This paper presents a Kerr-lens mode-locked Ti：sapphire laser at the repetition rate of 525 MHz, stable laser pulse as short as 10 fs with average output power of 480 mW is obtained. By injecting the pulse into photo...This paper presents a Kerr-lens mode-locked Ti：sapphire laser at the repetition rate of 525 MHz, stable laser pulse as short as 10 fs with average output power of 480 mW is obtained. By injecting the pulse into photonics crystal fibre, octave-spanning spectrum covered from 500 to 1050 nm is generated, carrier-envelope phase frequency with signal-to- noise ratio of 31dB is measured, which paves the way for the generation of a compact frequency comb.展开更多
We investigate the plasmonic-field-enhanced high-order harmonic generation（HHG） of H atom driven by few-cycle laser pulses, by solving the time-dependent Schr？dinger equation（TDSE）. Compared with the homogeneous ...We investigate the plasmonic-field-enhanced high-order harmonic generation（HHG） of H atom driven by few-cycle laser pulses, by solving the time-dependent Schr？dinger equation（TDSE）. Compared with the homogeneous field, HHG spectra generated by inhomogeneous field exhibit two-plateau structure. We analyze the origin of the two plateaus by using the semiclassical trajectory method. Our results from both classical and TDSE simulations show that the cutoffs of the two plateaus are dramatically affected by the carrier-envelope phase（CEP） of laser pulse in the inhomogeneous field, even for a little longer pulse. Thus, we can determine the CEP of driving laser based on the cutoff position of HHG generated in the inhomogeneous field.展开更多
In this paper the phase-dependent features of ultrashort laser pulse resonant propagation in a two-level dipolar molecule are demonstrated by solving full Maxwell-Bloch equations. The electronic properties of dipolar ...In this paper the phase-dependent features of ultrashort laser pulse resonant propagation in a two-level dipolar molecule are demonstrated by solving full Maxwell-Bloch equations. The electronic properties of dipolar molecule 4-trans-[p-（N, N-Di-n-butylamino）-p-stilbenylvinyl] pyridine （DBASVP） molecule, one-dimensional asymmetric organic molecule, is calculated by density functional theory at ab initio level. The numerical results show that the carrier propagation and the spectrum evolution of the pulse are sensitive to its initial phase and the phase sensitivity is more obvious for larger area pulse. The phase-dependent feature is more evident in dipolar molecule because the permanent dipole moment makes the nonlinear effects stronger.展开更多
The influence of the carrier-envelope phase on high-harmonic generation is investigated, both experimentally and theoretically, for three different interaction gas media, driven by mid-infrared, few-cycle and CEP-stab...The influence of the carrier-envelope phase on high-harmonic generation is investigated, both experimentally and theoretically, for three different interaction gas media, driven by mid-infrared, few-cycle and CEP-stabiUzed laser pulses. Different patterns of harmonic spectra with varying CEP for the three interaction gas media are observed. Furthermore, in comparing our experiment results to the previous works driven by near-infrared laser pulses, different phenomena are found. Through numerical simulation, we find that for the two different kinds of driving fields, i.e. mid-infrared and near-infrared laser pulses, different kinds of electron trajectories contribute to the generation of high harmonics.展开更多
The carrier-envelope phase （CEP） of few-cycle laser pulses is shown to have profound effects on the bound- state atomic coherence even in the weak-field regime where ionizations hardly take place, and a simple schem...The carrier-envelope phase （CEP） of few-cycle laser pulses is shown to have profound effects on the bound- state atomic coherence even in the weak-field regime where ionizations hardly take place, and a simple scheme is proposed to measure such CEP-dependent atomic coherence.展开更多
Using numerical solution of the full Maxwell-Bloch equations, which is obtained by the finite-difference time-domain method and the iterative predictor-orrector method, we investigate the modulation effect of relative...Using numerical solution of the full Maxwell-Bloch equations, which is obtained by the finite-difference time-domain method and the iterative predictor-orrector method, we investigate the modulation effect of relative carrierenvelope phase （hereinafter referred to as the relative phase） on resonant propagation of two-colour femtosecond ultrashort laser pulses in a V-type three-level atomic medium. It is found that the pulse splitting occurs for a smaller value of relative phase; when the value of relative phase increases to a certain value, only the variation of pulse shape is present and the pulse splitting does not occur any more; moreover, when the value of relative phase is smaller, the pulse group velocity is larger. The relative phase also has an obvious effect on population and spectral property. Different population transfers can be realized by adjusting the value of relative phase. Generally speaking, for the pulses with smaller areas their spectral strengths and frequency ranges decrease obviously with the value of relative phase increasing; for the pulses with larger areas, with value of the relative phase increasing, their spectral strengths decrease remarkably but the relative strengths of the higher frequency components increase significantly, while the spectral frequency range is not varied evidently.展开更多
The ELI ERIC facility offers international users ultrashort laser sources via the ALPS facility focusing on few-cycle laser drivers for attosecond pulses,particle beams and ultrahigh intensity interactions.The HR1 sys...The ELI ERIC facility offers international users ultrashort laser sources via the ALPS facility focusing on few-cycle laser drivers for attosecond pulses,particle beams and ultrahigh intensity interactions.The HR1 system supports attosecond high harmonic generation(HHG)and time-resolved spectroscopy at 100 kHz.However,its high repetition rate,while aiding statistical analysis,poses thermal challenges and limits certain applications requiring lower repetition rates.To address this,the HR Alignment laser system was developed for the HHG beamline at the ELI-ALPS facility.This new system delivers sub-6 fs,1 mJ pulses with a tunable repetition rate(from 10 Hz to 10 kHz)and carrier-envelope phase(CEP)stabilization.It utilizes an ytterbium-doped potassium gadolinium tungstate front-end,multi-pass cell compression,and chirped mirrors.Characterization confirms excellent energy and CEP stability(below 300 mrad),beam quality and temporal contrast,matching the HR1 laser's performance.This compact,stable system provides highflux attosecond generation for reaction microscopy enhancing ultrafast research in the ELI-ALPS facility.展开更多
Coherent combining of several low-energy few-cycle beams offers a reliable and feasible approach to producing fewcycle laser pulses with energies exceeding the multi-joule level.However,time synchronization and carrie...Coherent combining of several low-energy few-cycle beams offers a reliable and feasible approach to producing fewcycle laser pulses with energies exceeding the multi-joule level.However,time synchronization and carrier-envelope phase difference(ΔCEP)between pulses significantly affect the temporal waveform and intensity of the combined pulse,requiring precise measurement and control.Here,we propose a concise optical method based on the phase retrieval of spectral interference and quadratic function symmetry axis fitting to simultaneously measure the time synchronization andΔCEP between few-cycle pulses.The control precision of our coherent beam combining system can achieve a time delay stability within 42 as andΔCEP measurement precision of 40 mrad,enabling a maximum combining efficiency of 98.5%.This method can effectively improve the performance and stability of coherent beam combining systems for few-cycle lasers,which will facilitate the obtaining of high-quality few-cycle lasers with high energy.展开更多
We investigate off-axis phase-matched terahertz(THz)radiation in laser plasma pumped by few-cycle laser pulses.We find that the THz amplitude and angular distributions in the far field are sensitively dependent on the...We investigate off-axis phase-matched terahertz(THz)radiation in laser plasma pumped by few-cycle laser pulses.We find that the THz amplitude and angular distributions in the far field are sensitively dependent on the pump pulse’s focal carrier-envelope phase(CEP).Ring-like profiles of THz radiation are obtained at CEP values of 0.5πand 1.5π,due to the inversely symmetric local THz waveforms emitted before and after laser focus.Off-axis phase-matched THz radiation offers a tool to accurately measure the CEP of few-cycle pulses at the center of a medium.展开更多
By inversing the signal and idler in a two-stage noncollinear optical parametric amplifier which is,respectively,pumped by the second harmonic and fundamental wave of femtosecond Ti:sapphire laser at repetition rate o...By inversing the signal and idler in a two-stage noncollinear optical parametric amplifier which is,respectively,pumped by the second harmonic and fundamental wave of femtosecond Ti:sapphire laser at repetition rate of1 kHz,the carrier-envelope phase(CEP)passively stabilized pulses with a tunable wavelength from 1.1 to 1.6 lm are obtained with maximum energy of 95 lJ at 1.3 lm under the pump energy of 500 lJ.The CEP jitter of pulses is 108 mrad measured by an f-2f interferometer.This work demonstrates a new way to efficiently generate tunable near-infrared femtosecond laser pulses with self-stabilized CEP.展开更多
This paper reports the carrier-envelop phase (CEP) locking for the 5 fs re-compressed laser pulse generated from a chirped pulse amplified (CPA) Ti:sapphire laser at 1 kHz repetition rate. A phase locking feedback sys...This paper reports the carrier-envelop phase (CEP) locking for the 5 fs re-compressed laser pulse generated from a chirped pulse amplified (CPA) Ti:sapphire laser at 1 kHz repetition rate. A phase locking feedback system with two loops was designed to control the fast fluctuation arising from the seeding laser and the slow fluctuation arising from the sub-mJ amplified pulse. The principle and structure of the phase control system, including the CEP detection, servo loop design and phase locking result, are analyzed. The experiment shows that our phase locking system can be well used to establish the stable phase locking of few-cycle amplified laser pulse, and the CEP variation of below 53 mrad (rms) was demonstrated during a locking period of more than 3 h.展开更多
The intrinsic synchronization, multi-color outputs and related carrier-envelope phases (CEP) among pulses bring advantages to synchronously pumped femtosecond optical parametric oscillators and the pumping sources for...The intrinsic synchronization, multi-color outputs and related carrier-envelope phases (CEP) among pulses bring advantages to synchronously pumped femtosecond optical parametric oscillators and the pumping sources for broadband frequency comb generation and ultrashort waveform coherent syn-thesis. In this paper, we discuss our latest research results in this field, which cover the following as-pects: the phase relationship and energy conservation law in an OPO and related experimental verifi-cation; control of the pumping Ti:sapphire femtosecond laser's CEP by self-referencing technology, and its repetition-rate locking by piezoelectric transducer (PZT); CEP locking of the pulses from the OPO by beating the non-phase-matched visible outputs against pump supercontinuum to obtain a driving signal for a fast PZT on the OPO end mirror; the generation of a broadband frequency comb spanning from 400 nm to 2.4 μm with 1.2 kHz bandwidth; and the realization of coherent interference between phase controlled pump pulses and signal second harmonic pulses.展开更多
Photodetachment of H- irradiated by linearly polarized few-cycle laser field is investigated by time-dependent SchrSdinger equation numerically. The photo-electron left-right asymmetry parameter as a function of carri...Photodetachment of H- irradiated by linearly polarized few-cycle laser field is investigated by time-dependent SchrSdinger equation numerically. The photo-electron left-right asymmetry parameter as a function of carrier-envelop （CE） phase of few-cycle pulses is attained. We confirm the asymmetry of photoelectron distribution in H- photodetachment and find that the maximal asymmetry parameter of H- is equal to that of H atom under the same conditions but the corresponding CE phases are quite different. Thus a CE phase shift appears. Compared to that of H atom and field free electron, the zero asymmetry CE phase shift is sensitively affected by Coulomb field. The Coulomb effect on the asymmetry of H- photodetachment mainly behaves in the CE phase shift of H- instead of the amplitude of asymmetry parameter curve.展开更多
基金supported by National Natural Science Foundation of China (Grant Nos 60490281 and 60621063)National Basic Research Program of China (Grant No 2007CB815104)
文摘This paper presents a Kerr-lens mode-locked Ti：sapphire laser at the repetition rate of 525 MHz, stable laser pulse as short as 10 fs with average output power of 480 mW is obtained. By injecting the pulse into photonics crystal fibre, octave-spanning spectrum covered from 500 to 1050 nm is generated, carrier-envelope phase frequency with signal-to- noise ratio of 31dB is measured, which paves the way for the generation of a compact frequency comb.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11264036,11364038,and 11465016)
文摘We investigate the plasmonic-field-enhanced high-order harmonic generation（HHG） of H atom driven by few-cycle laser pulses, by solving the time-dependent Schr？dinger equation（TDSE）. Compared with the homogeneous field, HHG spectra generated by inhomogeneous field exhibit two-plateau structure. We analyze the origin of the two plateaus by using the semiclassical trajectory method. Our results from both classical and TDSE simulations show that the cutoffs of the two plateaus are dramatically affected by the carrier-envelope phase（CEP） of laser pulse in the inhomogeneous field, even for a little longer pulse. Thus, we can determine the CEP of driving laser based on the cutoff position of HHG generated in the inhomogeneous field.
基金Froject supported by the Shandong Natural Science Foundation （Grant No Y2004A08）, University Doctoral Subject Special Science and Technology Foundation （Grant No 20040445001） and the Key Laboratory for High Intensity 0ptics of Shanghai Institute of 0ptics and Fine Mechanics, Chinese Academy of Sciences.
文摘In this paper the phase-dependent features of ultrashort laser pulse resonant propagation in a two-level dipolar molecule are demonstrated by solving full Maxwell-Bloch equations. The electronic properties of dipolar molecule 4-trans-[p-（N, N-Di-n-butylamino）-p-stilbenylvinyl] pyridine （DBASVP） molecule, one-dimensional asymmetric organic molecule, is calculated by density functional theory at ab initio level. The numerical results show that the carrier propagation and the spectrum evolution of the pulse are sensitive to its initial phase and the phase sensitivity is more obvious for larger area pulse. The phase-dependent feature is more evident in dipolar molecule because the permanent dipole moment makes the nonlinear effects stronger.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11127901,61221064,11134010,11227902,11222439,and 11274325)the National Basic Research Program of China(Grant No.2011CB808103)the Funds from Shanghai Commission of Science and Technology(Grant No.12QA1403700)
文摘The influence of the carrier-envelope phase on high-harmonic generation is investigated, both experimentally and theoretically, for three different interaction gas media, driven by mid-infrared, few-cycle and CEP-stabiUzed laser pulses. Different patterns of harmonic spectra with varying CEP for the three interaction gas media are observed. Furthermore, in comparing our experiment results to the previous works driven by near-infrared laser pulses, different phenomena are found. Through numerical simulation, we find that for the two different kinds of driving fields, i.e. mid-infrared and near-infrared laser pulses, different kinds of electron trajectories contribute to the generation of high harmonics.
基金The project supported by National Natural Science Foundation of China under Grant Nos.10575040,90503010,and 10634060
文摘The carrier-envelope phase （CEP） of few-cycle laser pulses is shown to have profound effects on the bound- state atomic coherence even in the weak-field regime where ionizations hardly take place, and a simple scheme is proposed to measure such CEP-dependent atomic coherence.
基金Project supported by the National Basic Research Program of China (Grant No. 2006CB806000)the National Natural Science Foundation of China (Grant No. 10875072)the Open Fund of the State Key Laboratory of High Field Laser Physics, Shanghai Institute of Optics and Fine Mechanics
文摘Using numerical solution of the full Maxwell-Bloch equations, which is obtained by the finite-difference time-domain method and the iterative predictor-orrector method, we investigate the modulation effect of relative carrierenvelope phase （hereinafter referred to as the relative phase） on resonant propagation of two-colour femtosecond ultrashort laser pulses in a V-type three-level atomic medium. It is found that the pulse splitting occurs for a smaller value of relative phase; when the value of relative phase increases to a certain value, only the variation of pulse shape is present and the pulse splitting does not occur any more; moreover, when the value of relative phase is smaller, the pulse group velocity is larger. The relative phase also has an obvious effect on population and spectral property. Different population transfers can be realized by adjusting the value of relative phase. Generally speaking, for the pulses with smaller areas their spectral strengths and frequency ranges decrease obviously with the value of relative phase increasing; for the pulses with larger areas, with value of the relative phase increasing, their spectral strengths decrease remarkably but the relative strengths of the higher frequency components increase significantly, while the spectral frequency range is not varied evidently.
基金The ELI-ALPS project(GINOP-2.3.6-15-2015-00001)is supported by the European Unionco-financed by the European Regional Development Fund
文摘The ELI ERIC facility offers international users ultrashort laser sources via the ALPS facility focusing on few-cycle laser drivers for attosecond pulses,particle beams and ultrahigh intensity interactions.The HR1 system supports attosecond high harmonic generation(HHG)and time-resolved spectroscopy at 100 kHz.However,its high repetition rate,while aiding statistical analysis,poses thermal challenges and limits certain applications requiring lower repetition rates.To address this,the HR Alignment laser system was developed for the HHG beamline at the ELI-ALPS facility.This new system delivers sub-6 fs,1 mJ pulses with a tunable repetition rate(from 10 Hz to 10 kHz)and carrier-envelope phase(CEP)stabilization.It utilizes an ytterbium-doped potassium gadolinium tungstate front-end,multi-pass cell compression,and chirped mirrors.Characterization confirms excellent energy and CEP stability(below 300 mrad),beam quality and temporal contrast,matching the HR1 laser's performance.This compact,stable system provides highflux attosecond generation for reaction microscopy enhancing ultrafast research in the ELI-ALPS facility.
基金supported by the Key Projects of Intergovernmental International Scientific and Technological Innovation Cooperation(Grant No.2021YFE0116700)the National Natural Science Foundation of China(NSFC)(Grant Nos.12204500 and 12074399)+1 种基金the Shanghai Sailing Program(Grant No.22YF1455300)the Chinese Academy of Sciences(Grant Nos.XDA25020105,XDA25020103 and XDA25020101)。
文摘Coherent combining of several low-energy few-cycle beams offers a reliable and feasible approach to producing fewcycle laser pulses with energies exceeding the multi-joule level.However,time synchronization and carrier-envelope phase difference(ΔCEP)between pulses significantly affect the temporal waveform and intensity of the combined pulse,requiring precise measurement and control.Here,we propose a concise optical method based on the phase retrieval of spectral interference and quadratic function symmetry axis fitting to simultaneously measure the time synchronization andΔCEP between few-cycle pulses.The control precision of our coherent beam combining system can achieve a time delay stability within 42 as andΔCEP measurement precision of 40 mrad,enabling a maximum combining efficiency of 98.5%.This method can effectively improve the performance and stability of coherent beam combining systems for few-cycle lasers,which will facilitate the obtaining of high-quality few-cycle lasers with high energy.
文摘We investigate off-axis phase-matched terahertz(THz)radiation in laser plasma pumped by few-cycle laser pulses.We find that the THz amplitude and angular distributions in the far field are sensitively dependent on the pump pulse’s focal carrier-envelope phase(CEP).Ring-like profiles of THz radiation are obtained at CEP values of 0.5πand 1.5π,due to the inversely symmetric local THz waveforms emitted before and after laser focus.Off-axis phase-matched THz radiation offers a tool to accurately measure the CEP of few-cycle pulses at the center of a medium.
基金partly supported by the National Key Technology R&D Program of the Ministry of Science and Technology(2012BAC23B03)National Key Basic Research Program of China(2013CB922401)the National Natural Science Foundation of China(11074298,60878020)
文摘By inversing the signal and idler in a two-stage noncollinear optical parametric amplifier which is,respectively,pumped by the second harmonic and fundamental wave of femtosecond Ti:sapphire laser at repetition rate of1 kHz,the carrier-envelope phase(CEP)passively stabilized pulses with a tunable wavelength from 1.1 to 1.6 lm are obtained with maximum energy of 95 lJ at 1.3 lm under the pump energy of 500 lJ.The CEP jitter of pulses is 108 mrad measured by an f-2f interferometer.This work demonstrates a new way to efficiently generate tunable near-infrared femtosecond laser pulses with self-stabilized CEP.
基金Supported by the National Natural Science Foundation of China (Grant Nos. 60490281, 60621063 and 60608003)the Knowledge Innovation Program of the Chinese Academy of Sciences (Grant No. KJCX-SW-W14)the National Basic Research Program of China (Grant No. 2007CB815104)
文摘This paper reports the carrier-envelop phase (CEP) locking for the 5 fs re-compressed laser pulse generated from a chirped pulse amplified (CPA) Ti:sapphire laser at 1 kHz repetition rate. A phase locking feedback system with two loops was designed to control the fast fluctuation arising from the seeding laser and the slow fluctuation arising from the sub-mJ amplified pulse. The principle and structure of the phase control system, including the CEP detection, servo loop design and phase locking result, are analyzed. The experiment shows that our phase locking system can be well used to establish the stable phase locking of few-cycle amplified laser pulse, and the CEP variation of below 53 mrad (rms) was demonstrated during a locking period of more than 3 h.
基金Supported by UK Engineering and Physical Sciences Research Council (EPSRC), Coherent Inc.the National Natural Science Foundation of China (Grant No. 60308001)
文摘The intrinsic synchronization, multi-color outputs and related carrier-envelope phases (CEP) among pulses bring advantages to synchronously pumped femtosecond optical parametric oscillators and the pumping sources for broadband frequency comb generation and ultrashort waveform coherent syn-thesis. In this paper, we discuss our latest research results in this field, which cover the following as-pects: the phase relationship and energy conservation law in an OPO and related experimental verifi-cation; control of the pumping Ti:sapphire femtosecond laser's CEP by self-referencing technology, and its repetition-rate locking by piezoelectric transducer (PZT); CEP locking of the pulses from the OPO by beating the non-phase-matched visible outputs against pump supercontinuum to obtain a driving signal for a fast PZT on the OPO end mirror; the generation of a broadband frequency comb spanning from 400 nm to 2.4 μm with 1.2 kHz bandwidth; and the realization of coherent interference between phase controlled pump pulses and signal second harmonic pulses.
文摘Photodetachment of H- irradiated by linearly polarized few-cycle laser field is investigated by time-dependent SchrSdinger equation numerically. The photo-electron left-right asymmetry parameter as a function of carrier-envelop （CE） phase of few-cycle pulses is attained. We confirm the asymmetry of photoelectron distribution in H- photodetachment and find that the maximal asymmetry parameter of H- is equal to that of H atom under the same conditions but the corresponding CE phases are quite different. Thus a CE phase shift appears. Compared to that of H atom and field free electron, the zero asymmetry CE phase shift is sensitively affected by Coulomb field. The Coulomb effect on the asymmetry of H- photodetachment mainly behaves in the CE phase shift of H- instead of the amplitude of asymmetry parameter curve.
