussian vortex（CAiGV）beams in uniaxial crystals orthogonal to the optical axis analytically and numerically. We discuss how the linear chirp parameters, the quadratic chirp parameters, and the Gaussian factors influence the nonparaxial propagation dynamics of the CAiGV beams. The intensity, the energy flow, the beam center, and the angular momentum of the CAiGV beams are deeply investigated. It is shown that the Gaussian factors have a great effect on the intensity and the centroid positions of the CAiGV beams. With the Gaussian factors increasing, the intensity of CAiGV beams decreases rapidly. The main lobes of the transverse intensity distribution of the CAiGV beams are similar to triangles.展开更多
We studied the evolution of wavefront aberration(WFA) of a signal beam during amplification in a Ti:sapphire chirped pulse amplification(CPA) system. The results verified that the WFA of the amplified laser beam has l...We studied the evolution of wavefront aberration(WFA) of a signal beam during amplification in a Ti:sapphire chirped pulse amplification(CPA) system. The results verified that the WFA of the amplified laser beam has little relation with the change of the pump beam energies. Transverse parasitic lasing that might occur in CPA hardly affects the wavefront of the signal beam. Thermal effects were also considered in this study, and the results show that the thermal effect cumulated in multiple amplification processes also has no obvious influence on the wavefront of the signal beam for a single-shot frequency. The results presented in this paper confirmed experimentally that the amplification in a Ti:sapphire CPA system has little impact on the WFA of the signal beam and it is very helpful for wavefront correction of single-shot PW and multi-PW laser systems based on Ti:sapphire.展开更多
We theoretically investigate high-order harmonic and isolated attosecond pulse generation in a two-color chirped laser field,which is synthesized by a 9 fs/800 nm fundamental chirped pulse and a 9 fs/1600 nm controlli...We theoretically investigate high-order harmonic and isolated attosecond pulse generation in a two-color chirped laser field,which is synthesized by a 9 fs/800 nm fundamental chirped pulse and a 9 fs/1600 nm controlling chirped pulse.Our numerical results show that,by using this method,not only is the harmonic cutoff significantly extended to the 948th order harmonic,but also the bandwidth of the supercontinuum spectrum is effectively broadened to about 1342 eV.In addition,due to the introduction of the chirp,the long quantum path is suppressed and only the short one is selected,and then an isolated 28 as pulse with a bandwidth of 155 eV is obtained directly.展开更多
In this paper,we propose the novel system of multipoint measurement.The sensors of measurements are chirped Bragg grating and the interrogation of sensors is sub-carrier phase.The wavelength division multiplexing tech...In this paper,we propose the novel system of multipoint measurement.The sensors of measurements are chirped Bragg grating and the interrogation of sensors is sub-carrier phase.The wavelength division multiplexing technique is used for addressing a network of FBG sensors and the time-division multiplexing technique is used for multipoint measurements.In the system,the modulation frequency of 200 MHz is adopted.The range of dectetion is from 0 to 900μεand the resolution is 12με. The time of the sensor response is about 1ns.展开更多
Gallium nitride （GaN） based light-emitting diodes （LEDs） with chirped multiple quantum well （MQW） structures have been investigated experimentally and numerically in this paper. Compared to conventional LEDs wit...Gallium nitride （GaN） based light-emitting diodes （LEDs） with chirped multiple quantum well （MQW） structures have been investigated experimentally and numerically in this paper. Compared to conventional LEDs with uniform quantum wells （QWs）, LEDs with chirped MQW structures have better internal quantum efficiency （IQE） and carrier injection efficiency. The droop ratios of LEDs with chirped MQW structures show a remarkable improvement at 600 mA/mm2, reduced down from 28.6% （conventional uniform LEDs） to 23.7% （chirped MQWs-a） and 18.6% （chirped MQWs-b）, respectively. Meanwhile, the peak IQE increases from 76.9% （uniform LEDs） to 83.7% （chirped MQWs-a） and 88.6% （chirped MQWs-b）. The reservoir effect of chirped MQW structures is the significant reason as it could increase hole injection efficiency and radiative recombination. The leakage current and Auger recombination of chirped MQW structures can also be suppressed. Furthermore, the chirped MQWs-b structure with lower potential barriers can enhance the reservoir effect and obtain further improvement of the carrier injection efficiency and radiative recombination, as well as further suppressing efficiency droop.展开更多
We report on the fabrication and characterization of InAs/GaAs chirped multilayer quantum-dot superluminescent diodes(CMQD-SLDs)with and without direct Si doping in QDs.It was found that both the output power and the ...We report on the fabrication and characterization of InAs/GaAs chirped multilayer quantum-dot superluminescent diodes(CMQD-SLDs)with and without direct Si doping in QDs.It was found that both the output power and the spectral width of the CMQD-SLDs were significantly enhanced by direct Si doping in the QDs.The output power and spectral width have been increased by approximately 18.3%and 40%,respectively.Moreover,we shortened the cavity length of the doped CMQD-SLD and obtained a spectral width of 106 nm.In addition,the maximum output power and spectral width of the CMQD-SLD doped directly with Si can be further increased to 16.6 mW and 114 nm,respectively,through anti-reflection coating and device packaging.The device exhibited the smallest spectral dip of 0.2 dB when the spectrum was widest.The improved performances of the doped CMQD-SLD can be attributed to the direct doping of Si in the QDs,optimization of device structure and device packaging.展开更多
Using a time-dependent multilevel approach, we demonstrate that lithium atoms can be transferred to states of lower principle quantum number by exposing them to a frequency chirped microwave pulse. The population tran...Using a time-dependent multilevel approach, we demonstrate that lithium atoms can be transferred to states of lower principle quantum number by exposing them to a frequency chirped microwave pulse. The population transfer from n = 79 to n = 70 states of lithium atoms with more than 80% efficiency is achieved by means of the sequential two-photon △n=-1 transitions. It is shown that the coherent control of the population transfer can be accomplished by the optimization of the chirping parameters and microwave field strength. The calculation results agree well with the experimental ones and novel explanations have been given to understand the experimental results.展开更多
文摘In this paper, the nonlinear Schr?dinger equation combining quadratic-cubic nonlinearity is considered, which can be represented by an approximate model of relatively dense quasi-one-dimensional Bose-Einstein condensate. Based on the bifurcation theory, we proved the existence of solitary and periodic solutions. The methods we take are the trial equation method and the complete discrimination system for polynomial method. Therefore, we obtain the exact chirped solutions, which are more abundant in type and quantity than the existing results, so that the equation has more profound physical significance. These two methods are rigorously mathematical derivation and calculations, rather than based on certain conditional assumptions. In addition, we give some specific parameters to graphing the motion of the solutions, which helps to understand the propagation of nonlinear waves in fiber optic systems.
基金supported by the National Natural Science Foundation of China(Grant Nos.62227821,62025503,and 62205199).
文摘To capture the nonlinear dynamics and gain evolution in chirped pulse amplification(CPA)systems,the split-step Fourier method and the fourth-order Runge–Kutta method are integrated to iteratively address the generalized nonlinear Schrödinger equation and the rate equations.However,this approach is burdened by substantial computational demands,resulting in significant time expenditures.In the context of intelligent laser optimization and inverse design,the necessity for numerous simulations further exacerbates this issue,highlighting the need for fast and accurate simulation methodologies.Here,we introduce an end-to-end model augmented with active learning(E2E-AL)with decent generalization through different dedicated embedding methods over various parameters.On an identical computational platform,the artificial intelligence–driven model is 2000 times faster than the conventional simulation method.Benefiting from the active learning strategy,the E2E-AL model achieves decent precision with only two-thirds of the training samples compared with the case without such a strategy.Furthermore,we demonstrate a multi-objective inverse design of the CPA systems enabled by the E2E-AL model.The E2E-AL framework manifests the potential of becoming a standard approach for the rapid and accurate modeling of ultrafast lasers and is readily extended to simulate other complex systems.
基金Project supported by the Natural Science Foundation of Jilin Province of China(Grant No.20230101014JC)the National Natural Science Foundation of China(Grant No.12374265)。
文摘We investigate theoretically the effects of chirped laser pulses on high-order harmonic generation(HHG)from solids.We find that the harmonic spectra display redshifts for the driving laser pulses with negative chirp and blueshifts for those with positive chirp,which is due to the change in the instantaneous frequency of the driving laser for different chirped pulses.The analysis of crystal-momentum-resolved(k-resolved)HHG reveals that the frequency shifts are equal for the harmonics generated by different crystal momentum channels.The frequency shifts in the cutoff region are larger than those in the plateau region.With the increase of the absolute value of the chirp parameters,the frequency shifts of HHG become more significant,leading to the shifts from odd-to even-order harmonics.We also demonstrate that the frequency shifts of harmonic spectra are related to the duration of the chirped laser field,but are insensitive to the laser intensity and dephasing time.
基金Project supported by the Science and Technology Project of Hebei Education Department, China (Grant No. ZD2020200)the Innovation Capability Improvement Project of Hebei Province, China (Grant No. 22567605H)。
文摘The existence and stability of the fundamental, multi-peak, and twisted solitons in Kerr nonlinear media with chirped(amplitude-modulated) lattices are reported. We discover that the chirp rate and lattice depth can dramatically change the existence domain of solitons, the energy flow of solitons increases with increasing chirp rate or decreasing lattice depth.We also analyze how the chirp rate and lattice depth affect the stability of solitons. The stable domains of fundamental solitons and twisted solitons exhibit a multi-window distribution, while multi-peak solitons are unstable throughout the entire existence domain.
基金supported by the National Key Research and Development Program of China(Grant No.2022YFC2204601)the National Natural Science Foundation of China(Grant Nos.11925503 and 12275093)+1 种基金the Natural Science Foundation of Hubei Province(Grant No.2021CFB019)the State Key Laboratory of Applied Optics(Grant No.SKLAO2022001A10).
文摘Laser frequency combs,which are composed of a series of equally spaced coherent frequency components,have triggered revolutionary progress in precision spectroscopy and optical metrology.Length/distance is of fundamental importance in both science and technology.We describe a ranging scheme based on chirped pulse interferometry.In contrast to the traditional spectral interferometry,the local oscillator is strongly chirped which is able to meet the measurement pulses at arbitrary distances,and therefore,the dead zones can be removed.The distances can be precisely determined via two measurement steps based on the time-of-flight method and synthetic wavelength interferometry,respectively.To overcome the speed limitation of the optical spectrum analyzer,the spectrograms are stretched and detected by a fast photodetector and oscilloscope and consequently mapped into the time domain in real time.The experimental results indicate that the measurement uncertainty can be well within±2μm,compared with the reference distance meter.The Allan deviation can reach 0.4μm at 4 ns averaging time and 25 nm at 1μs and can achieve 2 nm at 100μs averaging time.We also measured a spinning disk with grooves of different depths to verify the measurement speed,and the results show that the grooves with about 150 m∕s line speed can be clearly captured.Our method provides a unique combination of non-dead zones,ultrafast measurement speed,high precision and accuracy,large ambiguity range,and only one single comb source.This system could offer a powerful solution for field measurements in practical applications in the future.
基金supported by the National Natural Science Foundation of China (Grant No. 12074329)Nanhu Scholars Program for Young Scholars of Xinyang Normal University。
文摘With a three-dimensional semiclassical ensemble method, we theoretically investigated the nonsequential double ionization of Ar driven by the spatially inhomogeneous few-cycle negatively chirped laser pulses. Our results show that the recollision time window can be precisely controlled within an isolated time interval of several hundred attoseconds, which is useful for understanding the subcycle correlated electron dynamics. More interestingly, the correlated electron momentum distribution (CEMD) exhibits a strong dependence on laser intensity. That is, at lower laser intensity, CEMD is located in the first quadrant. As the laser intensity increases,CEMD shifts almost completely to the second and fourth quadrants, and then gradually to the third quadrant.The underlying physics governing the CEMD's dependence on laser intensity is explained.
文摘This research examines the dynamics of a cosh-Gaussian laser pulse travelling through a vacuum and its impact on electron acceleration. We examine the impact of several critical factors, such as laser electric field amplitude, decentered parameter, beam waist, and laser chirp parameter, on the energy gain of electrons using coupled momentum equations. Our results indicate that the energy acquisition of electrons escalates with the amplitude of the laser electric field, decentered parameter, and chirp parameter. An appropriate beam waist is essential for attaining energyefficient electron acceleration in a vacuum. Through the optimization of these parameters, we get a maximum electron energy gain of 2.80 Ge V. This study highlights the significance of customized laser pulse attributes in improving electron acceleration and aids in the progression of high-energy particle physics.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11774131 and 91850114)
文摘The photoionization of a hydrogen atom from its ground state with ultra-fast chirped pulses is investigated by numerically solving the time-dependent Schrodinger equation within length,velocity,and Kramers-Henneberger gauges.Converged results for all gauges for chirp-free pulses agree with the prediction of dynamic interference for ground state hydrogen atoms predicted recently by Jiang and Burgdorfer[Opt.Express 26,19921(2018)].In addition,we investigated photoelectron spectra of hydrogen atoms by chirped laser pulses,and showed that dynamic interference effect will be weaken for pulses with increasing linear chirp.Our numerical results can be understood and discussed in terms of an interplay of photoelectron wavepackets from first and second halves of laser enevelop,including the ac Stark energy level shift of the photoelectron final state and atomic stabilization effect at ultra-high intensities.
基金supported by the National Natural Science Foundation of China (Grant No.10974068)
文摘This paper theoretically investigates the high-order harmonic generation cutoff extension using intense few-cycle linearly chirped laser pulses. It shows that the cutoff of the harmonic can be extended remarkably by optimising the chirping parameters. The time-frequency characteristics of high-order harmonics with different chirping parameters are analysed by means of wavelet transform of the dipole acceleration. It also gives out the classical three-step model pictures of electron. By superposing a properly selected range of the harmonic spectrum, it obtains an isolated 65as pulse.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11664035,11465016,11764038,11364038,and 11564033)
文摘Above-threshold ionization （ATI） of a hydrogen atom exposed to chirped laser fields is investigated theoretically by solving the time-dependent Schrodinger equation. By comparing the energy spectra, the two-dimensional momentum spectra, and the angular distributions of photoelectron for the laser pulses with different chirp rates, we show a very clear chirp dependence both in the multiphoton and tunneling ionization processes but no chirp dependence in the single-photon ionization. We find that the chirp dependence in the multiphoton ionization based ATI can be attributed to the excited bound states. In the single-photon and tunneling ionization regimes, the electron can be removed directly from the ground state and thus the excited states may not be very important. It indicates that the chirp dependence in the tunneling ionization based ATI processes is mainly due to the laser pulses with different chirp rates,
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11775083 and 11374108)
文摘In this article, we investigate the nonparaxial propagation properties of the chirped Airy Gaussian vortex（CAiGV）beams in uniaxial crystals orthogonal to the optical axis analytically and numerically. We discuss how the linear chirp parameters, the quadratic chirp parameters, and the Gaussian factors influence the nonparaxial propagation dynamics of the CAiGV beams. The intensity, the energy flow, the beam center, and the angular momentum of the CAiGV beams are deeply investigated. It is shown that the Gaussian factors have a great effect on the intensity and the centroid positions of the CAiGV beams. With the Gaussian factors increasing, the intensity of CAiGV beams decreases rapidly. The main lobes of the transverse intensity distribution of the CAiGV beams are similar to triangles.
基金Project supported by the National Natural Science Foundation of China(Grant No.61775223)the Strategic Priority Research Program of Chinese Academy of Sciences(Grant No.XDB1603)
文摘We studied the evolution of wavefront aberration(WFA) of a signal beam during amplification in a Ti:sapphire chirped pulse amplification(CPA) system. The results verified that the WFA of the amplified laser beam has little relation with the change of the pump beam energies. Transverse parasitic lasing that might occur in CPA hardly affects the wavefront of the signal beam. Thermal effects were also considered in this study, and the results show that the thermal effect cumulated in multiple amplification processes also has no obvious influence on the wavefront of the signal beam for a single-shot frequency. The results presented in this paper confirmed experimentally that the amplification in a Ti:sapphire CPA system has little impact on the WFA of the signal beam and it is very helpful for wavefront correction of single-shot PW and multi-PW laser systems based on Ti:sapphire.
基金Supported by the Science Foundation of Baoji University of Arts and Sciences of China under Grant Nos. Zk10122,ZK11061,ZK11135,ZK11060,and ZK1032
文摘We theoretically investigate high-order harmonic and isolated attosecond pulse generation in a two-color chirped laser field,which is synthesized by a 9 fs/800 nm fundamental chirped pulse and a 9 fs/1600 nm controlling chirped pulse.Our numerical results show that,by using this method,not only is the harmonic cutoff significantly extended to the 948th order harmonic,but also the bandwidth of the supercontinuum spectrum is effectively broadened to about 1342 eV.In addition,due to the introduction of the chirp,the long quantum path is suppressed and only the short one is selected,and then an isolated 28 as pulse with a bandwidth of 155 eV is obtained directly.
文摘In this paper,we propose the novel system of multipoint measurement.The sensors of measurements are chirped Bragg grating and the interrogation of sensors is sub-carrier phase.The wavelength division multiplexing technique is used for addressing a network of FBG sensors and the time-division multiplexing technique is used for multipoint measurements.In the system,the modulation frequency of 200 MHz is adopted.The range of dectetion is from 0 to 900μεand the resolution is 12με. The time of the sensor response is about 1ns.
基金supported by the National High Technology Research and Development Program of China(Grant No.2014AA032608)the Key Laboratory for Mechanical Behavior of Material of Xi’an Jiaotong University,China(Grant No.20121201)the Fundamental Research Funds for the Central Universities,China
文摘Gallium nitride （GaN） based light-emitting diodes （LEDs） with chirped multiple quantum well （MQW） structures have been investigated experimentally and numerically in this paper. Compared to conventional LEDs with uniform quantum wells （QWs）, LEDs with chirped MQW structures have better internal quantum efficiency （IQE） and carrier injection efficiency. The droop ratios of LEDs with chirped MQW structures show a remarkable improvement at 600 mA/mm2, reduced down from 28.6% （conventional uniform LEDs） to 23.7% （chirped MQWs-a） and 18.6% （chirped MQWs-b）, respectively. Meanwhile, the peak IQE increases from 76.9% （uniform LEDs） to 83.7% （chirped MQWs-a） and 88.6% （chirped MQWs-b）. The reservoir effect of chirped MQW structures is the significant reason as it could increase hole injection efficiency and radiative recombination. The leakage current and Auger recombination of chirped MQW structures can also be suppressed. Furthermore, the chirped MQWs-b structure with lower potential barriers can enhance the reservoir effect and obtain further improvement of the carrier injection efficiency and radiative recombination, as well as further suppressing efficiency droop.
基金Project supported by the National Natural Science Foundation of China (Grant Nos.62035012,62074143,and 62004191)Zhejiang Lab (Grant No.2020LC0AD02)
文摘We report on the fabrication and characterization of InAs/GaAs chirped multilayer quantum-dot superluminescent diodes(CMQD-SLDs)with and without direct Si doping in QDs.It was found that both the output power and the spectral width of the CMQD-SLDs were significantly enhanced by direct Si doping in the QDs.The output power and spectral width have been increased by approximately 18.3%and 40%,respectively.Moreover,we shortened the cavity length of the doped CMQD-SLD and obtained a spectral width of 106 nm.In addition,the maximum output power and spectral width of the CMQD-SLD doped directly with Si can be further increased to 16.6 mW and 114 nm,respectively,through anti-reflection coating and device packaging.The device exhibited the smallest spectral dip of 0.2 dB when the spectrum was widest.The improved performances of the doped CMQD-SLD can be attributed to the direct doping of Si in the QDs,optimization of device structure and device packaging.
基金Project supported by the National Natural Science Foundation of China (Grant No 10774039)
文摘Using a time-dependent multilevel approach, we demonstrate that lithium atoms can be transferred to states of lower principle quantum number by exposing them to a frequency chirped microwave pulse. The population transfer from n = 79 to n = 70 states of lithium atoms with more than 80% efficiency is achieved by means of the sequential two-photon △n=-1 transitions. It is shown that the coherent control of the population transfer can be accomplished by the optimization of the chirping parameters and microwave field strength. The calculation results agree well with the experimental ones and novel explanations have been given to understand the experimental results.
