Envelope-Driven Recollisions Triggered by an Elliptically Polarized Pulse

J. Dubois, C. Chandre, and T. Uzer

Phys. Rev. Lett. 124, 253203 – Published 26 June 2020

Abstract

Increasing ellipticity usually suppresses the recollision probability drastically. In contrast, we report on a recollision channel with large return energy and a substantial probability, regardless of the ellipticity. The laser envelope plays a dominant role in the energy gained by the electron, and in the conditions under which the electron comes back to the core. We show that this recollision channel efficiently triggers various nonlinear and nonperturbative phenomena—such as multiple ionization—with an elliptically polarized pulse.

Received 19 November 2019
Accepted 12 June 2020

DOI:https://doi.org/10.1103/PhysRevLett.124.253203

Physics Subject Headings (PhySH)

Atomic & molecular processes in external fields

Dynamical systems Hamiltonian systems

Nonlinear DynamicsAtomic, Molecular & Optical

Authors & Affiliations

J. Dubois ^1,*, C. Chandre ¹, and T. Uzer²

¹Aix Marseille Univ, CNRS, Centrale Marseille, I2M, Marseille, France
²School of Physics, Georgia Institute of Technology, Atlanta, Georgia 30332-0430, USA

^*Present address: Max Planck Institute for the Physics of Complex Systems, Dresden, Germany.

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Issue

Vol. 124, Iss. 25 — 26 June 2020

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Images

Figure 1
Typical recollision with high return energy in a $C P$ field. The laser envelope is trapezoidal 2-4-2 (see text), the laser intensity is $I = 8 \times 10^{14} W {cm}^{- 2}$ . The electron is initialized with energy $- I_{p} = - 5.8 eV$ . Left panel: Trajectory in the rotating frame $(\tilde{x}, \tilde{y})$ . The white and red circles are the position of the electron at the ionization and return time, respectively. The gray scale shows the value of the zero-velocity surface during the plateau. Right panels: The trajectory projected along the position and energy of Hamiltonian (3) at ionization $t_{i} \approx 0.3 T$ , the end of the ramp-up $2 T$ and return $t_{r} \approx 2.6 T$ (from left to right). The gray surface is the classically forbidden region for $\tilde{y} = 0$ [i.e., $H (\tilde{r}, \tilde{p}, t) < Z (\tilde{r}, t)$ ]. The blue curve is the zero-velocity surface at time $t = 0$ for $\tilde{y} = 0$ . The saddle point is the local maximum of the zero-velocity surface for negative $\tilde{x}$ . Distances and energies are in atomic units.
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Figure 2
Double ionization probability curves of Hamiltonian (5) as a function of the laser intensity for Mg and laser wavelength 780 nm. The thin-dotted curves are the NSDI probability curves.
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Figure 3
Distributions of the ionization time $t_{i}$ and the return $t_{r}$ of the recollisions of Hamiltonian (5) leading to NSDI for Mg and $C P$ pulses ( $ξ = 1$ ). The parameters are the same as in Fig. 2. The gray areas are where electrons undergo a recollision but do not lead to NSDI. The red dashed curve is our prediction of the ionization time of the outermost electron $t_{i}$ [23] for $I_{p} = 0.28 a . u .$ The vertical-dotted curve is where we expect over-the-barrier ionization, and the vertical dash-dotted curve is where we expect envelope-driven recollisions to gain enough energy to trigger NSDI [23]. In the inset, the red-dotted curves are $t_{r} = t_{i} + (n + 1 / 2) T$ with $n \in N^{⋆}$ .
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Figure 4
Phase diagram of the existence of envelope-driven recollisions. The black line is the critical ionization potential $I_{c} \approx 1.85 ω^{2 / 3}$ . The white (respectively, yellow and blue) markers are where no knee (respectively, a knee) is observed in the double ionization probability curves. The experimental measurements for He (white square) and Ne (white up-pointing triangle) at $λ = 614 nm$ are reported in Ref. [12]; for Ar (white diamond) and Xe (white star) at $λ = 800 nm$ are reported in Ref. [13]; for Mg (yellow circle) at $λ = 780 nm$ are reported in Ref. [14]; for Mg (blue asterisk) and Zn (white right-pointing triangle) at $λ = 800 nm$ ; and for Mg (white down-pointing triangle) at $λ = 1030 nm$ are reported in Ref. [16]. The color code is the guiding-center energy of the electron at the saddle point $E$ at time $t_{i}$ : red is where $E = 2 a . u .$ , white is where $E = 0$ (critical ionization potential), and green is where $E = - 1 a . u .$ .
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