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The laser field controlling on the nonlinear optical specifications of the electric field-triggered Rosen-Morse quantum well
摘要： We consider, for the first time, optical specifications such as the nonlinear optical rectification (NOR), the second harmonic generation (SHG) and the third harmonic generation (THG) of quantum well (QW) that has the Rosen-Morse potential confinement and is generated by GaAs/GaAlAs heterostructure. To do this, QW structure is firstly asymmetrized by applying an external electric field, as 10 kV/cm. Therefore, the electric field-triggered (F = 10 kV/cm) Rosen-Morse QW (eftRMQW) is taken into consideration throughout the study. In this study, it is elucidated that how to control NOR, SHG and THG optical responses through monochromatic linearly polarized intense laser field (ILF). In order to be able to investigate the ILF effects, the time-dependent of ILF is removed to potential energy term of the wave equation by using Kramers-Henneberger (KH) and the dipole approximations, building the laser-dressed potential. Then, the bound state energies and the wave functions of eftRMQW are obtained using the diagonalization method within the effective mass approach and the parabolic approximation. The influences of the ILF and structural parameters of eftRMQW on NOR, SHG and THG coefficients are discussed in detail. The optimum of structure is ferreted out for devices design and applications that will consider eftRMQW, and for this optimum the alternative parameter analysis is carried out.
关键词： Nonlinear optical properties,Laser field,Electric field,Rosen-Morse quantum well
更新于2025-09-23 15:21:01
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Semi-integer harmonic generation from an argon atom by bichromatic counter-rotating circularly polarized laser field
摘要： We theoretically investigated the properties of the high-order harmonic generation from an argon atom by bichromatic counter-rotating circularly polarized (BCCP) laser field. The harmonic spectra are gradually splitting and the harmonic orders move towards the higher frequency. Meanwhile, the integer and semi-integer harmonic emission will be generated when the frequency ratios of right- and left-circularly polarized laser are semi-integer. The emission mechanism of the semi-integer-order harmonics have been investigated by using the rules of photon absorption and emission.
关键词： bichromatic counter-rotating circularly polarized laser field,photon absorption and emission,high-order harmonic generation,semi-integer-order
更新于2025-09-23 15:21:01
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Electron-atom potential scattering in a corotating bicircular laser field
摘要： S-matrix theory is used in order to analyze the energy spectra of electron-atom potential scattering assisted by a bicircular (two-component circularly polarized) laser field having corotating field components. The double scattering (rescattering) is also included in the analysis by applying the second Born approximation in the expansion of the S-matrix element. We have investigated how the energy spectrum of scattered electrons is affected by the scattering angle. We have also analyzed the sensitivity of the energy spectrum to the relative phase and intensity ratio of the laser-field components. The calculated energy spectra are characterized by the plateau-like oscillatory structures with abrupt cutoffs. Positions of these cutoffs in the energy spectra are confirmed by a classical analysis. Rescattering effects can be observed in the calculated energy spectra for certain values of the scattering angle. These effects are represented by the second plateau in the energy spectrum. This is different from the process of above-threshold ionization/detachment by a bicircular laser field, where the (re)scattering effects in the photoelectron energy spectra cannot be observed in the case of corotating laser-field components.
关键词： bicircular laser field,relative phase,electron-atom scattering,rescattering effects,intensity ratio
更新于2025-09-23 15:21:01
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Momentum Spectroscopy for Multiple Ionization of Cold Rubidium in the Elliptically Polarized Laser Field
摘要： 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 × 1015 W/cm2). The complete vector momenta of Rb??+ ions up to charge state ?? = 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 over-barrier ionization model. Present momentum spectroscopy of cold heavy alkali atoms presents novel strong-field phenomena beyond the noble gases.
关键词： cold rubidium,MOTRIMS,elliptically polarized laser field,multiple ionization,momentum spectroscopy
更新于2025-09-23 15:21:01
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Nonadiabatic Dynamics in a Laser Field: Using Floquet Fewest Switches Surface Hopping To Calculate Electronic Populations for Slow Nuclear Velocities
摘要： We investigate two well-known approaches for extending the fewest switches surface hopping (FSSH) algorithm to periodic time-dependent couplings. The first formalism acts as if the instantaneous adiabatic electronic states were standard adiabatic states, which just happen to evolve in time. The second formalism replaces the role of the usual adiabatic states by the time-independent adiabatic Floquet states. For a set of modified Tully model problems, the Floquet FSSH (F-FSSH) formalism gives a better estimate for both transmission and reflection probabilities than the instantaneous adiabatic FSSH (IA-FSSH) formalism, especially for slow nuclear velocities. More importantly, only F-FSSH predicts the correct final scattering momentum. Finally, in order to use Floquet theory accurately, we find that it is crucial to account for the interference between wavepackets on different Floquet states. Our results should be of interest to all those interested in laser-induced molecular dynamics.
关键词： Electronic Populations,Nonadiabatic Dynamics,Floquet Fewest Switches Surface Hopping,Slow Nuclear Velocities,Laser Field
更新于2025-09-23 15:19:57
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Interferences driven by the few-cycle laser field in the photodetachment of Cl<sup>-</sup> ion
摘要： The time-dependent semiclassical theory is extended to study the photodetachment of negative ions with outer p-state electrons. The photodetachment cross section of Cl- ion is specially studied exposed to a few-cycle laser field. Considering the influence of laser field effects, the photodetachment cross section is found to oscillate complicatedly with increasing laser intensity and frequency. We demonstrate that different types of closed orbit have different impacts on the interference structures in the photodetachment cross section. Detailed analysis of the t-ti map of the detached electron reveals a remarkably correlation with the initial phase in the laser field. Additionally, the profiles of photodetachment cross section show strong dependence on the optical cycle number N in the laser field, indicating that it is an important parameter for controlling the photodetachment of negative ion. The method adopted in this work is universal, and can be applied to study the photodetachment of other halide negative ions in the laser field, such as F- ion, Br- ion, etc. This work provides a new method for the experimentalists to coherent control of the photodetachment process of negative ion using a few-cycle laser field.
关键词： few-cycle laser field,Photodetachment,Cl- ion
更新于2025-09-23 15:19:57
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Simulation of a hydrogen atom in a laser field using the time-dependent variational principle
摘要： The time-dependent variational principle is used to optimize the linear and nonlinear parameters of Gaussian basis functions to solve the time-dependent Schr?dinger equation in one and three dimensions for a one-body soft Coulomb potential in a laser field. The accuracy is tested comparing the solution to finite difference grid calculations using several examples. The approach is not limited to one particle systems and the example presented for two electrons demonstrates the potential to tackle larger systems using correlated basis functions.
关键词： laser field,time-dependent variational principle,time-dependent Schr?dinger equation,Gaussian basis functions,soft Coulomb potential
更新于2025-09-23 15:19:57
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Selection of the magnetic quantum number in resonant ionization of neon using an XUV-IR two-color laser field
摘要： A recent experiment [Villeneuve et al. Science 356, 1150 (2017)] has shown that two-color photoionization of neon by the combination of an attosecond XUV pulse train and a moderately strong, linearly polarized IR pulse can preferentially produce photoelectrons with orbital angular quantum number l = 3 (f-wave) and magnetic quantum number m = 0. This result was rationalized by the occurrence of different Stark shifts of m = 0 and |m| = 1 sub-levels in the IR laser field. Here we perform 3D time-dependent Schrodinger equation calculations with a neon effective potential to identify the mechanism for the selective excitation and ionization of m = 0 sub-levels. Calculations of the ionization and excitation yields as a function of the IR intensity and the XUV and IR photon energy reveal that a coupling between two dominant ionization channels involving 3p and 3d intermediate excitations is responsible for the observed m-level selectivity. We compare calculated and measured photoelectron velocity map images and ionization yields over a range of IR intensities and XUV and IR photon energies, and confirm that the m = 0 or |m| = 1 channel, and thus a single set of the quantum numbers, (Jion, l, m), can be selected by an appropriate choice of these parameters.
关键词： photoelectron velocity map images,XUV-IR laser field,neon,time-dependent Schrodinger equation,two-color photoionization,magnetic quantum number,Stark shifts
更新于2025-09-23 15:19:57
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Absorption and opacity threshold for a thin foil in a strong circularly polarized laser field
摘要： We show that a commonly accepted transparency threshold for a thin foil in a strong circularly polarized normally incident laser pulse needs a refinement. We present an analytical model that correctly accounts for laser absorption. The refined threshold is determined not solely by the laser amplitude, but by other parameters that are equally or even more important. Our predictions are in perfect agreement with particle-in-cell simulations. The refined criterion is crucial for configuring laser plasma experiments in the high-field domain. In addition, an opaque foil steepens the pulse front, which can be important for numerous applications.
关键词： particle-in-cell simulations,transparency threshold,circularly polarized laser field,laser absorption,thin foil
更新于2025-09-19 17:13:59
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Laser-induced self-assembly of quantum dots: Deterministic case versus brownian case
摘要： The process of aggregation of two colloidal quantum dots in the field of quasiresonant laser radiation is investigated via computer simulation. The cases of either completely deterministic movement of particles or the movement with the account for random forces are considered. The conditions of pair formation are determined in dependence on initial interparticle distance, on laser wavelength, and on their initial orientation with respect to polarization plane of laser radiation. It is shown that despite velocity of thermal motion dominates over the velocity of directional diffusion of quantum dots, the account for random forces weakly influences on the probability of pair formation, the latter being close to results obtained in the deterministic case. The reason for this weak influence of Brownian movement is the resonant increase of electrodynamics attraction force during certain time interval within the laser pulse.
关键词： Self-assembly of nanostructures,Laser field,Dipole-dipole interaction,Brownian dynamics
更新于2025-09-19 17:13:59