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Phase-coherence dynamics of frequency-comb emission via high-order harmonic generation in few-cycle pulse trains

Chinese Physics B 2023年第3期32卷 205-211页

作者：梁畅通张晶晶李鹏程 Research Center for Advanced Optics and Photoelectronics Department of PhysicsCollege of ScienceShantou UniversityShantou 515063China Key Laboratory of Intelligent Manufacturing Technology of the Ministry of Education Shantou UniversityShantou 515063China Institute of Applied Physics and Computational Mathematics Beijing 100088China

Frequency-comb emission via high-order harmonic generation(HHG)provides an alternative method for the coherent vacuum ultraviolet(VUV)and extreme ultraviolet(XUV)radiation at ultrahigh repetition *** particular,the temporal and spectral features of the HHG were shown to carry profound insight into frequency-comb emission *** we present an ab initio investigation of the temporal and spectral coherence of the frequency comb emitted in HHG of He atom driven by few-cycle pulse *** find that the emission of frequency combs features a destructive and constructive coherences caused by the phase interference of HHG,leading to suppression and enhancement of frequency-comb *** results reveal intriguing and substantially different nonlinear optical response behaviors for frequency-comb emission via *** dynamical origin of frequency-comb emission is clarified by analyzing the phase coherence in HHG processes in *** results provide fresh insight into the experimental realization of selective enhancement of frequency comb in the VUV–XUV regimes.

关键词： high-order harmonic generation frequency comb time-dependent Schro¨dinger equation intense laser field systems

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Probing subcycle spectral structures and dynamics of high-order harmonic generation in crystals

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Chinese Physics B 2022年第9期31卷 273-280页

作者： Long Lin Tong-Gang Jia Zhi-Bin Wang Peng-Cheng Li Research Center for Advanced Optics and Photoelectronics Department of PhysicsCollege of ScienceShantou UniversityShantou 515063China Key Laboratory of Intelligent Manufacturing Technology of MOE Shantou UniversityShantou 515063China College of Physics and Electronic Engineering Northwest Normal UniversityLanzhou 730070China

Subcycle spectral structures and dynamics of high-order harmonic generation(HHG)processes of atoms and molecules driven by intense laser fields on the attosecond time scale have been originally studied theoretically and ***,the time scale of HHG dynamics in crystals is in the order of sub-femtosecond,and the carrier dynamics of HHG in crystals driven by subcycle laser pulses are largely *** we perform a theoretical study of subcycle structures,spectra,and dynamics of HHG of crystals in mid-infrared laser fields subject to excitation by a subcycle laser pulse with a time *** HHG spectra as a function of time delay between two laser fields are cal-culated by using a single-band model for the intra-band carrier dynamics in crystal momentum space and by solving the time-dependent Schr?dinger equation in velocity gauge for the treatment of multi-band crystal *** results exhibit a complex time-delay-dependent oscillatory pattern,and the enhancement and suppression of the HHG related to subcycle pulse are observed at the given time delay in either single-band or multi-band crystal *** understand oscillation structures with respect to the dependence for the subcycle laser fields,the time-frequency characteristics of the HHG as well as the probability density distribution of the radiation are analyzed in detail.

关键词： high-order harmonic generation carrier dynamics subcycle laser pulses crystal systems

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Effect of orbital symmetry on atomic ionization in near-infrared laser fields

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Chinese Physics B 2025年第1期34卷 289-292页

作者： Manqi Xu Shilin Hu Li Guo Jing Chen Research Center for Advanced Optics and Photoelectronics Department of PhysicsCollege of ScienceShantou UniversityShantou 515063China Key Laboratory of Intelligent Manufacturing Technology of MOE Shantou UniversityShantou 515063China Department of Physics Shanghai Normal UniversityShanghai 200234China Hefei National Research Center for Physical Sciences at the Microscale and School of Physical Sciences Department of Modern PhysicsUniversity of Science and Technology of ChinaHefei 230026China Shenzhen Key Laboratory of Ultraintense Laser and Advanced Material Technology Center for Advanced Material Diagnostic Technologyand College of Engineering PhysicsShenzhen Technology UniversityShenzhen 518118China

We have performed a comparative study of the photoelectron spectra adopting different initial states(2s or 2_(p0))of hydrogen atoms in a near-infrared laser pulse by using the full three-dimensional time-dependent Schr?dinger *** is demonstrated that the atomic photoelectron spectra oscillate out of step as a function of electron kinetic energies for different initial states(2s or 2_(p0)),which is well reproduced by the simulations based on strong field approximation,and the above distinct feature is ascribed to the different interferences from the partial electron wave packets detached by positive and negative electric fields for different initial states of 2s and 2_(p0).

关键词： orbital symmetry photoelectron spectra strong-field approximation

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Multiple topological transitions and spectral singularities in non-Hermitian Floquet systems

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Physical Review B 2024年第15期110卷 155413页

作者： Weiwei Zhu Longwen Zhou Linhu Li Jiangbin Gong College of Physics and Optoelectronic Engineering Engineering Research Center of Advanced Marine Physical Instruments and Equipment of Education Ministry Qingdao Key Laboratory for Optics Photoelectronics Guangdong Provincial Key Laboratory of Quantum Metrology and Sensing & School of Physics and Astronomy Department of Physics

The interplay between Floquet driving and non-Hermitian gain/loss could give rise to intriguing phenomena including topological funneling of light, edge-state delocalization, anomalous topological transitions and Floquet non-Hermitian skin effects. In this work, we uncover two unique phenomena in Floquet systems caused by gain and loss. First, multiple topological transitions from anomalous Floquet second-order topological insulators to anomalous Floquet first-order topological insulators and then to normal insulators can be induced by gain and loss. Interestingly, the resulting anomalous Floquet insulators further carry hybrid skin-topological boundary modes, which could either be fully localized or localized to different edges at different time slices and traversing along all edges in a single driving period. The topological phase transitions are also shown to be detectable through studies of transmission properties in the setting of coupled ring resonators. Second, gain and loss are found to induce singularities in the Floquet spectral, around which anomalous transmissions at flat quasienergy bands are predicted. These discoveries not only enhanced our understanding of topological matter and phase transitions in driven non-Hermitian systems, but also promoted their experimental realizations in optical and acoustic settings.

关键词： Edge states Photonic crystals Quantum phase transitions Topological phase transition Floquet systems Non-Hermitian systems Bloch-Floquet theorem Tight-binding model Transfer matrix method

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Floquet π Exceptional Points

arXiv

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arXiv 2024年

作者： Zhu, Weiwei College of Physics and Optoelectronic Engineering Ocean University of China Qingdao266100 China Key Laboratory for Optics Photoelectronics Qingdao266100 China Engineering Research Center of Advanced Marine Physical Instruments and Equipment of MOE Qingdao266100 China

We report a new kind of exceptional points in periodically driven system, called Floquet π exceptional points, whose eigenvectors rotate on Bloch sphere and accumulate π geometric phase in one time period. The merging of two such kind exceptional points are constrained by their dynamical structure, meaning two order-1/2 exceptional points with same dynamical structure can merge to one order-1 one while those with opposite dynamical structure can not. We show they exist in Floquet bipartite lattices, and the order-1 Floquet π exceptional points appear at the phase transition point between quasimomentum gap phases and quasienergy gap phases. The scattering properties around the order-1 Floquet π exceptional points is quite novel, which is perfect transparency but detectable in reflection for one of two sides. Copyright © 2024, The Authors. All rights reserved.

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Coherent enhancement of a frequency comb modulated by a terahertz laser field in high-order harmonic generation

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Physical Review A 2023年第4期108卷 043101-043101页

作者： Yuan-Yuan Wu Chang-Tong Liang Bao-Guang Zhao Peng-Cheng Li Research Center for Advanced Optics and Photoelectronics Department of Physics College of Science Shantou University Shantou Guangdong 515063 China Key Laboratory of Intelligent Manufacturing Technology of MOE Shantou University Shantou Guangdong 515063 China Institute of Applied Physics and Computational Mathematics Beijing 100088 China

We present the coherent enhancement of the frequency comb via high-order harmonic generation (HHG) in a train of infrared laser pulses combined with terahertz (THz) laser fields. The HHG spectra are obtained by solving the three-dimensional time-dependent Schrödinger equation by means of the time-dependent generalized pseudospectral method. We find that the structure of the frequency comb via HHG becomes much smoother and more regular, and the yield of the comb is increased by nearly two orders of magnitude. By analyzing the phase coherence of HHG spectra, we demonstrate that the THz laser fields are responsible for the optimization of the structure and yield of the frequency comb since the constructive phase coherence of the HHG spectra is modulated by the THz field. The physical origin of the constructive phase coherence is thanks to the uniform ionization efficiency induced by the THz laser field for each laser pulse, which greatly improves the synchronization of the harmonic emission. Our finding provides a promising method for the enhancement of the frequency comb via HHG.

关键词： Atomic & molecular processes in external fields High-order harmonic generation Light-matter interaction Ultrafast phenomena

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Coherent Control of High Harmonic Generation Driven by Metal Nanotip Photoemission

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Chinese Physics Letters 2021年第6期38卷 30-34页

作者： Hongdan Zhang Xiwang Liu Facheng Jin Ming Zhu Shidong Yang Wenhui Dong Xiaohong Song Weifeng Yang Research Center for Advanced Optics and Photoelectronics Department of PhysicsCollege of ScienceShantou UniversityShantou 515063China Institute of Mathematics Shantou UniversityShantou 515063China Key Laboratory of Intelligent Manufacturing Technology of MOE Shantou UniversityShantou 515063China Faculty of Science Xi'an Aeronautical UniversityXi'an 710077China

Steering ultrafast electron dynamics with well-controlled laser fields is very important for generation of intense supercontinuum *** can be achieved through coherent control of the symmetry of the interaction between strong-field laser fields and a metal *** employ a scheme of two-color laser pulses combined with a weak static field to realize the control of a single quantum path to generate high harmonic generation from a single solid-state ***,a smooth and ultrabroad supercontinuum in the extreme ultraviolet region is obtained,which can produce a single attosecond *** findings are beneficial for efficient generation of isolated sub-100 as XUV pulses from solid-state sources.

关键词： Harmonic ultraviolet tip

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Parity effects in Rydberg-state excitation in intense laser fields

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Photonics Research 2024年第12期12卷 3033-3039页

作者： YANG LIU XIAOPENG YI QI CHEN TIAN SUN HANG LV SHILIN HU WILHELM BECKER HAIFENG XU JING CHEN Institute of Atomic and Molecular Physics Jilin UniversityChangchun 130012China Institute of Applied Physics and Computational Mathematics Beijing 100088China Research Center for Advanced Optics and Photoelectronics Department of PhysicsCollege of ScienceShantou UniversityShantou 515063China Key Laboratory of Intelligent Manufacturing Technology of MOE Shantou UniversityShantou 515063China Max-Born-Institut 12489 BerlinGermany Hefei National Laboratory Department of Modern PhysicsUniversity of Science and Technology of ChinaHefei 230026China Shenzhen Key Laboratory of Ultraintense Laser and Advanced Material Technology Center for Advanced Material Diagnostic Technologyand College of Engineering PhysicsShenzhen Technology UniversityShenzhen 518118China

Conservation of parity plays a fundamental role in our understanding of various quantum ***,it is difficult to observe in atomic and molecular processes induced by a strong laser field due to their multiphoton character and the large number of states *** we report an effect of parity in strong-field Rydberg-state excitation(RSE)by comparing the RSE probabilities of the N_(2) molecule and its companion atom Ar,which has a similar ionization potential but opposite parity of its ground ***,we observe an oscillatory structure as a function of intensity with a period of about 50 TW∕cm^(2) in the ratio between the RSE yields of the two species,which can be reproduced by simulations using the time-dependent Schrödinger equation(TDSE).We analyze a quantum-mechanical model,which allows for interference of electrons captured in different spatial regions of the Rydberg-state wave *** the intensity-dependent RSE yield,it results in peaks with alternating heights with a spacing of 25 TW∕cm^(2) and at the same intensity for both ***,due to the opposite parities of their ground states,pronounced RSE peaks in Ar correspond to less pronounced peaks in N_(2) and vice versa,which leads to the period of 50 TW∕cm^(2) in their *** work reveals a novel parity-related interference effect in the coherent-capture picture of the RSE process in intense laser fields.

关键词： function parity Rydberg

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Convenient connectorization technique between single mode polymer optical fiber and single mode silica optical fiber 8

Convenient connectorization technique between single mode po...

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8th Symposium on Novel Photoelectronic Detection Technology and Applications

作者： Yue, Xiaoyu Qu, Hang Min, Rui Woyessa, Getinet Bang, Ole Hu, Xuehao Research Center for Advanced Optics and Photoelectronics Department of Physics College of Science Shantou University Guangdong Shantou515063 China Key Laboratory of Intelligent Manufacturing Technology of MOE Shantou University Guangdong Shantou515063 China Center for Cognition and Neuroergonomics State Key Laboratory of Cognitive Neuroscience and Learning Beijing Normal University at Zhuhai Zhuhai519087 China DTU Fotonik Department of Photonics Engineering Technical University of Denmark Kgs. Lyngby 2800 Denmark

ISBN: (数字)9781510653122

ISBN: (纸本)9781510653115

Bragg gratings can now be produced in various types of polymer optical fibers. However, compared to silica optical fibers, it is still difficult to obtain highly reflective gratings in polymer optical fibers because of material swelling resulting from larger UV absorption. Thus, real-time grating evolution monitoring in whole inscription process is highly demanded. In this paper, a convenient method is systematically introduced using an objective imaging system for permanent fiber alignment between a polymer optical fiber and a silica optical fiber before inscription process allowing analyzing spectral evolution for further grating improvement. Finally, the performance of fiber connectorization is evaluated with a core coupling loss of ~ -6.33 dB. © 2022 SPIE

关键词： Fiber Bragg gratings

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Multiphoton quantum dynamics of many-electron atomic and molecular systems in intense laser fields

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Chinese Physics B 2020年第8期29卷 115-126页

作者： Peng-Cheng Li Shih-I Chu Research Center for Advanced Optics and Photoelectronics Department of PhysicsCollege of ScienceShantou UniversityShantou 515063China Key Laboratory of Intelligent Manufacturing Technology of MOE Shantou UniversityShantou 515063China Department of Chemistry University of KansasLawrenceKansas 66045USA

We present the recent new developments of time-dependent Schrödinger equation and time-dependent density-functional theory for accurate and efficient treatment of the electronic structure and time-dependent quantum dynamics of many-electron atomic and molecular systems in intense laser *** extend time-dependent generalized pseudospectral(TDGPS)numerical method developed for time-dependent wave equations in multielectron *** TDGPS method allows us to obtain highly accurate time-dependent wave functions with the use of only a modest number of spatial grid point for complex quantum dynamical *** usefulness of these procedures is illustrated by a few case studies of atomic and molecular processes of current interests in intense laser fields,including multiphoton ionization,above-threshold ionization,high-order harmonic generation,attosecond pulse generation,and quantum dynamical processes related to multielectron *** conclude this paper with some open questions and perspectives of multiphoton quantum dynamics of many-electron atomic and molecular systems in intense laser fields.

关键词： multiphoton ionization above-threshold ionization high-order harmonic generation attosecond pulse generation

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