Ionization and dissociation are fundamental processes that molecules undergo in intense femtosecond laser fields.Professor Fanao Kong is a pioneering researcher in this field within China.He has developed an orbital-b...Ionization and dissociation are fundamental processes that molecules undergo in intense femtosecond laser fields.Professor Fanao Kong is a pioneering researcher in this field within China.He has developed an orbital-based molecular ionization model and a laser field-assisted molecular dissociation model to elucidate experimental observations and predict potential applications.The predictions of these models have been corroborated by subsequent theoretical and experimental studies.This review highlights Professor Kong’s significant contributions to the study of molecular ionization and dissociation in intense femtosecond laser fields,emphasizing key advancements and outlining future directions in the field of strong-field laser chemistry.展开更多
Quantum coherence in quantum optics is an essential part of optical information processing and light manipulation.Alkali metal vapors,despite the numerous shortcomings,are traditionally used in quantum optics as a wor...Quantum coherence in quantum optics is an essential part of optical information processing and light manipulation.Alkali metal vapors,despite the numerous shortcomings,are traditionally used in quantum optics as a working medium due to convenient near-infrared excitation,strong dipole transitions and long-lived coherence.Here,we proposed and experimentally demonstrated photon retention and subsequent re-emittance with the quantum coherence in a system of coherently excited molecular nitrogen ions(N_(2)^(+))which are produced using a strong 800 nm femtosecond laser pulse.Such photon retention,facilitated by quantum coherence,keeps releasing directly-unmeasurable coherent photons for tens of picoseconds,but is able to be read out by a time-delayed femtosecond pulse centered at 1580 nm via two-photon resonant absorption,resulting in a strong radiation at 329.3 nm.We reveal a pivotal role of the excited-state population to transmit such extremely weak re-emitted photons in this system.This new finding unveils the nature of the coherent quantum control in N_(2)^(+)for the potential platform for optical information storage in the remote atmosphere,and facilitates further exploration of fundamental interactions in the quantum optical platform with strong-field ionized molecules.展开更多
Quantum interference occurs frequently in the interaction of laser radiation with materials,leading to a series of fascinating effects such as lasing without inversion,electromagnetically induced transparency,Fano res...Quantum interference occurs frequently in the interaction of laser radiation with materials,leading to a series of fascinating effects such as lasing without inversion,electromagnetically induced transparency,Fano resonance,etc.Such quantum interference effects are mostly enabled by single-photon resonance with transitions in the matter,regardless of how many optical frequencies are involved.Here,we report on quantum interference driven by multiple photons in the emission spectroscopy of nitrogen ions that are resonantly pumped by ultrafast infrared laser pulses.In the spectral domain,Fano resonance is observed in the emission spectrum,where a laser-assisted dynamic Stark effect creates the continuum.In the time domain,the fast-evolving emission is measured,revealing the nature of free-induction decay arising from quantum radiation and molecular cooperativity.These findings clarify the mechanism of coherent emission of nitrogen ions pumped with mid-infrared pump laser and are found to be universal.The present work opens a route to explore the important role of quantum interference during the interaction of intense laser pulses with materials near multiple photon resonance.展开更多
Solid-state high-order harmonic generation(HHG)presents a promising approach for achieving controllable broadband coherent light sources and dynamically detecting materials.In this study,we demonstrate the alloptical ...Solid-state high-order harmonic generation(HHG)presents a promising approach for achieving controllable broadband coherent light sources and dynamically detecting materials.In this study,we demonstrate the alloptical control of HHG in a strongly correlated system,vanadium dioxide(VO2),through photo-carrier doping.It has been discovered that HHG can be efficiently modified using a pump laser,achieving modulation depths approaching 100%(extinction ratio≥40 dB)on femtosecond timescales.Quantitative analysis reveals that the driving forces behind pump-dependent HHG are attributed to two distinct many-body dynamics:the scatteringinduced dephasing and the insulator-to-metal transition(IMT)caused by photo-induced electron shielding.These two dynamics play a crucial role in defining the intensity and transient response of the HHG.Furthermore,we demonstrate that it is possible to quantitatively extract the metallic phase fraction from time-resolved HHG(tr-HHG)signals throughout the IMT.This study highlights the benefits of utilizing many-body dynamics for controlling HHG and underscores the necessity for further theoretical research on HHG in strongly correlated systems.展开更多
基金supported by the National Key R&D Program of China(No.2023YFA1406801)the National Natural Science Foundation of China(Nos.12174011,12434013).
文摘Ionization and dissociation are fundamental processes that molecules undergo in intense femtosecond laser fields.Professor Fanao Kong is a pioneering researcher in this field within China.He has developed an orbital-based molecular ionization model and a laser field-assisted molecular dissociation model to elucidate experimental observations and predict potential applications.The predictions of these models have been corroborated by subsequent theoretical and experimental studies.This review highlights Professor Kong’s significant contributions to the study of molecular ionization and dissociation in intense femtosecond laser fields,emphasizing key advancements and outlining future directions in the field of strong-field laser chemistry.
基金the National Natural Science Foundation of China(11822410,12034013,11734009,and 11974245)the National Key R&D Program of China(2017YFA0303701 and 2019YFA0705000)+10 种基金the Shanghai Municipal Science and Technology Major Project(2019SHZDZX01)the Program of Shanghai Academic Research Leader(20XD1424200)the Natural Science Foundation of Shanghai(19ZR1475700)the Strategic Priority Research Program of Chinese Academy of Sciences(XDB16030300)the Key Research Program of Frontier Sciences of Chinese Academy of Sciences(QYZDJ-SSW-SLH010)the Youth Innovation Promotion Association of Chinese Academy of Sciences(2018284)NSF(ECCS-1509268,and CMMI-1826078)AFOSR(FA9550-20-1-0366)partially supported by the Fundamental Research Funds for the Central Universitiesthe support from the Program for Professor of Special Appointment(Eastern Scholar)at Shanghai Institutions of Higher Learningthe support from Shandong Quancheng Scholarship(00242019024)。
文摘Quantum coherence in quantum optics is an essential part of optical information processing and light manipulation.Alkali metal vapors,despite the numerous shortcomings,are traditionally used in quantum optics as a working medium due to convenient near-infrared excitation,strong dipole transitions and long-lived coherence.Here,we proposed and experimentally demonstrated photon retention and subsequent re-emittance with the quantum coherence in a system of coherently excited molecular nitrogen ions(N_(2)^(+))which are produced using a strong 800 nm femtosecond laser pulse.Such photon retention,facilitated by quantum coherence,keeps releasing directly-unmeasurable coherent photons for tens of picoseconds,but is able to be read out by a time-delayed femtosecond pulse centered at 1580 nm via two-photon resonant absorption,resulting in a strong radiation at 329.3 nm.We reveal a pivotal role of the excited-state population to transmit such extremely weak re-emitted photons in this system.This new finding unveils the nature of the coherent quantum control in N_(2)^(+)for the potential platform for optical information storage in the remote atmosphere,and facilitates further exploration of fundamental interactions in the quantum optical platform with strong-field ionized molecules.
基金supported in part by the National Natural Science Foundation of China(Grant Nos.12034013,12234020,12204308,12174011,and 12104380)the Shanghai Science and Technology Commission(Grant No.22ZR1444100)+1 种基金the Early Career Scheme(No.9048216)NSFC/RGC Collaborative Research Scheme(No.9054901)from the Research Grants Council of Hong Kong.
文摘Quantum interference occurs frequently in the interaction of laser radiation with materials,leading to a series of fascinating effects such as lasing without inversion,electromagnetically induced transparency,Fano resonance,etc.Such quantum interference effects are mostly enabled by single-photon resonance with transitions in the matter,regardless of how many optical frequencies are involved.Here,we report on quantum interference driven by multiple photons in the emission spectroscopy of nitrogen ions that are resonantly pumped by ultrafast infrared laser pulses.In the spectral domain,Fano resonance is observed in the emission spectrum,where a laser-assisted dynamic Stark effect creates the continuum.In the time domain,the fast-evolving emission is measured,revealing the nature of free-induction decay arising from quantum radiation and molecular cooperativity.These findings clarify the mechanism of coherent emission of nitrogen ions pumped with mid-infrared pump laser and are found to be universal.The present work opens a route to explore the important role of quantum interference during the interaction of intense laser pulses with materials near multiple photon resonance.
基金National Key Research and Development Program of China(2022YFA1604301,2023YFA1406801)National Natural Science Foundation of China(12174011,12404393,92250305).
文摘Solid-state high-order harmonic generation(HHG)presents a promising approach for achieving controllable broadband coherent light sources and dynamically detecting materials.In this study,we demonstrate the alloptical control of HHG in a strongly correlated system,vanadium dioxide(VO2),through photo-carrier doping.It has been discovered that HHG can be efficiently modified using a pump laser,achieving modulation depths approaching 100%(extinction ratio≥40 dB)on femtosecond timescales.Quantitative analysis reveals that the driving forces behind pump-dependent HHG are attributed to two distinct many-body dynamics:the scatteringinduced dephasing and the insulator-to-metal transition(IMT)caused by photo-induced electron shielding.These two dynamics play a crucial role in defining the intensity and transient response of the HHG.Furthermore,we demonstrate that it is possible to quantitatively extract the metallic phase fraction from time-resolved HHG(tr-HHG)signals throughout the IMT.This study highlights the benefits of utilizing many-body dynamics for controlling HHG and underscores the necessity for further theoretical research on HHG in strongly correlated systems.
