Strong-field approximation for intense-laser atom processes: the choice of gauge

From quantum to classical description of intense laser-atom physics with Bohmian trajectories

In this paper, Bohmian mechanics is introduced to the intense laser-atom physics. The motion of atomic electron in intense laser field is obtained from the Bohm-Newton equation. We find the quantum potential that dominates the quantum effect of a physical system becomes negligible as the electron is driven far away from the parent ion by the intense laser field, i.e. the behavior of the electron smoothly trends to be classical soon after the electron was ionized. Our numerical calculations present a direct positive evidence for the semiclassical trajectory methods in the intense laser-atom phy…

Probing the quantum vacuum with ultra intense laser pulses

This article presents: 1) The theoretical background of strong field physics and vacuum structure and stability; 2) The instrumental developments in the area of pulse lasers and considers the physics case for ultra intense laser facilities; and 3) Discussion of the applied and fundamental uses of ultra-intense lasers.

Generation of electron vortex states in ionization by intense and short laser pulses

The generation of electron vortex states in ionization by intense and short laser pulses is analyzed under the scope of the lowest-order Born approximation. For near infrared laser fields and nonrelativistic intensities of the order of $10^{16}$~W/cm$^2$, we show that one has to modify the nonrelativistic treatment of ionization by accounting for recoil and mass relativistic corrections. By using the corrected quasi-relativistic theory, the requirements for the observation of electron vortex states with non-negligible probability and large topological charge are determined.

Generation of isolated attosecond pulses by polarization gating of high-order harmonic emission from H$_2^+$ in intense ultrashort laser fields

Quantum-mechanical investigation is presented to study single attosecond pulse generation by gating high-order harmonic emission from H$_2^+$ molecule in intense laser pulses with time-dependent ellipticity. The high-order harmonic generation from H$_2^+$ molecule in superposition of a left and a right-hand circularly polarized Gaussian pulse is studied and the effect of time duration and carrier-envelope phase of laser field on single attosecond pulse generation is investigated. Using laser field formed by combination of a left and a right-hand elliptically polarized Gaussian pulse, the effec…

Efficient simulation of multielectron dynamics in molecules under intense laser pulses: Implementation of the multiconfiguration time-dependent Hartree-Fock method based on the adaptive finite element method

We present an implementation of the multiconfiguration time-dependent Hartree-Fock method based on the adaptive finite element method for molecules under intense laser pulses. For efficient simulations, orbital functions are propagated by a stable propagator using the short iterative Arnoldi scheme and our implementation is parallelized for distributed memory computing. This is demonstrated by simulating high-harmonic generation from a water molecule and achieves a simulation of multielectron dynamics with overwhelmingly less computational time, compared to our previous work.

Electrons in intense laser fields with local phase, polarization, and skyrmionic textures

Laser fields can be shaped on a subwavelength scale as to have a specific distribution in spin angular momentum, orbital structure, or topology. We study how these various features affect the strongly nonlinear electron dynamics. Specifically, we derive closed expressions for the wave function of an unbound electron subject to a generally structured, intense laser field and demonstrate its use for imprinting the orbital angular momentum of a propagating optical vortex onto photoelectrons emitted from atoms and traveling through the optical vortex. It is also shown that photoelectrons can be ac…

Quantum beats in the polarization response of a dielectric to intense few-cycle laser pulses

We have investigated the polarization response of a dielectric to intense few-cycle laser pulses with a focus on interband tunnelling. Once charge carriers are created in an initially empty conduction band, they make a significant contribution to the polarization response. In particular, the coherent superposition of conduction- and valence-band states results in quantum beats. This quantum-beat part of the polarization response is affected by the excitation dynamics and attosecond-scale motion of charge carriers in an intense laser field. Our analysis shows that, with the onset of Bloch oscil…

Harmonics generation and intense terahertz radiation from polar molecules at multiphoton resonant excitation in laser fields

The coherent radiation spectrum of two-level polar molecules with UV transition is studied at the multiphoton resonant excitation by a moderately strong laser field. The spectrum corresponding to harmonic generation and low-frequency radiation is investigated both analytically and numerically. Specifically, a mechanism for generation of intense smoothly tunable terahertz radiation by two-level molecular configurations (with dynamic Stark shifts) possessing permanent dipole moments, is considered.

Dimensional Scaling Treatment with Relativistic Corrections for Stable Multiply Charged Atomic Ions in High-Frequency Super-Intense Laser Fields

We present a theoretical framework which describes multiply-charged atomic ions, their stability within super-intense laser fields,also lay corrections to the systems due to relativistic effects. Dimensional scaling calculations with relativistic corrections for systems: H, H$^{-}$, H$^{2-}$, He, He$^{-}$, He$^{2-}$, He$^{3-}$ within super-intense laser fields were completed. Also completed were three-dimensional self consistent field calculations to verify the dimensionally scaled quantities. With the aforementioned methods the system's ability to stably bind 'additional' electrons through th…

外尔半金属中的强激光驱动现象

Intense Laser-Driven Phenomena In Weyl Semimetals

本论文围绕外尔半金属（WSM）中的强激光驱动现象展开多方面探究，旨在将其应用于新兴光波驱动拍赫兹电子学与量子技术领域。

Ionization of Xe in intense, two-cycle laser fields: Dependence on carrier-envelope phase

We report on tunnel ionization of Xe by 2-cycle, intense, infrared laser pulses and its dependence on carrier-envelope-phase (CEP). At low values of optical field ($E$), the ionization yield is maximum for cos-like pulses with the dependence becoming stronger for higher charge states. At higher $E$-values, the CEP dependence either washes out or flips. A simple phenomenological model is developed that predicts and confirms the observed results. CEP effects are seen to persist for 8-cycle pulses. Unexpectedly, electron rescattering plays an unimportant role in the observed CEP dependence. Our r…