We present an approach,a Terahertz streaking-assisted photoelectron spectrum(THz SAPS),to achieve direct observations of ultrafast coherence dynamics with timescales beyond the pulse duration.Using a 24 fs probe pulse...We present an approach,a Terahertz streaking-assisted photoelectron spectrum(THz SAPS),to achieve direct observations of ultrafast coherence dynamics with timescales beyond the pulse duration.Using a 24 fs probe pulse,the THz SAPS enables us to well visualize Rabi oscillations of 11.76 fs and quantum beats of 2.62 fs between the 5S_(1/2) and 5P_(3/2) in rubidium atoms.The numerical results show that the THz SAPS can simultaneously achieve high resolution in both frequency and time domains without the limitation of Heisenberg uncertainty of the probe pulse.The long probe pulse promises sufficiently high frequency resolution in photoelectron spectroscopy allowing to observe Autler-Townes splittings,whereas the streaking THz field enhances temporal resolution for not only Rabi oscillations but also quantum beats between the ground and excited states.The THz SAPS demonstrates a potential applicability for observation and manipulation of ultrafast coherence processes in frequency and time domains.展开更多
Bichromatic circularly polarized fields provide a useful tool to probe the ionization dynamics.In this work, we compare the photoelectron momentum distribution in few-cycle bichromatic field of different helicities.Th...Bichromatic circularly polarized fields provide a useful tool to probe the ionization dynamics.In this work, we compare the photoelectron momentum distribution in few-cycle bichromatic field of different helicities.The spectral features are analyzed with semiclassical trajectories derived from the strong field approximation.In particular, the interference fringes in momentum distribution are investigated by tracking the ionization time and tunneling exits of released photoelectrons.Different types of trajectories that contribute to the interference fringes are elucidated.展开更多
Employing recently developed magneto-optical trap recoil ion momentum spectroscopy(MOTRIMS)combined with cold atoms,strong laser pulse,and ultrafast technologies,we study momentum distributions of the multiply ionized...Employing recently developed magneto-optical trap recoil ion momentum spectroscopy(MOTRIMS)combined with cold atoms,strong laser pulse,and ultrafast technologies,we study momentum distributions of the multiply ionized cold rubidium(Rb)induced by the elliptically polarized laser pulses(35 fs,1.3×10^15 W/cm^2).The complete vector momenta of Rb^n+ions up to charge state n=4 are recorded with extremely high resolution(0.12 a.u.for Rb^+).Variations of characteristic multi-bands are displayed in momentum distributions because the ellipticity varies from the linear to circular polarization,are interpreted qualitatively with the classical overbarrier ionization model.Present momentum spectroscopy of cold heavy alkali atoms presents novel strong-field phenomena beyond the noble gases.展开更多
Biological proton pumps ferry protons in an active manner and have a high flux(a few to 10 protons/(s·nm^(2))).Integrating these features in an artificial membrane may open the way for a wide range of application...Biological proton pumps ferry protons in an active manner and have a high flux(a few to 10 protons/(s·nm^(2))).Integrating these features in an artificial membrane may open the way for a wide range of applications but it remains challenging.In this work,we employed a structural engineering strategy to construct an asymmetric photonic polymeric carbon nitride(C3N4)membrane that exhibited photo-driven high flux proton pumping performance.The ion transport path through the membrane is reminiscent of that in the high-flux asymmetric biological ion channel.In addition,it has a photonic structure that mimics the mosquito compound eyes with improved light adsorption.Finally,the asymmetric structure constitutes an isotype(n-n)heterojunction that enhances the separation of the light-induced electron-hole pairs.As a result,the membrane shows a flux of 89μA/cm^(2)under 100 mW/cm^(2)white light illumination(approximately one sun),the highest ever reported.This translates to a pumping rate of~6 proton/(s·nm^(2)),comparable to the biological counterpart.This work highlights the potential of multi-level structural engineering to construct high-performance bionic devices,and may find applications in solar energy harvesting and solar powered membrane process.展开更多
In this work, it has been demonstrated that in order to fully understand the terahertz(THz) pulse generation process during femtosecond laser filamentation, the interaction between THz wave and air plasma has to be ta...In this work, it has been demonstrated that in order to fully understand the terahertz(THz) pulse generation process during femtosecond laser filamentation, the interaction between THz wave and air plasma has to be taken into account. This interaction is mainly associated with the spatial confinement of the THz pulse by the plasma column, which could be described by the one-dimensional negative dielectric(1DND) waveguide model. By combining the 1 DND model with the conventional four-wave mixing(4WM) and photocurrent(PC) models,the variation of THz spectral amplitude and width obtained in experiments could be better understood. Finally, a three-step procedure, with 1DND bridging 4WM and PC processes, has been established for the first time to describe the underlying mechanism of THz radiation from plasma sources.展开更多
The origin of terahertz(THz)generation in a gas-phase medium is still in controversy,although the THz sources have been applied across many disciplines.Herein,the THz generation in a dual color field is investigated e...The origin of terahertz(THz)generation in a gas-phase medium is still in controversy,although the THz sources have been applied across many disciplines.Herein,the THz generation in a dual color field is investigated experimentally by precisely controlling the relative phase and polarization of dual-color lasers,where the accompanying third-harmonic generation is employed for in situ determination of the relative phase up to sub-wavelength accuracy.Joint studies with the strong approximation(SFA)theory reveal that the continuum-continuum(CC)transition within an escaped electron wave packet in the single atom gives birth to THz emission,without the necessity of considering the plasma effect.Meanwhile,we develop the analytic form from SFA-based CC description,which is able to reproduce and decompose the classical photocurrent model from the viewpoint of microscopic quantum theory,establishing the quantum-lassical correspondence and bringing a novel insight into the mechanism of THz generation.Present studies leave open the possibility for probing the ultrafast dynamics of continuum electrons and a new dimension for the study of THz-related science and methodology.展开更多
基金Supported by the National Natural Science Foundation of China(Grant Nos.11827806,11874368 and 61675213).
文摘We present an approach,a Terahertz streaking-assisted photoelectron spectrum(THz SAPS),to achieve direct observations of ultrafast coherence dynamics with timescales beyond the pulse duration.Using a 24 fs probe pulse,the THz SAPS enables us to well visualize Rabi oscillations of 11.76 fs and quantum beats of 2.62 fs between the 5S_(1/2) and 5P_(3/2) in rubidium atoms.The numerical results show that the THz SAPS can simultaneously achieve high resolution in both frequency and time domains without the limitation of Heisenberg uncertainty of the probe pulse.The long probe pulse promises sufficiently high frequency resolution in photoelectron spectroscopy allowing to observe Autler-Townes splittings,whereas the streaking THz field enhances temporal resolution for not only Rabi oscillations but also quantum beats between the ground and excited states.The THz SAPS demonstrates a potential applicability for observation and manipulation of ultrafast coherence processes in frequency and time domains.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11420101003,11604347,11827806,11874368,61675213,and 91636105)
文摘Bichromatic circularly polarized fields provide a useful tool to probe the ionization dynamics.In this work, we compare the photoelectron momentum distribution in few-cycle bichromatic field of different helicities.The spectral features are analyzed with semiclassical trajectories derived from the strong field approximation.In particular, the interference fringes in momentum distribution are investigated by tracking the ionization time and tunneling exits of released photoelectrons.Different types of trajectories that contribute to the interference fringes are elucidated.
基金National Natural Science Foundation of China(Grant Nos.1182780611874368+2 种基金6167521311822401and11674034)。
文摘Employing recently developed magneto-optical trap recoil ion momentum spectroscopy(MOTRIMS)combined with cold atoms,strong laser pulse,and ultrafast technologies,we study momentum distributions of the multiply ionized cold rubidium(Rb)induced by the elliptically polarized laser pulses(35 fs,1.3×10^15 W/cm^2).The complete vector momenta of Rb^n+ions up to charge state n=4 are recorded with extremely high resolution(0.12 a.u.for Rb^+).Variations of characteristic multi-bands are displayed in momentum distributions because the ellipticity varies from the linear to circular polarization,are interpreted qualitatively with the classical overbarrier ionization model.Present momentum spectroscopy of cold heavy alkali atoms presents novel strong-field phenomena beyond the noble gases.
基金This work was financially supported by the Natural Science Foundation of Shandong Province(Nos.ZR2019ZD47,ZR2019JQ05,ZR2018MB018,and ZR202103010934)the Key R&D Projects of Shandong Province(No.2022CXGC010302)+2 种基金the Education Department of Shandong Province(No.2019KJC006)the Shandong Energy Institute(No.SEI202124)the National Natural Science Foundation of China(Nos.22175104 and 21802080).
文摘Biological proton pumps ferry protons in an active manner and have a high flux(a few to 10 protons/(s·nm^(2))).Integrating these features in an artificial membrane may open the way for a wide range of applications but it remains challenging.In this work,we employed a structural engineering strategy to construct an asymmetric photonic polymeric carbon nitride(C3N4)membrane that exhibited photo-driven high flux proton pumping performance.The ion transport path through the membrane is reminiscent of that in the high-flux asymmetric biological ion channel.In addition,it has a photonic structure that mimics the mosquito compound eyes with improved light adsorption.Finally,the asymmetric structure constitutes an isotype(n-n)heterojunction that enhances the separation of the light-induced electron-hole pairs.As a result,the membrane shows a flux of 89μA/cm^(2)under 100 mW/cm^(2)white light illumination(approximately one sun),the highest ever reported.This translates to a pumping rate of~6 proton/(s·nm^(2)),comparable to the biological counterpart.This work highlights the potential of multi-level structural engineering to construct high-performance bionic devices,and may find applications in solar energy harvesting and solar powered membrane process.
基金National Key R&D Program of China(2017YFC0821300)National Natural Science Foundation of China(NSFC)(11704252,11574160,61722111)+6 种基金National Program on Key Basic Research Project of China(973Program)(2014CB339802,2014CB339806)Major National Development Project of Scientific Instrument and Equipment(2017YFF0106300,2016YFF0100503)Tianjin Research Program of Application Foundation and Advanced Technology(15JCZDJC31700)Key Scientific and Technological Project of Science and Technology Commission of Shanghai Municipality(STCSM)(15DZ0500102)Shanghai Leading Talent(2016-019)Young Yangtze River Scholar(Q2016212)Tianjin Special Program for Talent Development
文摘In this work, it has been demonstrated that in order to fully understand the terahertz(THz) pulse generation process during femtosecond laser filamentation, the interaction between THz wave and air plasma has to be taken into account. This interaction is mainly associated with the spatial confinement of the THz pulse by the plasma column, which could be described by the one-dimensional negative dielectric(1DND) waveguide model. By combining the 1 DND model with the conventional four-wave mixing(4WM) and photocurrent(PC) models,the variation of THz spectral amplitude and width obtained in experiments could be better understood. Finally, a three-step procedure, with 1DND bridging 4WM and PC processes, has been established for the first time to describe the underlying mechanism of THz radiation from plasma sources.
基金National Natural Science Foundation of China(11827806,11874368,61675213).
文摘The origin of terahertz(THz)generation in a gas-phase medium is still in controversy,although the THz sources have been applied across many disciplines.Herein,the THz generation in a dual color field is investigated experimentally by precisely controlling the relative phase and polarization of dual-color lasers,where the accompanying third-harmonic generation is employed for in situ determination of the relative phase up to sub-wavelength accuracy.Joint studies with the strong approximation(SFA)theory reveal that the continuum-continuum(CC)transition within an escaped electron wave packet in the single atom gives birth to THz emission,without the necessity of considering the plasma effect.Meanwhile,we develop the analytic form from SFA-based CC description,which is able to reproduce and decompose the classical photocurrent model from the viewpoint of microscopic quantum theory,establishing the quantum-lassical correspondence and bringing a novel insight into the mechanism of THz generation.Present studies leave open the possibility for probing the ultrafast dynamics of continuum electrons and a new dimension for the study of THz-related science and methodology.