Attosecond science is a growing new field of research and potential applications which relies on the development attosecond light sources. Achievements in generation application pulses enable to investigate electron dynamics nonlinear nonperturbative regime laser-matter interactions electron's natural time scale, attosecond. In this review, we describe circularly polarized their induce magnetic fields, tools for ultrafast magnetism. Simulations are performed aligned one-electron molecular...

High-order-harmonic generation (HHG) for the ${{\mathrm{H}}_{2}}^{+}$ molecule in a 3-fs, 800-nm few-cycle Gaussian laser pulse combined with static field is investigated by solving one-dimensional electronic and nuclear time-dependent Schr\"odinger equation within non-Born-Oppenheimer approximation. The spatial distribution HHG demonstrated results present recombination process of electron two nuclei, respectively. spectra shows that there little possibility nuclei around origin $z=0$ a.u....

Circularly polarized high harmonics (CHHs) have been observed in several solid targets under single-color circularly excitation. However, experimental observations show that CHHs cannot be efficiently generated monolayer molybdenum disulphide (${\text{MoS}}_{2}$) driving by a laser, thus letting its unique valley-selective circular dichroism (VSCD) to remain unexploited the harmonic generation process. Here we demonstrate efficient of ${\text{MoS}}_{2}$ driven counterrotating bicircular...

Using the three-dimensional classical ensemble method, we investigate nonsequential double-ionization (NSDI) process of Mg in few-cycle circularly polarized laser fields. We demonstrate time evolution distribution electron energy, repulsion energy between double-ionized electrons, distance nucleus and momentum electrons. By analyzing these theoretical results, find that a pulse would allow single recollision event. In addition, correlated distribution, angular ion with different delay time,...

We theoretically investigate the high-order harmonic generation (HHG) and isolated-attosecond-pulse from a full one-dimensional (1D) model of H${}_{2}$${}^{+}$ molecule in 3-fs, 800-nm laser pulses by using numerical solutions non-Born-Oppenheimer time-dependent Schr\"odinger equation (TDSE). The results with moving nuclei static are demonstrated. spectrum 22nd to cutoff becomes smooth fewer modulations an isolated-attosecond pulse duration 129 as is generated when we consider nuclear...

The carrier-envelop-phase (CEP) dependence of nonsequential double ionization (NSDI) atomic Ar with few-cycle elliptically polarized laser pulse is investigated using 2D classical ensemble method. We distinguish two particular recollision channels in NSDI, which are recollision-impact (RII) and recollision-induced excitation subsequent (RESI). separate the RII RESI according to delay time between final ionization. By tracing history trajectories, we find electron correlation spectra as well...

By solving a two-dimensional time-dependent Schrödinger equation we investigate high harmonic generation (HHG) and isolated attosecond pulse for the H2+ molecular ion in circularly polarized laser combined with Terahertz (THz) field. The intensity can be greatly enhanced continuum spectrum obtained when THz field is added. HHG process studied by semi-classical three-step model time-frequency analysis. Our studies show that only short trajectories contribute to HHG. Furthermore, present...

Coherent electron currents in circular charge transport are of great importance photoinduced processes, magneto-optics, and reaction dynamics molecules. We present ultrafast magnetic field generation by circularly polarized attosecond ultraviolet laser pulses molecular media. Simulations a one model ${\mathrm{H}}_{2}^{+}$ show that the induced exhibits periodic oscillations on time scales, which depends pulse alignment. attribute it to coherent electronic currents, arising from resonant...

The control of the spatial distribution in high-order harmonic generation (HHG) a H2+ molecule is theoretically investigated by combination mid-infrared laser pulse and terahertz (THz) field. We use THz to steer electron motion, numerical results show that cutoff from recombination with nucleus along negative-z direction enhanced case positive-z suppressed when field added. underlying physical mechanism illustrated semi-classical three step model ionization probability. time-frequency...

Nonsequential double ionization (NSDI) of carbon disulfide ${\mathrm{CS}}_{2}$ in strong 800-nm laser fields is studied experimentally and theoretically. A knee structure observed the intensity-dependent (DI) yield linearly polarized fields, which exhibits a dependence on ellipticity. The electron momentum distributions energy trajectories after DI both circularly are investigated by employing two-dimensional classical ensemble method. results clearly show evidence NSDI strong-field...

We investigate molecular photoelectron-momentum distribution (MPMD) and photoelectron angular (MPAD) of oriented ${\mathrm{H}}_{2}{}^{+}$ under frozen-nuclei approximation driven by elliptically polarized laser pulse numerically solving a two-dimensional time-dependent $\mathrm{Schr}\stackrel{\ifmmode \ddot{}\else \"{}\fi{}}{\mathrm{o}}\mathrm{dinger}$ equation. The results show that the MPMDs MPADs are sensitive to internuclear distance, which is illustrated initial evolution MPMDs. In...

Using the classical ensemble model, we investigate sensitivity of double ionization in circularly polarized laser fields to initial ensembles that are generated for an Ar atom with a definite total angular momentum. The numerical results show double-ionization probability counter-rotating case, where electrons initially rotate against field, can be much higher than corotating field. By analyzing energy distributions double-ionized versus time, find that, second electron occurs earlier and...

The high-order-harmonic generation (HHG) from the ${\mathrm{N}}_{2}$ molecule in an intense laser field is investigated by applying Lewenstein method. initial state constructed as a linear combination of highest occupied molecular orbital (HOMO) and lower-lying below HOMO, which well described Gaussian wave packet generated using gamess-uk package. HHG with different vibrational states are calculated our results show that harmonic intensity can be enhanced higher states, explained ionization...

We theoretically investigate high-order harmonic generation (HHG) in one-dimensional model solids with linearly polarized laser pulses. By identifying crystal-momentum-resolved contributions, we show that the reason behind odd-order harmonics-dominated spectrum originates from interferences between harmonics generated by different crystal momentum channels. Symmetry analysis constructive and destructive even-order are determined inversion symmetry of band dispersion time translation field....

The nonsequential double ionization (NSDI) of Mg atoms is investigated in both linearly and circularly polarized laser fields with different kinds potentials. numerical results indicate that the ``knee'' structure still exists 800-nm case potentials, which can be well explained by corresponding momentum position distribution electrons. Moreover, ionized electron energy at end pulse also shows behavior rescattering electrons between cases. Besides, we look into angular kind potentials to...

We theoretically study the selection of quantum path in high-order harmonics (HHG) and isolated attosecond pulse generation from a one-dimensional (1D) model molecule few-cycle inhomogeneous laser fields. show that inhomogeneity fields play an important role HHG process. The cutoff can be extended remarkably, harmonic spectrum becomes smooth has fewer modulations. investigate time-frequency profile time-dependent dipole, which shows short is enhanced long disappears spatially semi-classical...

The classical ensemble method is applied to study ionization processes of a one-dimensional model lithium atom interacting with an intense laser pulse. motion electrons described by the Hamiltonian canonical system equations. ratio double-to-single increasing intensity calculated and explained in terms energy distribution electrons. triple also investigated primary path found. Our results show clear transition from nonsequential sequential double as increases, which agreement quantum calculation.

We extend the coupled coherent-state (CCS) approach to simulate strong-field ionization of helium atoms at long wavelengths. This uses a basis trajectories guided by frozen Gaussian coherent states, sampled from Monte Carlo distribution, as initial states quantum time-dependent Schr\"odinger equations. The CCS move over averaged potentials, which can remove Columbic singularities exactly. low-energy structure is predicted our calculation and ``rescattering'' event clearly identified in...

We present ultrafast magnetic-field pulse generation in aligned molecules from numerical solutions of time-dependent Schr\"odinger equations. The one-electron molecular ion ${{\mathrm{H}}_{2}}^{+}$ as a benchmark model is used to describe the photophysics process. Schemes with bichromatic high-frequency corotating and counterrotating $(\ensuremath{\omega},2\ensuremath{\omega})$ ($\ensuremath{\omega},3\ensuremath{\omega})$ circularly polarized UV laser pulses are presented produce spatial...

We theoretically investigate the high-order harmonic generation and isolated attosecond pulse from a two-dimensional model of an Ar${}^{+}$ cluster in synthesized two-color laser pulse. A scheme to generate is proposed by using 4-fs 800-nm fundamental field combination with wavelength-adjustable weaker When number ions surrounding central atom 24 chosen be 1200 nm intensity $1\ifmmode\times\else\texttimes\fi{}{10}^{14}$ W/cm${}^{2}$, almost linearly polarized duration 45 as obtained...

We theoretically investigate the high-order harmonic generation (HHG) of helium atom driven by bichromatic counter-rotating circularly polarized laser fields. By changing intensity ratio two driving fields, spectral chirality HHG can be controlled. As increases, will change from positive- to negative-value around a large fields when total keeps unchanged. However, sign changed positive negative small changes. At this time, we effectively control helicity spectrum and polarization resulting...