14 results on '"Zhang, Qingbin"'
Search Results
2. Compact dual-crystal optical parametric amplification for broadband IR pulse generation using a collinear geometry.
- Author
-
Hong Z, Zhang Q, and Lu P
- Subjects
- Equipment Design, Equipment Failure Analysis, Infrared Rays, Amplifiers, Electronic, Fiber Optic Technology instrumentation, Lasers, Lighting instrumentation
- Abstract
A novel compact dual-crystal optical parametric amplification (DOPA) scheme, collinearly pumped by a Ti:sapphire laser (0.8 μm), is theoretically investigated for efficiently generating broadband IR pulses at non-degenerate wavelengths (1.2 μm~1.4 μm and 1.8 μm~2.1 μm). By inserting a pair of barium fluoride (BaF(2)) wedges between two thin β-barium borate (BBO) crystals, the group velocity mismatch (GVM) between the three interacting pulses can be compensated simultaneously. In this case, the obtained signal spectrum centered at 1.3 μm is nearly 20% broader and the conversion efficiency is increased, but also the pulse contrast and beam quality are improved due to the better temporal overlap. Furthermore, sub-two-cycle idler pulses with carrier-envelope phase (CEP) fluctuation of sub-100-mrad root mean square (RMS) can be generated. Because a tunable few-cycle IR pulse with millijoule energy is attainable in this scheme, it will contribute to ultrafast community and be particularly useful as a driving or controlling field for the generation of ultrafast coherent x-ray supercontinuum.
- Published
- 2013
- Full Text
- View/download PDF
3. Quantum-orbit analysis for yield and ellipticity of high order harmonic generation with elliptically polarized laser field.
- Author
-
Li Y, Zhu X, Zhang Q, Qin M, and Lu P
- Subjects
- Computer Simulation, Light, Lasers, Models, Theoretical, Scattering, Radiation
- Abstract
We perform a quantum-orbit analysis for the dependence of high-order-harmonic yield on the driving field ellipticity and the polarization properties of the generated high harmonics. The electron trajectories responsible for the emission of particular harmonics are identified. It is found that, in elliptically polarized driving field, the electrons have ellipticity-dependent initial velocities, which lead to the decrease of the ionization rate. Thus the harmonic yield steeply decreases with laser ellipticity. Besides, we show that the polarization properties of the harmonics are related to the complex momenta of the electron. The physical origin of the harmonic ellipticity is interpreted as the consequence of quantum-mechanical uncertainty of the electron momentum. Our results are verified with the experimental results as well as the numerical solutions of the time dependent Schrödinger equation from the literature.
- Published
- 2013
- Full Text
- View/download PDF
4. Ultra-broadband water window supercontinuum generation with high efficiency in a three-color laser field.
- Author
-
He L, Li Y, Zhang Q, and Lu P
- Subjects
- Computer Simulation, Computer-Aided Design, Equipment Design, Equipment Failure Analysis, Water, Color, Lasers, Models, Theoretical
- Abstract
We propose an efficient method to generate an ultra-broadband supercontinuum by using a three-color field synthesized by a 1600 nm driving pulse and two weak (3200 nm and 400 nm) control pulses. The results show that the acceleration and ionization steps in the HHG process are simultaneously controlled in our scheme, which can not only broaden the bandwidth but also enhance the harmonic yields of the generated spectrum. Thus a high-efficiency supercontinuum with the photon energies ranging from 205 eV to 480 eV is observed. Based on our 3D propagation simulations, we show that the short quantum path of the supercontinuum is well phase-matched and can be selected under suitable propagation conditions. Thereby, the modulation due to quantum path interference is largely reduced and intense isolated sub-100 as pulses with tunable central wavelengths are directly obtained within water window spectral region.
- Published
- 2013
- Full Text
- View/download PDF
5. Dramatic cutoff extension and broadband supercontinuum generation in multi-cycle two color pulses.
- Author
-
Luo J, Hong W, Zhang Q, Liu K, and Lu P
- Subjects
- Equipment Design, Equipment Failure Analysis, Color, Lasers
- Abstract
We propose a method to markedly increase the electron-recollision kinetic energy, using the combination of a 0.8 μm/13 fs driving pulse with a much weaker multi-cycle mid-infrared pulse at 10.4 μm. The results show that the synthesized field effectively lengthens the accelerated distance of electron wave packet and the harmonic cutoff is significantly extended to IP+26UP, which is covered with the water-window spectral region. In addition, only one single quantum path contributes to harmonics, and those higher than IP+15UP become continuous. This supercontinuum can support the generation of an isolated sub-100 as pulse with tunable central wavelength and also the pulse with the duration below one atomic unit of time (24 as). Moreover, our scheme can further extend to more longer driving pulses, which provides a dramatic approach for cutoff extension and broadband supercontinuum generation with multi-cycle pump pulses., (© 2012 Optical Society of America)
- Published
- 2012
- Full Text
- View/download PDF
6. Wavelength dependence of electron localization in the laser-driven dissociation of H2(+).
- Author
-
Liu K, Hong W, Zhang Q, and Lu P
- Subjects
- Computer Simulation, Electrons, Light, Scattering, Radiation, Hydrogen chemistry, Lasers, Models, Chemical
- Abstract
We theoretically investigate the laser wavelength dependence of asymmetric dissociation of H2(+). It is found that the electron localization in molecular dissociation is significantly manipulated by varying the wavelength of the driving field. Through creating a strong nuclear vibration in the laser-molecular interaction, our simulations demonstrate that the few-cycle mid-infrared pulse can effectively localize the electron at one of the dissociating nuclei with weak ionization. Moreover, we show that the observed phase-shift of the dissociation asymmetry is attributed to the different population transfers by the remaining fields after the internuclear distances reach the one-photon coupling point.
- Published
- 2011
- Full Text
- View/download PDF
7. Laser-polarization-dependent photoelectron angular distributions from polar molecules.
- Author
-
Zhu X, Zhang Q, Hong W, Lu P, and Xu Z
- Subjects
- Electrons, Photons, Scattering, Radiation, Static Electricity, Carbon Monoxide chemistry, Carbon Monoxide radiation effects, Lasers, Micromanipulation methods, Refractometry methods
- Abstract
Photoelectron angular distributions (PADs) of oriented polar molecules in response to different polarized lasers are systematically investigated. It is found that the PADs of polar CO molecules show three distinct styles excited by linearly, elliptically and circularly polarized lasers respectively. In the case of elliptical polarization, a deep suppression is observed along the major axis and the distribution concentrates approximately along the minor axis. Additionally, it is also found that the concentrated distributions rotate clockwise as the ellipticity increases. Our investigation presents a method to manipulate the motion and angular distribution of photoelectrons by varying the polarization of the exciting pulses, and also implies the possibility to control the processes in laser-molecule interactions in future work., (© 2011 Optical Society of America)
- Published
- 2011
- Full Text
- View/download PDF
8. Mid-infrared laser-driven broadband water-window supercontinuum generation from pre-excited medium.
- Author
-
Li Y, Hong W, Zhang Q, Wang S, and Lu P
- Subjects
- Computer Simulation, Infrared Rays, Light, Scattering, Radiation, Lasers, Models, Theoretical, Water chemistry
- Abstract
We theoretically investigate the broadband water-window supercontinuum generation from pre-excited medium with a mid-infrared pulse. We find that the wavelength scaling of the harmonic yield from near-visible (0.8 μm) to mid-infrared (1.8 μm) in single-atom level is λ(-2.7). Using an intense phase-stabilized few-cycle 1.6 μm laser pulse, a broadband water window supercontinuum with bandwidth of approximately 140 eV is obtained. We also investigate the macroscopic effects and find that large initial population of the excited state leads to the high-density of free electrons, which shift the carrier-envelop phase of the driving pulse and further diminish the water-window supercontinuum generation. The highly-ionized medium also results in poor temporal and spatial properties of the attosecond pulse. Instead, small initial population of the excited state can produce well phase-matched xuv supercontinuum in water-window region and an 100-as pulse with central wavelength of 2.8 nm and pulse energy of 0.15 nJ can be filtered out., (© 2011 Optical Society of America)
- Published
- 2011
- Full Text
- View/download PDF
9. Intense isolated attosecond pulse generation in pre-excited medium.
- Author
-
Hong W, Zhang Q, Zhu X, and Lu P
- Subjects
- Computer Simulation, Computer-Aided Design, Equipment Design, Equipment Failure Analysis, Light, Scattering, Radiation, Lasers, Lighting, Models, Theoretical
- Abstract
We present a theoretical study of isolated attosecond pulse generation in pre-excited medium driven by an intense few-cycle laser pulse. We show that the generation of the macroscopic xuv supercontinuum is governed by the initial population of the excited state. Large initial population of the excited state leads to the high density of the free electrons in the media and strongly changes macroscopic properties of the driving pulse and the supercontinuum, and diminishes the isolated attosecond pulse generation. Instead, small initial population of 5% in the pre-excited media subjected to the few-cycle driving pulse can produce well phase-matched xuv supercontinuum, and a pure intense isolated attosecond pulse with the pulse duration of approximately 150 as and the pulse energy up to 0.5 nJ is directly obtained.
- Published
- 2011
- Full Text
- View/download PDF
10. Double ionization of HeH+ molecules in intense laser fields.
- Author
-
Liao Q, Lu P, Zhang Q, Yang Z, and Wang X
- Subjects
- Computer Simulation, Helium radiation effects, Hydrogen radiation effects, Ions, Light, Radiation Dosage, Scattering, Radiation, Helium chemistry, Hydrogen chemistry, Lasers, Models, Chemical
- Abstract
We present quantum mechanical calculations of double ionization of HeH(+) molecules by intense laser pulses at various intensities. The resulting two-electron momentum distributions exhibit a clear asymmetry, which depends on the laser intensity. The asymmetric charge configuration of HeH(+) is responsible for the asymmetric two-electron momentum distributions. An approach to control the dynamics of double ionization of heteronuclear molecules is proposed.
- Published
- 2008
- Full Text
- View/download PDF
11. Multi-cycle laser-driven broadband supercontinuum with a modulated polarization gating.
- Author
-
Zhang Q, Lu P, Lan P, Hong W, and Yang Z
- Subjects
- Computer Simulation, Equipment Design, Equipment Failure Analysis, Light, Scattering, Radiation, Lasers, Models, Theoretical, Refractometry instrumentation
- Abstract
We propose a method to generate broadband supercontinuum with a modulated polarization gating in the multi-cycle regime. The polarization gating at 1600 nm is employed to intensify the ellipticity dependence of high harmonic signal, and the adding second harmonic (SH) field is used for modulating ionization ratio between the driving field half-cycles. It is shown that longer driving pulses (6 optical cycles, 32.4 fs) can be applied to confine the efficient recollision of electron wave packet to half an optical cycle. The produced bandwidth of the extreme ultraviolet (XUV) supercontinuum is about 280 eV, corresponding to a fourier-transform-limited pulse of 10 as. In addition, an attosecond pulse of about 100 as with tunable wavelength can be straightforwardly obtained just by filtering different range of the spectrum.
- Published
- 2008
- Full Text
- View/download PDF
12. Helicity dependent Wigner phase shift for photoionization in a circularly polarized laser field.
- Author
-
Wang, Run, Zhang, Qingbin, Cao, Chuanpeng, Li, Min, Liu, Kunlong, and Lu, Peixiang
- Subjects
- *
ATTOSECOND pulses , *COULOMB potential , *LASERS , *ATOMIC orbitals , *PHYSICISTS , *PHOTOIONIZATION , *SPINTRONICS - Abstract
The sensitivity of strong-field ionization to atomic orbital helicity has attracted much attention from physicists, due to its potential application in attosecond spectroscopy and spintronics. In order to intuitively observe the physical mechanisms of helicity-dependent ionization rates during photoionization, the concept of the Wigner phase can be used to characterize the different interactions between the rotating electrons and the Coulomb potential. Here, we find that in both one- and three-photon ionization schemes, the electrons liberated more easily by the circularly polarized laser field suffer less influence of the Coulomb potential during the propagation and then accumulate less Winger phase. This result indicates that the strength of the interaction between the rotating electrons and the Coulomb potential can explain the helicity-dependent ionization for different ionization mechanisms universally, which is also supported by our classical ensemble analysis. Our work provides an intuitive perspective towards the physics picture of ionization propensity rules. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
13. Probing time delay of strong-field resonant above-threshold ionization.
- Author
-
Xu, Shengliang, Zhang, Qingbin, Ran, Cheng, Huang, Xiang, Cao, Wei, and Lu, Peixiang
- Subjects
- *
RYDBERG states , *PHOTOELECTRONS , *MOMENTUM distributions , *LASER ultrasonics , *IMAGE reconstruction , *RESONANT vibration , *LASERS - Abstract
The high-resolution three-dimensional photoelectron momentum distributions via above-threshold ionization (ATI) of Xe atoms are measured in an intense near circularly polarized laser field using velocity map imaging and tomography reconstruction. Compared to the linearly polarized laser field, the employed near circularly polarized laser field imposes a more strict selection rule for the transition via resonant excitation, and therefore we can selectively enhance the resonant ATI through certain atomic Rydberg states. Our results show the self-reference ionization delay, which is determined from the difference between the measured streaking angles for nonadiabatic ATI via the 4f and 5f Rydberg states, is 45.6 as. Our method provides an accessible route to highlight the role of resonant transition between selected states, which will pave the way for fully understanding the ionization dynamics toward manipulating electron motion as well as reaction in an ultrafast time scale. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
14. Two-color laser driven enhanced electron emission from carbon nanotubes with long carrier lifetime.
- Author
-
Cao, Jinxing, Wang, Can, Hu, Feilong, Zhang, Qingbin, and Lu, Peixiang
- Subjects
- *
ELECTRON emission , *CARBON nanotubes , *FIELD emission , *CARBON emissions , *FEMTOSECOND lasers , *LASERS , *OPTOELECTRONIC devices - Abstract
Ultrafast electron pulses generated using femtosecond lasers offer a direct means for investigating ultrafast processes, but the yield of electron emission remains a significant practical limitation. This study demonstrates a substantial enhancement in yield of electron emission from carbon nanotubes induced by two-color (ω + 2 ω) pulses with an 80 MHz repetition rate and this enhancement is non-delay-dependent. Compared to the sum of photocurrents induced by each color pulse individually, the combined two-color pulses result in a remarkable enhancement in yield of electron emission by more than 25 times. We attribute this enhanced yield to carrier-assisted optical field emission: carbon nanotubes sustain high carrier concentration state under laser radiation thereby enhancing yield of electron emission. We propose the carrier migration emission model to provide a semi-quantitative description for the carrier-assisted optical field emission. This phenomenon introduces a new method to increase the yield of ultrafast electron pulses from CNTs and paves the way for next-generation ultrafast electron emitters and on chip ultrafast optoelectronic device. [Display omitted] [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
Catalog
Discovery Service for Jio Institute Digital Library
For full access to our library's resources, please sign in.