Xiaohong Song

Universität Paderborn, Paderborn, North Rhine-Westphalia, Germany

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Publications (30)78.22 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: We investigate the carrier–envelope phase dependence of the unipolar half-cycle soliton pulse generation when few-cycle ultrashort laser pulses propagate in resonant asymmetric media. It is found that the half-cycle soliton pulse generation depends on both the permanent dipole moment and the electric field shape of the incident few-cycle ultrashort pulse. The irradiation of low-frequency electromagnetic waves superposes with the incident few-cycle ultrashort pulse, which leads to the generation of half-cycle solitons in quantum systems with broken inversion symmetry. Since the electric field shape of the incident few-cycle ultrashort laser pulse depends sensitively on the carrier–envelope phase, the generated half-cycle solitons depend on the carrier–envelope phase of the incident pulse.
    Laser Physics Letters 04/2014; 11(5):056002. · 7.71 Impact Factor
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    ABSTRACT: We investigate the photoelectron momentum distribution of molecular-ion H2+driven by ultrashort intense circularly polarized laser pulses. Both numerical solutions of the time-dependent Schrödinger equation (TDSE) and a quasiclassical model indicate that the photoelectron holography (PH) with circularly polarized pulses can occur in molecule. It is demonstrated that the interference between the direct electron wave and rescattered electron wave from one core to its neighboring core induces the PH. Moreover, the results of the TDSE predict that there is a tilt angle between the interference pattern of the PH and the direction perpendicular to the molecular axis. Furthermore, the tilt angle is sensitively dependent on the wavelength of the driven circularly polarized pulse, which is confirmed by the quasiclassical calculations. The PH induced by circularly polarized laser pulses provides a tool to resolve the electron dynamics and explore the spatial information of molecular structures.
    Optics Express 02/2014; 22(3):2519-27. · 3.55 Impact Factor
  • 11/2013;
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    ABSTRACT: Using a finite-difference time-domain method, we theoretically investigate the optical spectra of crossing perpendicular photonic crystal waveguides with quantum dots embedded in the central rod. The waveguides are designed so that the light mainly propagates along one direction and the cross talk is greatly reduced in the transverse direction. It is shown that when a quantum dot (QD) is resonant with the cavity, strong coupling can be observed via both the transmission and crosstalk spectrum. If the cavity is far off-resonant from the QD, both the cavity mode and the QD signal can be detected in the transverse direction since the laser field is greatly suppressed in this direction. This structure could have strong implications for resonant excitation and in-plane detection of QD optical spectroscopy.
    Optics Express 06/2012; 20(13):14130-6. · 3.55 Impact Factor
  • Weifeng Yang, Xiaohong Song, Zhangjin Chen
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    ABSTRACT: The carrier-envelope phase (CEP)-dependent above-barrier ionization (ABI) has been investigated in order to probe the bound-state electron dynamics. It is found that when the system is initially prepared in the excited state, the ionization yield asymmetry between left and right sides can occur both in low-energy and high-energy parts of the photoelectron spectra. Moreover, in electron momentum map, a new interference effect along the direction perpendicular to the laser polarization is found. We show that this interference is related to the competition among different excited states. The interference effect is dependent on CEPs of few-cycle probe pulses, which can be used to trace the superposition information and control the electron wave packet of low excited states.
    Optics Express 05/2012; 20(11):12067-75. · 3.55 Impact Factor
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    ABSTRACT: We present a method to generate an extremely short unipolar half-cycle pulse based on resonant propagation of a few-cycle pulse through asymmetrical media with periodic subwavelength structure. Moreover, single- and few-cycle gap solitons with different frequencies are found to split from one incident few-cycle ultrashort pulse. These solitons with various frequencies provide evidence for the generation of different parametric waves during the strong light-matter coupling in asymmetrical media under the extreme nonlinear optics condition. Because of the pulse self-shaping process during the course of resonant propagation, the generated low-frequency sideband and another broadband continuum sideband ranging from the visible to the near-infrared regime couple together, which results in the generation of the subfemtosecond unipolar half-cycle pulse. A time-frequency analysis is preformed which corroborates the mechanism. The generated unipolar half-cycle pulse might be utilized to control and probe the ultrafast electronic dynamics.
    Physical Review A 11/2010; · 3.04 Impact Factor
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    ABSTRACT: We report a new quantum path interference effect of electron trajectories in high-order harmonic generation (HHG) from two-center molecules, in which the interference minima are mainly located in the high-energy portion of HHG spectrum. The quantum calculations of the time-frequency analyses and the classical results of the electron trajectories demonstrate very good agreement and reveal that the positions of the interference minima are associated with the cutoff of various kinds of molecular electron trajectories. The interference fringes within a half optical cycle can be clearly seen in the time-frequency analysis spectrum. Moreover, the characteristics of both the HHG in frequency domain and the corresponding attosecond pulse generation in time domain permit tracing back the interference information of these electron trajectories. These interference phenomena offer new possibilities for getting insight into the attosecond electronic dynamics in molecules.
    Optics Express 02/2010; 18(3):2558-65. · 3.55 Impact Factor
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    ABSTRACT: We investigate the local field effects in a ZnO dense medium. Our results show due to the local-field effects, the Lorentz shifts can be found in the reflected spectra driven by the few-cycle laser pulse. Moreover, the dynamic Lorentz shifts depend sensitively on the carrier-envelope phase (CEP) of the few-cycle laser pulse, which provides a useful means to obtain the CEP information by the frequency shifts.
    Optics Express 11/2009; 17(24):21754-61. · 3.55 Impact Factor
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    ABSTRACT: We investigate the transmitted spectra of a few-cycle ultrashort pulse in an inversion-asymmetric medium with a permanent dipole moment (PDM). Our results show that even-order harmonics can be generated in this medium. Moreover, the generated even-order harmonics depend strongly on the carrier-envelope phase (CEP) of initial incident few-cycle ultrashort pulses. Physical analysis of the re-emitted spectra of the medium reveals that the CEP-dependent spectral effect is originated from the inversion-asymmetric structure and the corresponding PDM effects: two-photon transition dominates in the nonlinear process and further induces the generations of the even-order harmonics. Furthermore, the orientation relation between the electric field peak of the pulse and the PDM results in even-order harmonic generations depending on the CEP.
    Journal of Physics B Atomic Molecular and Optical Physics 08/2009; 42(17):175601. · 2.03 Impact Factor
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    ABSTRACT: We investigate the spectra of two-colour few-cycle pulses in a semiconductor quantum well (QW) with consideration of quantum size effects. Our results show that, in the few-cycle regime, the spectral peak at 4ω0 can be achieved even under the condition of a two-colour ω0 − 3ω0 pulse combination. Moreover, when the quantum size is modified, the enlargement or suppression of the spectral peak at 4ω0 or 5ω0 can be selectively controlled by the relative phase of the two-colour few-cycle pulses.
    Journal of Physics B Atomic Molecular and Optical Physics 05/2009; 42(12):125604. · 2.03 Impact Factor
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    ABSTRACT: The carrier-envelope phase (CEP)–dependent spectral effect of the reflected few-cycle ultrashort pulse from a dense medium is investigated. It is shown that when adding static electric field, a pronounced CEP dependence of the reflected spectrum can be obtained. Moreover, the period of the CEP-dependent signal becomes 2π because the inversion symmetry for laser-matter interaction is broken, which allows for extraction of the CEP information in both sign and amplitude.
    Physical Review A 04/2009; 79(4). · 3.04 Impact Factor
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    ABSTRACT: We investigate the higher spectral component generations driven by a few-cycle laser pulse in a dense medium when a static electric field is present. Our results show that, when assisted by a static electric field, the dependence of the transmitted laser spectrum on the carrier-envelope phase (CEP) is significantly increased. Continuum and distinct peaks can be achieved by controlling the CEP of the few-cycle ultrashort laser pulse. Such a strong variation is due to the fact that the presence of the static electric field modifies the waveform of the combined electric field, which further affects the spectral distribution of the generated higher spectral components.
    Journal of Physics B Atomic Molecular and Optical Physics 02/2009; 42(5):055602. · 2.03 Impact Factor
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    ABSTRACT: We theoretically propose a method of generating a single sub-100 attosecond (as) pulse with a two-colour time-gating laser field. The field is synthesized by an 8 fs/800 nm (three optical cycles) pulse and a 24 fs/2400 nm (three optical cycles) pulse with an optimal time delay between them. In our simulation, we obtain a supercontinuum with an extremely broad spectrum of 150 eV and generate an isolated attosecond pulse with 96 as pulse duration without any dispersion compensation.
    Journal of Physics B Atomic Molecular and Optical Physics 05/2008; 41(11):115601. · 2.03 Impact Factor
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    ABSTRACT: We investigate the carrier-wave Rabi flopping effects in an asymmetric semiparabolic semiconductor quantum well (QW) with few-cycle pulse. It is found that higher spectral components of few-cycle ultrashort pulses in the semiparabolic QW depend crucially on the carrier-envelope phase (CEP) of the few-cycle ultrashort pulses: continuum and distinct peaks can be achieved by controlling the CEP. Our results demonstrate that by adjusting the CEP of few-cycle ultrashort pulses, the intersubband dynamics in the asymmetric semiparabolic QW can be controlled in an ultrashort timescale with moderate laser intensity.
    Optics Express 03/2008; 16(3):1487-96. · 3.55 Impact Factor
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    ABSTRACT: We theoretically demonstrate the generation of extreme ultraviolet supercontinua in an orthogonally polarized two-color few-cycle laser field. We show that the ionized electrons can be driven back to their parent ion after traveling along curved trajectories in a plane perpendicular to the beam propagation direction, giving rise to a train of attosecond pulses at different polarization angles. A single isolated attosecond pulse can be obtained by blocking the low-order high harmonics, which contribute to the formation of the satellite pulses.
    Optics Express 02/2008; 16(2):686-94. · 3.55 Impact Factor
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    ABSTRACT: We theoretically investigate carrier-envelope phase dependence of few-cycle ultrashort laser pulse propagation in a polar molecule medium. Our results show that a soliton pulse can be generated during the two-photon resonant propagation of few-cycle pulse in the polar molecule medium. Moreover, the main features of the soliton pulse, such as pulse duration and intensity, depend crucially on the carrier-envelope phase of the incident pulse, which could be utilized to determine the carrier-envelope phase of a few-cycle ultrashort laser pulse from a mode-locked oscillator.
    Physical Review Letters 10/2007; 99(13):133602. · 7.73 Impact Factor
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    ABSTRACT: By controlling the initial coherent preparation of the medium and the effective area of the incident ultrashort laser pulse, we demonstrate that highly efficient linear-to-circular and circular-to-linear light polarization conversion can be realized in a degenerate three-level medium due to the quantum interference effects between the two different transition paths.
    Conference on Lasers and Electro-Optics/Pacific Rim; 08/2007
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    ABSTRACT: We theoretically investigate the high-order harmonic generation in a helium atom with a two-color optical field synthesized by an intense 6 fs pulse at 800 nm and a relatively weak 21.3 fs pulse at 400 nm. When the frequency-doubled pulse is properly time shifted with respect to the fundamental pulse, an ultrabroad extreme ultraviolet supercontinuum spectrum with a 148 eV spectral width can be generated which directly creates an isolated 65 as pulse even without phase compensation. We explain this extraordinary phenomenon by analyzing maximum electron kinetic energies at different return times.
    Physical Review Letters 06/2007; 98(20):203901. · 7.73 Impact Factor
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    ABSTRACT: Property of the phase of the reemitted field in the semiconductor quantum wells (QWs) excited by femtosecond pulse train is investigated. It is shown that the phase evolution of the reemitted field is controlled by the relative phase between the successive pulses of the incident train. For all the odd pulses excitation, the reemitted field is from out-of-phase to in-phase, then again to out-of-phase with the incident pulses, whereas for all the even pulses excitation, the situation is the opposite, i.e., it is from in-phase to out-of-phase, then again to in-phase with the incident pulses.
    Chinese Optics Letters 05/2007; 5(5):304-307. · 1.07 Impact Factor
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    ABSTRACT: We investigate the propagation of an arbitrary elliptically polarized few-cycle ultrashort laser pulse in resonant two-level quantum systems using an iterative predictor-corrector finite-difference time-domain method. It is shown that when the initial effective area is equal to 2π, the effective area will remain invariant during the course of propagation, and a complete Rabi oscillation can be achieved. However, for an elliptically polarized few-cycle ultrashort laser pulse, polarization conversion can occur. Eventually, the laser pulse will evolve into two separate circularly polarized laser pulses with opposite helicities.
    Physical Review A 07/2006; 74(1). · 3.04 Impact Factor

Publication Stats

198 Citations
78.22 Total Impact Points

Institutions

  • 2012
    • Universität Paderborn
      • Department of Physics
      Paderborn, North Rhine-Westphalia, Germany
  • 2005–2010
    • Chinese Academy of Sciences
      • State Key Laboratory of High Field Laser Physics
      Peping, Beijing, China
  • 2004–2010
    • Northeast Institute of Geography and Agroecology
      • State Key Laboratory of High Field Laser Physics
      Beijing, Beijing Shi, China
  • 2003–2006
    • Shanghai Institute of Optics and Fine Mechanics, CAS
      Shanghai, Shanghai Shi, China