Raman laser pulses are used to induce coherent tunnelling between neighbouring sites of a vertical 1D optical lattice. Such tunneling occurs when the detuning of a probe laser from the atomic transition frequency matches multiples of the Bloch frequency, allowing for a spectroscopic control of the coupling between Wannier Stark (WS) states. In particular, we prepare coherent superpositions of WS states of adjacent sites, and investigate the coherence time of these superpositions by realizing a spatial interferometer. This scheme provides a powerful tool for coherent manipulation of external degrees of freedom of cold atoms, which is a key issue for quantum information processing.
The photoelectron momentum distribution in the strong-field ionization has a variety of structures that reveal the complicated dynamics of this process. Recently, we identified a low-energy interference structure in the case of a super-intense extreme ultraviolet (XUV) laser pulse and attributed it to the laser-induced electron Fresnel diffraction. This structure is determined by the laser-induced electron displacement [Geng L et al. 2021 Phys. Rev. A 104(2) L021102]. In the present work, we find that the Fresnel diffraction picture is also present in the tunneling and over-barrier regime of i…
Nonadiabatic tunneling in circularly polarized laser fields. III. Comparison with experiment
我们比较了Herath等人[T.赫拉特湖Yan，S. K.李和W。Li，Phys. Rev. Lett. 109，043004（2012）]在圆偏振激光场中的强场非绝热隧穿与我们的理论的原始预测[I. Barth和O. Smirnova，Phys. Rev A 84，063415（2011）]刺激这些实验。我们表明，理论和实验是在非常好的协议。我们还解释了为什么Herath等人[T.赫拉特湖Yan，S. K.李和W。Li，Phys. Rev. Lett. 109，043004（2012）]提出了与我们的理论的定量差异。我们确认，这些看似不一致的删除与我们的理论模型的准确应用。我们提出了一个实验，独特的确定电离价轨道p+或p-的偏好。
We study ionization of atoms in strong elliptically-polarized laser fields. We focus on the physical origin of the offset angle in the photoelectron momentum distribution and its possible relation to a specific time. By developing a model which is based on strong-field approximation and considers the classical Coulomb scattering, we are able to quantitatively explain recent attoclock experiments in a wide region of laser and atomic parameters. The offset angle can be understood as arising from the scattering of the electron by the ionic potential when the electron exits the laser-Coulomb-forme…
Diagnostics of ultra-intense laser pulses using tunneling ionization
我们重新审视最近提出的方案[M. F. Ciappina等人2019 Phys. Rev. A 99 043405]，用于精确测量高功率激光束焦点中的电磁辐射强度。该方法基于对原子多重顺序隧道电离的观察，建议根据具有一定电荷数的焦区离子的出现来确定峰值强度值。在这里，我们研究的方法的敏感性，两个基本因素：焦点体积效应和隧道电离模型选择计算电离率。我们表明，一方面，结果似乎几乎模型独立的氦和氢离子的电离，另一方面，焦点平均离开强度依赖的功能可见。我们的研究结果有利于极端激光强度的原子诊断的实际实施。
Classically allowed transport is shown to compete with quantum tunneling during the ionization of atoms by ultrashort and intense laser pulses, despite Keldysh parameters smaller than unity. This is done by comparing exact probability densities with the ones obtained from purely classical propagation using the Truncated Wigner Approximation. Not only is classical transport capable of moving trajectories away from the core, but it can also furnish ionization probabilities of the same order as the quantum ones for intensities currently employed in experiments. Our results have implications rangi…
Interaction of a strong laser pulse with matter transfers not only energy but also linear momentum of the photons. Recent experimental advances have made it possible to detect the small amount of linear momentum delivered to the photoelectrons in strong-field ionization of atoms. Linear momentum transfer is a unique signature of the laser-atom interaction beyond its dipolar limit. Here, we present a decomposition of the subcycle time-resolved linear momentum transfer in term of its multipolar components. We show that the magnetic dipole contribution dominates the linear momentum transfer durin…
Tunneling ionization of an atom in ultrashort laser pulses is considered. When the driving laser pulse is switched-on and -off with a steep slope, the photoelectron momentum distribution (PMD) shows an edge-effect because of the photoelectron diffraction by the time-slit of the pulse. The trivial diffraction pattern of the edge effect consisting of fast oscillations in the PMD disguises in the deep nonadiabatic regime the physically more interesting features in the spectrum which originate from the photoelectron dynamics. We point out the precise conditions how to avoid this scenario experimen…
We investigate the liberation of an atomic electron by a linearly polarized single-cycle near-infrared laser pulse having a peak intensity that ensures tunneling. Based on phase space analysis and energy distribution in the instantaneous potential, we reveal the importance of quantum interference between tunneling and over-the-barrier pathways of escape. Tunneling is blurred both in space and time, and the contribution of tunneling at the mean energy is almost negligible. We suggest and justify improved initial conditions for a classical particle approximation of strong-field ionization, based…
The electron nondipole dynamics in tunneling ionization in an elliptically polarized laser field is investigated theoretically using a relativistic Coulomb-corrected strong-field approximation (SFA) based on the eikonal approximation of the Klein-Gordon equation. We calculate attoclock angle-resolved light-front momentum distributions at different ellipticities of the laser field in quasistatic and nonadiabatic regimes and analyze them with an improved Simpleman model. The nondipole correlations between longitudinal and transverse momentum components are examined. Deviations of the photoelectr…
